/*
* cook.c - read and translate ELF files.
* Copyright (C) 1995 - 2006 Michael Riepe
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <private.h>
#ifndef lint
static const char rcsid[] = "@(#) $Id: cook.c,v 1.28 2006/07/07 22:15:50 michael Exp $";
#endif /* lint */
const Elf_Scn _elf_scn_init = INIT_SCN;
const Scn_Data _elf_data_init = INIT_DATA;
Elf_Type
_elf_scn_type(unsigned t) {
switch (t) {
case SHT_DYNAMIC: return ELF_T_DYN;
case SHT_DYNSYM: return ELF_T_SYM;
case SHT_HASH: return ELF_T_WORD;
case SHT_REL: return ELF_T_REL;
case SHT_RELA: return ELF_T_RELA;
case SHT_SYMTAB: return ELF_T_SYM;
case SHT_SYMTAB_SHNDX: return ELF_T_WORD; /* XXX: really? */
#if __LIBELF_SYMBOL_VERSIONS
#if __LIBELF_SUN_SYMBOL_VERSIONS
case SHT_SUNW_verdef: return ELF_T_VDEF;
case SHT_SUNW_verneed: return ELF_T_VNEED;
case SHT_SUNW_versym: return ELF_T_HALF;
#else /* __LIBELF_SUN_SYMBOL_VERSIONS */
case SHT_GNU_verdef: return ELF_T_VDEF;
case SHT_GNU_verneed: return ELF_T_VNEED;
case SHT_GNU_versym: return ELF_T_HALF;
#endif /* __LIBELF_SUN_SYMBOL_VERSIONS */
#endif /* __LIBELF_SYMBOL_VERSIONS */
}
return ELF_T_BYTE;
}
/*
* Check for overflow on 32-bit systems
*/
#define overflow(a,b,t) (sizeof(a) < sizeof(t) && (t)(a) != (b))
#define truncerr(t) ((t)==ELF_T_EHDR?ERROR_TRUNC_EHDR: \
((t)==ELF_T_PHDR?ERROR_TRUNC_PHDR: \
ERROR_INTERNAL))
#define memerr(t) ((t)==ELF_T_EHDR?ERROR_MEM_EHDR: \
((t)==ELF_T_PHDR?ERROR_MEM_PHDR: \
ERROR_INTERNAL))
Elf_Data*
_elf_xlatetom(const Elf *elf, Elf_Data *dst, const Elf_Data *src) {
if (elf->e_class == ELFCLASS32) {
return elf32_xlatetom(dst, src, elf->e_encoding);
}
#if __LIBELF64
else if (elf->e_class == ELFCLASS64) {
return elf64_xlatetom(dst, src, elf->e_encoding);
}
#endif /* __LIBELF64 */
seterr(ERROR_UNIMPLEMENTED);
return NULL;
}
static char*
_elf_item(void *buf, Elf *elf, Elf_Type type, size_t off) {
Elf_Data src, dst;
elf_assert(valid_type(type));
if (off < 0 || off > elf->e_size) {
seterr(ERROR_OUTSIDE);
return NULL;
}
src.d_type = type;
src.d_version = elf->e_version;
src.d_size = _fsize(elf->e_class, src.d_version, type);
elf_assert(src.d_size);
if ((elf->e_size - off) < src.d_size) {
seterr(truncerr(type));
return NULL;
}
dst.d_version = _elf_version;
dst.d_size = _msize(elf->e_class, dst.d_version, type);
elf_assert(dst.d_size);
if (!(dst.d_buf = buf) && !(dst.d_buf = malloc(dst.d_size))) {
seterr(memerr(type));
return NULL;
}
elf_assert(elf->e_data);
if (elf->e_rawdata) {
src.d_buf = elf->e_rawdata + off;
}
else {
src.d_buf = elf->e_data + off;
}
if (_elf_xlatetom(elf, &dst, &src)) {
return (char*)dst.d_buf;
}
if (dst.d_buf != buf) {
free(dst.d_buf);
}
return NULL;
}
static int
_elf_cook_phdr(Elf *elf) {
size_t num, off, entsz;
if (elf->e_class == ELFCLASS32) {
num = ((Elf32_Ehdr*)elf->e_ehdr)->e_phnum;
off = ((Elf32_Ehdr*)elf->e_ehdr)->e_phoff;
entsz = ((Elf32_Ehdr*)elf->e_ehdr)->e_phentsize;
}
#if __LIBELF64
else if (elf->e_class == ELFCLASS64) {
num = ((Elf64_Ehdr*)elf->e_ehdr)->e_phnum;
off = ((Elf64_Ehdr*)elf->e_ehdr)->e_phoff;
entsz = ((Elf64_Ehdr*)elf->e_ehdr)->e_phentsize;
/*
* Check for overflow on 32-bit systems
*/
if (overflow(off, ((Elf64_Ehdr*)elf->e_ehdr)->e_phoff, Elf64_Off)) {
seterr(ERROR_OUTSIDE);
return 0;
}
}
#endif /* __LIBELF64 */
else {
seterr(ERROR_UNIMPLEMENTED);
return 0;
}
if (off) {
Elf_Scn *scn;
size_t size;
unsigned i;
char *p;
if (num == PN_XNUM) {
/*
* Overflow in ehdr->e_phnum.
* Get real value from first SHDR.
*/
if (!(scn = elf->e_scn_1)) {
seterr(ERROR_NOSUCHSCN);
return 0;
}
if (elf->e_class == ELFCLASS32) {
num = scn->s_shdr32.sh_info;
}
#if __LIBELF64
else if (elf->e_class == ELFCLASS64) {
num = scn->s_shdr64.sh_info;
}
#endif /* __LIBELF64 */
/* we already had this
else {
seterr(ERROR_UNIMPLEMENTED);
return 0;
}
*/
}
size = _fsize(elf->e_class, elf->e_version, ELF_T_PHDR);
elf_assert(size);
#if ENABLE_EXTENDED_FORMAT
if (entsz < size) {
#else /* ENABLE_EXTENDED_FORMAT */
if (entsz != size) {
#endif /* ENABLE_EXTENDED_FORMAT */
seterr(ERROR_EHDR_PHENTSIZE);
return 0;
}
size = _msize(elf->e_class, _elf_version, ELF_T_PHDR);
elf_assert(size);
if (!(p = malloc(num * size))) {
seterr(memerr(ELF_T_PHDR));
return 0;
}
for (i = 0; i < num; i++) {
if (!_elf_item(p + i * size, elf, ELF_T_PHDR, off + i * entsz)) {
free(p);
return 0;
}
}
elf->e_phdr = p;
elf->e_phnum = num;
}
return 1;
}
static int
_elf_cook_shdr(Elf *elf) {
size_t num, off, entsz;
if (elf->e_class == ELFCLASS32) {
num = ((Elf32_Ehdr*)elf->e_ehdr)->e_shnum;
off = ((Elf32_Ehdr*)elf->e_ehdr)->e_shoff;
entsz = ((Elf32_Ehdr*)elf->e_ehdr)->e_shentsize;
}
#if __LIBELF64
else if (elf->e_class == ELFCLASS64) {
num = ((Elf64_Ehdr*)elf->e_ehdr)->e_shnum;
off = ((Elf64_Ehdr*)elf->e_ehdr)->e_shoff;
entsz = ((Elf64_Ehdr*)elf->e_ehdr)->e_shentsize;
/*
* Check for overflow on 32-bit systems
*/
if (overflow(off, ((Elf64_Ehdr*)elf->e_ehdr)->e_shoff, Elf64_Off)) {
seterr(ERROR_OUTSIDE);
return 0;
}
}
#endif /* __LIBELF64 */
else {
seterr(ERROR_UNIMPLEMENTED);
return 0;
}
if (off) {
struct tmp {
Elf_Scn scn;
Scn_Data data;
} *head;
Elf_Data src, dst;
Elf_Scn *scn;
Scn_Data *sd;
unsigned i;
if (off < 0 || off > elf->e_size) {
seterr(ERROR_OUTSIDE);
return 0;
}
src.d_type = ELF_T_SHDR;
src.d_version = elf->e_version;
src.d_size = _fsize(elf->e_class, src.d_version, ELF_T_SHDR);
elf_assert(src.d_size);
#if ENABLE_EXTENDED_FORMAT
if (entsz < src.d_size) {
#else /* ENABLE_EXTENDED_FORMAT */
if (entsz != src.d_size) {
#endif /* ENABLE_EXTENDED_FORMAT */
seterr(ERROR_EHDR_SHENTSIZE);
return 0;
}
dst.d_version = EV_CURRENT;
if (num == 0) {
union {
Elf32_Shdr sh32;
#if __LIBELF64
Elf64_Shdr sh64;
#endif /* __LIBELF64 */
} u;
/*
* Overflow in ehdr->e_shnum.
* Get real value from first SHDR.
*/
if (elf->e_size - off < entsz) {
seterr(ERROR_TRUNC_SHDR);
return 0;
}
if (elf->e_rawdata) {
src.d_buf = elf->e_rawdata + off;
}
else {
src.d_buf = elf->e_data + off;
}
dst.d_buf = &u;
dst.d_size = sizeof(u);
if (!_elf_xlatetom(elf, &dst, &src)) {
return 0;
}
elf_assert(dst.d_size == _msize(elf->e_class, EV_CURRENT, ELF_T_SHDR));
elf_assert(dst.d_type == ELF_T_SHDR);
if (elf->e_class == ELFCLASS32) {
num = u.sh32.sh_size;
}
#if __LIBELF64
else if (elf->e_class == ELFCLASS64) {
num = u.sh64.sh_size;
/*
* Check for overflow on 32-bit systems
*/
if (overflow(num, u.sh64.sh_size, Elf64_Xword)) {
seterr(ERROR_OUTSIDE);
return 0;
}
}
#endif /* __LIBELF64 */
}
if ((elf->e_size - off) / entsz < num) {
seterr(ERROR_TRUNC_SHDR);
return 0;
}
if (!(head = (struct tmp*)malloc(num * sizeof(struct tmp)))) {
seterr(ERROR_MEM_SCN);
return 0;
}
for (scn = NULL, i = num; i-- > 0; ) {
head[i].scn = _elf_scn_init;
head[i].data = _elf_data_init;
head[i].scn.s_link = scn;
if (!scn) {
elf->e_scn_n = &head[i].scn;
}
scn = &head[i].scn;
sd = &head[i].data;
if (elf->e_rawdata) {
src.d_buf = elf->e_rawdata + off + i * entsz;
}
else {
src.d_buf = elf->e_data + off + i * entsz;
}
dst.d_buf = &scn->s_uhdr;
dst.d_size = sizeof(scn->s_uhdr);
if (!_elf_xlatetom(elf, &dst, &src)) {
elf->e_scn_n = NULL;
free(head);
return 0;
}
elf_assert(dst.d_size == _msize(elf->e_class, EV_CURRENT, ELF_T_SHDR));
elf_assert(dst.d_type == ELF_T_SHDR);
scn->s_elf = elf;
scn->s_index = i;
scn->s_data_1 = sd;
scn->s_data_n = sd;
sd->sd_scn = scn;
if (elf->e_class == ELFCLASS32) {
Elf32_Shdr *shdr = &scn->s_shdr32;
scn->s_type = shdr->sh_type;
scn->s_size = shdr->sh_size;
scn->s_offset = shdr->sh_offset;
sd->sd_data.d_align = shdr->sh_addralign;
sd->sd_data.d_type = _elf_scn_type(scn->s_type);
}
#if __LIBELF64
else if (elf->e_class == ELFCLASS64) {
Elf64_Shdr *shdr = &scn->s_shdr64;
scn->s_type = shdr->sh_type;
scn->s_size = shdr->sh_size;
scn->s_offset = shdr->sh_offset;
sd->sd_data.d_align = shdr->sh_addralign;
/*
* Check for overflow on 32-bit systems
*/
if (overflow(scn->s_size, shdr->sh_size, Elf64_Xword)
|| overflow(scn->s_offset, shdr->sh_offset, Elf64_Off)
|| overflow(sd->sd_data.d_align, shdr->sh_addralign, Elf64_Xword)) {
seterr(ERROR_OUTSIDE);
return 0;
}
sd->sd_data.d_type = _elf_scn_type(scn->s_type);
/*
* QUIRKS MODE:
*
* Some 64-bit architectures use 64-bit entries in the
* .hash section. This violates the ELF standard, and
* should be fixed. It's mostly harmless as long as the
* binary and the machine running your program have the
* same byte order, but you're in trouble if they don't,
* and if the entry size is wrong.
*
* As a workaround, I let libelf guess the right size
* for the binary. This relies pretty much on the fact
* that the binary provides correct data in the section
* headers. If it doesn't, it's probably broken anyway.
* Therefore, libelf uses a standard conforming value
* when it's not absolutely sure.
*/
if (scn->s_type == SHT_HASH) {
int override = 0;
/*
* sh_entsize must reflect the entry size
*/
if (shdr->sh_entsize == ELF64_FSZ_ADDR) {
override++;
}
/*
* sh_size must be a multiple of sh_entsize
*/
if (shdr->sh_size % ELF64_FSZ_ADDR == 0) {
override++;
}
/*
* There must be room for at least 2 entries
*/
if (shdr->sh_size >= 2 * ELF64_FSZ_ADDR) {
override++;
}
/*
* sh_addralign must be correctly set
*/
if (shdr->sh_addralign == ELF64_FSZ_ADDR) {
override++;
}
/*
* The section must be properly aligned
*/
if (shdr->sh_offset % ELF64_FSZ_ADDR == 0) {
override++;
}
/* XXX: also look at the data? */
/*
* Make a conservative decision...
*/
if (override >= 5) {
sd->sd_data.d_type = ELF_T_ADDR;
}
}
/*
* END QUIRKS MODE.
*/
}
#endif /* __LIBELF64 */
/* we already had this
else {
seterr(ERROR_UNIMPLEMENTED);
return 0;
}
*/
sd->sd_data.d_size = scn->s_size;
sd->sd_data.d_version = _elf_version;
}
elf_assert(scn == &head[0].scn);
elf->e_scn_1 = &head[0].scn;
head[0].scn.s_freeme = 1;
}
return 1;
}
static int
_elf_cook_file(Elf *elf) {
elf->e_ehdr = _elf_item(NULL, elf, ELF_T_EHDR, 0);
if (!elf->e_ehdr) {
return 0;
}
/*
* Note: _elf_cook_phdr may require the first section header!
*/
if (!_elf_cook_shdr(elf)) {
return 0;
}
if (!_elf_cook_phdr(elf)) {
return 0;
}
return 1;
}
int
_elf_cook(Elf *elf) {
elf_assert(_elf_scn_init.s_magic == SCN_MAGIC);
elf_assert(_elf_data_init.sd_magic == DATA_MAGIC);
elf_assert(elf);
elf_assert(elf->e_magic == ELF_MAGIC);
elf_assert(elf->e_kind == ELF_K_ELF);
elf_assert(!elf->e_ehdr);
if (!valid_version(elf->e_version)) {
seterr(ERROR_UNKNOWN_VERSION);
}
else if (!valid_encoding(elf->e_encoding)) {
seterr(ERROR_UNKNOWN_ENCODING);
}
else if (valid_class(elf->e_class)) {
return _elf_cook_file(elf);
}
else {
seterr(ERROR_UNKNOWN_CLASS);
}
return 0;
}