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Introduce GetElfSegmentAddress() function

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Justine Tunney 2023-07-23 17:36:18 -07:00
parent 3d172c99fe
commit ff198e7577
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2 changed files with 49 additions and 0 deletions
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1
libc/elf/elf.h
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@ -21,6 +21,7 @@ Elf64_Shdr *GetElfSectionHeaderAddress(const Elf64_Ehdr *, size_t, Elf64_Half);
Elf64_Shdr *FindElfSectionByName(Elf64_Ehdr *, size_t, char *, const char *);
const char *GetElfString(const Elf64_Ehdr *, size_t, const char *, Elf64_Word);
void *GetElfSectionAddress(const Elf64_Ehdr *, size_t, const Elf64_Shdr *);
void *GetElfSegmentAddress(const Elf64_Ehdr *, size_t, const Elf64_Phdr *);
const char *GetElfSectionName(const Elf64_Ehdr *, size_t, Elf64_Shdr *);
char *GetElfSectionNameStringTable(const Elf64_Ehdr *, size_t);

48
libc/elf/getelfsegmentaddress.c Normal file
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@ -0,0 +1,48 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/elf/def.h"
#include "libc/elf/elf.h"
#include "libc/elf/scalar.h"
#include "libc/elf/struct/phdr.h"
#include "libc/stdckdint.h"
/**
* Returns pointer to ELF segment file content.
*
* This function computes `elf + p_offset` with safety checks.
*
* @param elf points to the start of the executable image data
* @param mapsize is the number of bytes of `elf` we can access
* @param phdr is from GetElfProgramHeaderAddress(), or null
* @return pointer to segment data within image, or null if
* 1. `phdr` was null, or
* 2. `p_filesz` was zero, or
* 3. content wasn't contained within `[elf,elf+mapsize)`, or
* 4. an arithmetic overflow occurred
*/
void *GetElfSegmentAddress(const Elf64_Ehdr *elf, // validated
size_t mapsize, // validated
const Elf64_Phdr *phdr) { // foreign
Elf64_Off last;
if (!phdr) return 0;
if (phdr->p_filesz <= 0) return 0;
if (ckd_add(&last, phdr->p_offset, phdr->p_filesz)) return 0;
if (last > mapsize) return 0;
return (char *)elf + phdr->p_offset;
}