dlopen() of a library that is already loaded fails. libelf_insert()
rejects a name that is already in the module registry with EEXIST, and
dlinsert() passes that straight out, so the second caller gets NULL.
POSIX says dlopen() shall return a handle to the object, and there is no
way today for two modules to hold the same library at once -- which is
what a shared library is for.
So dlopen() now takes another reference on a library that is already
there, and dlclose() only tears it down when the last handle goes. The
count lives in the dlfcn layer rather than in libelf_insert() so that
insmod keeps its own behaviour: a second insmod of the same name still
fails with EEXIST, which is right for a kernel module.
The module name is what makes any of this possible, and a PROTECTED build
did not have one. Names were defined for CONFIG_BUILD_FLAT or the kernel
side of a split build, on the reasoning that only the kernel needed them,
which predates dlopen() being usable from user space. Without a name the
user-space copy of libelf cannot recognise a second open of a library,
cannot count opens, and cannot make dlclose() mean anything -- two
dlopen()s there produce two independent copies of the library and lose
track of the first. Names are therefore defined wherever CONFIG_LIBC_DLFCN
is, which costs NAME_MAX per loaded module in that configuration.
The path no longer has to be copied either. The module name is the
basename of the file and libelf_insert() takes it as a const string, so
dlinsert() finds it with strrchr() instead of handing a writable
duplicate of the whole path to basename().
BUILD_KERNEL is deliberately untouched. dlopen() returns NULL there
unconditionally: dlinsert() is a stub, because sharing a library between
processes with separate address spaces needs the text in a shared region
and the data per process at a matching virtual address, which is a
different problem from this one.
Built for mps3-an547:picostest with and without CONFIG_LIBC_DLFCN, and
for stm32f4discovery:kostest, a PROTECTED configuration, with it enabled.
Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
debug.h is a NuttX-specific, non-POSIX header. Placing it in the
top-level include/ directory creates naming conflicts with external
projects that define their own debug.h.
This commit moves the canonical header to include/nuttx/debug.h,
following the NuttX convention for non-POSIX/non-standard headers,
and updates all in-tree references.
A backward-compatibility shim is left at include/debug.h that
emits a deprecation #warning and re-includes <nuttx/debug.h>,
allowing out-of-tree code to continue building while migrating.
Signed-off-by: Piyush Patle <piyushpatle228@gmail.com>
Renaming "modlib" to "libelf" is more in line with the implementation content,
which makes it easier for individual developers to understand the capabilities of this module.
CONFIG_LIBC_MODLIB -> CONFIG_LIBC_ELF
Signed-off-by: chao an <anchao.archer@bytedance.com>
2025-04-11 09:43:22 +08:00
Renamed from libs/libc/modlib/modlib_insert.c (Browse further)
