diff options
Diffstat (limited to 'src/modelops/relocate.c')
-rw-r--r-- | src/modelops/relocate.c | 139 |
1 files changed, 4 insertions, 135 deletions
diff --git a/src/modelops/relocate.c b/src/modelops/relocate.c index f04b7c0..90a319b 100644 --- a/src/modelops/relocate.c +++ b/src/modelops/relocate.c @@ -4,139 +4,8 @@ #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; @@ -156,7 +25,7 @@ void elfu_mRelocate(ElfuElf *metarget, ElfuScn *mstarget, ElfuScn *msrt) 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"); @@ -176,7 +45,7 @@ void elfu_mRelocate(ElfuElf *metarget, ElfuScn *mstarget, ElfuScn *msrt) 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: |