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An ET_DYN object is loaded into one allocation with its data behind its text, because its data references sit at a fixed distance from the code that makes them. An FDPIC object does not work that way: it reaches its data through a base register, so the two segments can be placed wherever suits, and the point of the format is that the read-only one is left on the media and executed there while only the writable one is copied. One copy of the text then serves every instance. So libelf_load() grows a second case. The object announces itself in the OS/ABI byte, which is noted once in libelf_loadhdrs() rather than re-derived; e_flags cannot be used for this, as an FDPIC object's are an unremarkable EABI version and testing them would reject every valid module. Text is taken from the media address plus the segment's own file offset -- the same arithmetic the ET_REL path already does with sh_offset -- and libelf_loadfile() does not read it. If the filesystem cannot show its media, the loader copies the text to RAM instead. The module then loses the shared text and the flash saving, but it runs. Obtaining that address needs two mechanisms, and they are not interchangeable. A compacting filesystem can move a file's blocks, so it hands out an address only with a pin that holds them still and expects the pin back; xipfs is the one in tree. A filesystem whose layout never changes has nothing to hold and answers FIOC_XIPBASE with a bare address; romfs and tmpfs are those. libelf_xipacquire() asks for the pin first, because a filesystem that needs one is not safe without it, and libelf_unload() gives it back. The loader asks for a pin only if it can hold one, or the pin would stay for ever. The pin is thus not specific to FDPIC. Any module that executes in place from a compacting filesystem takes one, and gives it back at unload. mmap() is not used, though both filesystems implement it. The mapping would be recorded against whichever task called the loader, while the release happens when the module's own task exits, which is a different group -- so the pin would outlive the module and the extent would never become movable again. Unloading has to change with placement: the existing path frees only textalloc because ET_DYN had a single allocation, which would leak an FDPIC object's data and free media the filesystem only lent us. Nothing here runs for a non-FDPIC object; every branch is behind the flag and the single-allocation path is untouched. Built and booted mps3-an547:picostest, which is CONFIG_ELF with CONFIG_PIC, with no change in behaviour. Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
183 lines
6.2 KiB
C
183 lines
6.2 KiB
C
/****************************************************************************
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* include/nuttx/elf.h
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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#ifndef __INCLUDE_NUTTX_ELF_H
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#define __INCLUDE_NUTTX_ELF_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <elf.h>
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#include <arch/elf.h>
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#include <stdbool.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define ELF_PRARGSZ (80) /* Number of chars for args */
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/* An architecture that has no FDPIC ABI recognises no FDPIC object. */
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#ifndef ELF_IS_FDPIC
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# define ELF_IS_FDPIC(ehdr) false
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#endif
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/****************************************************************************
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* Public Types
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****************************************************************************/
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#ifdef CONFIG_COREDUMP
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typedef struct elf_prpsinfo_s
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{
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char pr_state; /* Numeric process state */
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char pr_sname; /* Char for pr_state */
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char pr_zomb; /* Zombie */
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char pr_nice; /* Nice val */
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unsigned long pr_flag; /* Flags */
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unsigned short pr_uid;
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unsigned short pr_gid;
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int pr_pid;
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int pr_ppid;
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int pr_pgrp;
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int pr_sid;
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char pr_fname[16]; /* Filename of executable */
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char pr_psargs[ELF_PRARGSZ]; /* Initial part of arg list */
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} elf_prpsinfo_t;
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typedef struct elf_siginfo_s
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{
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int si_signo; /* Signal number */
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int si_code; /* Extra code */
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int si_errno; /* Errno */
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} elf_siginfo_t;
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typedef struct elf_timeval_s
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{
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long tv_sec; /* Seconds */
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long tv_usec; /* Microseconds */
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} elf_timeval_t;
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typedef struct elf_prstatus_s
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{
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elf_siginfo_t pr_info; /* Info associated with signal */
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short pr_cursig; /* Current signal */
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short pr_padding; /* Padding align */
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unsigned long pr_sigpend; /* Set of pending signals */
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unsigned long pr_sighold; /* Set of held signals */
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int pr_pid;
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int pr_ppid;
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int pr_pgrp;
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int pr_sid;
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elf_timeval_t pr_utime; /* User time */
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elf_timeval_t pr_stime; /* System time */
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elf_timeval_t pr_cutime; /* Cumulative user time */
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elf_timeval_t pr_cstime; /* Cumulative system time */
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elf_gregset_t pr_regs;
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int pr_fpvalid; /* True if math co-processor being used */
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} elf_prstatus_t;
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#endif
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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#if defined(__cplusplus)
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extern "C"
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{
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#endif
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/****************************************************************************
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* Name: up_checkarch
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*
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* Description:
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* Given the ELF header in 'hdr', verify that the module is appropriate
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* for the current, configured architecture. Every architecture that uses
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* the module loader must provide this function.
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*
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* Input Parameters:
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* hdr - The ELF header read from the module file.
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*
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* Returned Value:
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* True if the architecture supports this module file.
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*
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****************************************************************************/
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#ifdef CONFIG_LIBC_ARCH_ELF
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bool up_checkarch(FAR const Elf_Ehdr *hdr);
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#endif
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/****************************************************************************
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* Name: up_relocate and up_relocateadd
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*
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* Description:
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* Perform on architecture-specific ELF relocation. Every architecture
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* that uses the module loader must provide this function.
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*
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* Input Parameters:
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* rel - The relocation type
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* sym - The ELF symbol structure containing the fully resolved value.
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* There are a few relocation types for a few architectures that do
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* not require symbol information. For those, this value will be
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* NULL. Implementations of these functions must be able to handle
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* that case.
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* addr - The address that requires the relocation.
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*
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* Returned Value:
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* Zero (OK) if the relocation was successful. Otherwise, a negated errno
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* value indicating the cause of the relocation failure.
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*
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****************************************************************************/
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#ifdef CONFIG_LIBC_ARCH_ELF
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int up_relocate(FAR const Elf_Rel *rel, FAR const Elf_Sym *sym,
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uintptr_t addr, FAR void *arch_data);
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int up_relocateadd(FAR const Elf_Rela *rel, FAR const Elf_Sym *sym,
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uintptr_t addr, FAR void *arch_data);
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#endif
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/****************************************************************************
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* Name: up_init_exidx
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*
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* Description:
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* Initialize the exception index section.
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*
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* Input Parameters:
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* address - The exception index section address.
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* size - The exception index section size.
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*
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* Returned Value:
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* Zero (OK) if the initialization was successful. Otherwise, a negated
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* errno value indicating the cause of the failure.
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*
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****************************************************************************/
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#ifdef CONFIG_CXX_EXCEPTION
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int up_init_exidx(Elf_Addr address, Elf_Word size);
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#endif
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#if defined(__cplusplus)
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}
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#endif
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#endif /* __INCLUDE_NUTTX_ELF_H */
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