#include <assert.h>
#include <sys/types.h>
-#include <gelf.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
* 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)
+GElf_Xword elfu_mInsertSpaceBefore(ElfuElf *me, GElf_Off off, GElf_Xword size)
{
ElfuScn *ms;
ElfuPhdr *mp;
assert(me);
- // TODO: Take p_align into account
+ /* Round up size to 4096 bytes to keep page alignment on x86 when
+ * remapping existing data to lower addresses. */
+ size += (4096 - (size % 4096)) % 4096;
+ // TODO: Find alignment size by checking p_align in PHDRs
/* Move SHDRs and PHDRs */
if (me->ehdr.e_shoff >= off) {
/* mp->phdr.p_offset < off */
if (off < end) {
- /* Mark this as a modified area */
-
/* Insertion in the middle of PHDR, so let it span the new data */
mp->phdr.p_filesz += size;
mp->phdr.p_memsz += 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_mInsertSpaceAfter(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;
+}
+
+
+
+
+
+/* Update cross-references */
+static void shiftSections(ElfuElf *me, ElfuScn *first)
+{
+ ElfuScn *ms = first;
+ size_t firstIndex = elfu_mScnIndex(me, first);
+
+ do {
+ if (ms == me->shstrtab) {
+ me->ehdr.e_shstrndx++;
+ }
+
+ ms = CIRCLEQ_LOOP_NEXT(&me->scnList, ms, elem);
+ } while (ms != CIRCLEQ_FIRST(&me->scnList));
+
+ CIRCLEQ_FOREACH(ms, &me->scnList, elem) {
+ switch (ms->shdr.sh_type) {
+ case SHT_REL:
+ case SHT_RELA:
+ if (ms->shdr.sh_info >= firstIndex) {
+ ms->shdr.sh_info++;
+ }
+ case SHT_DYNAMIC:
+ case SHT_HASH:
+ case SHT_SYMTAB:
+ case SHT_DYNSYM:
+ case SHT_GNU_versym:
+ case SHT_GNU_verdef:
+ case SHT_GNU_verneed:
+ if (ms->shdr.sh_link >= firstIndex) {
+ ms->shdr.sh_link++;
+ }
+ }
+ }
+}
+
+
+/*
+ * Insert a section into an ELF model, /before/ a given other section
+ */
+void elfu_mInsertScnInChainBefore(ElfuElf *me, ElfuScn *oldscn, ElfuScn *newscn)
+{
+ assert(me);
+ assert(oldscn);
+ assert(newscn);
+
+ shiftSections(me, oldscn);
+
+ CIRCLEQ_INSERT_BEFORE(&me->scnList, oldscn, newscn, elem);
+}
+
+
+/*
+ * Insert a section into an ELF model, /after/ a given other section
+ */
+void elfu_mInsertScnInChainAfter(ElfuElf *me, ElfuScn *oldscn, ElfuScn *newscn)
+{
+ assert(me);
+ assert(oldscn);
+ assert(newscn);
+
+ if (oldscn != CIRCLEQ_LAST(&me->scnList)) {
+ shiftSections(me, CIRCLEQ_NEXT(oldscn, elem));
+ }
+
+ CIRCLEQ_INSERT_AFTER(&me->scnList, oldscn, newscn, elem);
+}
projects / centaur.git / blobdiff