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014ea57042
The ET_DYN path computes run-time addresses from link-time ones in five places, each open-coding the arithmetic, and two of them disagree about how: libelf_relocatedyn() adds textalloc to a relocation's r_offset in one branch and subtracts datasec before adding datastart in the next, while the value translation a few lines further down picks between those two forms with an explicit test on datasec. Collect that into libelf_addr(), which makes the test once: an address below the data segment's link-time base belongs to text, anything at or above it to data. This changes nothing today. libelf_elfsize() sets segpad = datasec - (text_vaddr + textsize) and libelf_load() then places datastart = textalloc + textsize + segpad so datastart - datasec is textalloc, and the data branch reduces to textalloc + vaddr -- exactly what the text branch returns, and exactly what adding a single load bias did before. The two forms are the same arithmetic written twice. They stop being the same once text and data are placed independently, which is what an FDPIC object requires: its two PT_LOAD segments are relocated separately so that the read-only one can be mapped in place on the media while only the writable one is copied. Having the translation in one function is what makes that possible without auditing every open-coded expression again. Built for mps3-an547:picostest, which is CONFIG_ELF with CONFIG_PIC, and boots identically to the same configuration without this change. Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
352 lines
12 KiB
C
352 lines
12 KiB
C
/****************************************************************************
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* libs/libc/elf/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 __LIBS_LIBC_LIBC_ELF_LIBC_ELF_H
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#define __LIBS_LIBC_LIBC_ELF_LIBC_ELF_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/addrenv.h>
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#include <nuttx/lib/elf.h>
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Name: libelf_verifyheader
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*
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* Description:
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* Given the header from a possible ELF executable, verify that it is
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* an ELF executable.
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_verifyheader(FAR const Elf_Ehdr *header);
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/****************************************************************************
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* Name: libelf_findsymtab
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*
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* Description:
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* Find the symbol table section.
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_findsymtab(FAR struct mod_loadinfo_s *loadinfo);
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/****************************************************************************
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* Name: libelf_readsym
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*
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* Description:
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* Read the ELF symbol structure at the specified index into memory.
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*
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* Input Parameters:
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* loadinfo - Load state information
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* index - Symbol table index
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* sym - Location to return the table entry
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_readsym(FAR struct mod_loadinfo_s *loadinfo, int index,
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FAR Elf_Sym *sym, FAR Elf_Shdr *shdr);
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/****************************************************************************
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* Name: libelf_symvalue
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*
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* Description:
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* Get the value of a symbol. The updated value of the symbol is returned
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* in the st_value field of the symbol table entry.
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*
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* Input Parameters:
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* modp - Module state information
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* loadinfo - Load state information
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* sym - Symbol table entry (value might be undefined)
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* sh_offset - Offset of strtab
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* exports - Pointer to the symbol table
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* nexports - Number of symbols in the symbol table*
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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* EINVAL - There is something inconsistent in the symbol table (should
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* only happen if the file is corrupted)
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* ENOSYS - Symbol lies in common
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* ESRCH - Symbol has no name
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* ENOENT - Symbol undefined and not provided via a symbol table
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*
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****************************************************************************/
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int libelf_symvalue(FAR struct module_s *modp,
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FAR struct mod_loadinfo_s *loadinfo, FAR Elf_Sym *sym,
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Elf_Off sh_offset,
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FAR const struct symtab_s *exports, int nexports);
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/****************************************************************************
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* Name: libelf_insertsymtab
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*
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* Description:
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* Insert a symbol table for the current module.
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*
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* Input Parameters:
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* modp - Module state information
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* loadinfo - Module load information
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* shdr - Symbol table section header
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* sym - Symbol table entry
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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* ENOMEM - Symbol undefined and not provided via a symbol table
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*
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****************************************************************************/
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int libelf_insertsymtab(FAR struct module_s *modp,
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FAR struct mod_loadinfo_s *loadinfo,
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FAR Elf_Shdr *shdr,
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FAR Elf_Sym *sym);
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/****************************************************************************
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* Name: libelf_findglobal
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*
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* Description:
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* Find a symbol in the global symbol table
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*
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* Input Parameters:
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* modp - Module state information
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* loadinfo - Module load information
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* shdr - Symbol table section header
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* sym - Symbol table entry
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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* ENOMEM - Symbol undefined and not provided via a symbol table
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*
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****************************************************************************/
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void *libelf_findglobal(FAR struct module_s *modp,
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FAR struct mod_loadinfo_s *loadinfo,
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FAR Elf_Shdr *shdr,
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FAR Elf_Sym *sym);
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/****************************************************************************
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* Name: libelf_loadhdrs
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*
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* Description:
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* Loads program and section headers into memory.
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_loadhdrs(FAR struct mod_loadinfo_s *loadinfo);
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/****************************************************************************
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* Name: libelf_sectname
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*
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* Description:
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* Get the symbol name in loadinfo->iobuffer[].
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_sectname(FAR struct mod_loadinfo_s *loadinfo,
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FAR const Elf_Shdr *shdr);
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/****************************************************************************
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* Name: libelf_allocbuffer
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*
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* Description:
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* Perform the initial allocation of the I/O buffer, if it has not already
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* been allocated.
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_allocbuffer(FAR struct mod_loadinfo_s *loadinfo);
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/****************************************************************************
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* Name: libelf_reallocbuffer
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*
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* Description:
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* Increase the size of I/O buffer by the specified buffer increment.
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_reallocbuffer(FAR struct mod_loadinfo_s *loadinfo,
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size_t increment);
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/****************************************************************************
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* Name: libelf_freebuffers
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*
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* Description:
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* Release all working buffers.
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*
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* Returned Value:
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* 0 (OK) is returned on success and a negated errno is returned on
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* failure.
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*
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****************************************************************************/
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int libelf_freebuffers(FAR struct mod_loadinfo_s *loadinfo);
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/****************************************************************************
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* Name: libelf_addr
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*
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* Description:
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* Translate a link-time address in a loaded object to the address it
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* occupies now. An address below the data segment's link-time base
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* belongs to text, anything at or above it to data.
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*
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* Input Parameters:
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* loadinfo - Load state information
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* vaddr - The link-time address to translate
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*
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* Returned Value:
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* The run-time address.
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*
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****************************************************************************/
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static inline uintptr_t libelf_addr(FAR struct mod_loadinfo_s *loadinfo,
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uintptr_t vaddr)
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{
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if (loadinfo->datasec != 0 && vaddr >= loadinfo->datasec)
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{
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return loadinfo->datastart + (vaddr - loadinfo->datasec);
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}
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return loadinfo->textalloc + vaddr;
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}
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#ifdef CONFIG_ARCH_ADDRENV
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/****************************************************************************
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* Name: libelf_addrenv_alloc
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*
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* Description:
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* Allocate memory for the ELF image (textalloc and datastart). If
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* CONFIG_ARCH_ADDRENV=n, textalloc will be allocated using kmm_zalloc()
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* and datastart will be a offset from textalloc. If
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* CONFIG_ARCH_ADDRENV=y, then textalloc and datastart will be allocated
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* using up_addrenv_create(). In either case, there will be a unique
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* instance of textalloc and datastart (and stack) for each instance of a
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* process.
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*
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* Input Parameters:
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* loadinfo - Load state information
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* textsize - The size (in bytes) of the .text address environment needed
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* for the ELF image (read/execute).
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* datasize - The size (in bytes) of the .bss/.data address environment
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* needed for the ELF image (read/write).
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*
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* Returned Value:
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* Zero (OK) on success; a negated errno value on failure.
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*
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****************************************************************************/
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int libelf_addrenv_alloc(FAR struct mod_loadinfo_s *loadinfo,
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size_t textsize, size_t datasize);
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/****************************************************************************
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* Name: libelf_addrenv_select
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*
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* Description:
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* Temporarily select the task's address environment.
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*
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* Input Parameters:
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* loadinfo - Load state information
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*
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* Returned Value:
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* Zero (OK) on success; a negated errno value on failure.
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*
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****************************************************************************/
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int libelf_addrenv_select(FAR struct mod_loadinfo_s *loadinfo);
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/****************************************************************************
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* Name: libelf_addrenv_restore
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*
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* Description:
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* Restore the address environment before libelf_addrenv_select() was
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* called.
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*
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* Input Parameters:
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* loadinfo - Load state information
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*
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* Returned Value:
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* Zero (OK) on success; a negated errno value on failure.
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*
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****************************************************************************/
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int libelf_addrenv_restore(FAR struct mod_loadinfo_s *loadinfo);
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/****************************************************************************
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* Name: libelf_addrenv_free
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*
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* Description:
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* Release the address environment previously created by
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* libelf_addrenv_alloc(). This function is called only under certain
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* error conditions after the module has been loaded but not yet started.
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* After the module has been started, the address environment will
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* automatically be freed when the module exits.
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*
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* Input Parameters:
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* loadinfo - Load state information
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*
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* Returned Value:
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* None.
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*
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****************************************************************************/
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void libelf_addrenv_free(FAR struct mod_loadinfo_s *loadinfo);
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#endif /* CONFIG_ARCH_ADDRENV */
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#endif /* __LIBS_LIBC_LIBC_ELF_LIBC_ELF_H */
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