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#include <assert.h>
#include <stdlib.h>
#include <sys/types.h>
#include <libelf/gelf.h>
#include <libelfu/libelfu.h>
typedef enum Destsegment {
DS_UNKNOWN,
DS_TEXT,
DS_DATA,
} Destsegment;
static Destsegment destsegment(ElfuScn *ms)
{
if (!(ms->shdr.sh_flags & SHF_ALLOC)) {
return DS_UNKNOWN;
}
if (!(ms->shdr.sh_flags & SHF_WRITE)
&& (ms->shdr.sh_flags & SHF_EXECINSTR)) {
return DS_TEXT;
} else if ((ms->shdr.sh_flags & SHF_WRITE)
&& !(ms->shdr.sh_flags & SHF_EXECINSTR)) {
return DS_DATA;
}
return DS_UNKNOWN;
}
static ElfuScn* insertSection(ElfuElf *me, ElfuElf *mrel, ElfuScn *ms)
{
ElfuPhdr *mp;
ElfuPhdr *first = NULL;
ElfuPhdr *last = NULL;
ElfuScn *newscn = NULL;
ElfuPhdr *injAnchor;
int searchForCode = 0;
switch (destsegment(ms)) {
case DS_TEXT:
searchForCode = 1;
case DS_DATA:
newscn = elfu_mCloneScn(ms);
if (!newscn) {
return NULL;
}
/* Find first and last LOAD PHDRs. */
CIRCLEQ_FOREACH(mp, &me->phdrList, elem) {
if (mp->phdr.p_type != PT_LOAD) {
continue;
}
if (!first || mp->phdr.p_vaddr < first->phdr.p_vaddr) {
first = mp;
}
if (!last || mp->phdr.p_vaddr > last->phdr.p_vaddr) {
/* No need to check p_memsz as segments may not overlap in memory. */
last = mp;
}
}
if (searchForCode) {
if ((first->phdr.p_flags & PF_X) && !(first->phdr.p_flags & PF_W)) {
injAnchor = first;
} else if ((last->phdr.p_flags & PF_X) && !(last->phdr.p_flags & PF_W)) {
injAnchor = last;
} else {
injAnchor = NULL;
}
} else {
if ((first->phdr.p_flags & PF_W) && !(first->phdr.p_flags & PF_X)) {
injAnchor = first;
} else if ((last->phdr.p_flags & PF_W) && !(last->phdr.p_flags & PF_X)) {
injAnchor = last;
} else {
injAnchor = NULL;
}
}
if (!injAnchor) {
ELFU_WARN("insertSection: Could not find injection anchor.\n"
" It has to be the first or last segment in the memory image.\n");
} else {
GElf_Off injOffset;
/* If the anchor is first or last, insert before or after */
if (injAnchor == first) {
/* Find first section and inject before it */
ElfuScn *firstScn = elfu_mScnFirstInSegment(me, injAnchor);
if (!firstScn) {
ELFU_WARN("insertSection: mScnFirstInSegment failed.\n");
// TODO: Error handling
} else {
injOffset = firstScn->shdr.sh_offset;
ELFU_INFO("Inserting %s at offset 0x%jx...\n",
elfu_mScnName(mrel, ms),
injOffset);
/* Make space */
elfu_mInsertSpaceBefore(me, injOffset, ms->shdr.sh_size);
/* Update memory offset */
newscn->shdr.sh_addr = injAnchor->phdr.p_vaddr;
/* Insert into chain of sections */
elfu_mInsertScnInChainBefore(me, firstScn, newscn);
}
} else {
/* Find last section and inject after it */
ElfuScn *lastScn = elfu_mScnLastInSegment(me, injAnchor);
if (!lastScn) {
ELFU_WARN("insertSection: mScnLastInSegment failed.\n");
// TODO: Error handling
} else {
injOffset = lastScn->shdr.sh_offset + elfu_gScnSizeFile(&lastScn->shdr);
ELFU_INFO("Expanding at offset 0x%jx...\n",
injOffset);
/* Expand NOBITS sections at injection site, if any. */
elfu_mExpandNobits(me, injOffset);
/* Recalculate injOffset in case we expanded a NOBITS section */
lastScn = elfu_mScnLastInSegment(me, injAnchor);
injOffset = lastScn->shdr.sh_offset + elfu_gScnSizeFile(&lastScn->shdr);
ELFU_INFO("Inserting %s at offset 0x%jx...\n",
elfu_mScnName(mrel, ms),
injOffset);
/* Make space */
elfu_mInsertSpaceAfter(me, injOffset, ms->shdr.sh_size);
/* Update memory offset */
newscn->shdr.sh_addr = injAnchor->phdr.p_vaddr + (injOffset - injAnchor->phdr.p_offset);
/* Insert into chain of sections */
elfu_mInsertScnInChainAfter(me, lastScn, newscn);
}
}
/* Update file offset in new section BEFORE we do anything else */
newscn->shdr.sh_offset = injOffset;
/* Inject name */
// TODO
newscn->shdr.sh_name = 0;
// TODO: Relocate
return newscn;
}
break;
case DS_UNKNOWN:
ELFU_WARN("insertSection: Don't know where to insert ' %s with flags %jd (type %d).\n",
elfu_mScnName(mrel, ms),
ms->shdr.sh_flags,
ms->shdr.sh_type);
default:
ELFU_WARN("insertSection: Skipping section %s with flags %jd (type %d).\n",
elfu_mScnName(mrel, ms),
ms->shdr.sh_flags,
ms->shdr.sh_type);
return NULL;
}
if (newscn) {
// TODO: Destroy newscn
}
return NULL;
}
void elfu_mReladd(ElfuElf *me, ElfuElf *mrel)
{
ElfuScn *ms;
assert(me);
assert(mrel);
/* For each section in object file, guess how to insert it */
CIRCLEQ_FOREACH(ms, &mrel->scnList, elem) {
ElfuScn *newscn;
switch(ms->shdr.sh_type) {
case SHT_NULL: /* 0 */
continue;
case SHT_PROGBITS: /* 1 */
/* Find a place where it belongs and shove it in. */
newscn = insertSection(me, mrel, ms);
if (!newscn) {
ELFU_WARN("mReladd: Could not insert section %s (type %d), skipping.\n",
elfu_mScnName(mrel, ms),
ms->shdr.sh_type);
}
break;
case SHT_SYMTAB: /* 2 */
case SHT_DYNSYM: /* 11 */
/* Merge with the existing table. Take care of string tables also. */
case SHT_STRTAB: /* 3 */
/* May have to be merged with the existing string table for
* the symbol table. */
case SHT_RELA: /* 4 */
case SHT_REL: /* 9 */
/* Possibly append this in memory to the section model
* that it describes. */
case SHT_NOBITS: /* 8 */
/* Expand this to SHT_PROGBITS, then insert as such. */
case SHT_HASH: /* 5 */
case SHT_DYNAMIC: /* 6 */
case SHT_SHLIB: /* 10 */
case SHT_SYMTAB_SHNDX: /* 18 */
/* Don't care about the next ones yet. I've never seen
* them and they can be implemented when necessary. */
case SHT_NOTE: /* 7 */
case SHT_INIT_ARRAY: /* 14 */
case SHT_FINI_ARRAY: /* 15 */
case SHT_PREINIT_ARRAY: /* 16 */
case SHT_GROUP: /* 17 */
case SHT_NUM: /* 19 */
default:
ELFU_WARN("mReladd: Skipping section %s (type %d).\n",
elfu_mScnName(mrel, ms),
ms->shdr.sh_type);
}
}
}
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