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-rw-r--r--include/libelfu/modelops.h5
-rw-r--r--include/libelfu/types.h1
-rw-r--r--src/modelops/fromFile.c14
-rw-r--r--src/modelops/reladd.c101
-rw-r--r--src/modelops/relocate.c32
-rw-r--r--src/modelops/toFile.c2
6 files changed, 126 insertions, 29 deletions
diff --git a/include/libelfu/modelops.h b/include/libelfu/modelops.h
index 3daef52..eee7c13 100644
--- a/include/libelfu/modelops.h
+++ b/include/libelfu/modelops.h
@@ -7,6 +7,9 @@
#include <libelfu/types.h>
+#define ELFU_SYMSTR(symtabscn, off) (((char*)(symtabscn)->linkptr->data.d_buf) + (off))
+
+
size_t elfu_mPhdrCount(ElfuElf *me);
void elfu_mPhdrUpdateChildOffsets(ElfuPhdr *mp);
@@ -42,6 +45,6 @@ void elfu_mDumpElf(ElfuElf *me);
ElfuElf* elfu_mFromElf(Elf *e);
void elfu_mToElf(ElfuElf *me, Elf *e);
-void elfu_mReladd(ElfuElf *me, ElfuElf *mrel);
+void elfu_mReladd(ElfuElf *me, const ElfuElf *mrel);
#endif
diff --git a/include/libelfu/types.h b/include/libelfu/types.h
index 37e25fa..e4dd26c 100644
--- a/include/libelfu/types.h
+++ b/include/libelfu/types.h
@@ -9,7 +9,6 @@
typedef struct ElfuSym {
GElf_Word name;
- char *nameptr;
GElf_Addr value;
GElf_Word size;
diff --git a/src/modelops/fromFile.c b/src/modelops/fromFile.c
index c46dd6c..28ecb85 100644
--- a/src/modelops/fromFile.c
+++ b/src/modelops/fromFile.c
@@ -5,17 +5,6 @@
#include <libelfu/libelfu.h>
-static char* symstr(ElfuScn *symtab, size_t off)
-{
- assert(symtab);
- assert(symtab->linkptr);
- assert(symtab->linkptr->data.d_buf);
- assert(off < symtab->linkptr->data.d_size);
-
- return &(((char*)symtab->linkptr->data.d_buf)[off]);
-}
-
-
static void parseSymtab32(ElfuScn *ms, ElfuScn**origScnArr)
{
size_t i;
@@ -31,19 +20,18 @@ static void parseSymtab32(ElfuScn *ms, ElfuScn**origScnArr)
assert(sym);
sym->name = cursym->st_name;
- sym->nameptr = symstr(ms, cursym->st_name);
sym->value = cursym->st_value;
sym->size = cursym->st_size;
sym->bind = ELF32_ST_BIND(cursym->st_info);
sym->type = ELF32_ST_TYPE(cursym->st_info);
sym->other = cursym->st_other;
+ sym->shndx = cursym->st_shndx;
switch (cursym->st_shndx) {
case SHN_UNDEF:
case SHN_ABS:
case SHN_COMMON:
sym->scnptr = NULL;
- sym->shndx = cursym->st_shndx;
break;
default:
sym->scnptr = origScnArr[cursym->st_shndx - 1];
diff --git a/src/modelops/reladd.c b/src/modelops/reladd.c
index 2fdfb48..936c0bd 100644
--- a/src/modelops/reladd.c
+++ b/src/modelops/reladd.c
@@ -213,16 +213,111 @@ static void* subScnAdd2(ElfuElf *mrel, ElfuScn *ms, void *aux1, void *aux2)
}
-void elfu_mReladd(ElfuElf *me, ElfuElf *mrel)
+
+static void insertSymClone(ElfuElf *me, const ElfuScn *oldmsst, const ElfuSym *oldsym)
+{
+ GElf_Xword newsize;
+ void *newbuf;
+ ElfuScn *newscn = NULL;
+ ElfuSym *newsym;
+ char *oldsymname;
+
+ assert(me);
+ assert(oldmsst);
+ assert(oldsym);
+
+ /* If the old symbol pointed to a section, find its clone in the target */
+ if (oldsym->scnptr) {
+ newscn = elfu_mScnByOldscn(me, oldsym->scnptr);
+
+ /* If we didn't copy the section referenced, we won't
+ * copy this symbol either */
+ if (!newscn) {
+ return;
+ }
+ }
+
+ // TODO: Allocate symtab if none present
+ assert(me->symtab);
+
+ /* Allocate memory for the cloned symbol */
+ newsym = malloc(sizeof(*newsym));
+ if (!newsym) {
+ ELFU_WARN("insertSymClone: malloc() failed for newsym.\n");
+ goto ERROR;
+ }
+
+ oldsymname = ELFU_SYMSTR(oldmsst, oldsym->name);
+
+ /* Expand .strtab, append symbol name, link newsym to it */
+ newsize = me->symtab->linkptr->shdr.sh_size + strlen(oldsymname) + 1;
+ newbuf = realloc(me->symtab->linkptr->data.d_buf, newsize);
+ if (!newbuf) {
+ ELFU_WARN("insertSymClone: realloc() failed for strtab.\n");
+ goto ERROR;
+ }
+
+ me->symtab->linkptr->data.d_buf = newbuf;
+
+ newsym->name = me->symtab->linkptr->shdr.sh_size;
+
+ strcpy(newbuf + newsym->name, oldsymname);
+
+ me->symtab->linkptr->data.d_size = newsize;
+ me->symtab->linkptr->shdr.sh_size = newsize;
+
+
+ /* Copy all other fields */
+ newsym->scnptr = newscn;
+ newsym->shndx = oldsym->shndx; /* If scnptr == NULL, this becomes relevant */
+ newsym->bind = oldsym->bind;
+ newsym->other = oldsym->other;
+ newsym->size = oldsym->size;
+ newsym->type = oldsym->type;
+ newsym->value = oldsym->value;
+
+ /* In executables, symbol addresses need to be in memory */
+ if (newscn) {
+ newsym->value += newscn->shdr.sh_addr;
+ }
+
+ /* Insert symbol */
+ CIRCLEQ_INSERT_TAIL(&me->symtab->symtab.syms, newsym, elem);
+
+ return;
+
+ ERROR:
+ if (newsym) {
+ free(newsym);
+ }
+}
+
+static void mergeSymtab(ElfuElf *me, const ElfuElf *mrel)
+{
+ ElfuSym *sym;
+
+ assert(me);
+ assert(mrel);
+
+ CIRCLEQ_FOREACH(sym, &mrel->symtab->symtab.syms, elem) {
+ insertSymClone(me, mrel->symtab, sym);
+ }
+}
+
+
+
+void elfu_mReladd(ElfuElf *me, const ElfuElf *mrel)
{
assert(me);
assert(mrel);
/* For each section in object file, guess how to insert it */
- elfu_mScnForall(mrel, subScnAdd1, me, NULL);
+ elfu_mScnForall((ElfuElf*)mrel, subScnAdd1, me, NULL);
+
+ mergeSymtab(me, mrel);
/* Do relocations and other stuff */
- elfu_mScnForall(mrel, subScnAdd2, me, NULL);
+ elfu_mScnForall((ElfuElf*)mrel, subScnAdd2, me, NULL);
/* Re-layout to accommodate new contents */
elfu_mLayoutAuto(me);
diff --git a/src/modelops/relocate.c b/src/modelops/relocate.c
index 0bd8ee8..ea84937 100644
--- a/src/modelops/relocate.c
+++ b/src/modelops/relocate.c
@@ -40,29 +40,36 @@ static GElf_Word pltLookupVal(ElfuElf *metarget, char *name)
}
- /* Look up name */
+ /* 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 (rel->type != R_386_JMP_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);
}
- if (!sym->nameptr) {
- continue;
- }
-
- if (!strcmp(sym->nameptr, name)) {
+ 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
@@ -83,6 +90,7 @@ static GElf_Word symtabLookupVal(ElfuElf *metarget, ElfuScn *msst, GElf_Word ent
{
GElf_Word i;
ElfuSym *sym;
+ char *symname;
assert(metarget);
assert(msst);
@@ -93,19 +101,21 @@ static GElf_Word symtabLookupVal(ElfuElf *metarget, ElfuScn *msst, GElf_Word ent
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) {
- assert(elfu_mScnByOldscn(metarget, sym->scnptr));
- return elfu_mScnByOldscn(metarget, sym->scnptr)->shdr.sh_addr + sym->value;
+ 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 .dyn.plt. If it cannot be found there then
+ /* 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, sym->nameptr);
+ return pltLookupVal(metarget, symname);
} else if (sym->shndx == SHN_ABS) {
return sym->value;
} else {
@@ -121,7 +131,7 @@ static GElf_Word symtabLookupVal(ElfuElf *metarget, ElfuScn *msst, GElf_Word ent
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, sym->nameptr);
+ ELFU_WARN("symtabLookupVal: Unknown symbol type %d for %s.\n", sym->type, symname);
return 0;
}
}
diff --git a/src/modelops/toFile.c b/src/modelops/toFile.c
index 66109df..434130e 100644
--- a/src/modelops/toFile.c
+++ b/src/modelops/toFile.c
@@ -11,6 +11,7 @@ static void flattenSymtab(ElfuElf *me)
elfu_mLayoutAuto(me);
+ /* Update section indexes and count symbols */
CIRCLEQ_FOREACH(sym, &me->symtab->symtab.syms, elem) {
if (sym->scnptr) {
sym->shndx = elfu_mScnIndex(me, sym->scnptr);
@@ -19,6 +20,7 @@ static void flattenSymtab(ElfuElf *me)
numsyms++;
}
+ /* Copy symbols to elfclass-specific format */
if (me->elfclass == ELFCLASS32) {
size_t newsize = (numsyms + 1) * sizeof(Elf32_Sym);
size_t i;
generated by cgit v1.2.3 (git 2.39.1) at 2024-10-16 13:27:52 +0000