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222
Documentation/guides/fork_vfork_migration.rst Normal file
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@ -0,0 +1,222 @@
=========================================
Migrating to separate ``fork``/``vfork``
=========================================
What changed
============
NuttX used to implement ``fork()`` and ``vfork()`` as the same function. Both
were thin libc wrappers around a single ``up_fork()`` syscall; ``vfork()``
differed only by a trailing ``waitpid()``. Underneath, the child joined the
parent's address environment -- the same ``addrenv_join()`` that
``pthread_create()`` uses -- and got a private *copy of the stack*. So the
child shared ``.data``, ``.bss`` and the heap with its parent, and ran
concurrently with it.
That was not ``fork()``. It was ``vfork()``-with-a-private-stack published
under ``fork()``'s name. The history says so plainly: the ``fork()`` this
replaces was NuttX's old ``vfork()``, renamed in 2023 without any change of
behaviour. And the consequence was silent: a program written against POSIX
``fork()`` compiled and ran, and its child's writes quietly landed in the
parent's variables.
There are now three distinct primitives:
.. list-table::
:header-rows: 1
:widths: 14 30 26 30
* - API
- Memory
- Parent
- Availability
* - ``fork()``
- child gets **its own copy** at the same virtual addresses
- runs concurrently
- ``CONFIG_ARCH_HAVE_FORK`` -- only where an address environment can be
duplicated
* - ``vfork()``
- child **shares** the parent's memory
- **suspended** until the child ``_exit()``\ s or ``exec()``\ s
- ``CONFIG_ARCH_HAVE_VFORK`` -- no address environment needed
* - ``task_fork()``
- child shares memory, private stack copy
- runs concurrently
- ``CONFIG_TASK_FORK`` -- on by default exactly where ``fork()`` existed
before
``task_fork()`` is the old behaviour under an honest name. Nothing was lost.
.. note::
``fork()`` is provided only where the architecture implements
``up_addrenv_fork()`` and therefore selects
``CONFIG_ARCH_HAVE_ADDRENV_FORK``; it becomes available architecture by
architecture as that hook lands. Check ``CONFIG_ARCH_HAVE_FORK`` in your
own configuration rather than assuming either way. Where it is unset,
``vfork()`` and ``task_fork()`` are what the configuration offers, and
``CONFIG_FORK_IS_TASK_FORK`` keeps the spelling ``fork()`` working for code
that cannot be changed.
This is a breaking change
=========================
Two things break, and they break loudly rather than quietly:
**Code calling** ``fork()`` **on a target without a duplicable address
environment no longer builds.** ``fork()`` is not declared in ``unistd.h``
there, so you get a compile error naming the function. That is the intended
outcome: a build error is strictly better than the silent wrongness it
replaces.
**Code calling** ``fork()`` **on a target that does have real** ``fork()``
**changes behaviour** -- from sharing to copying. Code that (perhaps
unknowingly) relied on the sharing will now see the parent and child diverge.
Which replacement do I want?
============================
Answer the question "why did I call ``fork()``?".
*I want the child to run a different program.*
Use :c:func:`posix_spawn` or ``task_spawn()``. This is the single most
common reason to call ``fork()``, NuttX has always provided a better answer
for it, and that answer does not have the pid discontinuity that
``fork()``\ +\ ``exec()`` has. If you must keep the two-step idiom, use
``vfork()`` + ``exec*()``: that is exactly what ``vfork()`` is for, and
unlike ``fork()`` it needs no duplicable address environment.
*I want a second flow of control that shares my memory.*
Use ``pthread_create()``. That is the same memory relationship, spelled
clearly, with a normal entry point instead of a function that returns twice.
If you specifically need the returns-twice shape -- for example you are
porting code and do not want to restructure it -- use ``task_fork()``. It
is a rename, not a rewrite:
.. code-block:: c
#include <sched.h>
pid = task_fork(); /* was: pid = fork(); */
*I want a genuinely independent copy of this process.*
Keep calling ``fork()``, and make sure your configuration selects
``CONFIG_ARCH_HAVE_FORK``. Be aware there is no copy-on-write: the copy is
eager, so forking a large process needs as much free memory as the process
occupies and fails with ``ENOMEM`` otherwise.
*I cannot change the code right now.*
Set ``CONFIG_FORK_IS_TASK_FORK=y``. This aliases ``fork()`` back to
``task_fork()``, restoring the previous behaviour **exactly** -- same
sharing, same concurrency, no new suspension. It is available on precisely
the configurations that had ``fork()`` before, and it depends on
``!ARCH_HAVE_FORK``: on a target that can provide real ``fork()``, aliasing
it back to sharing would reintroduce the very ambiguity this change removes,
so sharing-dependent callers there must be edited.
Configuration symbols
=====================
``CONFIG_ARCH_HAVE_TASK_FORK``
Hidden. The architecture can clone the calling task with a copied stack.
Inherits exactly the ``select`` lines that ``ARCH_HAVE_FORK`` used to have,
so no configuration that had ``fork()`` loses the machinery.
``CONFIG_TASK_FORK``
Provide ``task_fork()``. Defaults to ``y`` wherever
``ARCH_HAVE_TASK_FORK`` is selected, so no configuration that had ``fork()``
loses the primitive. Turn it off to leave a NuttX extension out of a build
that does not call it; the architecture entry point, the system call and the
libc stub go with it. ``vfork()`` and ``fork()`` are unaffected.
``CONFIG_ARCH_HAVE_VFORK``
Hidden. The architecture can implement POSIX ``vfork()``.
``CONFIG_ARCH_HAVE_ADDRENV_FORK``
Hidden. The architecture implements ``up_addrenv_fork()``, which duplicates
an address environment into freshly allocated pages mapped at the same
virtual addresses.
``CONFIG_ARCH_HAVE_FORK``
Hidden, derived: ``ARCH_ADDRENV && ARCH_HAVE_ADDRENV_FORK``. It no longer
means "``fork()`` exists"; it means "this configuration can provide POSIX
``fork()`` semantics".
``CONFIG_FORK_IS_TASK_FORK``
Visible, default ``n``. The legacy alias described above.
Notes for architecture maintainers
==================================
The register/stack snapshot machinery is common to all three primitives. Each
architecture exposes three entry points -- ``up_task_fork()``, ``up_vfork()``
and ``up_fork()`` -- which share one snapshot sequence and differ only in a
``FORK_TYPE_*`` selector (see ``include/nuttx/fork.h``) handed to
``nxtask_setup_fork()``. That is where the memory semantics are decided:
``addrenv_join()`` for ``task_fork()`` and ``vfork()``, ``addrenv_fork()`` for
``fork()``.
Adding real ``fork()`` to an architecture
-----------------------------------------
Two things are needed, and the second is the one that is easy to miss.
**Implement** ``up_addrenv_fork()``. It duplicates an address environment:
allocate fresh pages, copy the parent's contents into them, and map them at the
*same* virtual addresses. ``up_addrenv_clone()`` is not this -- it copies only
the representation and leaves both processes pointing at one set of page
tables. Then give ``ARCH_HAVE_ADDRENV_FORK`` a ``default y if <arch>`` line in
``arch/Kconfig``, and ``ARCH_HAVE_FORK`` follows.
**Build the child from the caller's saved system call frame.** In a kernel
build ``fork()`` is reached through a system call, so the return address and
stack pointer the architecture's fork entry point can observe for itself belong
to the *kernel*, not to the caller; a child built from those resumes at a
kernel address on a kernel stack. The architecture must record the caller's
exception frame when it traps -- ``xcp.sregs`` is the field that exists for
this -- and build the child from that instead, while a kernel thread that calls
the entry point directly still takes the ordinary path.
Nothing else is required: the ``up_fork()`` entry point and the libc wrapper
are already there and become live automatically.
Note that ``ARCH_HAVE_ADDRENV_FORK`` is about a *per-process* address
environment. A protected build has one address space carved up once at boot,
whether the boundaries are drawn by an MPU or by a fixed set of MMU mappings;
its ``up_addrenv_*()`` are stubs, and there is no mapping to duplicate at the
same virtual addresses. ``CONFIG_ARCH_ADDRENV`` being set is therefore not by
itself evidence that ``fork()`` can be provided. ``vfork()`` and
``task_fork()``, which share the parent's memory, work there as everywhere
else.
Known gaps
==========
``fork()`` **is gained one architecture at a time.** The generic machinery is
complete -- ``addrenv_fork()``, the ``up_addrenv_fork()`` hook, the syscall, the
libc wrapper and the ``ostest`` case -- so an architecture provides ``fork()``
by implementing ``up_addrenv_fork()`` and selecting
``CONFIG_ARCH_HAVE_ADDRENV_FORK``, with no further generic work.
**A windowed ABI needs its stack rebased, not just copied.** On Xtensa,
giving a child a relocated copy of the parent's stack takes more than the copy:
the register-window save areas embedded in the stack hold absolute stack
pointers, so each one has to be rebased along with the copy, or the child
reloads a pointer into the *parent's* stack on its very first window underflow.
That rebasing is architecture-specific and belongs with the Xtensa entry points
rather than here.
Note also on ``waitpid()`` after ``vfork()``
============================================
The ``vfork()`` parent is now resumed when the child's TCB is torn down, so by
the time it runs the child is completely gone. Where the child called
``exec()`` this makes no difference -- ``exec_swap()`` has already given the
loaded program the child's pid, and that program is still running, so
``waitpid()`` behaves normally. Where the child called ``_exit()``,
``waitpid()`` can only return its status if ``CONFIG_SCHED_CHILD_STATUS`` is
enabled; otherwise it returns ``ECHILD``, because NuttX does not retain the
status of a task that no longer exists. That is a pre-existing property of
that configuration, not a change: the previous implementation blocked in a
libc ``waitpid(WNOWAIT)`` and an application's own ``waitpid()`` afterwards hit
the same wall.

1
Documentation/guides/index.rst
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@ -37,6 +37,7 @@ Guides
logging_rambuffer.rst
ipv6.rst
integrate_newlib.rst
fork_vfork_migration.rst
protected_build.rst
platform_directories.rst
port_drivers_to_stm32f7.rst

21
Documentation/implementation/memory_configurations.rst
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@ -30,7 +30,7 @@ On-Demand Paging
NuttX also supports on-demand paging via ``CONFIG_PAGING``.
On-demand paging is a method of virtual memory management and requires
the the CPU architecutre support a MMU.
the the CPU architecture support a MMU.
In a system that uses on-demand paging, the OS responds to a page fault
by copying data from some storage media into physical memory and setting up
@ -410,7 +410,7 @@ of functions that:
1. Have only one ``.text`` space in RAM, but
2. Separate ``.data`` and ``.bass`` space, and are
3. Separately linked into with the program in each address environmnet.
3. Separately linked into with the program in each address environment.
(not implemented).
@ -484,7 +484,7 @@ at least in its current form.
That full implementation of ``mmap()`` plus the minor changes
to the NuttX ELF loader are all that are required to support fully
share-able ``.text`` sections – as well as the memory savings
from not carrying aroung the relocation and symbol information
from not carrying around the relocation and symbol information
(Not implemented).
@ -632,10 +632,13 @@ the contemplate in any real detail:
and swap the state into physical memory as needed?(not implemented).
* ``mmap()``. True shared memory and true file mapping could be supported.
I am repeating myself (not implemented).
* ``fork()``. The ``fork()`` interface could be supported. NuttX currently
supports the "crippled" version, ``vfork()`` but with these process address
environments, the real ``fork()`` interface could be supported.
(not implemented).
* ``fork()``. The real ``fork()`` interface can be supported on configurations
with a duplicable process address environment: an architecture implements
``up_addrenv_fork()``, selects ``CONFIG_ARCH_HAVE_ADDRENV_FORK``, and
``CONFIG_ARCH_HAVE_FORK`` follows. What is not implemented is
copy-on-write: the duplication copies the parent's pages eagerly, which
needs as much free memory as the parent occupies. Demand paging would fix
that.
* Dynamic Stack Allocation. Completely eliminate the need for constant tuning
of static stack sizes.(not implemented).
* Shared Libraries. Am I repeating myself again?(not implemented).
@ -688,8 +691,8 @@ There are two problems here:
So how do you create new tasks/processes in such a context.
There is only one way possible; by using an interface that takes a file name
as an argument (rather than absolute address).
New processes started with ``vfork()`` and ``exec()`` or with
``posix_spawn()`` should not have any of these issues.
New processes started with ``fork()`` or ``vfork()`` and ``exec()``, or with
``posix_spawn()``, should not have any of these issues.
ARM Memory Management

101
Documentation/reference/user/01_task_control.rst
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@ -59,9 +59,11 @@ Standard interfaces
- :c:func:`exit`
- :c:func:`getpid`
Standard ``vfork`` and ``exec[v|l]`` interfaces:
Standard ``fork``/``vfork`` and ``exec[v|l]`` interfaces:
- :c:func:`fork`
- :c:func:`vfork`
- :c:func:`task_fork` (non-standard)
- :c:func:`exec`
- :c:func:`execv`
- :c:func:`execl`
@ -347,6 +349,47 @@ Functions
**POSIX Compatibility:** Compatible with the POSIX interface of the same
name.
.. c:function:: pid_t fork(void)
``fork()`` creates a new process. The child process is an exact copy of
the calling process: it receives **its own copy** of the parent's memory,
at the same virtual addresses. Writes by the child are invisible to the
parent and writes by the parent are invisible to the child. The child may
modify anything, call any function, return from the function in which
``fork()`` was called, and run indefinitely; it runs concurrently with the
parent. None of ``vfork()``'s restrictions apply.
NOTE: ``fork()`` requires an address environment that can be
duplicated, and so it is available only where ``CONFIG_ARCH_HAVE_FORK``
is selected -- which in turn requires ``CONFIG_ARCH_ADDRENV`` and an
architecture that implements ``up_addrenv_fork()``. **Where it cannot
be provided, ``fork()`` is not provided at all**: the declaration is
absent from ``unistd.h`` and code that calls it fails to build. That
is deliberate. A build error naming the function is strictly better
than a ``fork()`` that silently gives the child the parent's memory.
See :doc:`/guides/fork_vfork_migration` for how to move code that
relied on the previous behaviour.
There is no copy-on-write, because NuttX has no demand paging to build
it on, so the copy is eager: forking a large process needs as much free
memory as the process occupies and fails with ``ENOMEM`` otherwise.
Spawn-heavy code should prefer :c:func:`posix_spawn` or
:c:func:`vfork`, on NuttX as anywhere.
Applications that want the historical NuttX ``fork()`` behaviour --
shared memory, private stack, both running -- should call
:c:func:`task_fork`. ``CONFIG_FORK_IS_TASK_FORK`` aliases ``fork()``
back to it on configurations that cannot provide real ``fork()``, for
legacy code that cannot be changed.
:return: Upon successful completion, ``fork()`` returns 0 to the child
process and returns the process ID of the child process to the parent
process. Otherwise, -1 is returned to the parent, no child process is
created, and ``errno`` is set to indicate the error.
**POSIX Compatibility:** Compatible with the POSIX interface of the same
name.
.. c:function:: pid_t vfork(void)
The ``vfork()`` function has the same effect as
@ -357,12 +400,18 @@ Functions
function before successfully calling ``_exit()`` or one of the ``exec``
family of functions.
NOTE: ``vfork()`` is not an independent NuttX feature, but is
implemented in architecture-specific logic (using only helper
functions from the NuttX core logic). As a result, ``vfork()`` may
not be available on all architectures. The current implementation in
NuttX arm64 only guarantees that ``vfork()`` works when
CONFIG_BUILD_FLAT=y.
The child **shares** the parent's memory -- nothing is copied, which is the
entire point of ``vfork()`` and the reason a caller chooses it -- and the
parent is **suspended** until the child calls ``_exit()`` or one of the
``exec`` family. That suspension is what makes the sharing safe, and it is
also the price: the restrictions above exist because the child is running
in the parent's address space on borrowed time.
NOTE: ``vfork()`` is implementable with or without an MMU and is
available wherever ``CONFIG_ARCH_HAVE_VFORK`` is selected. The
suspension lives in the kernel primitive rather than in a libc
``waitpid()``, so the parent is resumed at ``exec()`` as POSIX requires,
and ``vfork()`` does not depend on ``CONFIG_SCHED_WAITPID``.
:return: Upon successful completion, ``vfork()`` returns 0 to
the child process and returns the process ID of the child process to the
@ -372,6 +421,34 @@ Functions
**POSIX Compatibility:** Compatible with the BSD/Linux interface of the
same name. POSIX marks this interface as Obsolete.
.. c:function:: pid_t task_fork(void)
``task_fork()`` is a non-standard NuttX interface that clones the calling
task. The child shares the parent's ``.data``, ``.bss`` and heap -- it
joins the parent's address environment, exactly as a pthread does -- but
runs on a **private copy** of the parent's stack, and it runs concurrently
with the parent. Like ``fork()`` it returns twice.
This is neither ``fork()`` nor ``vfork()``. It is a task cloned at the
call site with the memory relationship of a thread; the nearest precedent
is Plan 9's ``rfork(RFPROC|RFMEM)``. It is the behaviour NuttX published
under the name ``fork()`` before these three interfaces were separated, and
it is preserved here under an honest name so that nothing is lost.
NOTE: available where ``CONFIG_TASK_FORK`` is enabled, which defaults to
the set of configurations that had ``fork()`` before the split, and can
be turned off. New code should prefer :c:func:`pthread_create`, which
is the same memory relationship spelled clearly, or :c:func:`posix_spawn`;
``task_fork()`` exists to give the historical behaviour a truthful name,
not to recommend it.
:return: Upon successful completion, ``task_fork()`` returns 0 to the child
and returns the process ID of the child to the parent. Otherwise, -1 is
returned to the parent, no child is created, and ``errno`` is set to
indicate the error.
**POSIX Compatibility:** Non-standard.
.. c:function:: int exec(FAR const char *filename, FAR char * const *argv, FAR const struct symtab_s *exports, int nexports)
This non-standard, NuttX function is similar to
@ -449,7 +526,15 @@ Functions
thread, then (2) call ``execv()`` or ``execl()`` to replace the new
thread with a program from the file system. Since the new thread will be
terminated by the ``execv()`` or ``execl()`` call, it really served no
purpose other than to support POSIX compatibility.
purpose other than to support POSIX compatibility. :c:func:`posix_spawn`
does the same job in one step and should be preferred.
Note also that ``exec()`` does not overlay the calling process: it starts
the new program as a separate task. ``exec_swap()`` then exchanges the two
pids, so that from the parent's point of view the pid ``vfork()`` returned
does name the running program -- but the ``vfork()`` stub itself exits, and
it is that exit which releases the suspended ``vfork()`` parent. The parent
therefore resumes at ``exec()``, as POSIX requires.
The non-standard binfmt function ``exec()`` needs to have (1) a symbol
table that provides the list of symbols exported by the base code, and

4
Documentation/standards/posix.rst
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@ -1421,7 +1421,7 @@ Multiple Processes:
+--------------------------------+---------+
| :c:func:`exit` | Yes |
+--------------------------------+---------+
| fork() | No |
| :c:func:`fork` | Cond. |
+--------------------------------+---------+
| :c:func:`getpgrp` | Yes |
+--------------------------------+---------+
@ -2364,7 +2364,7 @@ XSI Multiple Process:
+--------------------------------+---------+
| :c:func:`usleep` | Yes |
+--------------------------------+---------+
| :c:func:`vfork` | Yes |
| :c:func:`vfork` | Cond. |
+--------------------------------+---------+
| :c:func:`waitid` | Yes |
+--------------------------------+---------+

95
arch/Kconfig
View file

@ -11,7 +11,8 @@ config ARCH_ARM
bool "ARM"
select ARCH_HAVE_BACKTRACE
select ARCH_HAVE_INTERRUPTSTACK
select ARCH_HAVE_FORK
select ARCH_HAVE_TASK_FORK if !BUILD_KERNEL
select ARCH_HAVE_VFORK if !BUILD_KERNEL
select ARCH_HAVE_STACKCHECK
select ARCH_HAVE_CUSTOMOPT
select ARCH_HAVE_STDARG_H
@ -29,7 +30,8 @@ config ARCH_ARM64
select ARCH_64BIT
select ARCH_HAVE_BACKTRACE
select ARCH_HAVE_INTERRUPTSTACK
select ARCH_HAVE_FORK if !BUILD_KERNEL && !BUILD_PROTECTED
select ARCH_HAVE_TASK_FORK if !BUILD_KERNEL && !BUILD_PROTECTED
select ARCH_HAVE_VFORK if !BUILD_KERNEL && !BUILD_PROTECTED
select ARCH_HAVE_STACKCHECK
select ARCH_HAVE_CUSTOMOPT
select ARCH_HAVE_STDARG_H
@ -87,7 +89,8 @@ config ARCH_RISCV
select ARCH_HAVE_CPUINFO
select ARCH_HAVE_INTERRUPTSTACK
select ARCH_HAVE_STACKCHECK
select ARCH_HAVE_FORK
select ARCH_HAVE_TASK_FORK
select ARCH_HAVE_VFORK
select ARCH_HAVE_CUSTOMOPT
select ARCH_HAVE_SETJMP
select ARCH_HAVE_STDARG_H
@ -111,7 +114,8 @@ config ARCH_SIM
select ARCH_HAVE_TICKLESS
select ARCH_HAVE_POWEROFF
select ARCH_HAVE_TESTSET
select ARCH_HAVE_FORK if !HOST_WINDOWS
select ARCH_HAVE_TASK_FORK if !HOST_WINDOWS
select ARCH_HAVE_VFORK if !HOST_WINDOWS
select ARCH_HAVE_SETJMP
select ARCH_HAVE_CUSTOMOPT
select ARCH_HAVE_TCBINFO
@ -147,7 +151,8 @@ config ARCH_X86_64
select PCI_LATE_DRIVERS_REGISTER if PCI
select ARCH_TOOLCHAIN_GNU
select ARCH_HAVE_BACKTRACE
select ARCH_HAVE_FORK if !BUILD_KERNEL
select ARCH_HAVE_TASK_FORK if !BUILD_KERNEL
select ARCH_HAVE_VFORK if !BUILD_KERNEL
select ARCH_HAVE_SETJMP
select ARCH_HAVE_PERF_EVENTS
select ARCH_HAVE_POWEROFF
@ -482,9 +487,87 @@ config ARCH_HAVE_CPUID_MAPPING
default n
depends on ARCH_HAVE_MULTICPU
config ARCH_HAVE_FORK
config ARCH_HAVE_TASK_FORK
bool
default n
---help---
The architecture can clone the calling task: the child shares the
parent's .data/.bss/heap and runs on a private copy of the parent's
stack, concurrently with the parent. This is the non-POSIX
task_fork() primitive; it is neither fork() nor vfork().
config ARCH_HAVE_VFORK
bool
default n
---help---
The architecture can implement POSIX vfork(): the child shares the
parent's memory and the parent is suspended until the child calls
_exit() or one of the exec family of functions.
config ARCH_HAVE_ADDRENV_FORK
bool
default n
depends on ARCH_ADDRENV && !ARCH_STACK_DYNAMIC
---help---
The architecture implements up_addrenv_fork(), which duplicates an
address environment: the copy is backed by freshly allocated pages
holding a copy of the parent's contents, mapped at the same virtual
addresses. This is what POSIX fork() is built on.
No architecture selects this yet. Two things are needed. First,
up_addrenv_fork() itself. Second, the architecture must build the
child's register context from the *user's* saved system call frame:
in a kernel build fork() is reached through a system call, so the
return address and stack pointer the architecture's fork entry point
can see for itself are the kernel's, not the caller's, and a child
built from those resumes at a kernel address.
config ARCH_HAVE_FORK
bool
default y if ARCH_ADDRENV && ARCH_HAVE_ADDRENV_FORK
---help---
This configuration can provide POSIX fork() semantics: the child
receives its own copy of the parent's memory at the same virtual
addresses, may modify anything, may return from the function that
called fork(), and runs concurrently with the parent.
Where this is not selected fork() is not provided at all, and code
that calls it fails to build -- see FORK_IS_TASK_FORK.
config TASK_FORK
bool "Provide task_fork()"
default y
depends on ARCH_HAVE_TASK_FORK
---help---
Provide task_fork(), which clones the calling task: the child shares
the parent's .data/.bss/heap, runs on a private copy of the parent's
stack, and runs concurrently with the parent. This is the historical
NuttX fork() behaviour under its own name. It is not POSIX, and it is
neither fork() nor vfork().
Disable this to leave it out where nothing calls it. The saving is
small -- the architecture's entry point, the system call and the libc
stub -- but the primitive is a NuttX extension, so a configuration
that does not want it need not carry it. vfork() and fork() are
unaffected; each is selected on its own.
config FORK_IS_TASK_FORK
bool "Provide fork() as an alias for task_fork() (legacy)"
default n
depends on TASK_FORK && !ARCH_HAVE_FORK
---help---
Provide fork() on configurations that cannot implement POSIX fork()
semantics, by aliasing it to task_fork().
This preserves the historical NuttX fork() behaviour exactly: the
child shares the parent's data and heap, runs on a private copy of
the parent's stack, and runs concurrently with the parent. It does
NOT provide POSIX fork() semantics: writes by the child are visible
to the parent, and vice versa.
Enable this only to keep legacy applications building. New code
should call task_fork() explicitly, or use pthread_create() or
posix_spawn().
config ARCH_HAVE_CRC32
bool

136
arch/arm/src/common/arm_fork.c
View file

@ -49,47 +49,58 @@
* Name: arm_fork
*
* Description:
* The fork() function has the same effect as posix fork(), except that the
* behavior is undefined if the process created by fork() either modifies
* any data other than a variable of type pid_t used to store the return
* value from fork(), or returns from the function in which fork() was
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
* The common ARM worker behind up_task_fork(), up_vfork() and up_fork().
* All three snapshot the caller's registers identically; `type' -- one of
* the FORK_TYPE_* constants from include/nuttx/fork.h -- says which
* primitive was called, and is passed straight through to
* nxtask_setup_fork(), which is where the memory semantics are decided.
*
* What differs here is only the stack. Normally the child has a stack of
* its own, and this function fills it with a relocated copy of the
* parent's, rebasing the stack and frame pointers to match. When the
* child shares the parent's stack addresses -- a fork() child, inside its
* duplicated address environment -- there is nothing to relocate and the
* pointers are carried over unchanged.
*
* The overall sequence is:
*
* 1) User code calls fork(). fork() collects context information and
* transfers control up arm_fork().
* 2) arm_fork() and calls nxtask_setup_fork().
* 1) User code calls task_fork(), vfork() or fork(). The libc wrapper
* enters the matching architecture entry point, which collects context
* information and transfers control to arm_fork().
* 2) arm_fork() calls nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Establishing the child's address environment (for vfork() and
* task_fork(); a fork() child's is duplicated later, once its stack
* has been filled in -- see nxtask_start_fork())
* - Allocating the stack, or inheriting the parent's for fork()
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) arm_fork() provides any additional operating context. arm_fork must:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) arm_fork() then calls nxtask_start_fork()
* 6) nxtask_start_fork() then executes the child thread.
* 5) arm_fork() then calls nxtask_start_fork(), or nxtask_start_vfork()
* which additionally suspends the caller.
* 6) which executes the child thread.
*
* nxtask_abort_fork() may be called if an error occurs between steps 3 and
* 6.
*
* Input Parameters:
* context - Caller context information saved by fork()
* context - Caller context information saved by the entry point
* type - One of the FORK_TYPE_* constants
*
* Returned Value:
* Upon successful completion, fork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
* Upon successful completion, 0 is returned to the child and the process
* ID of the child is returned to the parent. Otherwise, -1 is returned to
* the parent, no child is created, and errno is set to indicate the error.
*
****************************************************************************/
pid_t arm_fork(const struct fork_s *context)
pid_t arm_fork(const struct fork_s *context, int type)
{
struct tcb_s *parent = this_task();
struct tcb_s *child;
@ -115,7 +126,7 @@ pid_t arm_fork(const struct fork_s *context)
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork((start_t)(context->lr & ~1));
child = nxtask_setup_fork((start_t)(context->lr & ~1), type);
if (!child)
{
serr("ERROR: nxtask_setup_fork failed\n");
@ -137,43 +148,60 @@ pid_t arm_fork(const struct fork_s *context)
sinfo("Parent: stackutil:%" PRIu32 "\n", stackutil);
/* Make some feeble effort to preserve the stack contents. This is
* feeble because the stack surely contains invalid pointers and other
* content that will not work in the child context. However, if the
* user follows all of the caveats of fork() usage, even this feeble
* effort is overkill.
*/
newtop = (uint32_t)child->stack_base_ptr +
child->adj_stack_size;
newsp = newtop - stackutil;
/* Move the register context to newtop. */
memcpy((void *)(newsp - XCPTCONTEXT_SIZE),
child->xcp.regs, XCPTCONTEXT_SIZE);
child->xcp.regs = (void *)(newsp - XCPTCONTEXT_SIZE);
memcpy((void *)newsp, (const void *)oldsp, stackutil);
/* Was there a frame pointer in place before? */
if (context->fp >= oldsp && context->fp < stacktop)
if (child->stack_base_ptr == parent->stack_base_ptr)
{
uint32_t frameutil = stacktop - context->fp;
newfp = newtop - frameutil;
/* The child is running at the parent's stack addresses, inside its
* own duplicated address environment. There is nothing to relocate:
* every stack address the child inherits is still the address it
* names.
*/
newsp = oldsp;
newfp = context->fp;
}
else
{
newfp = context->fp;
}
/* Make some feeble effort to preserve the stack contents. This is
* feeble because the stack surely contains invalid pointers and other
* content that will not work in the child context. However, if the
* user follows all of the caveats of task_fork() usage, even this
* feeble effort is overkill.
*
* For a POSIX fork() child the stack contents are not merely a feeble
* effort: the child is entitled to use them, and it does.
*/
sinfo("Old stack top:%08" PRIx32 " SP:%08" PRIx32 " FP:%08" PRIx32 "\n",
stacktop, oldsp, context->fp);
sinfo("New stack top:%08" PRIx32 " SP:%08" PRIx32 " FP:%08" PRIx32 "\n",
newtop, newsp, newfp);
newtop = (uint32_t)child->stack_base_ptr +
child->adj_stack_size;
newsp = newtop - stackutil;
/* Move the register context to newtop. */
memcpy((void *)(newsp - XCPTCONTEXT_SIZE),
child->xcp.regs, XCPTCONTEXT_SIZE);
child->xcp.regs = (void *)(newsp - XCPTCONTEXT_SIZE);
memcpy((void *)newsp, (const void *)oldsp, stackutil);
/* Was there a frame pointer in place before? */
if (context->fp >= oldsp && context->fp < stacktop)
{
uint32_t frameutil = stacktop - context->fp;
newfp = newtop - frameutil;
}
else
{
newfp = context->fp;
}
sinfo("Old stack top:%08" PRIx32 " SP:%08" PRIx32
" FP:%08" PRIx32 "\n", stacktop, oldsp, context->fp);
sinfo("New stack top:%08" PRIx32 " SP:%08" PRIx32
" FP:%08" PRIx32 "\n", newtop, newsp, newfp);
}
/* Update the stack pointer, frame pointer, and volatile registers. When
* the child TCB was initialized, all of the values were set to zero.
@ -245,9 +273,9 @@ pid_t arm_fork(const struct fork_s *context)
}
#endif
/* And, finally, start the child task. On a failure, nxtask_start_fork()
* will discard the TCB by calling nxtask_abort_fork().
/* And, finally, start the child task. A vfork() additionally suspends us
* until the child calls _exit() or exec().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, type);
}

1
arch/arm/src/common/arm_fork.h
View file

@ -28,6 +28,7 @@
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/fork.h>
/****************************************************************************
* Pre-processor Definitions

109
arch/arm/src/common/gnu/fork.S
View file

@ -1,5 +1,5 @@
/****************************************************************************
* arch/arm/src/common/fork.S
* arch/arm/src/common/gnu/fork.S
*
* SPDX-License-Identifier: Apache-2.0
*
@ -35,49 +35,80 @@
****************************************************************************/
/****************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_fork() function.
* The fork() function has the same effect as posix fork(), except that the
* behavior is undefined if the process created by fork() either modifies
* any data other than a variable of type pid_t used to store the return
* value from fork(), or returns from the function in which fork() was
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
* These are the architecture-specific entry points of NuttX's three
* cloning primitives. All three need exactly the same thing from
* assembly -- a snapshot of the caller's callee-saved registers, stack
* pointer and return address -- and differ only in what the C code then
* does with it, so they share one snapshot sequence and are distinguished
* by a FORK_TYPE_* constant passed to arm_fork() in r1.
*
* This thin layer implements fork by simply calling up_fork() with the
* fork() context as an argument. The overall sequence is:
* See include/nuttx/fork.h for what the three primitives mean.
*
* 1) User code calls fork(). fork() collects context information and
* transfers control up up_fork().
* 2) arm_fork() and calls nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* The overall sequence is:
*
* 1) User code calls task_fork(), vfork() or fork(). Each is a libc
* wrapper around the matching entry point here.
* 2) The entry point collects the context and calls arm_fork().
* 3) arm_fork() calls nxtask_setup_fork(), which allocates and configures
* the child task's TCB. This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Establishing the child's address environment
* - Allocating the stack, or inheriting the parent's for fork()
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) arm_fork() provides any additional operating context. arm_fork must:
* 4) arm_fork() provides any additional operating context:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) arm_fork() then calls nxtask_start_fork()
* 6) nxtask_start_fork() then executes the child thread.
* - Relocate the copied stack, unless the child shares the parent's
* 5) arm_fork() then calls nxtask_start_fork() or nxtask_start_vfork()
* 6) which executes the child thread.
*
* Input Parameters:
* None
*
* Returned Value:
* Upon successful completion, fork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
* Upon successful completion, 0 is returned to the child and the process
* ID of the child is returned to the parent. Otherwise, -1 is returned to
* the parent, no child is created, and errno is set to indicate the error.
*
****************************************************************************/
#ifdef CONFIG_TASK_FORK
.globl up_task_fork
#ifdef __ghs__
.type up_task_fork, $function
#else
.type up_task_fork, function
#endif
up_task_fork:
movs r2, #FORK_TYPE_TASK
b arm_fork_common
.size up_task_fork, .-up_task_fork
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl up_vfork
#ifdef __ghs__
.type up_vfork, $function
#else
.type up_vfork, function
#endif
up_vfork:
movs r2, #FORK_TYPE_VFORK
b arm_fork_common
.size up_vfork, .-up_vfork
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
.globl up_fork
#ifdef __ghs__
.type up_fork, $function
@ -86,6 +117,25 @@
#endif
up_fork:
movs r2, #FORK_TYPE_FORK
b arm_fork_common
.size up_fork, .-up_fork
#endif
/* The shared snapshot. r2 holds the FORK_TYPE_* selector on entry; it is
* call-clobbered and is not part of the snapshot, so it survives the
* sequence below untouched. lr still holds the original caller's return
* address, because the entry points above branched here rather than calling.
*/
#ifdef __ghs__
.type arm_fork_common, $function
#else
.type arm_fork_common, function
#endif
arm_fork_common:
/* Create a stack frame */
mov r0, sp /* Save the value of the stack on entry */
@ -104,9 +154,12 @@ up_fork:
mov r5, lr /* Copy lr to a low register */
stmia r1!, {r0,r5} /* Save sp and lr in the structure */
/* Then, call arm_fork(), passing it a pointer to the stack structure */
/* Then, call arm_fork(), passing it a pointer to the stack structure
* and the selector that says which primitive was called.
*/
mov r0, sp
mov r1, r2
bl arm_fork
/* Recover r4-r7 that were destroyed before arm_fork was called */
@ -114,12 +167,12 @@ up_fork:
mov r1, sp
ldmia r1!, {r4-r7}
/* Release the stack data and return the value returned by up_fork */
/* Release the stack data and return the value returned by arm_fork */
ldr r1, [sp, #FORK_LR_OFFSET]
mov r14, r1
add sp, sp, #FORK_SIZEOF
bx lr
.size up_fork, .-up_fork
.size arm_fork_common, .-arm_fork_common
.end

85
arch/arm/src/common/iar/fork.S
View file

@ -28,7 +28,7 @@
#include "arm_fork.h"
MODULE up_fork
MODULE arm_fork_common
SECTION .text:CODE:NOROOT(2), "ax"
/****************************************************************************
@ -39,7 +39,15 @@
* Public Symbols
****************************************************************************/
#ifdef CONFIG_TASK_FORK
PUBLIC up_task_fork
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
PUBLIC up_vfork
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
PUBLIC up_fork
#endif
EXTERN arm_fork
/****************************************************************************
@ -47,52 +55,76 @@
****************************************************************************/
/****************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_fork() function.
* The fork() function has the same effect as posix fork(), except that the
* behavior is undefined if the process created by fork() either modifies
* any data other than a variable of type pid_t used to store the return
* value from fork(), or returns from the function in which fork() was
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
* These are the architecture-specific entry points of NuttX's three
* cloning primitives. All three need exactly the same thing from
* assembly -- a snapshot of the caller's callee-saved registers, stack
* pointer and return address -- and differ only in what the C code then
* does with it, so they share one snapshot sequence and are distinguished
* by a FORK_TYPE_* constant passed to arm_fork() in r1.
*
* This thin layer implements fork by simply calling up_fork() with the
* fork() context as an argument. The overall sequence is:
* See include/nuttx/fork.h for what the three primitives mean.
*
* 1) User code calls fork(). fork() collects context information and
* transfers control up up_fork().
* 2) arm_fork() and calls nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* The overall sequence is:
*
* 1) User code calls task_fork(), vfork() or fork(). Each is a libc
* wrapper around the matching entry point here.
* 2) The entry point collects the context and calls arm_fork().
* 3) arm_fork() calls nxtask_setup_fork(), which allocates and configures
* the child task's TCB. This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Establishing the child's address environment
* - Allocating the stack, or inheriting the parent's for fork()
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) arm_fork() provides any additional operating context. arm_fork must:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) arm_fork() then calls nxtask_start_fork()
* 6) nxtask_start_fork() then executes the child thread.
* - Relocate the copied stack, unless the child shares the parent's
* 5) arm_fork() then calls nxtask_start_fork() or nxtask_start_vfork()
* 6) which executes the child thread.
*
* Input Parameters:
* None
*
* Returned Value:
* Upon successful completion, fork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
* Upon successful completion, 0 is returned to the child and the process
* ID of the child is returned to the parent. Otherwise, -1 is returned to
* the parent, no child is created, and errno is set to indicate the error.
*
****************************************************************************/
THUMB
#ifdef CONFIG_TASK_FORK
up_task_fork:
movs r2, #FORK_TYPE_TASK
b arm_fork_common
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
up_vfork:
movs r2, #FORK_TYPE_VFORK
b arm_fork_common
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
up_fork:
movs r2, #FORK_TYPE_FORK
b arm_fork_common
#endif
/* The shared snapshot. r2 holds the FORK_TYPE_* selector on entry; it is
* call-clobbered and is not part of the snapshot, and lr still holds the
* original caller's return address because the entry points above branched
* here rather than calling.
*/
arm_fork_common:
/* Create a stack frame */
mov r0, sp /* Save the value of the stack on entry */
@ -117,9 +149,12 @@ up_fork:
/* Floating point registers (not yet) */
/* Then, call arm_fork(), passing it a pointer to the stack structure */
/* Then, call arm_fork(), passing it a pointer to the stack structure
* and the selector that says which primitive was called.
*/
mov r0, sp
mov r1, r2
bl arm_fork
/* Release the stack data and return the value returned by arm_fork */

6
arch/arm64/src/common/arm64_fork.c
View file

@ -113,7 +113,7 @@ void arm64_fork_fpureg_save(struct fork_s *context)
*
****************************************************************************/
pid_t arm64_fork(const struct fork_s *context)
pid_t arm64_fork(const struct fork_s *context, int type)
{
struct tcb_s *parent = this_task();
struct tcb_s *child;
@ -125,7 +125,7 @@ pid_t arm64_fork(const struct fork_s *context)
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork((start_t)context->lr);
child = nxtask_setup_fork((start_t)context->lr, type);
if (!child)
{
serr("ERROR: nxtask_setup_fork failed\n");
@ -235,5 +235,5 @@ pid_t arm64_fork(const struct fork_s *context)
* will discard the TCB by calling nxtask_abort_fork().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, type);
}

1
arch/arm64/src/common/arm64_fork.h
View file

@ -28,6 +28,7 @@
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/fork.h>
#include <arch/irq.h>
/****************************************************************************

81
arch/arm64/src/common/arm64_fork_func.S
View file

@ -41,51 +41,77 @@
****************************************************************************/
/****************************************************************************
* Name: fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_fork() function.
* The fork() function has the same effect as posix fork(), except that the
* behavior is undefined if the process created by fork() either modifies
* any data other than a variable of type pid_t used to store the return
* value from fork(), or returns from the function in which fork() was
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
* These are the architecture-specific entry points of NuttX's three
* cloning primitives. All three need exactly the same thing from
* assembly -- a snapshot of the caller's registers, stack pointer and
* return address -- and differ only in what the C code then does with it,
* so they share one snapshot sequence and are distinguished by a
* FORK_TYPE_* constant passed to arm64_fork() in x1.
*
* This thin layer implements fork by simply calling up_fork() with the
* fork() context as an argument. The overall sequence is:
* See include/nuttx/fork.h for what the three primitives mean.
*
* 1) User code calls fork(). fork() collects context information and
* transfers control up up_fork().
* 2) arm64_fork() and calls nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* The overall sequence is:
*
* 1) User code calls task_fork(), vfork() or fork(). Each is a libc
* wrapper around the matching entry point here.
* 2) The entry point collects the context and calls arm64_fork().
* 3) arm64_fork() calls nxtask_setup_fork(), which allocates and
* configures the child task's TCB. This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Establishing the child's address environment
* - Allocating the stack, or inheriting the parent's for fork()
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) arm64_fork() provides any additional operating context. arm64_fork must:
* 4) arm64_fork() provides any additional operating context:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) arm64_fork() then calls nxtask_start_fork()
* 6) nxtask_start_fork() then executes the child thread.
* - Relocate the copied stack, unless the child shares the parent's
* 5) arm64_fork() then calls nxtask_start_fork() or nxtask_start_vfork()
* 6) which executes the child thread.
*
* Input Parameters:
* None
*
* Returned Value:
* Upon successful completion, fork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
* Upon successful completion, 0 is returned to the child and the process
* ID of the child is returned to the parent. Otherwise, -1 is returned to
* the parent, no child is created, and errno is set to indicate the error.
*
****************************************************************************/
#ifdef CONFIG_TASK_FORK
GTEXT(up_task_fork)
SECTION_FUNC(text, up_task_fork)
mov x1, #FORK_TYPE_TASK
b arm64_fork_common
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
GTEXT(up_vfork)
SECTION_FUNC(text, up_vfork)
mov x1, #FORK_TYPE_VFORK
b arm64_fork_common
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
GTEXT(up_fork)
SECTION_FUNC(text, up_fork)
mov x1, #FORK_TYPE_FORK
b arm64_fork_common
#endif
/* The shared snapshot. x1 holds the FORK_TYPE_* selector on entry and is
* carried through to arm64_fork(). It is saved into the snapshot along with
* the other argument registers, which is harmless: x0-x18 are caller-saved
* and arm64_fork() does not propagate them to the child.
*/
SECTION_FUNC(text, arm64_fork_common)
/* Create a stack frame */
sub sp, sp, #8 * FORK_REGS_SIZE /* Allocate the structure on the stack */
@ -118,14 +144,17 @@ SECTION_FUNC(text, up_fork)
#ifdef CONFIG_ARCH_FPU
mov x0, sp
stp x0, x30, [sp, #-16]!
str x1, [sp, #-16]! /* Preserve the FORK_TYPE_* selector */
bl arm64_fork_fpureg_save
ldr x1, [sp], #16
ldp x0, x30, [sp], #16
#endif
/* Then, call arm64_fork(), passing it a pointer to the stack structure */
/* Then, call arm64_fork(), passing it a pointer to the stack structure.
* x1 already holds the FORK_TYPE_* selector.
*/
mov x0, sp
mov x1, #0
bl arm64_fork
/* Release the stack data and return the value returned by arm64_fork */

13
arch/ceva/src/common/ceva_fork.c
View file

@ -40,7 +40,7 @@
****************************************************************************/
/****************************************************************************
* Name: ceva_fork
* Name: ceva_task_fork
*
* Description:
* The fork() function has the same effect as posix fork(), except that the
@ -83,7 +83,7 @@
*
****************************************************************************/
pid_t ceva_fork(const uint32_t *regs)
pid_t ceva_task_fork(const uint32_t *regs)
{
#ifdef CONFIG_SCHED_WAITPID
struct tcb_s *parent = this_task();
@ -97,9 +97,14 @@ pid_t ceva_fork(const uint32_t *regs)
void *argv;
int ret;
/* How large is the parent's stack argument area? */
argsize = (uintptr_t)parent->stack_base_ptr -
(uintptr_t)parent->stack_alloc_ptr;
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork(parent->start, &argsize);
child = nxtask_setup_fork(parent->start, FORK_TYPE_TASK);
if (!child)
{
serr("ERROR: nxtask_setup_fork failed\n");
@ -204,7 +209,7 @@ pid_t ceva_fork(const uint32_t *regs)
* will discard the TCB by calling nxtask_abort_fork().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, FORK_TYPE_TASK);
#else /* CONFIG_SCHED_WAITPID */
return (pid_t)ERROR;
#endif

32
arch/ceva/src/xc5/fork.S
View file

@ -34,30 +34,30 @@
****************************************************************************/
.file "fork.S"
.extern ceva_fork
.extern ceva_task_fork
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_fork
* Name: up_task_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_fork() function.
* The up_task_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_task_fork() function.
* The fork() function has the same effect as posix fork(), except that the behavior is
* undefined if the process created by fork() either modifies any data other than
* a variable of type pid_t used to store the return value from fork(), or returns
* from the function in which fork() was called, or calls any other function before
* successfully calling _exit() or one of the exec family of functions.
*
* This thin layer implements fork by simply calling up_fork() with the fork()
* This thin layer implements fork by simply calling up_task_fork() with the fork()
* context as an argument. The overall sequence is:
*
* 1) User code calls fork(). fork() collects context information and
* transfers control up up_fork().
* 2) ceva_fork()and calls nxtask_forksetup().
* transfers control up up_task_fork().
* 2) ceva_task_fork()and calls nxtask_forksetup().
* 3) task_forksetup() allocates and configures the child task's TCB. This
* consists of:
* - Allocation of the child task's TCB.
@ -65,11 +65,11 @@
* - Configuration of environment variables
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state()
* 4) ceva_fork() provides any additional operating context. ceva_fork must:
* 4) ceva_task_fork() provides any additional operating context. ceva_task_fork must:
* - Allocate and initialize the stack
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) ceva_fork() then calls nxtask_forkstart()
* 5) ceva_task_fork() then calls nxtask_forkstart()
* 6) nxtask_forkstart() then executes the child thread.
*
* Input Parameters:
@ -84,10 +84,10 @@
****************************************************************************/
.text
.public up_fork
.func_start 3 up_fork
.public up_task_fork
.func_start 3 up_task_fork
up_fork:
up_task_fork:
/* Create a stack frame */
subs sp, #XCPTCONTEXT_SIZE, sp
@ -98,19 +98,19 @@ up_fork:
mov sp, a1
trap
/* Then, call ceva_fork(), passing it a pointer to the stack structure */
/* Then, call ceva_task_fork(), passing it a pointer to the stack structure */
mov sp, a0
nop
push {dw} retreg
callr {t} ceva_fork
callr {t} ceva_task_fork
pop {dw} retreg
nop
/* Release the stack data and return the value returned by ceva_fork */
/* Release the stack data and return the value returned by ceva_task_fork */
adds sp, #XCPTCONTEXT_SIZE, sp
ret
.func_end 3 up_fork
.func_end 3 up_task_fork

32
arch/ceva/src/xm6/fork.S
View file

@ -44,30 +44,30 @@
****************************************************************************/
.file "fork.S"
.extern up_fork
.extern up_task_fork
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_fork
* Name: up_task_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_fork() function.
* The up_task_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_task_fork() function.
* The fork() function has the same effect as posix fork(), except that the behavior is
* undefined if the process created by fork() either modifies any data other than
* a variable of type pid_t used to store the return value from fork(), or returns
* from the function in which fork() was called, or calls any other function before
* successfully calling _exit() or one of the exec family of functions.
*
* This thin layer implements fork by simply calling up_fork() with the fork()
* This thin layer implements fork by simply calling up_task_fork() with the fork()
* context as an argument. The overall sequence is:
*
* 1) User code calls fork(). fork() collects context information and
* transfers control up up_fork().
* 2) ceva_fork()and calls nxtask_forksetup().
* transfers control up up_task_fork().
* 2) ceva_task_fork()and calls nxtask_forksetup().
* 3) task_forksetup() allocates and configures the child task's TCB. This
* consists of:
* - Allocation of the child task's TCB.
@ -75,11 +75,11 @@
* - Configuration of environment variables
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state()
* 4) ceva_fork() provides any additional operating context. ceva_fork must:
* 4) ceva_task_fork() provides any additional operating context. ceva_task_fork must:
* - Allocate and initialize the stack
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) ceva_fork() then calls nxtask_forkstart()
* 5) ceva_task_fork() then calls nxtask_forkstart()
* 6) nxtask_forkstart() then executes the child thread.
*
* Input Parameters:
@ -94,10 +94,10 @@
****************************************************************************/
.text
.public up_fork
.func_start 3 up_fork
.public up_task_fork
.func_start 3 up_task_fork
up_fork:
up_task_fork:
/* Create a stack frame */
modr (sp.ui).ui +#-XCPTCONTEXT_SIZE /* Allocate the structure on the stack */
@ -108,18 +108,18 @@ up_fork:
mov sp.ui, r1.ui
trap {t0}
/* Then, call ceva_fork(), passing it a pointer to the stack structure */
/* Then, call ceva_task_fork(), passing it a pointer to the stack structure */
mov sp.ui, r0.ui
nop
push retreg.ui
callr #ceva_fork, ?prx.b
callr #ceva_task_fork, ?prx.b
pop retreg.ui
nop
/* Release the stack data and return the value returned by ceva_fork */
/* Release the stack data and return the value returned by ceva_task_fork */
modr (sp.ui).ui +#XCPTCONTEXT_SIZE
ret ?prx.b
.func_end 3 up_fork
.func_end 3 up_task_fork

3
arch/mips/Kconfig
View file

@ -56,7 +56,8 @@ endchoice
config ARCH_MIPS32
bool
default n
select ARCH_HAVE_FORK
select ARCH_HAVE_TASK_FORK
select ARCH_HAVE_VFORK
config ARCH_MIPS_M4K
bool

2
arch/mips/src/mips32/Kconfig
View file

@ -93,7 +93,7 @@ config MIPS32_TOOLCHAIN_MICROCHIP_XC32_LICENSED
config MIPS32_FRAMEPOINTER
bool "ABI Uses Frame Pointer"
default n
depends on ARCH_HAVE_FORK
depends on ARCH_HAVE_TASK_FORK
---help---
Register r30 may be a frame pointer in some ABIs. Or may just be
saved register s8. It makes a difference for fork handling.

58
arch/mips/src/mips32/fork.S
View file

@ -44,7 +44,7 @@
************************************************************************************/
/************************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
@ -88,15 +88,57 @@
.text
.align 2
.globl up_fork
.type up_fork, function
.set nomips16
#ifdef CONFIG_MIPS_MICROMIPS
.set micromips
#endif
.ent up_fork
#ifdef CONFIG_TASK_FORK
.globl up_task_fork
.type up_task_fork, function
.ent up_task_fork
up_task_fork:
li $a1, FORK_TYPE_TASK
b mips_fork_common
nop
.end up_task_fork
.size up_task_fork, .-up_task_fork
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl up_vfork
.type up_vfork, function
.ent up_vfork
up_vfork:
li $a1, FORK_TYPE_VFORK
b mips_fork_common
nop
.end up_vfork
.size up_vfork, .-up_vfork
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
.globl up_fork
.type up_fork, function
.ent up_fork
up_fork:
li $a1, FORK_TYPE_FORK
b mips_fork_common
nop
.end up_fork
.size up_fork, .-up_fork
#endif
/* The shared snapshot. $a1 holds the FORK_TYPE_* selector on entry and
* is carried through to mips_fork(); it is not part of the snapshot, and
* $ra still holds the original caller's return address because the entry
* points above branched here rather than calling.
*/
.type mips_fork_common, function
.ent mips_fork_common
mips_fork_common:
/* Create a stack frame */
move $t0, $sp /* Save the value of the stack on entry */
@ -130,7 +172,9 @@ up_fork:
/* Floating point registers (not yet) */
/* Then, call mips_fork(), passing it a pointer to the stack structure */
/* Then, call mips_fork(), passing it a pointer to the stack structure.
* $a1 already holds the FORK_TYPE_* selector.
*/
move $a0, $sp
jal mips_fork
@ -142,5 +186,5 @@ up_fork:
addiu $sp, $sp, FORK_SIZEOF
j $ra
.end up_fork
.size up_fork, .-up_fork
.end mips_fork_common
.size mips_fork_common, .-mips_fork_common

8
arch/mips/src/mips32/mips_fork.c
View file

@ -89,7 +89,7 @@
*
****************************************************************************/
pid_t mips_fork(const struct fork_s *context)
pid_t mips_fork(const struct fork_s *context, int type)
{
struct tcb_s *parent = this_task();
struct tcb_s *child;
@ -113,7 +113,7 @@ pid_t mips_fork(const struct fork_s *context)
context->fp, context->sp, context->ra, context->gp);
#else
sinfo("fp:%08" PRIx32 " sp:%08" PRIx32 " ra:%08" PRIx32 "\n",
context->fp context->sp, context->ra);
context->fp, context->sp, context->ra);
#endif
#else
sinfo("s5:%08" PRIx32 " s6:%08" PRIx32 " s7:%08" PRIx32
@ -130,7 +130,7 @@ pid_t mips_fork(const struct fork_s *context)
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork((start_t)context->ra);
child = nxtask_setup_fork((start_t)context->ra, type);
if (!child)
{
sinfo("nxtask_setup_fork failed\n");
@ -217,5 +217,5 @@ pid_t mips_fork(const struct fork_s *context)
* will discard the TCB by calling nxtask_abort_fork().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, type);
}

1
arch/mips/src/mips32/mips_fork.h
View file

@ -28,6 +28,7 @@
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/fork.h>
#include <arch/mips32/irq.h>
/****************************************************************************

4
arch/risc-v/src/common/CMakeLists.txt
View file

@ -86,7 +86,9 @@ if(CONFIG_STACK_COLORATION)
list(APPEND SRCS riscv_checkstack.c)
endif()
if(CONFIG_ARCH_HAVE_FORK)
if(CONFIG_TASK_FORK
OR CONFIG_ARCH_HAVE_VFORK
OR CONFIG_ARCH_HAVE_FORK)
list(APPEND SRCS fork.S riscv_fork.c)
endif()

2
arch/risc-v/src/common/Make.defs
View file

@ -86,7 +86,7 @@ ifeq ($(CONFIG_STACK_COLORATION),y)
CMN_CSRCS += riscv_checkstack.c
endif
ifeq ($(CONFIG_ARCH_HAVE_FORK),y)
ifneq ($(CONFIG_TASK_FORK)$(CONFIG_ARCH_HAVE_VFORK)$(CONFIG_ARCH_HAVE_FORK),)
CMN_ASRCS += fork.S
CMN_CSRCS += riscv_fork.c
endif

104
arch/risc-v/src/common/fork.S
View file

@ -39,59 +39,95 @@
.file "fork.S"
.globl riscv_fork
#ifdef CONFIG_TASK_FORK
.globl up_task_fork
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl up_vfork
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
.globl up_fork
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_fork() function.
* The fork() function has the same effect as posix fork(), except that the
* behavior is undefined if the process created by fork() either modifies
* any data other than a variable of type pid_t used to store the return
* value from fork(), or returns from the function in which fork() was
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
* These are the architecture-specific entry points of NuttX's three
* cloning primitives. All three need exactly the same thing from
* assembly -- a snapshot of the caller's callee-saved registers, stack
* pointer and return address -- and differ only in what the C code then
* does with it, so they share one snapshot sequence and are distinguished
* by a FORK_TYPE_* constant passed to riscv_fork() in a1.
*
* This thin layer implements fork by simply calling up_fork() with the
* fork() context as an argument. The overall sequence is:
* See include/nuttx/fork.h for what the three primitives mean.
*
* 1) User code calls fork(). fork() collects context information and
* transfers control up up_fork().
* 2) riscv_fork() and calls nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) riscv_fork() provides any additional operating context. riscv_fork must:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) riscv_fork() then calls nxtask_start_fork()
* 6) nxtask_start_fork() then executes the child thread.
* The overall sequence is:
*
* 1) User code calls task_fork(), vfork() or fork(). Each is a libc
* wrapper around the matching entry point here.
* 2) The entry point collects the context and calls riscv_fork().
* 3) riscv_fork() calls nxtask_setup_fork(), which allocates and
* configures the child task's TCB.
* 4) riscv_fork() provides any additional operating context and relocates
* the copied stack.
* 5) riscv_fork() then calls nxtask_start_fork(), or nxtask_start_vfork()
* which additionally suspends the caller.
* 6) which executes the child thread.
*
* Input Parameters:
* None
*
* Returned Value:
* Upon successful completion, fork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
* Upon successful completion, 0 is returned to the child and the process
* ID of the child is returned to the parent. Otherwise, -1 is returned to
* the parent, no child is created, and errno is set to indicate the error.
*
****************************************************************************/
#ifdef CONFIG_TASK_FORK
.type up_task_fork, function
up_task_fork:
li a1, FORK_TYPE_TASK
j riscv_fork_common
.size up_task_fork, .-up_task_fork
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
.type up_vfork, function
up_vfork:
li a1, FORK_TYPE_VFORK
j riscv_fork_common
.size up_vfork, .-up_vfork
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
.type up_fork, function
up_fork:
li a1, FORK_TYPE_FORK
j riscv_fork_common
.size up_fork, .-up_fork
#endif
/* The shared snapshot. a1 holds the FORK_TYPE_* selector on entry and is
* carried through to riscv_fork(); it is not part of the snapshot, and ra
* still holds the original caller's return address because the entry points
* above jumped here rather than calling.
*/
.type riscv_fork_common, function
riscv_fork_common:
#ifdef CONFIG_LIB_SYSCALL
/* When coming via system call, everything is in place already */
@ -150,7 +186,9 @@ up_fork:
FSTORE fs11, FORK_FS11_OFFSET(sp)
#endif
/* Then, call riscv_fork(), passing it a pointer to the stack frame */
/* Then, call riscv_fork(), passing it a pointer to the stack frame. a1
* already holds the FORK_TYPE_* selector.
*/
mv a0, sp
call riscv_fork
@ -162,5 +200,5 @@ up_fork:
ret
#endif
.size up_fork, .-up_fork
.size riscv_fork_common, .-riscv_fork_common
.end

20
arch/risc-v/src/common/riscv_fork.c
View file

@ -41,7 +41,8 @@
#include "sched/sched.h"
#ifdef CONFIG_ARCH_HAVE_FORK
#if defined(CONFIG_TASK_FORK) || defined(CONFIG_ARCH_HAVE_VFORK) || \
defined(CONFIG_ARCH_HAVE_FORK)
/****************************************************************************
* Pre-processor Definitions
@ -102,7 +103,7 @@
#ifdef CONFIG_LIB_SYSCALL
pid_t riscv_fork(const struct fork_s *context)
pid_t riscv_fork(const struct fork_s *context, int type)
{
struct tcb_s *parent = this_task();
struct tcb_s *child;
@ -117,7 +118,7 @@ pid_t riscv_fork(const struct fork_s *context)
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork((start_t)parent->xcp.sregs[REG_RA]);
child = nxtask_setup_fork((start_t)parent->xcp.sregs[REG_RA], type);
if (!child)
{
sinfo("nxtask_setup_fork failed\n");
@ -184,12 +185,12 @@ pid_t riscv_fork(const struct fork_s *context)
* will discard the TCB by calling nxtask_abort_fork().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, type);
}
#else
pid_t riscv_fork(const struct fork_s *context)
pid_t riscv_fork(const struct fork_s *context, int type)
{
struct tcb_s *parent = this_task();
struct tcb_s *child;
@ -215,7 +216,7 @@ pid_t riscv_fork(const struct fork_s *context)
context->fp, context->sp, context->ra, context->gp);
#else
sinfo("fp:%" PRIxREG " sp:%" PRIxREG " ra:%" PRIxREG "\n",
context->fp context->sp, context->ra);
context->fp, context->sp, context->ra);
#endif
#else
sinfo("s5:%" PRIxREG " s6:%" PRIxREG " s7:%" PRIxREG " s8:%" PRIxREG "\n",
@ -231,7 +232,7 @@ pid_t riscv_fork(const struct fork_s *context)
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork((start_t)(uintptr_t)context->ra);
child = nxtask_setup_fork((start_t)(uintptr_t)context->ra, type);
if (!child)
{
sinfo("nxtask_setup_fork failed\n");
@ -346,8 +347,9 @@ pid_t riscv_fork(const struct fork_s *context)
* will discard the TCB by calling nxtask_abort_fork().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, type);
}
#endif /* CONFIG_LIB_SYSCALL */
#endif /* CONFIG_ARCH_HAVE_FORK */
#endif /* CONFIG_TASK_FORK || CONFIG_ARCH_HAVE_VFORK ||
* CONFIG_ARCH_HAVE_FORK */

1
arch/risc-v/src/common/riscv_fork.h
View file

@ -28,6 +28,7 @@
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/fork.h>
#include <arch/irq.h>
#include "riscv_internal.h"

2
arch/sim/src/Makefile
View file

@ -95,7 +95,7 @@ ifeq ($(CONFIG_SCHED_BACKTRACE),y)
CSRCS += sim_backtrace.c
endif
ifeq ($(CONFIG_ARCH_HAVE_FORK),y)
ifneq ($(CONFIG_TASK_FORK)$(CONFIG_ARCH_HAVE_VFORK)$(CONFIG_ARCH_HAVE_FORK),)
CSRCS += sim_fork.c
endif

4
arch/sim/src/sim/CMakeLists.txt
View file

@ -82,7 +82,9 @@ if(CONFIG_SCHED_BACKTRACE)
list(APPEND SRCS sim_backtrace.c)
endif()
if(CONFIG_ARCH_HAVE_FORK)
if(CONFIG_TASK_FORK
OR CONFIG_ARCH_HAVE_VFORK
OR CONFIG_ARCH_HAVE_FORK)
list(APPEND SRCS sim_fork.c)
endif()

41
arch/sim/src/sim/sim_fork.c
View file

@ -34,6 +34,7 @@
#include <nuttx/debug.h>
#include <nuttx/compiler.h>
#include <nuttx/fork.h>
#include <nuttx/sched.h>
#include <nuttx/arch.h>
#include <arch/irq.h>
@ -45,7 +46,7 @@
****************************************************************************/
/****************************************************************************
* Name: sim_fork
* Name: sim_fork_internal
*
* Description:
* The fork() function has the same effect as posix fork(), except that the
@ -88,7 +89,7 @@
#ifdef CONFIG_SIM_ASAN
nosanitize_address
#endif
pid_t sim_fork(const xcpt_reg_t *context)
static pid_t sim_fork_internal(const xcpt_reg_t *context, int type)
{
struct tcb_s *parent = this_task();
struct tcb_s *child;
@ -106,7 +107,7 @@ pid_t sim_fork(const xcpt_reg_t *context)
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork((start_t)context[JB_PC]);
child = nxtask_setup_fork((start_t)context[JB_PC], type);
if (!child)
{
serr("ERROR: nxtask_setup_fork failed\n");
@ -175,5 +176,37 @@ pid_t sim_fork(const xcpt_reg_t *context)
* will discard the TCB by calling nxtask_abort_fork().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, type);
}
/****************************************************************************
* Name: sim_task_fork, sim_vfork, sim_fork
*
* Description:
* The three primitives, each a name for one FORK_TYPE_* value. The
* simulator's assembly entry points call these directly rather than
* carrying a selector through setjmp(), which would have to survive a call
* that is allowed to clobber every argument register.
*
****************************************************************************/
#ifdef CONFIG_TASK_FORK
pid_t sim_task_fork(const xcpt_reg_t *context)
{
return sim_fork_internal(context, FORK_TYPE_TASK);
}
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
pid_t sim_vfork(const xcpt_reg_t *context)
{
return sim_fork_internal(context, FORK_TYPE_VFORK);
}
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
pid_t sim_fork(const xcpt_reg_t *context)
{
return sim_fork_internal(context, FORK_TYPE_FORK);
}
#endif

57
arch/sim/src/sim/sim_fork_arm.S
View file

@ -43,7 +43,19 @@
************************************************************************************/
/************************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* These are the architecture-specific entry points of NuttX's three
* cloning primitives; see include/nuttx/fork.h for what the three mean.
* They are identical apart from the C worker each calls, which is how the
* primitives are distinguished.
*
* On the simulator the caller's context is captured with setjmp() rather
* than by hand, and the child re-enters through longjmp() -- which is why
* each entry point tests setjmp()'s return value to tell which of the two
* returns it is on.
*
*
* Description:
* The up_fork() function is the base of fork() function that provided in
@ -86,6 +98,42 @@
************************************************************************************/
.text
#ifdef CONFIG_TASK_FORK
.globl up_task_fork
.type up_task_fork, @function
up_task_fork:
sub sp, sp, #XCPTCONTEXT_SIZE
mov r0, sp
bl setjmp
subs r0, #1
beq 1f
bl sim_task_fork
1:
add sp, sp, #XCPTCONTEXT_SIZE
bx lr
.size up_task_fork, . - up_task_fork
#endif /* CONFIG_TASK_FORK */
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl up_vfork
.type up_vfork, @function
up_vfork:
sub sp, sp, #XCPTCONTEXT_SIZE
mov r0, sp
bl setjmp
subs r0, #1
beq 1f
bl sim_vfork
1:
add sp, sp, #XCPTCONTEXT_SIZE
bx lr
.size up_vfork, . - up_vfork
#endif /* CONFIG_ARCH_HAVE_VFORK */
#ifdef CONFIG_ARCH_HAVE_FORK
.globl up_fork
.type up_fork, @function
up_fork:
@ -94,10 +142,11 @@ up_fork:
bl setjmp
subs r0, #1
jz child
beq 1f
bl sim_fork
child:
1:
add sp, sp, #XCPTCONTEXT_SIZE
ret
bx lr
.size up_fork, . - up_fork
#endif /* CONFIG_ARCH_HAVE_FORK */
.end

70
arch/sim/src/sim/sim_fork_arm64.S
View file

@ -52,7 +52,19 @@
***************************************************************************/
/****************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* These are the architecture-specific entry points of NuttX's three
* cloning primitives; see include/nuttx/fork.h for what the three mean.
* They are identical apart from the C worker each calls, which is how the
* primitives are distinguished.
*
* On the simulator the caller's context is captured with setjmp() rather
* than by hand, and the child re-enters through longjmp() -- which is why
* each entry point tests setjmp()'s return value to tell which of the two
* returns it is on.
*
*
* Description:
* The up_fork() function is the base of fork() function that provided in
@ -96,9 +108,59 @@
***************************************************************************/
.text
.globl SYMBOL(up_fork)
.align 4
#ifdef CONFIG_TASK_FORK
.globl SYMBOL(up_task_fork)
SYMBOL(up_task_fork):
stp x29, x30, [sp] /* save FP/LR register */
sub sp, sp, #XCPTCONTEXT_SIZE /* area from stack for setjmp() */
mov x0, sp /* pass stack area to setjmp() */
bl SYMBOL(setjmp) /* save register for longjmp() */
subs x0, x0, #1 /* 0: parent / 1: child */
cbz x0, 1f /* child --> return */
mov x0, sp /* pass stack area to the worker */
bl SYMBOL(sim_task_fork) /* further process task creation */
1:
add sp, sp, #XCPTCONTEXT_SIZE /* release area from stack */
ldp x29, x30, [sp] /* restore FP/LR register */
ret
#endif /* CONFIG_TASK_FORK */
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl SYMBOL(up_vfork)
SYMBOL(up_vfork):
stp x29, x30, [sp] /* save FP/LR register */
sub sp, sp, #XCPTCONTEXT_SIZE /* area from stack for setjmp() */
mov x0, sp /* pass stack area to setjmp() */
bl SYMBOL(setjmp) /* save register for longjmp() */
subs x0, x0, #1 /* 0: parent / 1: child */
cbz x0, 1f /* child --> return */
mov x0, sp /* pass stack area to the worker */
bl SYMBOL(sim_vfork) /* further process task creation */
1:
add sp, sp, #XCPTCONTEXT_SIZE /* release area from stack */
ldp x29, x30, [sp] /* restore FP/LR register */
ret
#endif /* CONFIG_ARCH_HAVE_VFORK */
#ifdef CONFIG_ARCH_HAVE_FORK
.globl SYMBOL(up_fork)
SYMBOL(up_fork):
stp x29, x30, [sp] /* save FP/LR register */
@ -110,7 +172,7 @@ SYMBOL(up_fork):
subs x0, x0, #1 /* 0: parent / 1: child */
cbz x0, 1f /* child --> return */
mov x0, sp /* pass stack area to sim_fork() */
mov x0, sp /* pass stack area to the worker */
bl SYMBOL(sim_fork) /* further process task creation */
1:
@ -118,5 +180,5 @@ SYMBOL(up_fork):
ldp x29, x30, [sp] /* restore FP/LR register */
ret
#endif /* CONFIG_ARCH_HAVE_FORK */
.end

65
arch/sim/src/sim/sim_fork_x86.S
View file

@ -51,7 +51,19 @@
************************************************************************************/
/************************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* These are the architecture-specific entry points of NuttX's three
* cloning primitives; see include/nuttx/fork.h for what the three mean.
* They are identical apart from the C worker each calls, which is how the
* primitives are distinguished.
*
* On the simulator the caller's context is captured with setjmp() rather
* than by hand, and the child re-enters through longjmp() -- which is why
* each entry point tests setjmp()'s return value to tell which of the two
* returns it is on.
*
*
* Description:
* The up_fork() function is the base of fork() function that provided in
@ -94,6 +106,52 @@
************************************************************************************/
.text
#ifdef CONFIG_TASK_FORK
.globl SYMBOL(up_task_fork)
#ifdef __ELF__
.type SYMBOL(up_task_fork), @function
#endif
SYMBOL(up_task_fork):
sub $XCPTCONTEXT_SIZE, %esp
push %esp
call SYMBOL(setjmp)
sub $1, %eax
jz 1f
call SYMBOL(sim_task_fork)
1:
add $XCPTCONTEXT_SIZE+4, %esp
ret
#ifdef __ELF__
.size SYMBOL(up_task_fork), . - SYMBOL(up_task_fork)
#endif
#endif /* CONFIG_TASK_FORK */
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl SYMBOL(up_vfork)
#ifdef __ELF__
.type SYMBOL(up_vfork), @function
#endif
SYMBOL(up_vfork):
sub $XCPTCONTEXT_SIZE, %esp
push %esp
call SYMBOL(setjmp)
sub $1, %eax
jz 1f
call SYMBOL(sim_vfork)
1:
add $XCPTCONTEXT_SIZE+4, %esp
ret
#ifdef __ELF__
.size SYMBOL(up_vfork), . - SYMBOL(up_vfork)
#endif
#endif /* CONFIG_ARCH_HAVE_VFORK */
#ifdef CONFIG_ARCH_HAVE_FORK
.globl SYMBOL(up_fork)
#ifdef __ELF__
.type SYMBOL(up_fork), @function
@ -105,11 +163,12 @@ SYMBOL(up_fork):
call SYMBOL(setjmp)
sub $1, %eax
jz child
jz 1f
call SYMBOL(sim_fork)
child:
1:
add $XCPTCONTEXT_SIZE+4, %esp
ret
#ifdef __ELF__
.size SYMBOL(up_fork), . - SYMBOL(up_fork)
#endif
#endif /* CONFIG_ARCH_HAVE_FORK */

75
arch/sim/src/sim/sim_fork_x86_64.S
View file

@ -51,7 +51,19 @@
************************************************************************************/
/************************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* These are the architecture-specific entry points of NuttX's three
* cloning primitives; see include/nuttx/fork.h for what the three mean.
* They are identical apart from the C worker each calls, which is how the
* primitives are distinguished.
*
* On the simulator the caller's context is captured with setjmp() rather
* than by hand, and the child re-enters through longjmp() -- which is why
* each entry point tests setjmp()'s return value to tell which of the two
* returns it is on.
*
*
* Description:
* The up_fork() function is the base of fork() function that provided in
@ -94,6 +106,62 @@
************************************************************************************/
.text
#ifdef CONFIG_TASK_FORK
.globl SYMBOL(up_task_fork)
#ifdef __ELF__
.type SYMBOL(up_task_fork), @function
#endif
SYMBOL(up_task_fork):
sub $XCPTCONTEXT_SIZE, %rsp
#ifdef CONFIG_SIM_X8664_MICROSOFT
mov %rsp, %rcx
#else /* if defined(CONFIG_SIM_X8664_SYSTEMV) */
mov %rsp, %rdi
#endif
call SYMBOL(setjmp)
sub $1, %eax
jz 1f
call SYMBOL(sim_task_fork)
1:
add $XCPTCONTEXT_SIZE, %rsp
ret
#ifdef __ELF__
.size SYMBOL(up_task_fork), . - SYMBOL(up_task_fork)
#endif
#endif /* CONFIG_TASK_FORK */
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl SYMBOL(up_vfork)
#ifdef __ELF__
.type SYMBOL(up_vfork), @function
#endif
SYMBOL(up_vfork):
sub $XCPTCONTEXT_SIZE, %rsp
#ifdef CONFIG_SIM_X8664_MICROSOFT
mov %rsp, %rcx
#else /* if defined(CONFIG_SIM_X8664_SYSTEMV) */
mov %rsp, %rdi
#endif
call SYMBOL(setjmp)
sub $1, %eax
jz 1f
call SYMBOL(sim_vfork)
1:
add $XCPTCONTEXT_SIZE, %rsp
ret
#ifdef __ELF__
.size SYMBOL(up_vfork), . - SYMBOL(up_vfork)
#endif
#endif /* CONFIG_ARCH_HAVE_VFORK */
#ifdef CONFIG_ARCH_HAVE_FORK
.globl SYMBOL(up_fork)
#ifdef __ELF__
.type SYMBOL(up_fork), @function
@ -109,12 +177,13 @@ SYMBOL(up_fork):
call SYMBOL(setjmp)
sub $1, %eax
jz child
jz 1f
call SYMBOL(sim_fork)
child:
1:
add $XCPTCONTEXT_SIZE, %rsp
ret
#ifdef __ELF__
.size SYMBOL(up_fork), . - SYMBOL(up_fork)
#endif
#endif /* CONFIG_ARCH_HAVE_FORK */

4
arch/x86_64/src/common/CMakeLists.txt
View file

@ -34,7 +34,9 @@ set(SRCS
x86_64_tcbinfo.c
x86_64_tlb.c)
if(CONFIG_ARCH_HAVE_FORK)
if(CONFIG_TASK_FORK
OR CONFIG_ARCH_HAVE_VFORK
OR CONFIG_ARCH_HAVE_FORK)
list(APPEND SRCS x86_64_fork.c fork.S)
endif()

2
arch/x86_64/src/common/Make.defs
View file

@ -29,7 +29,7 @@ CMN_CSRCS += x86_64_getintstack.c x86_64_initialize.c x86_64_nputs.c
CMN_CSRCS += x86_64_modifyreg8.c x86_64_modifyreg16.c x86_64_modifyreg32.c
CMN_CSRCS += x86_64_switchcontext.c x86_64_tlb.c
ifeq ($(CONFIG_ARCH_HAVE_FORK),y)
ifneq ($(CONFIG_TASK_FORK)$(CONFIG_ARCH_HAVE_VFORK)$(CONFIG_ARCH_HAVE_FORK),)
CMN_CSRCS += x86_64_fork.c
CMN_ASRCS += fork.S
endif

35
arch/x86_64/src/common/fork.S
View file

@ -36,7 +36,7 @@
****************************************************************************/
/****************************************************************************
* Name: up_fork
* Name: up_task_fork, up_vfork, up_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
@ -95,10 +95,43 @@
* | ......... |
*/
#ifdef CONFIG_TASK_FORK
.globl up_task_fork
.type up_task_fork, @function
up_task_fork:
movq $FORK_TYPE_TASK, %rsi
jmp x86_64_fork_common
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
.globl up_vfork
.type up_vfork, @function
up_vfork:
movq $FORK_TYPE_VFORK, %rsi
jmp x86_64_fork_common
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
.globl up_fork
.type up_fork, @function
up_fork:
movq $FORK_TYPE_FORK, %rsi
jmp x86_64_fork_common
#endif
/* The shared snapshot. %rsi holds the FORK_TYPE_* selector on entry and is
* carried through to x86_64_fork() as its second argument. Note that the
* return address the entry points pushed is still on the stack -- they
* jumped here rather than calling -- so the %rsp recovered below is the
* original caller's.
*/
.type x86_64_fork_common, @function
x86_64_fork_common:
movq %rsp, %rax
addq $8, %rax
movq %ss, %rdi

6
arch/x86_64/src/common/x86_64_fork.c
View file

@ -89,7 +89,7 @@
*
****************************************************************************/
pid_t x86_64_fork(const struct fork_s *context)
pid_t x86_64_fork(const struct fork_s *context, int type)
{
struct tcb_s *parent = this_task();
struct tcb_s *child;
@ -110,7 +110,7 @@ pid_t x86_64_fork(const struct fork_s *context)
/* Allocate and initialize a TCB for the child task. */
child = nxtask_setup_fork((start_t)context->rip);
child = nxtask_setup_fork((start_t)context->rip, type);
if (!child)
{
serr("ERROR: nxtask_setup_fork failed\n");
@ -195,5 +195,5 @@ pid_t x86_64_fork(const struct fork_s *context)
* will discard the TCB by calling nxtask_abort_fork().
*/
return nxtask_start_fork(child);
return nxtask_start_fork(child, type);
}

1
arch/x86_64/src/common/x86_64_fork.h
View file

@ -28,6 +28,7 @@
****************************************************************************/
#include <nuttx/config.h>
#include <nuttx/fork.h>
/****************************************************************************
* Pre-processor Definitions

25
include/nuttx/addrenv.h
View file

@ -394,6 +394,31 @@ int addrenv_attach(FAR struct tcb_s *tcb, FAR struct addrenv_s *addrenv);
int addrenv_join(FAR struct tcb_s *ptcb, FAR struct tcb_s *tcb);
/****************************************************************************
* Name: addrenv_fork
*
* Description:
* Duplicate the parent's address environment for a POSIX fork() child and
* attach it: the child gets its own pages holding a copy of the parent's
* contents, mapped at the same virtual addresses. Contrast
* addrenv_join(), which gives the child the parent's memory.
*
* Input Parameters:
* ptcb - The tcb of the parent process.
* tcb - The tcb of the child process.
*
* Returned Value:
* This is a NuttX internal function so it follows the convention that
* 0 (OK) is returned on success and a negated errno is returned on
* failure. -ENOMEM is returned if there is not enough free memory to
* hold a copy of the parent.
*
****************************************************************************/
#ifdef CONFIG_ARCH_HAVE_FORK
int addrenv_fork(FAR struct tcb_s *ptcb, FAR struct tcb_s *tcb);
#endif
/****************************************************************************
* Name: addrenv_leave
*

76
include/nuttx/arch.h
View file

@ -249,12 +249,53 @@ extern initializer_t _einit[];
* logic from architecture-specific code.
****************************************************************************/
/****************************************************************************
* Name: up_task_fork
*
* Description:
* Architecture-specific base of task_fork(): the child shares the
* parent's memory, runs on a private copy of the parent's stack, and runs
* concurrently. Neither fork() nor vfork(); see up_fork(), up_vfork().
*
* Returned Value:
* Upon successful completion, up_task_fork() returns 0 to the child and
* returns the process ID of the child to the parent. Otherwise, -1 is
* returned to the parent, no child is created, and errno is set to
* indicate the error.
*
****************************************************************************/
#ifdef CONFIG_TASK_FORK
pid_t up_task_fork(void);
#endif
/****************************************************************************
* Name: up_vfork
*
* Description:
* Architecture-specific base of vfork(): the child shares the parent's
* memory and the parent is suspended until the child _exit()s or exec()s.
* The child runs on a relocated copy of the parent's stack.
*
* Returned Value:
* Upon successful completion, up_vfork() returns 0 to the child and
* returns the process ID of the child to the parent. Otherwise, -1 is
* returned to the parent, no child is created, and errno is set to
* indicate the error.
*
****************************************************************************/
#ifdef CONFIG_ARCH_HAVE_VFORK
pid_t up_vfork(void);
#endif
/****************************************************************************
* Name: up_fork
*
* Description:
* The up_fork() function is the base of fork() function that provided in
* libc, and fork() is implemented as a wrapper of up_fork() function.
* Architecture-specific base of POSIX fork(): the child receives its own
* copy of the parent's memory at the same virtual addresses and runs
* concurrently. Available only where CONFIG_ARCH_HAVE_FORK is selected.
*
* Returned Value:
* Upon successful completion, up_fork() returns 0 to the child process
@ -264,7 +305,9 @@ extern initializer_t _einit[];
*
****************************************************************************/
#ifdef CONFIG_ARCH_HAVE_FORK
pid_t up_fork(void);
#endif
/****************************************************************************
* Name: up_initialize
@ -1327,6 +1370,35 @@ int up_addrenv_clone(FAR const arch_addrenv_t *src,
FAR arch_addrenv_t *dest);
#endif
/****************************************************************************
* Name: up_addrenv_fork
*
* Description:
* Duplicate an address environment for POSIX fork(): allocate fresh
* pages for the destination, copy the source's contents into them, and map
* them at the same virtual addresses. Unlike up_addrenv_clone(), which
* copies only the representation and leaves both pointing at the same page
* tables, the result is independent of the source.
*
* Implemented only where CONFIG_ARCH_HAVE_ADDRENV_FORK is selected.
*
* Input Parameters:
* src - The address environment to be duplicated.
* dest - The location to receive the duplicate. It is wiped by this
* function before anything is allocated into it.
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure. -ENOMEM is
* returned if there are not enough free pages to hold the copy, in which
* case nothing is left allocated.
*
****************************************************************************/
#ifdef CONFIG_ARCH_HAVE_ADDRENV_FORK
int up_addrenv_fork(FAR const arch_addrenv_t *src,
FAR arch_addrenv_t *dest);
#endif
/****************************************************************************
* Name: up_addrenv_attach
*

53
include/nuttx/fork.h Normal file
View file

@ -0,0 +1,53 @@
/****************************************************************************
* include/nuttx/fork.h
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
#ifndef __INCLUDE_NUTTX_FORK_H
#define __INCLUDE_NUTTX_FORK_H
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Which primitive a clone of the calling task implements. Passed to
* nxtask_setup_fork(), which is where the memory semantics are decided.
* Macros rather than an enumeration: the architecture entry points are
* assembly and load them into a register.
*
* FORK_TYPE_TASK task_fork(): shares memory, private stack copy, both
* run. Not POSIX.
* FORK_TYPE_VFORK vfork(): shares memory, parent suspended until the
* child _exit()s or exec()s.
* FORK_TYPE_FORK fork(): child gets its own copy of the parent's memory
* at the same virtual addresses, both run.
*/
#define FORK_TYPE_TASK 0
#define FORK_TYPE_VFORK 1
#define FORK_TYPE_FORK 2
#endif /* __INCLUDE_NUTTX_FORK_H */

63
include/nuttx/sched.h
View file

@ -420,6 +420,23 @@ struct task_join_s
pthread_addr_t exit_value; /* Returned data */
};
/* struct vfork_s ***********************************************************/
/* The rendezvous between a suspended vfork() parent and its child. This
* lives in the frame of nxtask_start_vfork() on the parent's stack: the
* parent is blocked in that frame for the whole lifetime of the child, so
* the storage is alive exactly as long as it is needed, and no allocation
* is required on a path that must not fail.
*/
#ifdef CONFIG_ARCH_HAVE_VFORK
struct vfork_s
{
sem_t sem; /* Posted when the child is done */
bool released; /* Guards against a second post */
};
#endif
/* struct task_group_s ******************************************************/
/* All threads created by pthread_create belong in the same task group (along
@ -650,6 +667,14 @@ struct tcb_s
/* after the frame has been */
/* removed from the stack. */
/* vfork() Support ********************************************************/
#ifdef CONFIG_ARCH_HAVE_VFORK
FAR struct vfork_s *vfork_rel; /* Non-NULL in a vfork() child: */
/* the suspended parent to release */
/* when this task is torn down. */
#endif
/* External Module Support ************************************************/
#ifdef CONFIG_PIC
@ -1134,34 +1159,54 @@ void nxtask_startup(main_t entrypt, int argc, FAR char *argv[]);
#endif
/****************************************************************************
* Internal fork support. The overall sequence is:
* Internal support for the three cloning primitives -- task_fork(), vfork()
* and fork(). See include/nuttx/fork.h for what distinguishes them; the
* sequence below is common to all three, and `type' is one of the
* FORK_TYPE_* constants defined there.
*
* 1) User code calls fork(). fork() is provided in architecture-specific
* code.
* 2) fork()and calls nxtask_setup_fork().
* 1) User code calls task_fork(), vfork() or fork(). Each is a libc wrapper
* around up_task_fork(), up_vfork() or up_fork() respectively, which are
* provided in architecture-specific code.
* 2) The architecture-specific code snapshots the caller's registers and
* calls nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Establishing the child's address environment: joined to the parent's
* for task_fork() and vfork(), duplicated from it for fork()
* - Allocating the stack, or inheriting the parent's for fork()
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) fork() provides any additional operating context. fork must:
* 4) The architecture-specific code provides any additional operating
* context:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) fork() then calls nxtask_start_fork()
* - Relocate the copied stack, unless the child shares the parent's
* 5) It then calls nxtask_start_fork(), or nxtask_start_vfork() which
* additionally suspends the caller.
* 6) nxtask_start_fork() then executes the child thread.
*
* nxtask_abort_fork() may be called if an error occurs between
* steps 3 and 6.
*
* nxtask_vfork_resume() releases a suspended vfork() parent. It is called
* from nxsched_release_tcb(), the last point in the child's life -- by which
* time the child is off the ready-to-run list and an exec()ing child has
* already handed its pid to the program it loaded.
*
****************************************************************************/
FAR struct tcb_s *nxtask_setup_fork(start_t retaddr);
pid_t nxtask_start_fork(FAR struct tcb_s *child);
FAR struct tcb_s *nxtask_setup_fork(start_t retaddr, int type);
pid_t nxtask_start_fork(FAR struct tcb_s *child, int type);
void nxtask_abort_fork(FAR struct tcb_s *child, int errcode);
#ifdef CONFIG_ARCH_HAVE_VFORK
pid_t nxtask_start_vfork(FAR struct tcb_s *child);
void nxtask_vfork_resume(FAR struct tcb_s *child);
#endif
/****************************************************************************
* Name: nxtask_argvstr
*

10
include/sched.h
View file

@ -233,6 +233,16 @@ int task_create_with_stack(FAR const char *name, int priority,
int task_delete(pid_t pid);
int task_restart(pid_t pid);
/* Clone the calling task: the child shares the parent's memory, runs on a
* private copy of the parent's stack, and runs concurrently. Returns twice,
* like fork(). Not POSIX; new code should prefer pthread_create() or
* posix_spawn().
*/
#ifdef CONFIG_TASK_FORK
pid_t task_fork(void);
#endif
int task_setcancelstate(int state, FAR int *oldstate);
int task_setcanceltype(int type, FAR int *oldtype);
void task_testcancel(void);

8
include/sys/syscall_lookup.h
View file

@ -116,6 +116,14 @@ SYSCALL_LOOKUP(nxsem_wait_slow, 1)
/* The following can be individually enabled */
#ifdef CONFIG_TASK_FORK
SYSCALL_LOOKUP(up_task_fork, 0)
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
SYSCALL_LOOKUP(up_vfork, 0)
#endif
#ifdef CONFIG_ARCH_HAVE_FORK
SYSCALL_LOOKUP(up_fork, 0)
#endif

9
include/unistd.h
View file

@ -347,8 +347,17 @@ extern "C"
/* Task Control Interfaces */
/* fork() is declared only where POSIX fork() semantics can be provided, so
* that calling it elsewhere is a build error rather than a silent change of
* meaning. See CONFIG_FORK_IS_TASK_FORK, and task_fork() in sched.h.
*/
#if defined(CONFIG_ARCH_HAVE_FORK) || defined(CONFIG_FORK_IS_TASK_FORK)
pid_t fork(void);
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
pid_t vfork(void);
#endif
pid_t getpid(void);
pid_t getpgid(pid_t pid);
pid_t getpgrp(void);

6
libs/libbuiltin/libgcc/gcov.c
View file

@ -468,10 +468,16 @@ void __gcov_execle(void)
{
}
/* GCC redirects fork() in instrumented code to __gcov_fork(), so this is
* reachable only where unistd.h declares fork() at all.
*/
#if defined(CONFIG_ARCH_HAVE_FORK) || defined(CONFIG_FORK_IS_TASK_FORK)
pid_t __gcov_fork(void)
{
return fork();
}
#endif
void __gcov_dump(void)
{

4
libs/libc/libc.csv
View file

@ -70,7 +70,7 @@
"flockfile","stdio.h","!defined(CONFIG_FILE_STREAM)","void","FAR FILE *"
"fnmatch","fnmatch.h","","int","FAR const char *","FAR const char *","int"
"fopen","stdio.h","defined(CONFIG_FILE_STREAM)","FAR FILE *","FAR const char *","FAR const char *"
"fork","unistd.h","!defined(CONFIG_BUILD_KERNEL) && defined(CONFIG_ARCH_HAVE_FORK)","pid_t"
"fork","unistd.h","!defined(CONFIG_BUILD_KERNEL) && (defined(CONFIG_ARCH_HAVE_FORK) || defined(CONFIG_FORK_IS_TASK_FORK))","pid_t"
"fprintf","stdio.h","defined(CONFIG_FILE_STREAM)","int","FAR FILE *","FAR const IPTR char *","..."
"fputc","stdio.h","defined(CONFIG_FILE_STREAM)","int","int","FAR FILE *"
"fputs","stdio.h","defined(CONFIG_FILE_STREAM)","int","FAR const IPTR char *","FAR FILE *"
@ -326,6 +326,7 @@
"swprintf","wchar.h","","int","FAR wchar_t *","size_t","FAR const wchar_t *","..."
"sysconf","unistd.h","","long","int"
"syslog","syslog.h","","void","int","FAR const IPTR char *","..."
"task_fork","sched.h","!defined(CONFIG_BUILD_KERNEL) && defined(CONFIG_TASK_FORK)","pid_t"
"task_testcancel","sched.h","defined(CONFIG_CANCELLATION_POINTS)","void"
"task_tls_alloc","nuttx/tls.h","!defined(CONFIG_BUILD_KERNEL) && CONFIG_TLS_TASK_NELEM > 0","int","tls_dtor_t"
"task_tls_get_value","nuttx/tls.h","CONFIG_TLS_TASK_NELEM > 0","uintptr_t","int"
@ -348,6 +349,7 @@
"usleep","unistd.h","","int","useconds_t"
"vasprintf","stdio.h","","int","FAR char **","FAR const IPTR char *","va_list"
"versionsort","dirent.h","","int","FAR const struct dirent **","FAR const struct dirent **"
"vfork","unistd.h","!defined(CONFIG_BUILD_KERNEL) && defined(CONFIG_ARCH_HAVE_VFORK)","pid_t"
"vfprintf","stdio.h","defined(CONFIG_FILE_STREAM)","int","FAR FILE *","FAR const IPTR char *","va_list"
"vprintf","stdio.h","","int","FAR const IPTR char *","va_list"
"vscanf","stdio.h","defined(CONFIG_FILE_STREAM)","int","FAR const IPTR char *","va_list"

Can't render this file because it has a wrong number of fields in line 3.

4
libs/libc/unistd/CMakeLists.txt
View file

@ -104,7 +104,9 @@ if(NOT CONFIG_DISABLE_MOUNTPOINTS)
list(APPEND SRCS lib_truncate.c lib_posix_fallocate.c)
endif()
if(CONFIG_ARCH_HAVE_FORK)
if(CONFIG_TASK_FORK
OR CONFIG_ARCH_HAVE_VFORK
OR CONFIG_ARCH_HAVE_FORK)
list(APPEND SRCS lib_fork.c)
endif()

2
libs/libc/unistd/Make.defs
View file

@ -54,7 +54,7 @@ ifneq ($(CONFIG_DISABLE_MOUNTPOINTS),y)
CSRCS += lib_truncate.c lib_posix_fallocate.c
endif
ifeq ($(CONFIG_ARCH_HAVE_FORK),y)
ifneq ($(CONFIG_TASK_FORK)$(CONFIG_ARCH_HAVE_VFORK)$(CONFIG_ARCH_HAVE_FORK),)
CSRCS += lib_fork.c
endif

172
libs/libc/unistd/lib_fork.c
View file

@ -28,13 +28,15 @@
#include <nuttx/arch.h>
#include <nuttx/tls.h>
#include <sched.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>
#include <nuttx/debug.h>
#if defined(CONFIG_ARCH_HAVE_FORK)
#if defined(CONFIG_TASK_FORK) || defined(CONFIG_ARCH_HAVE_VFORK) || \
defined(CONFIG_ARCH_HAVE_FORK)
/****************************************************************************
* Private Functions
@ -136,11 +138,109 @@ static void atfork_parent(void)
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: task_fork
*
* Description:
* Clone the calling task: the child shares the parent's memory, runs on
* a private copy of the parent's stack, and runs concurrently. Not POSIX.
* Wrapper of the up_task_fork() syscall.
*
* Returned Value:
* Upon successful completion, task_fork() returns 0 to the child and
* returns the process ID of the child to the parent. Otherwise, -1 is
* returned to the parent, no child is created, and errno is set to
* indicate the error.
*
****************************************************************************/
#ifdef CONFIG_TASK_FORK
pid_t task_fork(void)
{
pid_t pid;
#ifdef CONFIG_PTHREAD_ATFORK
atfork_prepare();
#endif
pid = up_task_fork();
#ifdef CONFIG_PTHREAD_ATFORK
if (pid == 0)
{
atfork_child();
}
else
{
atfork_parent();
}
#endif
return pid;
}
#endif /* CONFIG_TASK_FORK */
/****************************************************************************
* Name: vfork
*
* Description:
* The vfork() function is equivalent to fork(), except that the behavior
* is undefined if the process created by vfork() either modifies any data
* other than a variable of type pid_t used to store the return value from
* vfork(), or returns from the function in which vfork() was called, or
* calls any other function before successfully calling _exit() or one of
* the exec family of functions.
*
* The child shares the parent's memory and the parent is suspended until
* the child _exit()s or exec()s. The suspension lives in the kernel, so
* vfork() does not depend on CONFIG_SCHED_WAITPID. Wrapper of the
* up_vfork() syscall.
*
* Returned Value:
* Upon successful completion, vfork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
*
****************************************************************************/
#ifdef CONFIG_ARCH_HAVE_VFORK
pid_t vfork(void)
{
pid_t pid;
#ifdef CONFIG_PTHREAD_ATFORK
atfork_prepare();
#endif
pid = up_vfork();
#ifdef CONFIG_PTHREAD_ATFORK
if (pid == 0)
{
atfork_child();
}
else
{
atfork_parent();
}
#endif
return pid;
}
#endif /* CONFIG_ARCH_HAVE_VFORK */
/****************************************************************************
* Name: fork
*
* Description:
* The fork() function is a wrapper of up_fork() syscall
* POSIX fork(). The child receives its own copy of the parent's memory,
* at the same virtual addresses. It may modify anything, call anything,
* return from the function that called fork(), and it runs concurrently
* with the parent. None of vfork()'s restrictions apply.
*
* Provided only where CONFIG_ARCH_HAVE_FORK is selected; elsewhere fork()
* is not declared at all, so calling it is a build error.
* CONFIG_FORK_IS_TASK_FORK aliases it to task_fork() for legacy code.
* Wrapper of the up_fork() syscall.
*
* Returned Value:
* Upon successful completion, fork() returns 0 to the child process and
@ -150,6 +250,7 @@ static void atfork_parent(void)
*
****************************************************************************/
#if defined(CONFIG_ARCH_HAVE_FORK)
pid_t fork(void)
{
pid_t pid;
@ -172,67 +273,12 @@ pid_t fork(void)
return pid;
}
#if defined(CONFIG_SCHED_WAITPID)
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: vfork
*
* Description:
* The vfork() function is implemented based on fork() function, on
* vfork(), the parent task need to wait until the child task is performing
* exec or running finished.
*
* Returned Value:
* Upon successful completion, vfork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
*
****************************************************************************/
pid_t vfork(void)
#elif defined(CONFIG_FORK_IS_TASK_FORK)
pid_t fork(void)
{
int status = 0;
int ret;
pid_t pid;
#ifdef CONFIG_PTHREAD_ATFORK
atfork_prepare();
#endif
pid = up_fork();
#ifdef CONFIG_PTHREAD_ATFORK
if (pid == 0)
{
atfork_child();
}
else
{
atfork_parent();
}
#endif
if (pid != 0)
{
/* we are in parent task, and we need to wait the child task
* until running finished or performing exec
*/
ret = waitpid(pid, &status, WNOWAIT);
if (ret < 0)
{
serr("ERROR: waitpid failed: %d\n", get_errno());
}
}
return pid;
return task_fork();
}
#endif
#endif /* CONFIG_SCHED_WAITPID */
#endif /* CONFIG_ARCH_HAVE_FORK */
#endif /* CONFIG_TASK_FORK || CONFIG_ARCH_HAVE_VFORK ||
* CONFIG_ARCH_HAVE_FORK */

65
sched/addrenv/addrenv.c
View file

@ -27,6 +27,7 @@
#include <nuttx/config.h>
#include <assert.h>
#include <errno.h>
#include <nuttx/debug.h>
#include <nuttx/addrenv.h>
@ -292,6 +293,70 @@ int addrenv_join(FAR struct tcb_s *ptcb, FAR struct tcb_s *tcb)
return OK;
}
#ifdef CONFIG_ARCH_HAVE_FORK
/****************************************************************************
* Name: addrenv_fork
*
* Description:
* Duplicate the parent process's address environment for a POSIX fork()
* child, and attach the duplicate to the child.
*
* This is the counterpart of addrenv_join(): where join gives the child
* the parent's memory, fork gives it a copy -- its own pages, holding a
* snapshot of the parent's contents, mapped at the same virtual addresses.
* Mapping at the same addresses is what lets the copy be exact: every
* pointer the parent held into its own memory remains valid in the child,
* including the pointers inside the copied heap's own metadata.
*
* The copy is eager -- there is no copy-on-write, because NuttX has no
* demand paging to build it on -- so forking a large process needs as much
* free memory as the process occupies, and fails with -ENOMEM if that is
* not available. That is the nature of the primitive on this class of
* system, not a defect of this implementation; spawn-heavy code should
* prefer posix_spawn() or vfork().
*
* Input Parameters:
* ptcb - The tcb of the parent process
* tcb - The tcb of the child process
*
* Returned Value:
* This is a NuttX internal function so it follows the convention that
* 0 (OK) is returned on success and a negated errno is returned on
* failure.
*
****************************************************************************/
int addrenv_fork(FAR struct tcb_s *ptcb, FAR struct tcb_s *tcb)
{
FAR struct addrenv_s *addrenv;
int ret;
DEBUGASSERT(ptcb->addrenv_own != NULL);
addrenv = addrenv_allocate();
if (addrenv == NULL)
{
return -ENOMEM;
}
/* Duplicate the parent's regions into freshly allocated pages, mapped at
* the same virtual addresses.
*/
ret = up_addrenv_fork(&ptcb->addrenv_own->addrenv, &addrenv->addrenv);
if (ret < 0)
{
berr("ERROR: up_addrenv_fork failed: %d\n", ret);
addrenv_drop(addrenv, false);
return ret;
}
/* Hand the reference taken by addrenv_allocate() to the child */
return addrenv_attach(tcb, addrenv);
}
#endif /* CONFIG_ARCH_HAVE_FORK */
/****************************************************************************
* Name: addrenv_leave
*

9
sched/sched/sched_releasetcb.c
View file

@ -174,6 +174,15 @@ int nxsched_release_tcb(FAR struct tcb_s *tcb, uint8_t ttype)
nxtask_joindestroy(tcb);
#endif
#ifdef CONFIG_ARCH_HAVE_VFORK
/* Release a suspended vfork() parent here, the last point in the
* child's life: exec_swap() has already handed its pid to any
* program it loaded.
*/
nxtask_vfork_resume(tcb);
#endif
/* And, finally, release the TCB itself */
if (tcb->flags & TCB_FLAG_FREE_TCB)

4
sched/task/CMakeLists.txt
View file

@ -46,7 +46,9 @@ if(CONFIG_SCHED_HAVE_PARENT)
list(APPEND SRCS task_getppid.c task_reparent.c)
endif()
if(CONFIG_ARCH_HAVE_FORK)
if(CONFIG_TASK_FORK
OR CONFIG_ARCH_HAVE_VFORK
OR CONFIG_ARCH_HAVE_FORK)
list(APPEND SRCS task_fork.c)
endif()

2
sched/task/Make.defs
View file

@ -30,7 +30,7 @@ ifeq ($(CONFIG_SCHED_HAVE_PARENT),y)
CSRCS += task_getppid.c task_reparent.c
endif
ifeq ($(CONFIG_ARCH_HAVE_FORK),y)
ifneq ($(CONFIG_TASK_FORK)$(CONFIG_ARCH_HAVE_VFORK)$(CONFIG_ARCH_HAVE_FORK),)
CSRCS += task_fork.c
endif

11
sched/task/task_exit.c
View file

@ -157,5 +157,16 @@ int nxtask_exit(void)
rtcb->lockcount--;
#ifndef CONFIG_SMP
/* Publish anything woken while the TCB was being released. lockcount was
* raised directly rather than through sched_lock(), so the matching
* decrement above does not merge g_pendingtasks the way sched_unlock()
* would, and a vfork() parent released by nxsched_release_tcb() would be
* stranded there. SMP has no pending list to merge.
*/
nxsched_merge_pending();
#endif
return ret;
}

466
sched/task/task_fork.c
View file

@ -34,7 +34,10 @@
#include <errno.h>
#include <nuttx/debug.h>
#include <nuttx/fork.h>
#include <nuttx/kmalloc.h>
#include <nuttx/queue.h>
#include <nuttx/semaphore.h>
#include "sched/sched.h"
#include "environ/environ.h"
@ -42,9 +45,112 @@
#include "task/task.h"
#include "tls/tls.h"
/* fork() requires architecture-specific support as well as waipid(). */
/* This file is the common core of task_fork(), vfork() and fork(); it is
* built if the architecture can provide any one of them.
*/
#ifdef CONFIG_ARCH_HAVE_FORK
#if defined(CONFIG_TASK_FORK) || defined(CONFIG_ARCH_HAVE_VFORK) || \
defined(CONFIG_ARCH_HAVE_FORK)
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_HAVE_FORK)
static void fork_inherit_stack(FAR struct tcb_s *parent,
FAR struct tcb_s *child);
static void fork_inherit_tls(FAR struct tcb_s *child);
static void fork_restore_parent_env(void);
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_HAVE_FORK)
/****************************************************************************
* Name: fork_inherit_stack
*
* Description:
* Give the fork() child the parent's stack at the parent's virtual
* address rather than a relocated copy. The child's address environment
* is a duplicate, so the parent's stack is already there -- same contents,
* same address, its own pages -- and nothing needs allocating or copying.
*
* A relocated stack would break plain C: a pointer to a local taken
* before the fork would name the parent's copy, not the child's live
* object.
*
* TCB_FLAG_FREE_STACK is left clear: the stack belongs to the duplicated
* image and is released with it, so up_release_stack() must not free it.
*
* Input Parameters:
* parent - The parent task's TCB
* child - The child task's TCB
*
****************************************************************************/
static void fork_inherit_stack(FAR struct tcb_s *parent,
FAR struct tcb_s *child)
{
child->stack_alloc_ptr = parent->stack_alloc_ptr;
child->stack_base_ptr = parent->stack_base_ptr;
child->adj_stack_size = parent->adj_stack_size;
child->flags &= ~TCB_FLAG_FREE_STACK;
}
/****************************************************************************
* Name: fork_inherit_tls
*
* Description:
* Retarget the thread-local storage the fork() child inherited.
*
* tls_dup_info() cannot be used: it carves a fresh TLS block off the
* stack, which on an inherited stack would carve a second one and shift
* stack_base_ptr away from the parent's. The child's copy is already in
* place, so only the fields naming the task itself need correcting.
*
* The write lands in user memory at an address the parent also occupies,
* so the child's address environment must be current for it -- otherwise
* the parent's own TLS is what gets modified.
*
* Input Parameters:
* child - The child task's TCB
*
* Returned Value:
* Zero (OK) on success; a negated errno value on failure.
*
****************************************************************************/
static void fork_inherit_tls(FAR struct tcb_s *child)
{
FAR struct tls_info_s *info = (FAR struct tls_info_s *)
child->stack_alloc_ptr;
info->tl_task = child->group->tg_info;
info->tl_tid = child->pid;
}
/****************************************************************************
* Name: fork_restore_parent_env
*
* Description:
* Undo the addrenv_select() that nxtask_setup_fork() made on the child's
* behalf, putting the caller back in its own address environment. The
* environment to go back to does not have to be remembered: the caller is
* the parent, and what was current before was the parent's own.
*
****************************************************************************/
static void fork_restore_parent_env(void)
{
addrenv_restore(this_task()->addrenv_own);
}
#endif /* CONFIG_ARCH_ADDRENV && CONFIG_ARCH_HAVE_FORK */
/****************************************************************************
* Public Functions
@ -54,37 +160,22 @@
* Name: nxtask_setup_fork
*
* Description:
* The fork() function has the same effect as posix fork(), except that the
* behavior is undefined if the process created by fork() either modifies
* any data other than a variable of type pid_t used to store the return
* value from fork(), or returns from the function in which fork() was
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
* Allocate and initialize the child task's TCB. This is one step in the
* sequence common to task_fork(), vfork() and fork(); see the comment
* above the prototype in include/nuttx/sched.h for the whole sequence, and
* include/nuttx/fork.h for what the three primitives mean.
*
* This function provides one step in the overall fork() sequence: It
* Allocates and initializes the child task's TCB. The overall sequence
* is:
* Exactly two things depend on `type':
*
* 1) User code calls fork(). fork() is provided in
* architecture-specific code.
* 2) fork()and calls nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) up_fork() provides any additional operating context. up_fork must:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) up_fork() then calls nxtask_start_fork()
* 6) nxtask_start_fork() then executes the child thread.
* - the address environment: task_fork() and vfork() join the parent's,
* fork() duplicates it.
* - the stack: a task_fork() or vfork() child gets its own, which the
* architecture code fills with a relocated copy; a fork() child inherits
* the parent's address (fork_inherit_stack()).
*
* Input Parameters:
* retaddr - Return address
* argsize - Location to return the argument size
* retaddr - Address at which the child resumes
* type - One of the FORK_TYPE_* constants
*
* Returned Value:
* Upon successful completion, nxtask_setup_fork() returns a pointer to
@ -93,7 +184,7 @@
*
****************************************************************************/
FAR struct tcb_s *nxtask_setup_fork(start_t retaddr)
FAR struct tcb_s *nxtask_setup_fork(start_t retaddr, int type)
{
FAR struct tcb_s *ptcb = this_task();
FAR struct tcb_s *parent;
@ -105,6 +196,8 @@ FAR struct tcb_s *nxtask_setup_fork(start_t retaddr)
int ret;
DEBUGASSERT(retaddr != NULL);
DEBUGASSERT(type == FORK_TYPE_TASK || type == FORK_TYPE_VFORK ||
type == FORK_TYPE_FORK);
/* Get the type of the fork'ed task (kernel or user) */
@ -160,16 +253,80 @@ FAR struct tcb_s *nxtask_setup_fork(start_t retaddr)
}
#if defined(CONFIG_ARCH_ADDRENV)
/* Join the parent address environment */
if (ttype != TCB_FLAG_TTYPE_KERNEL)
{
ret = addrenv_join(parent, child);
if (type != FORK_TYPE_FORK)
{
/* task_fork() and vfork(): join the parent address environment,
* exactly as pthread_create() does. The child shares .data, .bss
* and the heap.
*/
ret = addrenv_join(parent, child);
}
#ifdef CONFIG_ARCH_HAVE_FORK
else
{
/* POSIX fork(): duplicate the parent's address environment now,
* before anything else is set up. The duplicate holds a copy of
* the parent's contents -- including its stack -- at the parent's
* virtual addresses, which is what lets the child go on to inherit
* the stack address rather than be given a relocated copy. See
* fork_inherit_stack().
*/
ret = addrenv_fork(parent, child);
if (ret >= 0)
{
/* Make the child's address environment current for the rest of
* the setup, and for the architecture code that runs after it.
*
* From here on, everything written on the child's behalf
* has to land in the child's image rather than the parent's,
* because
* the two occupy the same virtual addresses: its thread-local
* storage, and -- on architectures that keep the register save
* area on the user stack rather than on a kernel stack -- the
* register context the child is resumed from. Writing those
* under the parent's environment corrupts the parent and
* leaves the child reading whatever the snapshot happened to
* contain.
*
* Reads are unaffected: everything the setup reads from the
* parent -- environ, the argument vector -- is legible at the
* same address in the child, precisely because it is a copy.
*
* nxtask_start_fork() puts the parent's environment back.
*/
FAR struct addrenv_s *oldenv;
ret = addrenv_select(child->addrenv_own, &oldenv);
}
}
#else
/* An address environment without ARCH_HAVE_FORK -- a protected build
* over an MMU, for instance. There is an address environment to join,
* but no POSIX fork() to duplicate it for, so the branch above is not
* compiled and `type' can never be FORK_TYPE_FORK here.
*/
DEBUGASSERT(type != FORK_TYPE_FORK);
#endif
if (ret < 0)
{
goto errout_with_tcb;
}
}
#else
/* Without address environments there is only one address space, so
* everything except the stack is shared no matter which primitive was
* called. POSIX fork() cannot be provided at all, and CONFIG_ARCH_HAVE_
* FORK is not selected, so `type' can never be FORK_TYPE_FORK here.
*/
DEBUGASSERT(type != FORK_TYPE_FORK);
#endif
/* Duplicate the parent tasks environment */
@ -193,12 +350,27 @@ FAR struct tcb_s *nxtask_setup_fork(start_t retaddr)
argv = nxsched_get_stackargs(parent);
nxtask_setup_name(child, argv[0]);
/* Allocate the stack for the TCB */
/* Allocate the stack for the TCB, or inherit the parent's */
stack_size = (uintptr_t)ptcb->stack_base_ptr -
(uintptr_t)ptcb->stack_alloc_ptr + ptcb->adj_stack_size;
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_HAVE_FORK)
if (type == FORK_TYPE_FORK && ttype != TCB_FLAG_TTYPE_KERNEL)
{
/* The child's copy of the parent's stack is already in place, at the
* parent's address, courtesy of the duplication above.
*/
fork_inherit_stack(parent, child);
ret = OK;
}
else
#endif
{
stack_size = (uintptr_t)ptcb->stack_base_ptr -
(uintptr_t)ptcb->stack_alloc_ptr + ptcb->adj_stack_size;
ret = up_create_stack(child, stack_size, ttype);
}
ret = up_create_stack(child, stack_size, ttype);
if (ret < OK)
{
goto errout_with_tcb;
@ -235,20 +407,35 @@ FAR struct tcb_s *nxtask_setup_fork(start_t retaddr)
goto errout_with_tcb;
}
/* Setup thread local storage */
/* Set up thread local storage and the argument vector.
*
* A fork() child that inherited its stack already has both, byte for
* byte, at the addresses the parent has them at -- they came across with
* the rest of the image. Re-creating them would carve fresh frames off a
* stack that already contains them, moving stack_base_ptr away from the
* parent's and undoing the inheritance. Only the TLS fields that name
* the task itself need correcting.
*/
ret = tls_dup_info(child, parent);
if (ret < OK)
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_HAVE_FORK)
if (type == FORK_TYPE_FORK && ttype != TCB_FLAG_TTYPE_KERNEL)
{
goto errout_with_tcb;
fork_inherit_tls(child);
}
/* Setup to pass parameters to the new task */
ret = nxtask_setup_stackargs(child, argv[0], &argv[1]);
if (ret < OK)
else
#endif
{
goto errout_with_tcb;
ret = tls_dup_info(child, parent);
if (ret < OK)
{
goto errout_with_tcb;
}
ret = nxtask_setup_stackargs(child, argv[0], &argv[1]);
if (ret < OK)
{
goto errout_with_tcb;
}
}
/* Now we have enough in place that we can join the group */
@ -258,6 +445,18 @@ FAR struct tcb_s *nxtask_setup_fork(start_t retaddr)
return child;
errout_with_tcb:
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_HAVE_FORK)
/* Get back into the parent's address environment before unwinding. If the
* duplication above never happened this is the environment we are already
* in, and addrenv_restore() is then a no-op.
*/
if (type == FORK_TYPE_FORK && ttype != TCB_FLAG_TTYPE_KERNEL)
{
fork_restore_parent_env();
}
#endif
nxsched_release_tcb((FAR struct tcb_s *)child, ttype);
errout:
set_errno(-ret);
@ -268,58 +467,51 @@ errout:
* Name: nxtask_start_fork
*
* Description:
* The fork() function has the same effect as fork(), except that the
* behavior is undefined if the process created by fork() either modifies
* any data other than a variable of type pid_t used to store the return
* value from fork(), or returns from the function in which fork() was
* called, or calls any other function before successfully calling _exit()
* or one of the exec family of functions.
* The last step of all three primitives: finish the child and run it.
* The architecture-specific code calls this once it has built the child's
* register context and stack.
*
* This function provides one step in the overall fork() sequence: It
* starts execution of the previously initialized TCB. The overall
* sequence is:
*
* 1) User code calls fork()
* 2) Architecture-specific code provides fork()and calls
* nxtask_setup_fork().
* 3) nxtask_setup_fork() allocates and configures the child task's TCB.
* This consists of:
* - Allocation of the child task's TCB.
* - Initialization of file descriptors and streams
* - Configuration of environment variables
* - Allocate and initialize the stack
* - Setup the input parameters for the task.
* - Initialization of the TCB (including call to up_initial_state())
* 4) fork() provides any additional operating context. fork must:
* - Initialize special values in any CPU registers that were not
* already configured by up_initial_state()
* 5) fork() then calls nxtask_start_fork()
* 6) nxtask_start_fork() then executes the child thread.
* For vfork() this additionally suspends the caller.
*
* Input Parameters:
* child - The tcb_s struct instance that created by
* nxtask_setup_fork() method
* wait_child - whether need to wait until the child is running finished
* child - The tcb_s struct instance created by nxtask_setup_fork()
* type - One of the FORK_TYPE_* constants
*
* Returned Value:
* Upon successful completion, fork() returns 0 to the child process and
* returns the process ID of the child process to the parent process.
* Otherwise, -1 is returned to the parent, no child process is created,
* and errno is set to indicate the error.
* The process ID of the child, or ERROR on failure.
*
****************************************************************************/
pid_t nxtask_start_fork(FAR struct tcb_s *child)
pid_t nxtask_start_fork(FAR struct tcb_s *child, int type)
{
pid_t pid;
sinfo("Starting Child TCB=%p\n", child);
sinfo("Starting Child TCB=%p type=%d\n", child, type);
DEBUGASSERT(child);
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_HAVE_FORK)
/* The architecture code has finished writing the child's image, so put the
* parent back in its own address environment. See nxtask_setup_fork().
*/
if (type == FORK_TYPE_FORK &&
(child->flags & TCB_FLAG_TTYPE_MASK) != TCB_FLAG_TTYPE_KERNEL)
{
fork_restore_parent_env();
}
#endif
/* Get the assigned pid before we start the task */
pid = child->pid;
#ifdef CONFIG_ARCH_HAVE_VFORK
if (type == FORK_TYPE_VFORK)
{
return nxtask_start_vfork(child);
}
#endif
/* Activate the task */
nxtask_activate(child);
@ -327,6 +519,99 @@ pid_t nxtask_start_fork(FAR struct tcb_s *child)
return pid;
}
#ifdef CONFIG_ARCH_HAVE_VFORK
/****************************************************************************
* Name: nxtask_start_vfork
*
* Description:
* Start execution of a vfork() child and suspend the caller until the
* child calls _exit() or one of the exec family of functions.
*
* The suspension lives here, in the kernel primitive, rather than in a
* libc waitpid() as it once did. Two things follow from that. The parent
* is released when the child's TCB is torn down (see
* nxtask_vfork_resume()), which for an exec()ing child is immediately
* after exec_swap() has handed the child's pid to the program it loaded --
* so the parent resumes at exec(), holding a pid that names the running
* program, as POSIX requires. And vfork() no longer depends on
* CONFIG_SCHED_WAITPID.
*
* Input Parameters:
* child - The tcb_s struct instance created by nxtask_setup_fork()
*
* Returned Value:
* The process ID of the child.
*
****************************************************************************/
pid_t nxtask_start_vfork(FAR struct tcb_s *child)
{
struct vfork_s vfork;
pid_t pid;
int ret;
sinfo("Starting vfork Child TCB=%p\n", child);
DEBUGASSERT(child);
/* The rendezvous lives in this frame. We are about to block in it and
* will not leave until the child has posted, so it outlives every use.
*/
nxsem_init(&vfork.sem, 0, 0);
vfork.released = false;
child->vfork_rel = &vfork;
pid = child->pid;
nxtask_activate(child);
/* Wait for the child to _exit() or exec(). This is not a cancellation
* point and must not be interrupted by a signal: the child may be running
* on our stack, so returning early would corrupt it.
*/
do
{
ret = nxsem_wait_uninterruptible(&vfork.sem);
}
while (ret == -EINTR);
nxsem_destroy(&vfork.sem);
return pid;
}
/****************************************************************************
* Name: nxtask_vfork_resume
*
* Description:
* Release the vfork() parent suspended on this child, if there is one.
*
* Called from nxsched_release_tcb(), the last point in the child's life,
* by which time an exec()ing child has already handed its pid to the
* program it loaded. nxtask_abort_fork() reaches it too, so a fork that
* fails after the rendezvous also releases the parent.
*
* Input Parameters:
* child - The TCB being torn down
*
* Returned Value:
* None
*
****************************************************************************/
void nxtask_vfork_resume(FAR struct tcb_s *child)
{
FAR struct vfork_s *vfork = child->vfork_rel;
if (vfork != NULL && !vfork->released)
{
vfork->released = true;
child->vfork_rel = NULL;
nxsem_post(&vfork->sem);
}
}
#endif /* CONFIG_ARCH_HAVE_VFORK */
/****************************************************************************
* Name: nxtask_abort_fork
*
@ -340,6 +625,20 @@ pid_t nxtask_start_fork(FAR struct tcb_s *child)
void nxtask_abort_fork(FAR struct tcb_s *child, int errcode)
{
#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_HAVE_FORK)
/* A child holding an address environment of its own, rather than a
* reference to the caller's, is a fork() child, and nxtask_setup_fork()
* left that environment selected. Get back into the parent's before
* unwinding. See nxtask_setup_fork().
*/
if (child->addrenv_own != NULL &&
child->addrenv_own != this_task()->addrenv_own)
{
fork_restore_parent_env();
}
#endif
/* The TCB was added to the active task list by nxtask_setup_scheduler() */
dq_rem((FAR dq_entry_t *)child, list_inactivetasks());
@ -350,4 +649,5 @@ void nxtask_abort_fork(FAR struct tcb_s *child, int errcode)
set_errno(errcode);
}
#endif /* CONFIG_ARCH_HAVE_FORK */
#endif /* CONFIG_TASK_FORK || CONFIG_ARCH_HAVE_VFORK ||
* CONFIG_ARCH_HAVE_FORK */

2
syscall/syscall.csv
View file

@ -203,6 +203,8 @@
"unlink","unistd.h","!defined(CONFIG_DISABLE_MOUNTPOINT)","int","FAR const char *"
"unsetenv","stdlib.h","!defined(CONFIG_DISABLE_ENVIRON)","int","FAR const char *"
"up_fork","nuttx/arch.h","defined(CONFIG_ARCH_HAVE_FORK)","pid_t"
"up_task_fork","nuttx/arch.h","defined(CONFIG_TASK_FORK)","pid_t"
"up_vfork","nuttx/arch.h","defined(CONFIG_ARCH_HAVE_VFORK)","pid_t"
"utimens","sys/stat.h","","int","FAR const char *","const struct timespec [2]|FAR const struct timespec *"
"wait","sys/wait.h","defined(CONFIG_SCHED_WAITPID) && defined(CONFIG_SCHED_HAVE_PARENT)","pid_t","FAR int *"
"waitid","sys/wait.h","defined(CONFIG_SCHED_WAITPID) && defined(CONFIG_SCHED_HAVE_PARENT)","int","idtype_t","id_t"," FAR siginfo_t *","int"

Can't render this file because it has a wrong number of fields in line 2.