#include <libelfu/libelfu.h>
-static void* subFindByName(ElfuElf *me, ElfuScn *ms, void *aux1, void *aux2)
-{
- char *name = (char*)aux1;
- (void)aux2;
-
- if (elfu_mScnName(me, ms)) {
- if (!strcmp(elfu_mScnName(me, ms), name)) {
- return ms;
- }
- }
-
- /* Continue */
- return NULL;
-}
-
-/* Hazard a guess where a function may be found in the PLT */
-static GElf_Word pltLookupVal(ElfuElf *metarget, char *name)
-{
- ElfuScn *relplt;
- ElfuScn *plt;
- ElfuRel *rel;
- GElf_Word j;
-
- relplt = elfu_mScnForall(metarget, subFindByName, ".rel.plt", NULL);
- if (!relplt) {
- ELFU_WARN("dynsymLookupVal: Could not find .rel.plt section in destination ELF.\n");
- return 0;
- }
-
- plt = elfu_mScnForall(metarget, subFindByName, ".plt", NULL);
- if (!plt) {
- ELFU_WARN("dynsymLookupVal: Could not find .plt section in destination ELF.\n");
- return 0;
- }
-
-
- /* Look up name. If the j-th entry in .rel.plt has the name we are
- * looking for, we assume that the (j+1)-th entry in .plt is machine
- * code to jump to the function.
- * Your mileage may vary, but it works on my GNU binaries. */
- assert(relplt->linkptr);
- j = 0;
- CIRCLEQ_FOREACH(rel, &relplt->reltab.rels, elem) {
- GElf_Word i;
- ElfuSym *sym;
- char *symname;
-
- j++;
-
- /* We only consider runtime relocations for functions.
- * Technically, these relocations write the functions' addresses
- * to the GOT, not the PLT, after the dynamic linker has found
- * them. */
- if ((metarget->elfclass == ELFCLASS32 && rel->type != R_386_JMP_SLOT)
- || (metarget->elfclass == ELFCLASS64 && rel->type != R_X86_64_JUMP_SLOT)) {
- continue;
- }
-
- /* Get the (rel->sym)-th symbol from the symbol table that
- * .rel.plt points to. */
- sym = CIRCLEQ_FIRST(&relplt->linkptr->symtab.syms);
- for (i = 1; i < rel->sym; i++) {
- sym = CIRCLEQ_NEXT(sym, elem);
- }
-
- symname = ELFU_SYMSTR(relplt->linkptr, sym->name);
- if (!strcmp(symname, name)) {
- /* If this is the symbol we are looking for, then in an x86 binary
- * the jump to the dynamic symbol is probably at offset (j * 16)
- * from the start of the PLT, where j is the PLT entry and 16 is
- * the number of bytes the machine code in a PLT entry take. */
- GElf_Addr addr = plt->shdr.sh_addr + (16 * j);
- ELFU_DEBUG("dynsymLookupVal: Guessing symbol '%s' is in destination memory at %jx (PLT entry #%d).\n", name, addr, j);
- return addr;
- }
- }
-
- ELFU_WARN("dynsymLookupVal: Could not find symbol '%s' in destination ELF.\n", name);
-
- return 0;
-}
-
-
-static GElf_Word symtabLookupVal(ElfuElf *metarget, ElfuScn *msst, GElf_Word entry)
-{
- GElf_Word i;
- ElfuSym *sym;
- char *symname;
-
- assert(metarget);
- assert(msst);
- assert(entry > 0);
- assert(!CIRCLEQ_EMPTY(&msst->symtab.syms));
-
- sym = CIRCLEQ_FIRST(&msst->symtab.syms);
- for (i = 1; i < entry; i++) {
- sym = CIRCLEQ_NEXT(sym, elem);
- }
- symname = ELFU_SYMSTR(msst, sym->name);
-
- switch (sym->type) {
- case STT_NOTYPE:
- case STT_OBJECT:
- case STT_FUNC:
- if (sym->scnptr) {
- ElfuScn *newscn = elfu_mScnByOldscn(metarget, sym->scnptr);
- assert(newscn);
- return newscn->shdr.sh_addr + sym->value;
- } else if (sym->shndx == SHN_UNDEF) {
- /* Look the symbol up in .rel.plt. If it cannot be found there then
- * .rel.dyn may need to be expanded with a COPY relocation so the
- * dynamic linker fixes up the (TODO). */
- return pltLookupVal(metarget, symname);
- } else if (sym->shndx == SHN_ABS) {
- return sym->value;
- } else {
- ELFU_WARN("symtabLookupVal: Symbol binding COMMON is not supported, using 0.\n");
- return 0;
- }
- break;
- case STT_SECTION:
- assert(sym->scnptr);
- assert(elfu_mScnByOldscn(metarget, sym->scnptr));
- return elfu_mScnByOldscn(metarget, sym->scnptr)->shdr.sh_addr;
- case STT_FILE:
- ELFU_WARN("symtabLookupVal: Symbol type FILE is not supported, using 0.\n");
- return 0;
- default:
- ELFU_WARN("symtabLookupVal: Unknown symbol type %d for %s.\n", sym->type, symname);
- return 0;
- }
-}
-
+/* Apply relocation information from section *msrt to data in
+ * section *mstarget (which is stored in *metarget). */
void elfu_mRelocate(ElfuElf *metarget, ElfuScn *mstarget, ElfuScn *msrt)
{
ElfuRel *rel;
if (metarget->elfclass == ELFCLASS32) {
Elf32_Word a32 = rel->addendUsed ? rel->addend : *dest32;
Elf32_Addr p32 = mstarget->shdr.sh_addr + rel->offset;
- Elf32_Addr s32 = symtabLookupVal(metarget, msrt->linkptr, rel->sym);
+ Elf32_Addr s32 = elfu_mSymtabLookupVal(metarget, msrt->linkptr, rel->sym);
switch(rel->type) {
case R_386_NONE:
ELFU_DEBUG("Skipping relocation: R_386_NONE\n");
assert(rel->addendUsed);
Elf64_Word a64 = rel->addend;
Elf64_Addr p64 = mstarget->shdr.sh_addr + rel->offset;
- Elf64_Addr s64 = symtabLookupVal(metarget, msrt->linkptr, rel->sym);
+ Elf64_Addr s64 = elfu_mSymtabLookupVal(metarget, msrt->linkptr, rel->sym);
switch(rel->type) {
case R_X86_64_NONE:
projects / centaur.git / blobdiff