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/* Update p_align of the first PT_LOAD segment.
Copyright (C) 2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <stdio.h>
#include <stdbool.h>
#include <unistd.h>
#include <fcntl.h>
#include <link.h>
#include <error.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/mman.h>
const char *file_name;
static size_t update_p_align (size_t);
int
main (int argc, char ** argv)
{
if (argc != 2)
{
printf ("Usage: %s: file\n", argv[0]);
return 0;
}
file_name = argv[1];
struct stat statbuf;
int errno_saved;
if (stat (file_name, &statbuf) < 0)
error (1, errno, "%s: not exist", file_name);
ElfW(Ehdr) *ehdr;
if (statbuf.st_size < sizeof (*ehdr))
error (1, 0, "%s: too small", file_name);
int fd = open (file_name, O_RDWR);
if (fd < 0)
error (1, errno, "%s: can't open", file_name);
/* Map in the whole file. */
void *base = mmap (NULL, statbuf.st_size, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
if (base == MAP_FAILED)
{
errno_saved = errno;
close (fd);
error (1, errno_saved, "%s: failed to map", file_name);
}
ehdr = (ElfW(Ehdr) *) base;
if (ehdr->e_ident[EI_MAG0] != ELFMAG0
|| ehdr->e_ident[EI_MAG1] != ELFMAG1
|| ehdr->e_ident[EI_MAG2] != ELFMAG2
|| ehdr->e_ident[EI_MAG3] != ELFMAG3)
{
close (fd);
error (1, 0, "%s: bad ELF header", file_name);
}
if (ehdr->e_type != ET_DYN)
{
close (fd);
error (1, 0, "%s: not shared library", file_name);
}
bool unsupported_class = true;
switch (ehdr->e_ident[EI_CLASS])
{
default:
break;
case ELFCLASS32:
unsupported_class = __ELF_NATIVE_CLASS != 32;
break;
case ELFCLASS64:
unsupported_class = __ELF_NATIVE_CLASS != 64;
break;
}
if (unsupported_class)
{
close (fd);
error (1, 0, "%s: unsupported ELF class: %d",
file_name, ehdr->e_ident[EI_CLASS]);
}
size_t phdr_size = sizeof (ElfW(Phdr)) * ehdr->e_phentsize;
if (statbuf.st_size < (ehdr->e_phoff + phdr_size))
{
close (fd);
error (1, 0, "%s: too small", file_name);
}
ElfW(Phdr) *phdr = (ElfW(Phdr) *) (base + ehdr->e_phoff);
for (int i = 0; i < ehdr->e_phnum; i++, phdr++)
if (phdr->p_type == PT_LOAD)
{
/* Update p_align of the first PT_LOAD segment. */
phdr->p_align = update_p_align (phdr->p_align);
break;
}
munmap (base, statbuf.st_size);
close (fd);
return 0;
}
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