/* p_vmlinx.cpp -- pack vmlinux ET_EXEC file (before bootsect or setup) This file is part of the UPX executable compressor. Copyright (C) 2004 John Reiser Copyright (C) 1996-2004 Markus Franz Xaver Johannes Oberhumer Copyright (C) 1996-2004 Laszlo Molnar 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 markus@oberhumer.com ml1050@cdata.tvnet.hu John Reiser jreiser@users.sourceforge.net */ #include "conf.h" #include "file.h" #include "filter.h" #include "packer.h" #include "p_vmlinx.h" static const #include "stub/l_vmlinx.h" /************************************************************************* // **************************************************************************/ PackVmlinuxI386::PackVmlinuxI386(InputFile *f) : super(f), n_ptload(0), phdri(NULL), shdri(NULL) { } PackVmlinuxI386::~PackVmlinuxI386() { delete [] phdri; delete [] shdri; } const int *PackVmlinuxI386::getCompressionMethods(int method, int level) const { return Packer::getDefaultCompressionMethods_le32(method, level); } const int *PackVmlinuxI386::getFilters() const { static const int filters[] = { 0x49, -1 }; return filters; } static int __acc_cdecl_qsort compare_Phdr(void const *const aa, void const *const bb) { Elf_LE32_Phdr const *const a = (Elf_LE32_Phdr const *)aa; Elf_LE32_Phdr const *const b = (Elf_LE32_Phdr const *)bb; unsigned const xa = a->p_type - Elf_LE32_Phdr::PT_LOAD; unsigned const xb = b->p_type - Elf_LE32_Phdr::PT_LOAD; if (xa < xb) return -1; // PT_LOAD first if (xa > xb) return 1; if (a->p_paddr < b->p_paddr) return -1; // ascending by .p_paddr if (a->p_paddr > b->p_paddr) return 1; return 0; } // // Examples as of 2004-07-16 [readelf --segments vmlinux # before fiddling]: // //----- kernel-2.6.7 plain [defconfig?] //Program Headers(2): // Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align // LOAD 0x001000 0x00100000 0x00100000 0x1c7e61 0x1c7e61 R E 0x1000 // LOAD 0x1c8e64 0x002c8e64 0x002c8e64 0x00000 0x00000 RW 0x1000 // //----- kernel-2.6.7-1.488 Fedora Core 3 test 1 //Program Headers(5): // Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align // LOAD 0x001000 0x02100000 0x02100000 0x202246 0x202246 R E 0x1000 // LOAD 0x204000 0xffff3000 0x02303000 0x00664 0x00664 R E 0x1000 // LOAD 0x205000 0x02304000 0x02304000 0x43562 0x43562 R 0x1000 // LOAD 0x249000 0x02348000 0x02348000 0x81800 0xcb0fc RWE 0x1000 // STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RWE 0x4 // bool PackVmlinuxI386::canPack() { fi->seek(0, SEEK_SET); fi->readx(&ehdri, sizeof(ehdri)); // now check the ELF header if (memcmp(&ehdri, "\x7f\x45\x4c\x46\x01\x01\x01", 7) // ELF 32-bit LSB || !memcmp(&ehdri.e_ident[8], "FreeBSD", 7) // branded || ehdri.e_machine != 3 // Intel 80386 || ehdri.e_version != 1 // version ) return false; // additional requirements for vmlinux if (ehdri.e_ehsize != sizeof(ehdri) // different ? || ehdri.e_phoff != sizeof(ehdri) // Phdrs not contiguous with Ehdr || ehdri.e_phentsize!=sizeof(Elf_LE32_Phdr) || ehdri.e_type!=Elf_LE32_Ehdr::ET_EXEC || 0x00100000!=(0x001fffff & ehdri.e_entry) // entry not an odd 1MB ) { return false; } phdri = new Elf_LE32_Phdr[(unsigned) ehdri.e_phnum]; fi->seek(ehdri.e_phoff, SEEK_SET); fi->readx(phdri, ehdri.e_phnum * sizeof(*phdri)); // Put PT_LOAD together at the beginning, ascending by .p_paddr. qsort(phdri, ehdri.e_phnum, sizeof(*phdri), compare_Phdr); // Check that PT_LOADs form one contiguous chunk of the file. for (unsigned j = 0; j < ehdri.e_phnum; ++j) { if (Elf_LE32_Phdr::PT_LOAD==phdri[j].p_type) { if (0xfff & (phdri[j].p_offset | phdri[j].p_paddr | phdri[j].p_align | phdri[j].p_vaddr) ) { return false; } if (0 < j) { unsigned const sz = -phdri[j-1].p_align & (phdri[j-1].p_align -1 + phdri[j-1].p_filesz); if ((sz + phdri[j-1].p_offset)!=phdri[j].p_offset) { return false; } } ++n_ptload; sz_ptload = phdri[j].p_filesz + phdri[j].p_offset - phdri[0].p_offset; } } return 0 < n_ptload; } int PackVmlinuxI386::buildLoader(const Filter *ft) { // prepare loader initLoader(nrv_loader, sizeof(nrv_loader)); addLoader("LINUX000", (0x40==(0xf0 & ft->id)) ? "LXCKLLT1" : (ft->id ? "LXCALLT1" : ""), "LXMOVEUP", getDecompressor(), NULL ); if (ft->id) { assert(ft->calls > 0); if (0x40==(0xf0 & ft->id)) { addLoader("LXCKLLT9", NULL); } else { addLoader("LXCALLT9", NULL); } addFilter32(ft->id); } addLoader("LINUX990""IDENTSTR""UPX1HEAD", NULL); return getLoaderSize(); } void PackVmlinuxI386::pack(OutputFile *fo) { unsigned fo_off = 0; Elf_LE32_Ehdr ehdro; LE32 tmp_le32; // NULL // .text(PT_LOADs) .note(1st page) .note(rest) // .shstrtab /* .symtab .strtab */ Elf_LE32_Shdr shdro[1+3+1/*+2*/]; memset(shdro, 0, sizeof(shdro)); char const shstrtab[]= "\0.text\0.note\0.shstrtab\0.symtab\0.strtab"; char const *p = shstrtab; ibuf.alloc(file_size); obuf.allocForCompression(file_size); // .e_ident, .e_machine, .e_version, .e_flags memcpy(&ehdro, &ehdri, sizeof(ehdro)); ehdro.e_type = Elf_LE32_Ehdr::ET_REL; ehdro.e_entry = 0; ehdro.e_phoff = 0; ehdro.e_shoff = 0; // later ehdro.e_phentsize = 0; ehdro.e_phnum = 0; ehdro.e_shnum = 1+3+1/*+2*/; ehdro.e_shstrndx = 4; fo->write(&ehdro, sizeof(ehdro)); fo_off+= sizeof(ehdro); ph.u_len = sz_ptload; fi->seek(phdri[0].p_offset, SEEK_SET); fi->readx(ibuf, ph.u_len); checkAlreadyPacked(ibuf + ph.u_len - 1024, 1024); // prepare filter ph.filter = 0; Filter ft(ph.level); ft.buf_len = ph.u_len; ft.addvalue = 0; compressWithFilters(&ft, 1 << 20); const unsigned lsize = getLoaderSize(); MemBuffer loader(lsize); memcpy(loader, getLoader(), lsize); patchPackHeader(loader, lsize); patch_le32(loader, lsize, "ULEN", ph.u_len); patchFilter32(loader, lsize, &ft); while (0!=*p++) ; shdro[1].sh_name = ptr_diff(p, shstrtab); shdro[1].sh_type = Elf_LE32_Shdr::SHT_PROGBITS; shdro[1].sh_flags = Elf_LE32_Shdr::SHF_ALLOC | Elf_LE32_Shdr::SHF_EXECINSTR; shdro[1].sh_offset = fo_off; shdro[1].sh_size = 1+ 4+ ph.c_len + lsize; shdro[1].sh_addralign = 1; unsigned char const call = 0xE8; // opcode for CALL d32 fo->write(&call, 1); fo_off+=1; tmp_le32 = ph.c_len; fo->write(&tmp_le32, 4); fo_off += 4; fo->write(obuf, ph.c_len); fo_off += ph.c_len; fo->write(loader, lsize); fo_off += lsize; verifyOverlappingDecompression(); // .note with 1st page -------------------------------- ph.u_len = phdri[0].p_offset; fi->seek(0, SEEK_SET); fi->readx(ibuf, ph.u_len); compress(ibuf, obuf); while (0!=*p++) ; shdro[2].sh_name = ptr_diff(p, shstrtab); shdro[2].sh_type = Elf_LE32_Shdr::SHT_NOTE; shdro[2].sh_offset = fo_off; shdro[2].sh_size = sizeof(ph.u_len) + ph.c_len; shdro[2].sh_addralign = 1; tmp_le32 = ph.u_len; fo->write(&tmp_le32, 4); fo->write(obuf, ph.c_len); fo_off += shdro[2].sh_size; // .note with rest -------------------------------- ph.u_len = file_size - (sz_ptload + phdri[0].p_offset); fi->seek(sz_ptload + phdri[0].p_offset, SEEK_SET); fi->readx(ibuf, ph.u_len); // Temporarily decrease ph.level by about (1+ log2(sz_rest / sz_ptload)) // to avoid spending unreasonable effort compressing large symbol tables // that are discarded 99.9% of the time anyway. int const old_level = ph.level; for (unsigned v = ((ph.u_len>>3) + ph.u_len) / sz_ptload; 0 < v; v>>=1) { if (0== --ph.level) { ph.level = 1; } } compress(ibuf, obuf); ph.level = old_level; // while (0!=*p++) ; // name is the same shdro[3].sh_name = ptr_diff(p, shstrtab); shdro[3].sh_type = Elf_LE32_Shdr::SHT_NOTE; shdro[3].sh_offset = fo_off; shdro[3].sh_size = sizeof(ph.u_len) + ph.c_len; shdro[3].sh_addralign = 1; tmp_le32 = ph.u_len; fo->write(&tmp_le32, 4); fo->write(obuf, ph.c_len); fo_off += shdro[3].sh_size; while (0!=*p++) ; shdro[4].sh_name = ptr_diff(p, shstrtab); shdro[4].sh_type = Elf_LE32_Shdr::SHT_STRTAB; shdro[4].sh_offset = fo_off; shdro[4].sh_size = 1+ sizeof(shstrtab); // 1+: terminating '\0' shdro[4].sh_addralign = 1; fo->write(shstrtab, shdro[4].sh_size); fo_off += shdro[4].sh_size; #if 0 /*{ no symbols! */ while (0!=*p++) ; fo_off = ~3 & (3+ fo_off); shdro[5].sh_name = ptr_diff(p, shstrtab); shdro[5].sh_type = Elf_LE32_Shdr::SHT_SYMTAB; shdro[5].sh_offset = fo_off; shdro[5].sh_size = 16; // XXX ? shdro[5].sh_link = 6; // to .strtab for symbols shdro[5].sh_addralign = 4; shdro[5].sh_entsize = 16; // XXX Elf32_Sym fo->seek(fo_off, SEEK_SET); fo->write("\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16); fo_off += 16; while (0!=*p++) ; shdro[6].sh_name = ptr_diff(p, shstrtab); shdro[6].sh_type = Elf_LE32_Shdr::SHT_STRTAB; shdro[6].sh_offset = fo_off; shdro[6].sh_size = 1; // XXX ? shdro[6].sh_addralign = 1; fo->write("", 1); fo_off += 1; #endif /*}*/ fo_off = ~3 & (3+ fo_off); fo->seek(fo_off, SEEK_SET); ehdro.e_shoff = fo_off; fo->write(shdro, sizeof(shdro)); fo->seek(0, SEEK_SET); fo->write(&ehdro, sizeof(ehdro)); if (!checkFinalCompressionRatio(fo)) throwNotCompressible(); } /************************************************************************* // unpack **************************************************************************/ int PackVmlinuxI386::canUnpack() { fi->seek(0, SEEK_SET); fi->readx(&ehdri, sizeof(ehdri)); // now check the ELF header if (memcmp(&ehdri, "\x7f\x45\x4c\x46\x01\x01\x01", 7) // ELF 32-bit LSB || !memcmp(&ehdri.e_ident[8], "FreeBSD", 7) // branded || ehdri.e_machine != 3 // Intel 80386 || ehdri.e_version != 1 // version || ehdri.e_type != Elf_LE32_Ehdr::ET_REL || ehdri.e_shnum < 4 || (unsigned)file_size < (ehdri.e_shnum * sizeof(Elf_LE32_Shdr) + ehdri.e_shoff) ) return false; // find the .shstrtab section char shstrtab[40]; Elf_LE32_Shdr *p, *p_shstrtab=0; shdri = new Elf_LE32_Shdr[(unsigned) ehdri.e_shnum]; fi->seek(ehdri.e_shoff, SEEK_SET); fi->readx(shdri, ehdri.e_shnum * sizeof(*shdri)); int j; for (p = shdri, j= ehdri.e_shnum; --j>=0; ++p) { if (Elf_LE32_Shdr::SHT_STRTAB==p->sh_type && p->sh_size <= sizeof(shstrtab) && (p->sh_size + p->sh_offset) <= (unsigned) file_size && (10+ p->sh_name) <= p->sh_size // 1+ strlen(".shstrtab") ) { fi->seek(p->sh_offset, SEEK_SET); fi->readx(shstrtab, p->sh_size); if (0==strcmp(".shstrtab", shstrtab + p->sh_name)) { p_shstrtab = p; break; } } } if (0==p_shstrtab) { return false; } // check for .text .note .note and sane (.sh_size + .sh_offset) p_note0 = p_note1 = p_text = 0; for (p= shdri, j= ehdri.e_shnum; --j>=0; ++p) { if ((unsigned)file_size < (p->sh_size + p->sh_offset) || p_shstrtab->sh_size < (5+ p->sh_name) ) { continue; } if (0==strcmp(".text", shstrtab + p->sh_name)) { p_text = p; } if (0==strcmp(".note", shstrtab + p->sh_name)) { if (0==p_note0) { p_note0 = p; } else if (0==p_note1) { p_note1 = p; } } } if (0==p_text || 0==p_note0 || 0==p_note1) { return false; } char buf[1024]; fi->seek(p_text->sh_offset + p_text->sh_size - sizeof(buf), SEEK_SET); fi->readx(buf, sizeof(buf)); if (!getPackHeader(buf, sizeof(buf))) return false; return true; } void PackVmlinuxI386::unpack(OutputFile *fo) { unsigned char buf[5]; PackHeader const ph_tmp(ph); fi->seek(p_note0->sh_offset, SEEK_SET); fi->readx(&buf[0], 4); ph.u_len = get_le32(buf); ph.c_len = p_note0->sh_size - 4; ibuf.alloc(ph.c_len); fi->readx(ibuf, ph.c_len); obuf.allocForUncompression(ph.u_len); decompress(ibuf, obuf, false); fo->write(obuf, ph.u_len); obuf.dealloc(); ibuf.dealloc(); ph = ph_tmp; fi->seek(p_text->sh_offset, SEEK_SET); fi->readx(&buf[0], 5); if (0xE8!=buf[0] || get_le32(&buf[1]) != ph.c_len) { throwCantUnpack(".text corrupted"); } ibuf.alloc(ph.c_len); fi->readx(ibuf, ph.c_len); obuf.allocForUncompression(ph.u_len); decompress(ibuf, obuf); Filter ft(ph.level); ft.init(ph.filter, 0); ft.cto = (unsigned char) ph.filter_cto; ft.unfilter(obuf, ph.u_len); fo->write(obuf, ph.u_len); obuf.dealloc(); ibuf.dealloc(); fi->seek(p_note1->sh_offset, SEEK_SET); fi->readx(&buf[0], 4); ph.u_len = get_le32(buf); ph.c_len = p_note1->sh_size - 4; ibuf.alloc(ph.c_len); fi->readx(ibuf, p_note1->sh_size - sizeof(ph.u_len)); obuf.allocForUncompression(ph.u_len); decompress(ibuf, obuf, false); fo->write(obuf, ph.u_len); obuf.dealloc(); ibuf.dealloc(); ph = ph_tmp; } // // Example usage within build system of Linux kernel-2.6.7: // //----- arch/i386/boot/compressed/Makefile //# //# linux/arch/i386/boot/compressed/Makefile //# //# create a compressed vmlinux image from the original vmlinux //# // //targets := vmlinux upx-head.o upx-piggy.o // //LDFLAGS_vmlinux := -Ttext $(IMAGE_OFFSET) -e startup_32 // //$(obj)/vmlinux: $(obj)/upx-head.o $(obj)/upx-piggy.o FORCE // $(call if_changed,ld) // @: // //$(obj)/upx-piggy.o: vmlinux FORCE // rm -f $(obj)/upx-piggy.o // upx -o $(obj)/upx-piggy.o $< //----- // //----- arch/i386/boot/compressed/upx-head.S //#include // // .text //startup_32: .globl startup_32 # In: %esi=0x90000 setup data "real_mode pointer" // cli # but if it matters, then there is a race! // // movl $ __BOOT_DS,%eax // movl %eax,%ss; movl $0x99000,%esp # 2.6.7 setup had ss:sp of 9000:8ffe // /* Avoid EBDA (Extended BIOS Data Area) below 0xA0000. */ // // pushl $0; popf # subsumes "cli; cld"; also clears NT for buggy BIOS // // movl %eax,%ds # all non-code segments identical // movl %eax,%es // movl %eax,%fs // movl %eax,%gs // // movl $ 0x100000,%eax # destination of uncompression (and entry point) // pushl $ __BOOT_CS ///* Fall into .text of upx-compressed vmlinux. */ //----- // // Example test jig: // gcc -o test-piggy -nostartfiles -nostdlib test-piggy.o piggy.o // gdb test-piggy // (gdb) run >dumped //----- test-piggy.S //#include //#include // //dump: // movl $0x456789,%edx # length MODIFY THIS VALUE TO SUIT YOUR CASE // movl $0x100000,%ecx # base // movl $1,%ebx # stdout // movl $ __NR_write,%eax // int $0x80 // nop // hlt //mmap: // pushl %ebx // leal 2*4(%esp),%ebx // pushl $ __NR_mmap; popl %eax // int $0x80 // popl %ebx // ret $6*4 // //_start: .globl _start // nop // int3 # enter debugger! // pushl $0 // pushl $0 // pushl $ MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED // pushl $ PROT_EXEC | PROT_WRITE | PROT_READ // pushl $0x600000 # 6MB // pushl $0x100000 # 1MB // call mmap // push %cs ///* Fall into .text of upx-compressed vmlinux. */ //----- /* vi:ts=4:et */