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/* This file is part of centaur.
*
* centaur is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License 2 as
* published by the Free Software Foundation.
* centaur 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 General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with centaur. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libelfu/libelfu.h>
#include <string.h>
static void* subFindByAddr(ElfuElf *me, ElfuScn *ms, void *aux1, void *aux2)
{
GElf_Addr a = *(GElf_Addr*)aux1;
if (OVERLAPPING(ms->shdr.sh_addr, ms->shdr.sh_size, a, 1)) {
return ms;
}
/* Continue */
return NULL;
}
void elfu_mDetour(ElfuElf *me, GElf_Addr from, GElf_Addr to)
{
ElfuScn *ms;
GElf_Word scnoffset;
unsigned char detourcode[] = {0xe9, 0xfc, 0xff, 0xff, 0xff};
ms = elfu_mScnForall(me, subFindByAddr, &from, NULL);
if (!ms) {
ELFU_WARN("mDetour: Cannot find address %x in any section.\n",
(unsigned)from);
return;
}
if (ms->shdr.sh_type != SHT_PROGBITS) {
ELFU_WARN("mDetour: Cannot detour in non-PROGBITS section %s.\n",
elfu_mScnName(me, ms));
return;
}
scnoffset = from - ms->shdr.sh_addr;
if (ms->shdr.sh_size - scnoffset < 5) {
ELFU_WARN("mDetour: Not enough space to insert a detour.\n");
return;
}
ELFU_DEBUG("mDetour: Detouring at address %x in section %s to %x.\n",
(unsigned)from,
elfu_mScnName(me, ms),
(unsigned)to);
*(Elf32_Word*)(detourcode + 1) = to - from - 5;
memcpy(ms->databuf + scnoffset, detourcode, 5);
}
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