int elfu_mCheck(ElfuElf *me)
{
size_t numSecs;
ElfuScn **sortedSecs;
size_t i;
sortedSecs = elfu_mScnSortedByOffset(me, &numSecs);
if (!sortedSecs) {
return -1;
}
/* Check for overlapping sections */
for (i = 0; i < numSecs - 1; i++) {
if (sortedSecs[i]->shdr.sh_offset + SCNFILESIZE(&sortedSecs[i]->shdr)
> sortedSecs[i+1]->shdr.sh_offset) {
ELFU_WARN("elfu_check: Found overlapping sections: %s and %s.\n",
elfu_mScnName(me, sortedSecs[i]),
elfu_mScnName(me, sortedSecs[i+1]));
}
}
/* Check for sections overlapping with EHDR */
for (i = 0; i < numSecs; i++) {
if (sortedSecs[i]->shdr.sh_offset < me->ehdr.e_ehsize) {
ELFU_WARN("elfu_check: Found section overlapping with EHDR: %s.\n",
elfu_mScnName(me, sortedSecs[i]));
}
}
/* Check for sections overlapping with PHDRs */
for (i = 0; i < numSecs; i++) {
if (OVERLAPPING(sortedSecs[i]->shdr.sh_offset,
SCNFILESIZE(&sortedSecs[i]->shdr),
me->ehdr.e_phoff,
me->ehdr.e_phentsize * me->ehdr.e_phnum)) {
ELFU_WARN("elfu_check: Found section overlapping with PHDRs: %s.\n",
elfu_mScnName(me, sortedSecs[i]));
}
}
free(sortedSecs);
return 0;
}
int elfu_eCheck(Elf *e)
{
int elfclass;
GElf_Ehdr ehdr;
GElf_Phdr *phdrs = NULL;
GElf_Shdr *shdrs = NULL;
size_t i, j, numPhdr, numShdr;
int retval = 0;
assert(e);
elfclass = gelf_getclass(e);
if (elfclass == ELFCLASSNONE) {
ELFU_WARNELF("getclass");
goto ERROR;
}
if (!gelf_getehdr(e, &ehdr)) {
ELFU_WARNELF("gelf_getehdr");
goto ERROR;
}
if (ehdr.e_machine != EM_386 && ehdr.e_machine != EM_X86_64) {
ELFU_WARN("Sorry, only x86-32 and x86-64 ELF files are supported at the moment.\n");
goto ERROR;
}
if (elf_getphdrnum(e, &numPhdr)) {
ELFU_WARNELF("elf_getphdrnum");
goto ERROR;
}
if (elf_getshdrnum(e, &numShdr)) {
ELFU_WARNELF("elf_getshdrnum");
goto ERROR;
}
if (numPhdr > 0) {
phdrs = malloc(numPhdr * sizeof(GElf_Phdr));
if (!phdrs) {
ELFU_WARN("elfu_eCheck: malloc() failed for phdrs.\n");
goto ERROR;
}
/* Attempt to load all PHDRs at once to catch any errors early */
for (i = 0; i < numPhdr; i++) {
GElf_Phdr phdr;
if (gelf_getphdr(e, i, &phdr) != &phdr) {
ELFU_WARN("gelf_getphdr() failed for #%d: %s\n", i, elf_errmsg(-1));
goto ERROR;
}
phdrs[i] = phdr;
}
/* Check that LOAD PHDR memory ranges do not overlap, and that others
* are either fully contained in a LOAD range, or not at all. */
for (i = 0; i < numPhdr; i++) {
if (phdrs[i].p_type != PT_LOAD) {
continue;
}
for (j = 0; j < numPhdr; j++) {
if (j == i || phdrs[j].p_type != PT_LOAD) {
continue;
}
if (OVERLAPPING(phdrs[i].p_vaddr, phdrs[i].p_memsz,
phdrs[j].p_vaddr, phdrs[j].p_memsz)) {
if (phdrs[j].p_type == PT_LOAD) {
ELFU_WARN("elfu_eCheck: Found LOAD PHDRs that overlap in memory.\n");
goto ERROR;
} else if (!FULLY_OVERLAPPING(phdrs[i].p_vaddr, phdrs[i].p_memsz,
phdrs[j].p_vaddr, phdrs[j].p_memsz)) {
ELFU_WARN("elfu_eCheck: PHDRs %d and %d partially overlap in memory.\n", i, j);
goto ERROR;
}
}
}
}
}
if (numShdr > 1) {
/* SHDRs should not overlap with PHDRs. */
if (OVERLAPPING(ehdr.e_shoff, numShdr * ehdr.e_shentsize,
ehdr.e_phoff, numPhdr * ehdr.e_phentsize)) {
ELFU_WARN("elfu_eCheck: SHDRs overlap with PHDRs.\n");
goto ERROR;
}
shdrs = malloc(numShdr * sizeof(GElf_Shdr));
if (!shdrs) {
ELFU_WARN("elfu_eCheck: malloc() failed for shdrs.\n");
goto ERROR;
}
/* Attempt to load all SHDRs at once to catch any errors early */
for (i = 1; i < numShdr; i++) {
Elf_Scn *scn;
GElf_Shdr shdr;
scn = elf_getscn(e, i);
if (!scn) {
ELFU_WARN("elf_getscn() failed for #%d: %s\n", i, elf_errmsg(-1));
}
if (gelf_getshdr(scn, &shdr) != &shdr) {
ELFU_WARNELF("gelf_getshdr");
goto ERROR;
}
shdrs[i] = shdr;
}
/* Check that Section memory ranges do not overlap.
* NB: Section 0 is reserved and thus ignored. */
for (i = 1; i < numShdr; i++) {
/* Section should not overlap with EHDR. */
if (shdrs[i].sh_offset == 0) {
ELFU_WARN("elfu_eCheck: Section %d overlaps with EHDR.\n", i);
goto ERROR;
}
/* Section should not overlap with PHDRs. */
if (OVERLAPPING(shdrs[i].sh_offset, SCNFILESIZE(&shdrs[i]),
ehdr.e_phoff, numPhdr * ehdr.e_phentsize)) {
ELFU_WARN("elfu_eCheck: Section %d overlaps with PHDR.\n", i);
goto ERROR;
}
/* Section should not overlap with SHDRs. */
if (OVERLAPPING(shdrs[i].sh_offset, SCNFILESIZE(&shdrs[i]),
ehdr.e_shoff, numShdr * ehdr.e_shentsize)) {
ELFU_WARN("elfu_eCheck: Section %d overlaps with SHDRs.\n", i);
goto ERROR;
}
for (j = 1; j < numShdr; j++) {
if (j == i) {
continue;
}
/* Sections must not overlap in memory. */
if (shdrs[i].sh_addr != 0
&& shdrs[j].sh_addr != 0
&& OVERLAPPING(shdrs[i].sh_addr, shdrs[i].sh_size,
shdrs[j].sh_addr, shdrs[j].sh_size)) {
ELFU_WARN("elfu_eCheck: Sections %d and %d overlap in memory.\n", i, j);
goto ERROR;
}
/* Sections must not overlap in file. */
if (OVERLAPPING(shdrs[i].sh_offset, SCNFILESIZE(&shdrs[i]),
shdrs[j].sh_offset, SCNFILESIZE(&shdrs[j]))) {
ELFU_WARN("elfu_eCheck: Sections %d and %d overlap in file.\n", i, j);
goto ERROR;
}
/* We may not have more than one symbol table */
if (shdrs[i].sh_type == SHT_SYMTAB && shdrs[j].sh_type == SHT_SYMTAB) {
ELFU_WARN("elfu_eCheck: Found more than one SYMTAB section.\n");
goto ERROR;
}
/* We may not have more than one dynamic symbol table */
if (shdrs[i].sh_type == SHT_DYNSYM && shdrs[j].sh_type == SHT_DYNSYM) {
ELFU_WARN("elfu_eCheck: Found more than one DYNSYM section.\n");
goto ERROR;
}
}
/* Section addr/offset should match parent PHDR.
* Find parent PHDR: */
for (j = 0; j < numPhdr; j++) {
if (PHDR_CONTAINS_SCN_IN_MEMORY(&phdrs[j], &shdrs[i])) {
GElf_Off shoff = phdrs[j].p_offset + (shdrs[i].sh_addr - phdrs[j].p_vaddr);
if ((shdrs[i].sh_offset != shoff && shdrs[i].sh_type != SHT_NOBITS)
|| !PHDR_CONTAINS_SCN_IN_FILE(&phdrs[j], &shdrs[i])) {
ELFU_WARN("elfu_eCheck: SHDR %d and PHDR %d report conflicting file/memory regions.\n", i, j);
goto ERROR;
}
}
}
/* sh_link members should not point to sections out of range. */
if (shdrs[i].sh_link >= numShdr) {
ELFU_WARN("elfu_eCheck: Bogus sh_link in SHDR %d.\n", i);
}
}
}
DONE:
if (phdrs) {
free(phdrs);
}
if (shdrs) {
free(shdrs);
}
return retval;
ERROR:
ELFU_WARN("elfu_eCheck: Errors found.\n");
retval = -1;
goto DONE;
}
