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pjs/tools/elf-dynstr-gc/elf-gc-dynstr.c

1083 строки
26 KiB
C
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/* elf_gc_dynst
*
* This is a program that removes unreferenced strings from the .dynstr
* section in ELF shared objects. It also shrinks the .dynstr section and
* relocates all symbols after it.
*
* This program was written and copyrighted by:
* Alexander Larsson <alla@lysator.liu.se>
*
*
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
* License for the specific language governing rights and limitations
* under the License.
*/
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <elf.h>
#include <glib.h>
Elf32_Ehdr *elf_header = NULL;
#define FILE_OFFSET(offset) ((unsigned char *)(elf_header) + (offset))
struct dynamic_symbol {
Elf32_Word old_index;
Elf32_Word new_index;
char *string;
};
GHashTable *used_dynamic_symbols = NULL;
/* Data is dynamic_symbols, hashes on old_index */
Elf32_Word hole_index;
Elf32_Word hole_end;
Elf32_Word hole_len;
Elf32_Addr hole_addr_start;
Elf32_Addr hole_addr_remap_start;
Elf32_Addr hole_addr_remap_end;
Elf32_Shdr *
elf_find_section_num(int section_index)
{
Elf32_Shdr *section;
Elf32_Word sectionsize;
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
sectionsize = elf_header->e_shentsize;
section = (Elf32_Shdr *)((char *)section + sectionsize*section_index);
return section;
}
Elf32_Shdr *
elf_find_section_named(char *name)
{
Elf32_Shdr *section;
Elf32_Shdr *strtab_section;
Elf32_Word sectionsize;
int numsections;
char *strtab;
int i = 0;
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
strtab_section = elf_find_section_num(elf_header->e_shstrndx);
strtab = (char *)FILE_OFFSET(strtab_section->sh_offset);
sectionsize = elf_header->e_shentsize;
numsections = elf_header->e_shnum;
for (i=0;i<numsections;i++) {
if (strcmp(&strtab[section->sh_name], name) == 0) {
return section;
}
section = (Elf32_Shdr *)((char *)section + sectionsize);
}
return NULL;
}
Elf32_Shdr *
elf_find_section(Elf32_Word sh_type)
{
Elf32_Shdr *section;
Elf32_Word sectionsize;
int numsections;
int i = 0;
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
sectionsize = elf_header->e_shentsize;
numsections = elf_header->e_shnum;
for (i=0;i<numsections;i++) {
if (section->sh_type == sh_type) {
return section;
}
section = (Elf32_Shdr *)((char *)section + sectionsize);
}
return NULL;
}
Elf32_Shdr *
elf_find_next_higher_section(Elf32_Word offset)
{
Elf32_Shdr *section;
Elf32_Shdr *higher;
Elf32_Word sectionsize;
int numsections;
int i = 0;
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
sectionsize = elf_header->e_shentsize;
numsections = elf_header->e_shnum;
higher = NULL;
for (i=0;i<numsections;i++) {
if (section->sh_offset >= offset) {
if (higher == NULL) {
higher = section;
} else if (section->sh_offset < higher->sh_offset) {
higher = section;
}
}
section = (Elf32_Shdr *)((char *)section + sectionsize);
}
return higher;
}
Elf32_Word
vma_to_offset(Elf32_Addr addr)
{
Elf32_Shdr *section;
Elf32_Shdr *higher;
Elf32_Word sectionsize;
int numsections;
int i = 0;
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
sectionsize = elf_header->e_shentsize;
numsections = elf_header->e_shnum;
higher = NULL;
for (i=0;i<numsections;i++) {
if ( (addr >= section->sh_addr) &&
(addr < section->sh_addr + section->sh_size) ) {
return section->sh_offset + (addr-section->sh_addr);
}
section = (Elf32_Shdr *)((char *)section + sectionsize);
}
fprintf(stderr, "Warning, unable to convert address %d (0x%x) to file offset\n",
addr, addr);
return 0;
}
void
find_segment_addr_min_max(Elf32_Word file_offset,
Elf32_Addr *start, Elf32_Addr *end)
{
Elf32_Phdr *segment;
Elf32_Word segmentsize;
int numsegments;
int i = 0;
segment = (Elf32_Phdr *)FILE_OFFSET(elf_header->e_phoff);
segmentsize = elf_header->e_phentsize;
numsegments = elf_header->e_phnum;
for (i=0;i<numsegments;i++) {
if ((file_offset >= segment->p_offset) &&
(file_offset < segment->p_offset + segment->p_filesz)) {
*start = segment->p_vaddr;
*end = segment->p_vaddr + segment->p_memsz;
return;
}
segment = (Elf32_Phdr *)((char *)segment + segmentsize);
}
fprintf(stderr, "Error: Couldn't find segment in find_segment_addr_min_max()\n");
}
void *
dynamic_find_tag(Elf32_Shdr *dynamic, Elf32_Sword d_tag)
{
int i;
Elf32_Dyn *element;
element = (Elf32_Dyn *)FILE_OFFSET(dynamic->sh_offset);
for (i=0; element[i].d_tag != DT_NULL; i++) {
if (element[i].d_tag = d_tag) {
return FILE_OFFSET(element[i].d_un.d_ptr);
}
}
return NULL;
}
Elf32_Word
fixup_offset(Elf32_Word offset)
{
if (offset >= hole_index) {
return offset - hole_len;
}
return offset;
}
Elf32_Word
fixup_size(Elf32_Word offset, Elf32_Word size)
{
/* Note: Doesn't handle the cases where the hole and the size intersect
partially. */
if ( (hole_index >= offset) &&
(hole_index < offset + size)){
return size - hole_len;
}
return size;
}
Elf32_Addr
fixup_addr(Elf32_Addr addr)
{
if (addr == 0)
return 0;
/*
if ( (addr < hole_addr_remap_start) ||
(addr >= hole_addr_remap_end))
return addr;
*/
if (addr >= hole_addr_start) {
return addr - hole_len;
}
return addr;
}
Elf32_Word
fixup_addr_size(Elf32_Addr addr, Elf32_Word size)
{
/* Note: Doesn't handle the cases where the hole and the size intersect
partially. */
/*
if ( (addr < hole_addr_remap_start) ||
(addr >= hole_addr_remap_end))
return size;
*/
if ( (hole_addr_start >= addr) &&
(hole_addr_start < addr + size)){
return size - hole_len;
}
return size;
}
void
possibly_add_string(int name_idx, const char *name)
{
struct dynamic_symbol *dynamic_symbol;
if (name_idx != 0) {
dynamic_symbol = g_hash_table_lookup(used_dynamic_symbols, (gpointer) name_idx);
if (dynamic_symbol == NULL) {
dynamic_symbol = g_new(struct dynamic_symbol, 1);
dynamic_symbol->old_index = name_idx;
dynamic_symbol->new_index = 0;
dynamic_symbol->string = g_strdup(name);
g_hash_table_insert(used_dynamic_symbols, (gpointer)name_idx, dynamic_symbol);
/*printf("added dynamic string: %s (%d)\n", dynamic_symbol->string, name_idx);*/
}
}
}
Elf32_Word
fixup_string(Elf32_Word old_idx)
{
struct dynamic_symbol *dynamic_symbol;
if (old_idx == 0)
return 0;
dynamic_symbol = g_hash_table_lookup(used_dynamic_symbols, (gpointer) old_idx);
if (dynamic_symbol == NULL) {
fprintf(stderr, "AAAAAAAAAAAARGH!? Unknown string found in fixup (index: %d)!\n", old_idx);
return 0;
}
return dynamic_symbol->new_index;
}
void
add_strings_from_dynsym(Elf32_Shdr *dynsym, char *strtab)
{
Elf32_Sym *symbol;
Elf32_Sym *symbol_end;
Elf32_Word entry_size;
symbol = (Elf32_Sym *)FILE_OFFSET(dynsym->sh_offset);
symbol_end = (Elf32_Sym *)FILE_OFFSET(dynsym->sh_offset + dynsym->sh_size);
entry_size = dynsym->sh_entsize;
while (symbol < symbol_end) {
int name_idx;
struct dynamic_symbol *dynamic_symbol;
name_idx = symbol->st_name;
possibly_add_string(name_idx, &strtab[name_idx]);
symbol = (Elf32_Sym *)((char *)symbol + entry_size);
}
}
void
fixup_strings_in_dynsym(Elf32_Shdr *dynsym)
{
Elf32_Sym *symbol;
Elf32_Sym *symbol_end;
Elf32_Word entry_size;
symbol = (Elf32_Sym *)FILE_OFFSET(dynsym->sh_offset);
symbol_end = (Elf32_Sym *)FILE_OFFSET(dynsym->sh_offset + dynsym->sh_size);
entry_size = dynsym->sh_entsize;
while (symbol < symbol_end) {
int name_idx;
struct dynamic_symbol *dynamic_symbol;
symbol->st_name = fixup_string(symbol->st_name);
symbol = (Elf32_Sym *)((char *)symbol + entry_size);
}
}
void
add_strings_from_dynamic(Elf32_Shdr *dynamic, char *strtab)
{
int i;
int name_idx;
Elf32_Dyn *element;
Elf32_Word entry_size;
entry_size = dynamic->sh_entsize;
element = (Elf32_Dyn *)FILE_OFFSET(dynamic->sh_offset);
while (element->d_tag != DT_NULL) {
switch(element->d_tag) {
case DT_NEEDED:
case DT_SONAME:
case DT_RPATH:
name_idx = element->d_un.d_val;
/*if (name_idx) printf("d_tag: %d\n", element->d_tag);*/
possibly_add_string(name_idx, &strtab[name_idx]);
break;
default:
/*printf("unhandled d_tag: %d (0x%x)\n", element->d_tag, element->d_tag);*/
}
element = (Elf32_Dyn *)((char *)element + entry_size);
}
}
void
fixup_strings_in_dynamic(Elf32_Shdr *dynamic)
{
int i;
int name_idx;
Elf32_Dyn *element;
Elf32_Word entry_size;
entry_size = dynamic->sh_entsize;
element = (Elf32_Dyn *)FILE_OFFSET(dynamic->sh_offset);
while (element->d_tag != DT_NULL) {
switch(element->d_tag) {
case DT_NEEDED:
case DT_SONAME:
case DT_RPATH:
element->d_un.d_val = fixup_string(element->d_un.d_val);
break;
default:
/*printf("unhandled d_tag: %d (0x%x)\n", element->d_tag, element->d_tag);*/
}
element = (Elf32_Dyn *)((char *)element + entry_size);
}
}
void
add_strings_from_ver_d(Elf32_Shdr *ver_d, char *strtab)
{
Elf32_Verdaux *veraux;
Elf32_Verdef *verdef;
int num_aux;
int name_idx;
int i;
int cont;
verdef = (Elf32_Verdef *)FILE_OFFSET(ver_d->sh_offset);
do {
num_aux = verdef->vd_cnt;
veraux = (Elf32_Verdaux *)((char *)verdef + verdef->vd_aux);
for (i=0; i<num_aux; i++) {
name_idx = veraux->vda_name;
possibly_add_string(name_idx, &strtab[name_idx]);
veraux = (Elf32_Verdaux *)((char *)veraux + veraux->vda_next);
}
cont = verdef->vd_next != 0;
verdef = (Elf32_Verdef *)((char *)verdef + verdef->vd_next);
} while (cont);
}
void
fixup_strings_in_ver_d(Elf32_Shdr *ver_d)
{
Elf32_Verdaux *veraux;
Elf32_Verdef *verdef;
int num_aux;
int name_idx;
int i;
int cont;
verdef = (Elf32_Verdef *)FILE_OFFSET(ver_d->sh_offset);
do {
num_aux = verdef->vd_cnt;
veraux = (Elf32_Verdaux *)((char *)verdef + verdef->vd_aux);
for (i=0; i<num_aux; i++) {
veraux->vda_name = fixup_string(veraux->vda_name);
veraux = (Elf32_Verdaux *)((char *)veraux + veraux->vda_next);
}
cont = verdef->vd_next != 0;
verdef = (Elf32_Verdef *)((char *)verdef + verdef->vd_next);
} while (cont);
}
void
add_strings_from_ver_r(Elf32_Shdr *ver_r, char *strtab)
{
Elf32_Vernaux *veraux;
Elf32_Verneed *verneed;
int num_aux;
int name_idx;
int i;
int cont;
verneed = (Elf32_Verneed *)FILE_OFFSET(ver_r->sh_offset);
do {
name_idx = verneed->vn_file;
possibly_add_string(name_idx, &strtab[name_idx]);
num_aux = verneed->vn_cnt;
veraux = (Elf32_Vernaux *)((char *)verneed + verneed->vn_aux);
for (i=0; i<num_aux; i++) {
name_idx = veraux->vna_name;
possibly_add_string(name_idx, &strtab[name_idx]);
veraux = (Elf32_Vernaux *)((char *)veraux + veraux->vna_next);
}
cont = verneed->vn_next != 0;
verneed = (Elf32_Verneed *)((char *)verneed + verneed->vn_next);
} while (cont);
}
void
fixup_strings_in_ver_r(Elf32_Shdr *ver_r)
{
Elf32_Vernaux *veraux;
Elf32_Verneed *verneed;
int num_aux;
int name_idx;
int i;
int cont;
verneed = (Elf32_Verneed *)FILE_OFFSET(ver_r->sh_offset);
do {
verneed->vn_file = fixup_string(verneed->vn_file);
num_aux = verneed->vn_cnt;
veraux = (Elf32_Vernaux *)((char *)verneed + verneed->vn_aux);
for (i=0; i<num_aux; i++) {
veraux->vna_name = fixup_string(veraux->vna_name);
veraux = (Elf32_Vernaux *)((char *)veraux + veraux->vna_next);
}
cont = verneed->vn_next != 0;
verneed = (Elf32_Verneed *)((char *)verneed + verneed->vn_next);
} while (cont);
}
gboolean sum_size(gpointer key,
struct dynamic_symbol *sym,
int *size)
{
*size += strlen(sym->string) + 1;
return 1;
}
struct index_n_dynstr {
int index;
char *dynstr;
};
gboolean output_string(gpointer key,
struct dynamic_symbol *sym,
struct index_n_dynstr *x)
{
sym->new_index = x->index;
memcpy(x->dynstr + x->index, sym->string, strlen(sym->string) + 1);
x->index += strlen(sym->string) + 1;
return 1;
}
char *
generate_new_dynstr(Elf32_Word *size_out)
{
int size;
char *new_dynstr;
struct index_n_dynstr x;
size = 1; /* first a zero */
g_hash_table_foreach (used_dynamic_symbols,
(GHFunc)sum_size,
&size);
new_dynstr = g_malloc(size);
new_dynstr[0] = 0;
x.index = 1;
x.dynstr = new_dynstr;
g_hash_table_foreach (used_dynamic_symbols,
(GHFunc)output_string,
&x);
*size_out = size;
return new_dynstr;
}
void
remap_sections(void)
{
Elf32_Shdr *section;
Elf32_Word sectionsize;
int numsections;
int i = 0;
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
sectionsize = elf_header->e_shentsize;
numsections = elf_header->e_shnum;
for (i=0;i<numsections;i++) {
section->sh_size = fixup_size(section->sh_offset, section->sh_size);
section->sh_offset = fixup_offset(section->sh_offset);
section->sh_addr = fixup_addr(section->sh_addr);
section = (Elf32_Shdr *)((char *)section + sectionsize);
}
}
void
remap_segments(void)
{
Elf32_Phdr *segment;
Elf32_Word segmentsize;
int numsegments;
int i = 0;
segment = (Elf32_Phdr *)FILE_OFFSET(elf_header->e_phoff);
segmentsize = elf_header->e_phentsize;
numsegments = elf_header->e_phnum;
for (i=0;i<numsegments;i++) {
segment->p_filesz = fixup_size(segment->p_offset, segment->p_filesz);
segment->p_offset = fixup_offset(segment->p_offset);
segment->p_memsz = fixup_addr_size(segment->p_vaddr, segment->p_memsz);
segment->p_vaddr = fixup_addr(segment->p_vaddr);
segment->p_paddr = segment->p_vaddr;
segment = (Elf32_Phdr *)((char *)segment + segmentsize);
}
}
void
remap_elf_header(void)
{
elf_header->e_phoff = fixup_offset(elf_header->e_phoff);
elf_header->e_shoff = fixup_offset(elf_header->e_shoff);
elf_header->e_entry = fixup_addr(elf_header->e_entry);
}
void
remap_symtab(Elf32_Shdr *symtab)
{
Elf32_Sym *symbol;
Elf32_Sym *symbol_end;
Elf32_Word entry_size;
symbol = (Elf32_Sym *)FILE_OFFSET(symtab->sh_offset);
symbol_end = (Elf32_Sym *)FILE_OFFSET(symtab->sh_offset + symtab->sh_size);
entry_size = symtab->sh_entsize;
while (symbol < symbol_end) {
symbol->st_value = fixup_addr(symbol->st_value);
symbol = (Elf32_Sym *)((char *)symbol + entry_size);
}
}
/* Ugly global variables: */
Elf32_Addr got_data_start = 0;
Elf32_Addr got_data_end = 0;
void
remap_rel_section(Elf32_Rel *rel, Elf32_Word size, Elf32_Word entry_size)
{
Elf32_Rel *rel_end;
Elf32_Word offset;
Elf32_Addr *addr;
rel_end = (Elf32_Rel *)((char *)rel + size);
while (rel < rel_end) {
if (ELF32_R_TYPE(rel->r_info) == R_386_RELATIVE) {
/* We need to relocate the data this is pointing to too. */
offset = vma_to_offset(rel->r_offset);
if ( (offset >= got_data_start) &&
(offset < got_data_end) ) {
/*printf("RELATIVE REL in .rel.got, skipping\n");*/
} else {
addr = (Elf32_Addr *)FILE_OFFSET(offset);
*addr = fixup_addr(*addr);
}
}
rel->r_offset = fixup_addr(rel->r_offset);
rel = (Elf32_Rel *)((char *)rel + entry_size);
}
}
void
remap_rela_section(Elf32_Rela *rela, Elf32_Word size, Elf32_Word entry_size)
{
Elf32_Rela *rela_end;
Elf32_Addr *addr;
Elf32_Word offset;
rela_end = (Elf32_Rela *)((char *)rela + size);
while (rela < rela_end) {
if (ELF32_R_TYPE(rela->r_info) == R_386_RELATIVE) {
/* We need to relocate the data this is pointing to too. */
offset = vma_to_offset(rela->r_offset);
if ( (offset >= got_data_start) &&
(offset < got_data_end) ) {
/*printf("RELATIVE RELA in .rel.got, skipping\n");*/
} else {
addr = (Elf32_Addr *)FILE_OFFSET(offset);
*addr = fixup_addr(*addr);
}
}
rela->r_offset = fixup_addr(rela->r_offset);
rela = (Elf32_Rela *)((char *)rela + entry_size);
}
}
void
remap_reloc(void)
{
Elf32_Shdr *section;
Elf32_Word sectionsize;
Elf32_Word offset;
int numsections;
int i = 0;
/* This is old code. relocations are now handled from remap_dynamic() */
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
sectionsize = elf_header->e_shentsize;
numsections = elf_header->e_shnum;
for (i=0;i<numsections;i++) {
if (section->sh_type == SHT_REL) {
Elf32_Rel *rel;
rel = (Elf32_Rel *)FILE_OFFSET(section->sh_offset);
remap_rel_section(rel, section->sh_size, section->sh_entsize);
} else if (section->sh_type == SHT_RELA) {
Elf32_Rela *rel;
rel = (Elf32_Rela *)FILE_OFFSET(section->sh_offset);
remap_rela_section(rel, section->sh_size, section->sh_entsize);
}
section = (Elf32_Shdr *)((char *)section + sectionsize);
}
}
void
remap_i386_got(void)
{
Elf32_Shdr *got_section;
Elf32_Addr *got;
Elf32_Addr *got_end;
Elf32_Word entry_size;
got_section = elf_find_section_named(".got");
if (got_section == NULL) {
fprintf(stderr, "Warning, no .got section\n");
return;
}
got_data_start = got_section->sh_offset;
got_data_end = got_section->sh_offset + got_section->sh_size;
got = (Elf32_Addr *)FILE_OFFSET(got_section->sh_offset);
got_end = (Elf32_Addr *)FILE_OFFSET(got_section->sh_offset + got_section->sh_size);
entry_size = got_section->sh_entsize;
*got= fixup_addr(*got); /* Pointer to .dynamic */
got = (Elf32_Addr *)((char *)got + 2*entry_size); /* Skip two reserved entries. */
while (got < got_end) {
if (*got != 0)
*got= fixup_addr(*got);
got = (Elf32_Addr *)((char *)got + entry_size);
}
}
Elf32_Word
get_dynamic_val(Elf32_Shdr *dynamic, Elf32_Sword tag)
{
Elf32_Dyn *element;
Elf32_Word entry_size;
entry_size = dynamic->sh_entsize;
element = (Elf32_Dyn *)FILE_OFFSET(dynamic->sh_offset);
while (element->d_tag != DT_NULL) {
if (element->d_tag == tag) {
return element->d_un.d_val;
}
element = (Elf32_Dyn *)((char *)element + entry_size);
}
return 0;
}
void
remap_dynamic(Elf32_Shdr *dynamic, Elf32_Word new_dynstr_size)
{
Elf32_Dyn *element;
Elf32_Word entry_size;
Elf32_Word rel_size;
Elf32_Word rel_entry_size;
Elf32_Rel *rel;
Elf32_Rela *rela;
entry_size = dynamic->sh_entsize;
element = (Elf32_Dyn *)FILE_OFFSET(dynamic->sh_offset);
while (element->d_tag != DT_NULL) {
switch(element->d_tag) {
case DT_STRSZ:
element->d_un.d_val = new_dynstr_size;
break;
case DT_PLTGOT:
case DT_HASH:
case DT_STRTAB:
case DT_INIT:
case DT_FINI:
case DT_VERDEF:
case DT_VERNEED:
case DT_VERSYM:
element->d_un.d_ptr = fixup_addr(element->d_un.d_ptr);
break;
case DT_JMPREL:
rel_size = get_dynamic_val(dynamic, DT_PLTRELSZ);
if (get_dynamic_val(dynamic, DT_PLTREL) == DT_REL) {
rel_entry_size = get_dynamic_val(dynamic, DT_RELENT);
rel = (Elf32_Rel *)FILE_OFFSET(vma_to_offset(element->d_un.d_ptr));
remap_rel_section(rel, rel_size, rel_entry_size);
} else {
rel_entry_size = get_dynamic_val(dynamic, DT_RELAENT);
rela = (Elf32_Rela *)FILE_OFFSET(vma_to_offset(element->d_un.d_ptr));
remap_rela_section(rela, rel_size, rel_entry_size);
}
element->d_un.d_ptr = fixup_addr(element->d_un.d_ptr);
break;
case DT_REL:
rel_size = get_dynamic_val(dynamic, DT_RELSZ);
rel_entry_size = get_dynamic_val(dynamic, DT_RELENT);
rel = (Elf32_Rel *)FILE_OFFSET(vma_to_offset(element->d_un.d_ptr));
remap_rel_section(rel, rel_size, rel_entry_size);
element->d_un.d_ptr = fixup_addr(element->d_un.d_ptr);
break;
case DT_RELA:
rel_size = get_dynamic_val(dynamic, DT_RELASZ);
rel_entry_size = get_dynamic_val(dynamic, DT_RELAENT);
rela = (Elf32_Rela *)FILE_OFFSET(vma_to_offset(element->d_un.d_ptr));
remap_rela_section(rela, rel_size, rel_entry_size);
element->d_un.d_ptr = fixup_addr(element->d_un.d_ptr);
break;
default:
/*printf("unhandled d_tag: %d (0x%x)\n", element->d_tag, element->d_tag);*/
}
element = (Elf32_Dyn *)((char *)element + entry_size);
}
}
align_hole(Elf32_Word *start, Elf32_Word *end)
{
Elf32_Word len;
Elf32_Word align;
Elf32_Shdr *section;
Elf32_Word sectionsize;
int numsections;
int i = 0;
int unaligned;
len = *end - *start;
align = 0;
sectionsize = elf_header->e_shentsize;
numsections = elf_header->e_shnum;
do {
section = (Elf32_Shdr *)FILE_OFFSET(elf_header->e_shoff);
unaligned = 0;
for (i=0;i<numsections;i++) {
if ( (section->sh_addralign > 1) &&
( (section->sh_offset-len + align)%section->sh_addralign != 0) ) {
unaligned = 1;
}
section = (Elf32_Shdr *)((char *)section + sectionsize);
}
if (unaligned) {
align++;
}
} while (unaligned);
*start += align;
}
int
main(int argc, char *argv[])
{
int fd;
unsigned char *mapping;
Elf32_Word size;
struct stat statbuf;
Elf32_Shdr *dynamic;
Elf32_Shdr *dynsym;
Elf32_Shdr *symtab;
Elf32_Shdr *dynstr;
Elf32_Shdr *hash;
Elf32_Shdr *higher_section;
int dynstr_index;
Elf32_Shdr *ver_r;
Elf32_Shdr *ver_d;
char *dynstr_data;
char *new_dynstr;
Elf32_Word old_dynstr_size;
Elf32_Word new_dynstr_size;
if (argc != 2) {
fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
return 1;
}
fd = open(argv[1], O_RDWR);
if (fd == -1) {
fprintf(stderr, "Cannot open file %s\n", argv[1]);
return 1;
}
if (fstat(fd, &statbuf) == -1) {
fprintf(stderr, "Cannot stat file %s\n", argv[1]);
return 1;
}
size = statbuf.st_size;
mapping = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (mapping == (unsigned char *)-1) {
fprintf(stderr, "Cannot mmap file %s\n", argv[1]);
return 1;
}
used_dynamic_symbols = g_hash_table_new(g_direct_hash, g_direct_equal);
elf_header = (Elf32_Ehdr *)mapping;
if (strncmp((void *)elf_header, ELFMAG, SELFMAG)!=0) {
fprintf(stderr, "Not an ELF file\n");
return 1;
}
if (elf_header->e_ident[EI_VERSION] != EV_CURRENT) {
fprintf(stderr, "Wrong ELF file version\n");
return 1;
}
if (elf_header->e_ident[EI_CLASS] != ELFCLASS32) {
fprintf(stderr, "Only 32bit ELF files supported\n");
return 1;
}
if ( (elf_header->e_ident[EI_DATA] != ELFDATA2LSB) ||
(elf_header->e_machine != EM_386) ) {
fprintf(stderr, "Only intel LSB binaries are supported right now\n");
return 1;
}
if (elf_header->e_type != ET_DYN) {
fprintf(stderr, "Not an ELF shared object\n");
return 1;
}
dynamic = elf_find_section(SHT_DYNAMIC);
dynsym = elf_find_section(SHT_DYNSYM);
symtab = elf_find_section(SHT_SYMTAB);
dynstr_index = dynsym->sh_link;
dynstr = elf_find_section_num(dynstr_index);
dynstr_data = FILE_OFFSET(dynstr->sh_offset);
old_dynstr_size = dynstr->sh_size;
ver_d = elf_find_section(SHT_GNU_verdef);
ver_r = elf_find_section(SHT_GNU_verneed);
hash = elf_find_section(SHT_HASH);
/* Generate hash table with all used strings: */
add_strings_from_dynsym(dynsym, dynstr_data);
add_strings_from_dynamic(dynamic, dynstr_data);
if (ver_d && (ver_d->sh_link == dynstr_index))
add_strings_from_ver_d(ver_d, dynstr_data);
if (ver_r && (ver_r->sh_link == dynstr_index))
add_strings_from_ver_r(ver_r, dynstr_data);
/* Generate new dynstr section from the used strings hashtable: */
new_dynstr = generate_new_dynstr(&new_dynstr_size);
/*
printf("New dynstr size: %d\n", new_dynstr_size);
printf("Old dynstr size: %d\n", old_dynstr_size);
*/
if (new_dynstr_size >= old_dynstr_size) {
fprintf(stderr, "Couldn't GC any strings, exiting.\n");
return 0;
}
/* Fixup all references: */
fixup_strings_in_dynsym(dynsym);
fixup_strings_in_dynamic(dynamic);
if (ver_d && (ver_d->sh_link == dynstr_index))
fixup_strings_in_ver_d(ver_d);
if (ver_r && (ver_r->sh_link == dynstr_index))
fixup_strings_in_ver_r(ver_r);
/* Copy over the new dynstr: */
memcpy(dynstr_data, new_dynstr, new_dynstr_size);
memset(dynstr_data + new_dynstr_size, ' ', old_dynstr_size-new_dynstr_size);
/* Compact the dynstr section and the file: */
/* 1. Set up the data for the fixup_offset() function: */
hole_index = dynstr->sh_offset + new_dynstr_size;
higher_section = elf_find_next_higher_section(hole_index);
hole_end = higher_section->sh_offset;
align_hole(&hole_index, &hole_end);
hole_len = hole_end - hole_index;
hole_addr_start = hole_index; /* TODO: Fix this to something better */
find_segment_addr_min_max(dynstr->sh_offset,
&hole_addr_remap_start, &hole_addr_remap_end);
/*
printf("Hole remap: 0x%lx - 0x%lx\n", hole_addr_remap_start, hole_addr_remap_end);
printf("hole: %lu - %lu (%lu bytes)\n", hole_index, hole_end, hole_len);
printf("hole: 0x%lx - 0x%lx (0x%lx bytes)\n", hole_index, hole_end, hole_len);
*/
/* 2. Change all section and segment sizes and offsets: */
remap_symtab(dynsym);
if (symtab)
remap_symtab(symtab);
remap_i386_got();
remap_dynamic(dynamic, new_dynstr_size);
remap_sections(); /* After this line the section headers are wrong */
remap_segments();
remap_elf_header();
/* 3. Do the real compacting. */
memmove(mapping + hole_index,
mapping + hole_index + hole_len,
size - (hole_index + hole_len));
munmap(mapping, size);
ftruncate(fd, size - hole_len);
close(fd);
}
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