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/* Check for text relocations in DSOs.
Copyright (C) 2002, 2003, 2006 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contribute by Ulrich Drepper <drepper@redhat.com>. 2002.
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
<http://www.gnu.org/licenses/>. */
#include <byteswap.h>
#include <elf.h>
#include <endian.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef BITS
# define AB(name) _AB (name, BITS)
# define _AB(name, bits) __AB (name, bits)
# define __AB(name, bits) name##bits
# define E(name) _E (name, BITS)
# define _E(name, bits) __E (name, bits)
# define __E(name, bits) Elf##bits##_##name
# define SWAP(val) \
({ __typeof (val) __res; \
if (((ehdr.e_ident[EI_DATA] == ELFDATA2MSB \
&& BYTE_ORDER == LITTLE_ENDIAN) \
|| (ehdr.e_ident[EI_DATA] == ELFDATA2LSB \
&& BYTE_ORDER == BIG_ENDIAN)) \
&& sizeof (val) != 1) \
{ \
if (sizeof (val) == 2) \
__res = bswap_16 (val); \
else if (sizeof (val) == 4) \
__res = bswap_32 (val); \
else \
__res = bswap_64 (val); \
} \
else \
__res = (val); \
__res; })
static int
AB(handle_file) (const char *fname, int fd)
{
E(Ehdr) ehdr;
if (pread (fd, &ehdr, sizeof (ehdr), 0) != sizeof (ehdr))
{
read_error:
printf ("%s: read error: %m\n", fname);
return 1;
}
const size_t phnum = SWAP (ehdr.e_phnum);
const size_t phentsize = SWAP (ehdr.e_phentsize);
/* Read the program header. */
E(Phdr) *phdr = alloca (phentsize * phnum);
if (pread (fd, phdr, phentsize * phnum, SWAP (ehdr.e_phoff))
!= phentsize * phnum)
goto read_error;
/* Search for the PT_DYNAMIC entry. */
size_t cnt;
E(Phdr) *dynphdr = NULL;
for (cnt = 0; cnt < phnum; ++cnt)
if (SWAP (phdr[cnt].p_type) == PT_DYNAMIC)
dynphdr = &phdr[cnt];
else if (SWAP (phdr[cnt].p_type) == PT_LOAD
&& (SWAP (phdr[cnt].p_flags) & (PF_X | PF_W)) == (PF_X | PF_W))
{
printf ("%s: segment %zu is executable and writable\n",
fname, cnt);
#if !defined __sparc__ \
&& !defined __alpha__ \
&& (!defined __powerpc__ || defined __powerpc64__ || defined HAVE_PPC_SECURE_PLT)
/* sparc, sparc64, alpha and powerpc32 (the last one only when using
-mbss-plt) are expected to have PF_X | PF_W segment containing .plt
section, it is part of their ABI. It is bad security wise, nevertheless
this test shouldn't fail because of this. */
return 1;
#endif
}
if (dynphdr == NULL)
{
printf ("%s: no DYNAMIC segment found\n", fname);
return 1;
}
/* Read the dynamic segment. */
size_t pmemsz = SWAP(dynphdr->p_memsz);
E(Dyn) *dyn = alloca (pmemsz);
if (pread (fd, dyn, pmemsz, SWAP(dynphdr->p_offset)) != pmemsz)
goto read_error;
/* Search for an DT_TEXTREL entry of DT_FLAGS with the DF_TEXTREL
bit set. */
for (cnt = 0; (cnt + 1) * sizeof (E(Dyn)) - 1 < pmemsz; ++cnt)
{
unsigned int tag = SWAP (dyn[cnt].d_tag);
if (tag == DT_NULL)
/* We reached the end. */
break;
if (tag == DT_TEXTREL
|| (tag == DT_FLAGS
&& (SWAP (dyn[cnt].d_un.d_val) & DF_TEXTREL) != 0))
{
/* Urgh! The DSO has text relocations. */
printf ("%s: text relocations used\n", fname);
return 1;
}
}
printf ("%s: OK\n", fname);
return 0;
}
# undef BITS
#else
# define BITS 32
# include "check-textrel.c"
# define BITS 64
# include "check-textrel.c"
static int
handle_file (const char *fname)
{
int fd = open (fname, O_RDONLY);
if (fd == -1)
{
printf ("cannot open %s: %m\n", fname);
return 1;
}
/* Read was is supposed to be the ELF header. Read the initial
bytes to determine whether this is a 32 or 64 bit file. */
char ident[EI_NIDENT];
if (read (fd, ident, EI_NIDENT) != EI_NIDENT)
{
printf ("%s: read error: %m\n", fname);
close (fd);
return 1;
}
if (memcmp (&ident[EI_MAG0], ELFMAG, SELFMAG) != 0)
{
printf ("%s: not an ELF file\n", fname);
close (fd);
return 1;
}
int result;
if (ident[EI_CLASS] == ELFCLASS64)
result = handle_file64 (fname, fd);
else
result = handle_file32 (fname, fd);
close (fd);
return result;
}
int
main (int argc, char *argv[])
{
int cnt;
int result = 0;
for (cnt = 1; cnt < argc; ++cnt)
result |= handle_file (argv[cnt]);
return result;
}
#endif
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