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upx/src/p_lx_elf.cpp
John Reiser 3f7b642c7d Linux i386 allow compression of position-independent main executables (gcc -pie). 
p_elf.h p_lx_elf.cpp p_lx_elf.h p_lx_exc.cpp
	stub/fold_elf86.asm stub/fold_elf86.h stub/l_lx_elf.c
	stub/l_lx_elf86.asm stub/l_lx_elf86.h stub/l_lx_elf86.lds
	stub/linux.hh

committer: jreiser <jreiser> 1126886896 +0000
2005-09-16 16:08:16 +00:00

1119 lines
35 KiB
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/* p_lx_elf.cpp --
This file is part of the UPX executable compressor.
Copyright (C) 1996-2004 Markus Franz Xaver Johannes Oberhumer
Copyright (C) 1996-2004 Laszlo Molnar
Copyright (C) 2000-2004 John F. Reiser
All Rights Reserved.
UPX and the UCL library are free software; you can redistribute them
and/or modify them under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING.
If not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
Markus F.X.J. Oberhumer Laszlo Molnar John F. Reiser
markus@oberhumer.com ml1050@cdata.tvnet.hu jreiser@BitWagon.com
*/
#include "conf.h"
#include "file.h"
#include "filter.h"
#include "linker.h"
#include "packer.h"
#include "p_elf.h"
#include "p_unix.h"
#include "p_lx_exc.h"
#include "p_lx_elf.h"
#define PT_LOAD Elf32_Phdr::PT_LOAD
int
PackLinuxElf32::checkEhdr(
Elf32_Ehdr const *ehdr,
unsigned char e_machine,
unsigned char ei_class,
unsigned char ei_data
) const
{
const unsigned char * const buf = ehdr->e_ident;
if (0!=memcmp(buf, "\x7f\x45\x4c\x46", 4) // "\177ELF"
|| buf[Elf32_Ehdr::EI_CLASS]!=ei_class
|| buf[Elf32_Ehdr::EI_DATA] !=ei_data ) {
return -1;
}
if (!memcmp(buf+8, "FreeBSD", 7)) // branded
return 1;
int const type = get_native16(&ehdr->e_type);
if (type != Elf32_Ehdr::ET_EXEC && type != Elf32_Ehdr::ET_DYN)
return 2;
if (get_native16(&ehdr->e_machine) != e_machine)
return 3;
if (get_native32(&ehdr->e_version) != Elf32_Ehdr::EV_CURRENT)
return 4;
if (get_native16(&ehdr->e_phnum) < 1)
return 5;
if (get_native16(&ehdr->e_phentsize) != sizeof(Elf32_Phdr))
return 6;
// check for Linux kernels
unsigned const entry = get_native32(&ehdr->e_entry);
if (entry == 0xC0100000) // uncompressed vmlinux
return 1000;
if (entry == 0x00001000) // compressed vmlinux
return 1001;
if (entry == 0x00100000) // compressed bvmlinux
return 1002;
// FIXME: add more checks for kernels
// FIXME: add special checks for other ELF i386 formats, like
// NetBSD, OpenBSD, Solaris, ....
// success
return 0;
}
PackLinuxElf32::PackLinuxElf32(InputFile *f)
: super(f), phdri(NULL)
{
}
PackLinuxElf32::~PackLinuxElf32()
{
delete[] phdri;
}
int const *
PackLinuxElf32::getCompressionMethods(int method, int level) const
{
// No real dependency on LE32.
return Packer::getDefaultCompressionMethods_le32(method, level);
}
int const *
PackLinuxElf32ppc::getCompressionMethods(int method, int level) const
{
// No real dependency on LE32.
static const int m_nrv2e[] = { M_NRV2E_LE32, -1 };
static const int m_nrv2b[] = { M_NRV2B_LE32, -1 };
/*return Packer::getDefaultCompressionMethods_le32(method, level);*/
// 2005-04-23 FIXME: stub/l_lx_elfppc32.S hardwires ppc_d_nrv2e.S
UNUSED(method); UNUSED(level); UNUSED(m_nrv2b);
return m_nrv2e;
}
int const *
PackLinuxElf32ppc::getFilters() const
{
static const int filters[] = {
0xd0, -1
};
return filters;
}
void PackLinuxElf32::patchLoader() { }
void PackLinuxElf32::updateLoader(OutputFile *fo)
{
set_native32(&elfout.ehdr.e_entry, fo->getBytesWritten() +
get_native32(&elfout.phdr[0].p_vaddr));
}
int
PackLinuxElf32::buildLinuxLoader(
upx_byte const *const /*proto*/,
unsigned const /*szproto*/,
upx_byte const *const /*fold*/,
unsigned const /*szfold*/,
Filter const */*ft*/
)
{
return 0;
}
PackLinuxElf32ppc::PackLinuxElf32ppc(InputFile *f)
: super(f)
{
}
PackLinuxElf32ppc::~PackLinuxElf32ppc()
{
}
static unsigned
umax(unsigned a, unsigned b)
{
if (a <= b) {
return b;
}
return a;
}
int
PackLinuxElf32ppc::buildLinuxLoader(
upx_byte const *const proto,
unsigned const szproto,
upx_byte const *const fold,
unsigned const szfold,
Filter const */*ft*/
)
{
int eof_empty = -1;
initLoader(&eof_empty, 4096, 0, 0);
struct b_info h; memset(&h, 0, sizeof(h));
unsigned fold_hdrlen = 0;
unsigned sz_unc=0, sz_cpr;
if (0 < szfold) {
cprElfHdr1 const *const hf = (cprElfHdr1 const *)fold;
fold_hdrlen = umax(0x80, sizeof(hf->ehdr) +
get_native16(&hf->ehdr.e_phentsize) * get_native16(&hf->ehdr.e_phnum) +
sizeof(l_info) );
sz_unc = ((szfold < fold_hdrlen) ? 0 : (szfold - fold_hdrlen));
set_native32(&h.sz_unc, ((szfold < fold_hdrlen) ? 0 : (szfold - fold_hdrlen)));
h.b_method = (unsigned char) ph.method;
h.b_ftid = (unsigned char) ph.filter;
h.b_cto8 = (unsigned char) ph.filter_cto;
}
unsigned char const *const uncLoader = fold_hdrlen + fold;
unsigned char *const cprLoader = new unsigned char[sizeof(h) + sz_unc];
if (0 < szfold) {
int r = upx_compress(uncLoader, sz_unc, sizeof(h) + cprLoader, &sz_cpr,
NULL, ph.method, 10, NULL, NULL );
set_native32(&h.sz_cpr, sz_cpr);
if (r != UPX_E_OK || sz_cpr >= sz_unc)
throwInternalError("loader compression failed");
}
memcpy(cprLoader, &h, sizeof(h));
// This adds the definition to the "library", to be used later.
linker->addSection("FOLDEXEC", cprLoader, sizeof(h) + sz_cpr);
delete [] cprLoader;
//int const GAP = 128; // must match stub/l_mac_ppc.S
//segcmdo.vmsize += sz_unc - sz_cpr + GAP + 64;
linker->addSection("ELFPPC32", proto, szproto);
addLoader("ELFPPC32", 0);
addLoader("FOLDEXEC", 0);
return getLoaderSize();
}
static const
#include "stub/l_lx_elfppc32.h"
static const
#include "stub/fold_elfppc32.h"
int
PackLinuxElf32ppc::buildLoader(const Filter *ft)
{
return buildLinuxLoader(
linux_elfppc32_loader, sizeof(linux_elfppc32_loader),
linux_elfppc32_fold, sizeof(linux_elfppc32_fold), ft );
}
bool
PackLinuxElf32ppc::canPack()
{
unsigned char buf[sizeof(Elf32_Ehdr) + 14*sizeof(Elf32_Phdr)];
COMPILE_TIME_ASSERT(sizeof(buf) <= 512);
exetype = 0;
fi->readx(buf, sizeof(buf));
fi->seek(0, SEEK_SET);
Elf32_Ehdr const *const ehdr = (Elf32_Ehdr const *)buf;
// now check the ELF header
if (checkEhdr(ehdr, Elf32_Ehdr::EM_PPC,
Elf32_Ehdr::ELFCLASS32, Elf32_Ehdr::ELFDATA2MSB) != 0)
return false;
// additional requirements for linux/elf386
if (get_native16(&ehdr->e_ehsize) != sizeof(*ehdr)) {
throwCantPack("invalid Ehdr e_ehsize; try `--force-execve'");
return false;
}
unsigned const e_phoff = get_native32(&ehdr->e_phoff);
if (e_phoff != sizeof(*ehdr)) {// Phdrs not contiguous with Ehdr
throwCantPack("non-contiguous Ehdr/Phdr; try `--force-execve'");
return false;
}
// The first PT_LOAD must cover the beginning of the file (0==p_offset).
unsigned const e_phnum = get_native16(&ehdr->e_phnum);
Elf32_Phdr const *phdr = (Elf32_Phdr const *)(buf + e_phoff);
for (unsigned j=0; j < e_phnum; ++phdr, ++j) {
if (j >= 14)
return false;
if (phdr->PT_LOAD == get_native32(&phdr->p_type)) {
// Just avoid the "rewind" when unpacking?
//if (phdr->p_offset != 0) {
// throwCantPack("invalid Phdr p_offset; try `--force-execve'");
// return false;
//}
// detect possible conflict upon invocation
unsigned const p_vaddr = get_native32(&phdr->p_vaddr);
if (p_vaddr < (unsigned)(0x400000 + file_size)
|| p_vaddr < (unsigned)(0x400000 + file_size) ) {
throwAlreadyPackedByUPX(); // not necessarily, but mostly true
return false;
}
exetype = 1;
break;
}
}
if (!super::canPack())
return false;
assert(exetype == 1);
// set options
opt->o_unix.blocksize = blocksize = file_size;
return true;
}
off_t
PackLinuxElf32::getbrk(const Elf32_Phdr *phdr, int e_phnum) const
{
off_t brka = 0;
for (int j = 0; j < e_phnum; ++phdr, ++j) {
if (PT_LOAD == get_native32(&phdr->p_type)) {
off_t b = get_native32(&phdr->p_vaddr) + get_native32(&phdr->p_memsz);
if (b > brka)
brka = b;
}
}
return brka;
}
void
PackLinuxElf32::generateElfHdr(
OutputFile */*fo*/,
void const *proto,
unsigned const brka
)
{
cprElfHdr2 *const h2 = (cprElfHdr2 *)&elfout;
cprElfHdr3 *const h3 = (cprElfHdr3 *)&elfout;
memcpy(h3, proto, sizeof(*h3)); // reads beyond, but OK
assert(get_native32(&h2->ehdr.e_phoff) == sizeof(Elf32_Ehdr));
h2->ehdr.e_shoff = 0;
assert(get_native16(&h2->ehdr.e_ehsize) == sizeof(Elf32_Ehdr));
assert(get_native16(&h2->ehdr.e_phentsize) == sizeof(Elf32_Phdr));
h2->ehdr.e_shentsize = 0;
h2->ehdr.e_shnum = 0;
h2->ehdr.e_shstrndx = 0;
#if 0 //{
unsigned identsize;
char const *const ident = getIdentstr(&identsize);
#endif //}
sz_elf_hdrs = sizeof(*h2) - sizeof(linfo); // default
set_native32(&h2->phdr[0].p_filesz, sizeof(*h2)); // + identsize;
h2->phdr[0].p_memsz = h2->phdr[0].p_filesz;
// Info for OS kernel to set the brk()
if (brka) {
set_native32(&h2->phdr[1].p_type, PT_LOAD); // be sure
set_native32(&h2->phdr[1].p_offset, 0xfff&brka);
set_native32(&h2->phdr[1].p_vaddr, brka);
set_native32(&h2->phdr[1].p_paddr, brka);
h2->phdr[1].p_filesz = 0;
h2->phdr[1].p_memsz = 0;
}
}
void
PackLinuxElf32ppc::generateElfHdr(
OutputFile *fo,
void const *proto,
unsigned const brka
)
{
super::generateElfHdr(fo, proto, brka);
if (ph.format==UPX_F_LINUX_ELFPPC32) {
cprElfHdr2 *const h2 = (cprElfHdr2 *)&elfout;
assert(2==get_native16(&h2->ehdr.e_phnum));
set_native32(&h2->phdr[0].p_flags, Elf32_Phdr::PF_W | get_native32(&h2->phdr[0].p_flags));
memset(&h2->linfo, 0, sizeof(h2->linfo));
fo->write(h2, sizeof(*h2));
}
else {
assert(false); // unknown ph.format, PackLinuxElf32ppc::generateElfHdr
}
}
static const
#include "stub/l_lx_elf86.h"
static const
#include "stub/fold_elf86.h"
void PackLinuxElf32::pack1(OutputFile *fo, Filter &/*ft*/)
{
fi->seek(0, SEEK_SET);
fi->readx(&ehdri, sizeof(ehdri));
unsigned const e_phoff = get_native32(&ehdri.e_phoff);
unsigned const e_phnum = get_native16(&ehdri.e_phnum);
assert(e_phoff == sizeof(Elf32_Ehdr)); // checked by canPack()
sz_phdrs = e_phnum * get_native16(&ehdri.e_phentsize);
phdri = new Elf32_Phdr[e_phnum];
fi->seek(e_phoff, SEEK_SET);
fi->readx(phdri, sz_phdrs);
generateElfHdr(fo, linux_elfppc32_fold, getbrk(phdri, e_phnum) );
}
void PackLinuxElf32::pack2(OutputFile *fo, Filter &ft)
{
Extent x;
unsigned k;
// count passes, set ptload vars
ui_total_passes = 0;
off_t ptload0hi = 0, ptload1lo = 0, ptload1sz = 0;
unsigned const e_phnum = get_native16(&ehdri.e_phnum);
for (k = 0; k < e_phnum; ++k) {
if (PT_LOAD == get_native32(&phdri[k].p_type)) {
x.offset = get_native32(&phdri[k].p_offset);
x.size = get_native32(&phdri[k].p_filesz);
if (0 == ptload0hi) {
ptload0hi = x.offset + x.size;
}
else if (0 == ptload1lo) {
ptload1lo = x.offset;
ptload1sz = x.size;
}
ui_total_passes++;
}
}
if (0!=ptload1sz && ptload0hi < ptload1lo)
ui_total_passes++;
// compress extents
unsigned total_in = 0;
unsigned total_out = 0;
ui_pass = -1; // Compressing Elf headers is invisible to UI.
x.offset = 0;
x.size = sizeof(Elf32_Ehdr) + sz_phdrs;
{
int const old_level = ph.level; ph.level = 10;
packExtent(x, total_in, total_out, 0, fo);
ph.level = old_level;
}
ui_pass = 0;
ft.addvalue = 0;
int nx = 0;
for (k = 0; k < e_phnum; ++k) if (PT_LOAD==get_native32(&phdri[k].p_type)) {
if (ft.id < 0x40) {
// FIXME: ?? ft.addvalue = phdri[k].p_vaddr;
}
x.offset = get_native32(&phdri[k].p_offset);
x.size = get_native32(&phdri[k].p_filesz);
if (0 == nx) { // 1st PT_LOAD must cover Ehdr at 0==p_offset
unsigned const delta = sizeof(Elf32_Ehdr) + sz_phdrs;
if (ft.id < 0x40) {
// FIXME: ?? ft.addvalue += delta;
}
x.offset += delta;
x.size -= delta;
}
// compressWithFilters() always assumes a "loader", so would
// throw NotCompressible for small .data Extents, which PowerPC
// sometimes marks as PF_X anyway. So filter only first segment.
packExtent(x, total_in, total_out,
((0==nx && (Elf32_Phdr::PF_X & get_native32(&phdri[k].p_flags)))
? &ft : 0 ), fo );
++nx;
}
if (0!=ptload1sz && ptload0hi < ptload1lo) { // alignment hole?
x.offset = ptload0hi;
x.size = ptload1lo - ptload0hi;
packExtent(x, total_in, total_out, 0, fo);
}
if ((off_t)total_in < file_size) { // non-PT_LOAD stuff
x.offset = total_in;
x.size = file_size - total_in;
packExtent(x, total_in, total_out, 0, fo);
}
if ((off_t)total_in != file_size)
throwEOFException();
set_native32(&elfout.phdr[0].p_filesz, fo->getBytesWritten());
}
void PackLinuxElf32ppc::pack3(OutputFile *fo, Filter &ft)
{
unsigned disp;
unsigned const zero = 0;
unsigned len = fo->getBytesWritten();
fo->write(&zero, 3& -len); // align to 0 mod 4
len += (3& -len) + sizeof(disp);
set_native32(&disp, 4+ len - sz_elf_hdrs); // 4: sizeof(instruction)
fo->write(&disp, sizeof(disp));
super::pack3(fo, ft);
}
void PackLinuxElf32::pack4(OutputFile *fo, Filter &ft)
{
overlay_offset = sz_elf_hdrs + sizeof(linfo);
unsigned const zero = 0;
unsigned len = fo->getBytesWritten();
fo->write(&zero, 3& -len); // align to 0 mod 4
len += 3& -len;
set_native32(&elfout.phdr[0].p_filesz, len);
super::pack4(fo, ft); // write PackHeader and overlay_offset
#define PAGE_MASK (~0u<<12)
// pre-calculate for benefit of runtime disappearing act via munmap()
set_native32(&elfout.phdr[0].p_memsz, PAGE_MASK & (~PAGE_MASK + len));
#undef PAGE_MASK
// rewrite Elf header
if (Elf32_Ehdr::ET_DYN==ehdri.e_type) {
unsigned const base= elfout.phdr[0].p_vaddr;
elfout.ehdr.e_type= Elf32_Ehdr::ET_DYN;
elfout.ehdr.e_phnum= 1;
elfout.ehdr.e_entry -= base;
elfout.phdr[0].p_vaddr -= base;
elfout.phdr[0].p_paddr -= base;
elfout.phdr[0].p_flags |= Elf32_Phdr::PF_W;
}
fo->seek(0, SEEK_SET);
fo->rewrite(&elfout, sz_elf_hdrs);
fo->rewrite(&linfo, sizeof(linfo));
}
void PackLinuxElf32::unpack(OutputFile *fo)
{
#define MAX_ELF_HDR 512
char bufehdr[MAX_ELF_HDR];
Elf32_Ehdr *const ehdr = (Elf32_Ehdr *)bufehdr;
Elf32_Phdr const *phdr = (Elf32_Phdr *)(1+ehdr);
unsigned szb_info = sizeof(b_info);
{
fi->seek(0, SEEK_SET);
fi->readx(bufehdr, MAX_ELF_HDR);
unsigned const e_entry = get_native32(&ehdr->e_entry);
if (e_entry < 0x401180
&& ehdr->e_machine==Elf32_Ehdr::EM_386) { /* old style, 8-byte b_info */
szb_info = 2*sizeof(unsigned);
}
}
fi->seek(overlay_offset, SEEK_SET);
p_info hbuf;
fi->readx(&hbuf, sizeof(hbuf));
unsigned orig_file_size = get_native32(&hbuf.p_filesize);
blocksize = get_native32(&hbuf.p_blocksize);
if (file_size > (off_t)orig_file_size || blocksize > orig_file_size)
throwCantUnpack("file header corrupted");
ibuf.alloc(blocksize + OVERHEAD);
b_info bhdr; memset(&bhdr, 0, sizeof(bhdr));
fi->readx(&bhdr, szb_info);
ph.u_len = get_native32(&bhdr.sz_unc);
ph.c_len = get_native32(&bhdr.sz_cpr);
ph.filter_cto = bhdr.b_cto8;
// Uncompress Ehdr and Phdrs.
fi->readx(ibuf, ph.c_len);
decompress(ibuf, (upx_byte *)ehdr, false);
unsigned total_in = 0;
unsigned total_out = 0;
unsigned c_adler = upx_adler32(NULL, 0);
unsigned u_adler = upx_adler32(NULL, 0);
off_t ptload0hi=0, ptload1lo=0, ptload1sz=0;
// decompress PT_LOAD
bool first_PF_X = true;
unsigned const phnum = get_native16(&ehdr->e_phnum);
fi->seek(- (off_t) (szb_info + ph.c_len), SEEK_CUR);
for (unsigned j=0; j < phnum; ++phdr, ++j) {
if (PT_LOAD==get_native32(&phdr->p_type)) {
unsigned const filesz = get_native32(&phdr->p_filesz);
unsigned const offset = get_native32(&phdr->p_offset);
if (0==ptload0hi) {
ptload0hi = filesz + offset;
}
else if (0==ptload1lo) {
ptload1lo = offset;
ptload1sz = filesz;
}
if (fo)
fo->seek(offset, SEEK_SET);
if (Elf32_Phdr::PF_X & get_native32(&phdr->p_flags)) {
unpackExtent(filesz, fo, total_in, total_out,
c_adler, u_adler, first_PF_X, szb_info);
first_PF_X = false;
}
else {
unpackExtent(filesz, fo, total_in, total_out,
c_adler, u_adler, false, szb_info);
}
}
}
if (0!=ptload1sz && ptload0hi < ptload1lo) { // alignment hole?
if (fo)
fo->seek(ptload0hi, SEEK_SET);
unpackExtent(ptload1lo - ptload0hi, fo, total_in, total_out,
c_adler, u_adler, false, szb_info);
}
if (total_out != orig_file_size) { // non-PT_LOAD stuff
if (fo)
fo->seek(0, SEEK_END);
unpackExtent(orig_file_size - total_out, fo, total_in, total_out,
c_adler, u_adler, false, szb_info);
}
// check for end-of-file
fi->readx(&bhdr, szb_info);
unsigned const sz_unc = ph.u_len = get_native32(&bhdr.sz_unc);
if (sz_unc == 0) { // uncompressed size 0 -> EOF
// note: magic is always stored le32
unsigned const sz_cpr = get_le32(&bhdr.sz_cpr);
if (sz_cpr != UPX_MAGIC_LE32) // sz_cpr must be h->magic
throwCompressedDataViolation();
}
else { // extra bytes after end?
throwCompressedDataViolation();
}
// update header with totals
ph.c_len = total_in;
ph.u_len = total_out;
// all bytes must be written
if (total_out != orig_file_size)
throwEOFException();
// finally test the checksums
if (ph.c_adler != c_adler || ph.u_adler != u_adler)
throwChecksumError();
#undef MAX_ELF_HDR
}
/*************************************************************************
//
**************************************************************************/
PackLinuxI386elf::PackLinuxI386elf(InputFile *f) :
super(f), phdri(NULL),
file_image(NULL), dynseg(NULL), hashtab(NULL), dynstr(NULL), dynsym(NULL)
{
}
PackLinuxI386elf::~PackLinuxI386elf()
{
delete[] file_image;
delete[] phdri;
}
int const *
PackLinuxI386elf::getFilters() const
{
static const int filters[] = {
0x49, 0x46,
// FIXME 2002-11-11: We use stub/fold_elf86.asm, which calls the
// decompressor multiple times, and unfilter is independent of decompress.
// Currently only filters 0x49, 0x46, 0x80..0x87 can handle this;
// and 0x80..0x87 are regarded as "untested".
#if 0
0x26, 0x24, 0x11, 0x14, 0x13, 0x16, 0x25, 0x15, 0x12,
#endif
#if 0
0x83, 0x36, 0x26,
0x86, 0x80,
0x84, 0x87, 0x81,
0x82, 0x85,
0x24, 0x16, 0x13, 0x14, 0x11, 0x25, 0x15, 0x12,
#endif
-1 };
return filters;
}
int
PackLinuxI386elf::buildLoader(const Filter *ft)
{
unsigned char tmp[sizeof(linux_i386elf_fold)];
memcpy(tmp, linux_i386elf_fold, sizeof(linux_i386elf_fold));
checkPatch(NULL, 0, 0, 0); // reset
if (opt->o_unix.is_ptinterp) {
unsigned j;
for (j = 0; j < sizeof(linux_i386elf_fold)-1; ++j) {
if (0x60==tmp[ j]
&& 0x47==tmp[1+j] ) {
/* put INC EDI before PUSHA: inhibits auxv_up for PT_INTERP */
tmp[ j] = 0x47;
tmp[1+j] = 0x60;
break;
}
}
}
return buildLinuxLoader(
linux_i386elf_loader, sizeof(linux_i386elf_loader),
tmp, sizeof(linux_i386elf_fold), ft );
}
void PackLinuxI386elf::patchLoader() { }
bool PackLinuxI386elf::canPack()
{
unsigned char buf[sizeof(Elf32_Ehdr) + 14*sizeof(Elf32_Phdr)];
COMPILE_TIME_ASSERT(sizeof(buf) <= 512);
exetype = 0;
fi->readx(buf, sizeof(buf));
fi->seek(0, SEEK_SET);
Elf32_Ehdr const *const ehdr = (Elf32_Ehdr const *)buf;
// now check the ELF header
if (checkEhdr(ehdr) != 0)
return false;
// additional requirements for linux/elf386
if (ehdr->e_ehsize != sizeof(*ehdr)) {
throwCantPack("invalid Ehdr e_ehsize; try `--force-execve'");
return false;
}
if (ehdr->e_phoff != sizeof(*ehdr)) {// Phdrs not contiguous with Ehdr
throwCantPack("non-contiguous Ehdr/Phdr; try `--force-execve'");
return false;
}
// The first PT_LOAD must cover the beginning of the file (0==p_offset).
Elf32_Phdr const *phdr = (Elf32_Phdr const *)(buf + ehdr->e_phoff);
for (unsigned j=0; j < ehdr->e_phnum; ++phdr, ++j) {
if (j >= 14) // 512 bytes holds Elf32_Ehdr + Elf32_Phdr[0..13]
return false;
if (phdr->PT_LOAD == phdr->p_type) {
if (phdr->p_offset != 0) {
throwCantPack("invalid Phdr p_offset; try `--force-execve'");
return false;
}
// detect possible conflict upon invocation
if (ehdr->e_type!=Elf32_Ehdr::ET_DYN
&& (phdr->p_vaddr < (unsigned)(0xc00000 + file_size)
|| phdr->p_paddr < (unsigned)(0xc00000 + file_size) ) ) {
throwAlreadyPackedByUPX(); // not necessarily, but mostly true
return false;
}
exetype = 1;
break;
}
}
// We want to compress position-independent executable (gcc -pie)
// main programs, but compressing a shared library must be avoided
// because the result is no longer usable. In theory, there is no way
// to tell them apart: both are just ET_DYN. Also in theory,
// neither the presence nor the absence of any particular symbol name
// can be used to tell them apart; there are counterexamples.
// However, we will use the following heuristic suggested by
// Peter S. Mazinger <ps.m@gmx.net> September 2005:
// If a ET_DYN has __libc_start_main as a global undefined symbol,
// then the file is a position-independent executable main program
// (that depends on libc.so.6) and is eligible to be compressed.
// Otherwise (no __libc_start_main as global undefined): skip it.
if (Elf32_Ehdr::ET_DYN==ehdr->e_type) {
// The DT_STRTAB has no designated length. Read the whole file.
file_image = new char[file_size];
fi->seek(0, SEEK_SET);
fi->readx(file_image, file_size);
ehdri= *ehdr;
phdri= (Elf32_Phdr *)(ehdr->e_phoff + file_image); // do not free() !!
int j= ehdr->e_phnum;
Elf32_Phdr const *phdr= phdri;
for (; --j>=0; ++phdr) if (Elf32_Phdr::PT_DYNAMIC==phdr->p_type) {
dynseg= (Elf32_Dyn const *)(phdr->p_offset + file_image);
break;
}
// elf_find_dynamic() returns 0 if 0==dynseg.
hashtab= (unsigned int const *)elf_find_dynamic(Elf32_Dyn::DT_HASH);
dynstr= (char const *)elf_find_dynamic(Elf32_Dyn::DT_STRTAB);
dynsym= (Elf32_Sym const *)elf_find_dynamic(Elf32_Dyn::DT_SYMTAB);
// elf_lookup() returns 0 if any required table is missing.
Elf32_Sym const *const lsm = elf_lookup("__libc_start_main");
phdri = 0; // done "borrowing" this member
if (0==lsm || lsm->st_shndx!=Elf32_Sym::SHN_UNDEF
|| lsm->st_info!=lsm->Elf32_Sym::St_info(Elf32_Sym::STB_GLOBAL, Elf32_Sym::STT_FUNC)
|| lsm->st_other!=Elf32_Sym::STV_DEFAULT ) {
return false;
}
}
if (!super::canPack())
return false;
assert(exetype == 1);
// set options
opt->o_unix.blocksize = blocksize = file_size;
return true;
}
unsigned
PackLinuxI386elf::elf_get_offset_from_address(unsigned const addr) const
{
Elf32_Phdr const *phdr = phdri;
int j = ehdri.e_phnum;
for (; --j>=0; ++phdr) if (PT_LOAD == phdr->p_type) {
unsigned const t = addr - phdr->p_vaddr;
if (t < phdr->p_filesz) {
return t + phdr->p_offset;
}
}
return 0;
}
void const *
PackLinuxI386elf::elf_find_dynamic(unsigned int const key) const
{
Elf32_Dyn const *dynp= dynseg;
if (dynp)
for (; Elf32_Dyn::DT_NULL!=dynp->d_tag; ++dynp) if (dynp->d_tag == key) {
unsigned const t= elf_get_offset_from_address(dynp->d_val);
if (t) {
return t + file_image;
}
break;
}
return 0;
}
unsigned PackLinuxI386elf::elf_hash(char const *p)
{
unsigned h;
for (h= 0; 0!=*p; ++p) {
h = *p + (h<<4);
{
unsigned const t = 0xf0000000u & h;
h &= ~t;
h ^= t>>24;
}
}
return h;
}
Elf32_Sym const *PackLinuxI386elf::elf_lookup(char const *name) const
{
if (hashtab && dynsym && dynstr) {
unsigned const nbucket = hashtab[0];
unsigned const *const buckets = &hashtab[2];
unsigned const *const chains = &buckets[nbucket];
unsigned const m = elf_hash(name) % nbucket;
unsigned si;
for (si= buckets[m]; 0!=si; si= chains[si]) {
char const *const p= dynsym[si].st_name + dynstr;
if (0==strcmp(name, p)) {
return &dynsym[si];
}
}
}
return 0;
}
void PackLinuxI386elf::pack1(OutputFile *fo, Filter &)
{
fi->seek(0, SEEK_SET);
fi->readx(&ehdri, sizeof(ehdri));
assert(ehdri.e_phoff == sizeof(Elf32_Ehdr)); // checked by canPack()
sz_phdrs = ehdri.e_phnum * ehdri.e_phentsize;
phdri = new Elf32_Phdr[(unsigned)ehdri.e_phnum];
fi->seek(ehdri.e_phoff, SEEK_SET);
fi->readx(phdri, sz_phdrs);
generateElfHdr(fo, linux_i386elf_fold, getbrk(phdri, ehdri.e_phnum) );
}
void PackLinuxI386elf::pack2(OutputFile *fo, Filter &ft)
{
Extent x;
unsigned k;
// count passes, set ptload vars
ui_total_passes = 0;
off_t ptload0hi = 0, ptload1lo = 0, ptload1sz = 0;
for (k = 0; k < ehdri.e_phnum; ++k) {
if (PT_LOAD == phdri[k].p_type) {
x.offset = phdri[k].p_offset;
x.size = phdri[k].p_filesz;
if (0 == ptload0hi) {
ptload0hi = x.offset + x.size;
}
else if (0 == ptload1lo) {
ptload1lo = x.offset;
ptload1sz = x.size;
}
ui_total_passes++;
}
}
if (0!=ptload1sz && ptload0hi < ptload1lo)
ui_total_passes++;
// compress extents
unsigned total_in = 0;
unsigned total_out = 0;
ui_pass = -1; // Compressing Elf headers is invisible to UI.
x.offset = 0;
x.size = sizeof(Elf32_Ehdr) + sz_phdrs;
{
int const old_level = ph.level; ph.level = 10;
packExtent(x, total_in, total_out, 0, fo);
ph.level = old_level;
}
ui_pass = 0;
ft.addvalue = 0;
int nx = 0;
for (k = 0; k < ehdri.e_phnum; ++k) if (PT_LOAD==phdri[k].p_type) {
if (ft.id < 0x40) {
// FIXME: ?? ft.addvalue = phdri[k].p_vaddr;
}
x.offset = phdri[k].p_offset;
x.size = phdri[k].p_filesz;
if (0 == nx) { // 1st PT_LOAD must cover Ehdr at 0==p_offset
unsigned const delta = sizeof(Elf32_Ehdr) + sz_phdrs;
if (ft.id < 0x40) {
// FIXME: ?? ft.addvalue += delta;
}
x.offset += delta;
x.size -= delta;
}
packExtent(x, total_in, total_out,
((Elf32_Phdr::PF_X & phdri[k].p_flags)
? &ft : 0 ), fo );
++nx;
}
if (0!=ptload1sz && ptload0hi < ptload1lo) { // alignment hole?
x.offset = ptload0hi;
x.size = ptload1lo - ptload0hi;
packExtent(x, total_in, total_out, 0, fo);
}
if ((off_t)total_in < file_size) { // non-PT_LOAD stuff
x.offset = total_in;
x.size = file_size - total_in;
packExtent(x, total_in, total_out, 0, fo);
}
if ((off_t)total_in != file_size)
throwEOFException();
elfout.phdr[0].p_filesz = fo->getBytesWritten();
}
void PackLinuxI386elf::pack3(OutputFile *fo, Filter &ft)
{
unsigned disp;
unsigned len = fo->getBytesWritten();
unsigned const zero = 0;
fo->write(&zero, 3& -len); // align to 0 mod 4
len += (3& -len);
set_native32(&disp, len);
fo->write(&disp, sizeof(disp));
// We have packed multiple blocks, so PackLinuxI386::buildLinuxLoader
// needs an adjusted ph.c_len in order to get alignment correct.
unsigned const save_c_len = ph.c_len;
ph.c_len = sizeof(disp) + len - (
// Elf32_Edhr
sizeof(elfout.ehdr) +
// Elf32_Phdr: 1 for exec86, 2 for sh86, 3 for elf86
(elfout.ehdr.e_phentsize * elfout.ehdr.e_phnum) +
// checksum UPX! lsize version format
sizeof(l_info) +
// PT_DYNAMIC with DT_NEEDED "forwarded" from original file
((elfout.ehdr.e_phnum==3) ? (unsigned) elfout.phdr[2].p_memsz : 0u) +
// p_progid, p_filesize, p_blocksize
sizeof(p_info) +
// compressed data
b_len );
buildLoader(&ft); /* redo for final .align constraints */
ph.c_len = save_c_len;
super::pack3(fo, ft);
}
void PackLinuxI386elf::pack4(OutputFile *fo, Filter &ft)
{
super::pack4(fo, ft); // write PackHeader and overlay_offset
#if 0 /*{ where was this done already? FIXME */
#define PAGE_MASK (~0u<<12)
// pre-calculate for benefit of runtime disappearing act via munmap()
set_native32(&elfout.phdr[0].p_memsz, PAGE_MASK & (~PAGE_MASK + len));
#undef PAGE_MASK
#endif /*}*/
// rewrite Elf header
if (Elf32_Ehdr::ET_DYN==ehdri.e_type) {
// File being compressed was -pie.
// Turn the stub into -pie, too.
unsigned const base= elfout.phdr[0].p_vaddr;
elfout.ehdr.e_type= Elf32_Ehdr::ET_DYN;
elfout.ehdr.e_phnum= 1;
elfout.ehdr.e_entry -= base;
elfout.phdr[0].p_vaddr -= base;
elfout.phdr[0].p_paddr -= base;
elfout.phdr[0].p_flags |= Elf32_Phdr::PF_W;
}
fo->seek(0, SEEK_SET);
fo->rewrite(&elfout, sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr));
//fo->rewrite(&linfo, sizeof(linfo));
}
void PackLinuxI386elf::unpack(OutputFile *fo)
{
#define MAX_ELF_HDR 512
char bufehdr[MAX_ELF_HDR];
Elf32_Ehdr *const ehdr = (Elf32_Ehdr *)bufehdr;
Elf32_Phdr const *phdr = (Elf32_Phdr *)(1+ehdr);
unsigned szb_info = sizeof(b_info);
{
fi->seek(0, SEEK_SET);
fi->readx(bufehdr, MAX_ELF_HDR);
unsigned const e_entry = get_native32(&ehdr->e_entry);
if (e_entry < 0x401180) { /* old style, 8-byte b_info */
szb_info = 2*sizeof(unsigned);
}
}
fi->seek(overlay_offset, SEEK_SET);
p_info hbuf;
fi->readx(&hbuf, sizeof(hbuf));
unsigned orig_file_size = get_native32(&hbuf.p_filesize);
blocksize = get_native32(&hbuf.p_blocksize);
if (file_size > (off_t)orig_file_size || blocksize > orig_file_size)
throwCantUnpack("file header corrupted");
ibuf.alloc(blocksize + OVERHEAD);
b_info bhdr; memset(&bhdr, 0, sizeof(bhdr));
fi->readx(&bhdr, szb_info);
ph.u_len = get_native32(&bhdr.sz_unc);
ph.c_len = get_native32(&bhdr.sz_cpr);
ph.filter_cto = bhdr.b_cto8;
// Uncompress Ehdr and Phdrs.
fi->readx(ibuf, ph.c_len);
decompress(ibuf, (upx_byte *)ehdr, false);
unsigned total_in = 0;
unsigned total_out = 0;
unsigned c_adler = upx_adler32(NULL, 0);
unsigned u_adler = upx_adler32(NULL, 0);
off_t ptload0hi=0, ptload1lo=0, ptload1sz=0;
// decompress PT_LOAD
bool first_PF_X = true;
fi->seek(- (off_t) (szb_info + ph.c_len), SEEK_CUR);
for (unsigned j=0; j < ehdr->e_phnum; ++phdr, ++j) {
if (PT_LOAD==phdr->p_type) {
if (0==ptload0hi) {
ptload0hi = phdr->p_filesz + phdr->p_offset;
}
else if (0==ptload1lo) {
ptload1lo = phdr->p_offset;
ptload1sz = phdr->p_filesz;
}
if (fo)
fo->seek(phdr->p_offset, SEEK_SET);
if (Elf32_Phdr::PF_X & phdr->p_flags) {
unpackExtent(phdr->p_filesz, fo, total_in, total_out,
c_adler, u_adler, first_PF_X, szb_info);
first_PF_X = false;
}
else {
unpackExtent(phdr->p_filesz, fo, total_in, total_out,
c_adler, u_adler, false, szb_info);
}
}
}
if (0!=ptload1sz && ptload0hi < ptload1lo) { // alignment hole?
if (fo)
fo->seek(ptload0hi, SEEK_SET);
unpackExtent(ptload1lo - ptload0hi, fo, total_in, total_out,
c_adler, u_adler, false, szb_info);
}
if (total_out != orig_file_size) { // non-PT_LOAD stuff
if (fo)
fo->seek(0, SEEK_END);
unpackExtent(orig_file_size - total_out, fo, total_in, total_out,
c_adler, u_adler, false, szb_info);
}
// check for end-of-file
fi->readx(&bhdr, szb_info);
unsigned const sz_unc = ph.u_len = get_native32(&bhdr.sz_unc);
if (sz_unc == 0) { // uncompressed size 0 -> EOF
// note: magic is always stored le32
unsigned const sz_cpr = get_le32(&bhdr.sz_cpr);
if (sz_cpr != UPX_MAGIC_LE32) // sz_cpr must be h->magic
throwCompressedDataViolation();
}
else { // extra bytes after end?
throwCompressedDataViolation();
}
// update header with totals
ph.c_len = total_in;
ph.u_len = total_out;
// all bytes must be written
if (total_out != orig_file_size)
throwEOFException();
// finally test the checksums
if (ph.c_adler != c_adler || ph.u_adler != u_adler)
throwChecksumError();
#undef MAX_ELF_HDR
}
/*
vi:ts=4:et
*/
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