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#include <assert.h>
#include <sys/types.h>
#include <libelf/gelf.h>
#include <libelfu/libelfu.h>
// TODO: Take p_align into account
/*
* Insert space at a given position in the file by moving everything
* after it towards the end of the file, and everything before it
* towards lower memory regions where it is mapped.
*
* off must not be in the middle of any data structure, such as
* PHDRs, SHDRs, or sections. Behaviour is undefined if it is.
*
* PHDRs will be patched such that everything AFTER off is mapped to
* the same address in memory, and everything BEFORE it is shifted to
* lower addresses, making space for the new data in-between.
*/
GElf_Xword elfu_mInsertBefore(ElfuElf *me, GElf_Off off, GElf_Xword size)
{
ElfuScn *ms;
ElfuPhdr *mp;
assert(me);
/* Move SHDRs and PHDRs */
if (me->ehdr.e_shoff >= off) {
me->ehdr.e_shoff += size;
}
if (me->ehdr.e_phoff >= off) {
me->ehdr.e_phoff += size;
}
/* Patch PHDRs to include new data */
CIRCLEQ_FOREACH(mp, &me->phdrList, elem) {
GElf_Off end = mp->phdr.p_offset + mp->phdr.p_filesz;
if (mp->phdr.p_offset >= off) {
/* Insertion before PHDR's content, so it's just shifted */
mp->phdr.p_offset += size;
} else {
/* mp->phdr.p_offset < off */
if (off < end) {
/* Insertion in the middle of PHDR, so let it span the new data */
mp->phdr.p_filesz += size;
mp->phdr.p_memsz += size;
mp->phdr.p_vaddr -= size;
mp->phdr.p_paddr -= size;
} else {
/* Insertion after PHDR's content, so it may need to be
remapped. This will happen in a second pass.
*/
}
}
}
/* For each LOAD header, find clashing headers that need to be
remapped to lower memory areas.
*/
CIRCLEQ_FOREACH(mp, &me->phdrList, elem) {
if (mp->phdr.p_type == PT_LOAD) {
ElfuPhdr *mp2;
CIRCLEQ_FOREACH(mp2, &me->phdrList, elem) {
if (mp2->phdr.p_type != PT_LOAD
&& mp2->phdr.p_offset + mp2->phdr.p_filesz <= off) {
/* The PHDR ends in the file before the injection site */
GElf_Off vend1 = mp->phdr.p_vaddr + mp->phdr.p_memsz;
GElf_Off pend1 = mp->phdr.p_paddr + mp->phdr.p_memsz;
GElf_Off vend2 = mp2->phdr.p_vaddr + mp2->phdr.p_memsz;
GElf_Off pend2 = mp2->phdr.p_paddr + mp2->phdr.p_memsz;
/* If mp and mp2 now overlap in memory */
if ((mp2->phdr.p_vaddr < vend1 && vend2 > mp->phdr.p_vaddr)
|| (mp2->phdr.p_paddr < pend1 && pend2 > mp->phdr.p_paddr)) {
/* Move mp2 down in memory, as mp has been resized.
Maintaining the relative offset between them is the best
guess at maintaining consistency.
*/
mp2->phdr.p_vaddr -= size;
mp2->phdr.p_paddr -= size;
}
}
}
}
}
/* Move the sections themselves */
CIRCLEQ_FOREACH(ms, &me->scnList, elem) {
if (ms->shdr.sh_offset >= off) {
ms->shdr.sh_offset += size;
} else {
/* sh_offset < off */
/* If this was in a LOAD segment, it has been adjusted there
and this synchronises it.
If not, it doesn't matter anyway.
*/
ms->shdr.sh_addr -= size;
}
}
return size;
}
/*
* Insert space at a given position in the file by moving everything
* after it towards the end of the file, and towards higher memory
* regions where it is mapped.
*
* off must not be in the middle of any data structure, such as
* PHDRs, SHDRs, or sections. Behaviour is undefined if it is.
*
* PHDRs will be patched such that everything AFTER off is shifted to
* higher addresses, making space for the new data in-between.
*
* CAUTION: This also moves NOBITS sections. If such are present,
* use mExpandNobits() first and then inject at the end of
* the expansion site.
*/
GElf_Xword elfu_mInsertAfter(ElfuElf *me, GElf_Off off, GElf_Xword size)
{
ElfuScn *ms;
ElfuPhdr *mp;
assert(me);
/* Move SHDRs and PHDRs */
if (me->ehdr.e_shoff >= off) {
me->ehdr.e_shoff += size;
}
if (me->ehdr.e_phoff >= off) {
me->ehdr.e_phoff += size;
}
/* Patch PHDRs to include new data */
CIRCLEQ_FOREACH(mp, &me->phdrList, elem) {
GElf_Off end = mp->phdr.p_offset + mp->phdr.p_filesz;
if (mp->phdr.p_offset >= off) {
/* Insertion before PHDR's content, so it's shifted. */
mp->phdr.p_offset += size;
/* It may also need to be remapped. See second pass below. */
} else {
/* mp->phdr.p_offset < off */
if (off < end) {
/* Insertion in the middle of PHDR, so let it span the new data */
mp->phdr.p_filesz += size;
mp->phdr.p_memsz += size;
} else {
/* Insertion after PHDR's content. Nothing to do. */
}
}
}
/* For each LOAD header, find clashing headers that need to be
remapped to higher memory areas.
*/
CIRCLEQ_FOREACH(mp, &me->phdrList, elem) {
if (mp->phdr.p_type == PT_LOAD) {
ElfuPhdr *mp2;
CIRCLEQ_FOREACH(mp2, &me->phdrList, elem) {
if (mp2->phdr.p_type != PT_LOAD
&& mp2->phdr.p_offset + mp2->phdr.p_filesz > off) {
/* The PHDR now ends in the file after the injection site */
GElf_Off vend1 = mp->phdr.p_vaddr + mp->phdr.p_memsz;
GElf_Off pend1 = mp->phdr.p_paddr + mp->phdr.p_memsz;
GElf_Off vend2 = mp2->phdr.p_vaddr + mp2->phdr.p_memsz;
GElf_Off pend2 = mp2->phdr.p_paddr + mp2->phdr.p_memsz;
/* If mp and mp2 now overlap in memory */
if ((mp2->phdr.p_vaddr < vend1 && vend2 > mp->phdr.p_vaddr)
|| (mp2->phdr.p_paddr < pend1 && pend2 > mp->phdr.p_paddr)) {
/* Move mp2 up in memory, as mp has been resized.
Maintaining the relative offset between them is the best
guess at maintaining consistency.
*/
mp2->phdr.p_vaddr += size;
mp2->phdr.p_paddr += size;
}
}
}
}
}
/* Move the sections themselves */
CIRCLEQ_FOREACH(ms, &me->scnList, elem) {
if (ms->shdr.sh_offset >= off) {
ms->shdr.sh_offset += size;
/* If this was in a LOAD segment, it has been adjusted there
and this synchronises it.
If not, it doesn't matter anyway.
*/
ms->shdr.sh_addr += size;
}
}
return size;
}
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