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upx_itoa() in assembler to enforce no relocation
Makefile l_lx_exec.c upx_itoa.asm committer: jreiser <jreiser> 1037070863 +0000
This commit is contained in:
John Reiser
parent
f3b64cfe78
commit
de6e8c8020
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@ -322,11 +322,14 @@ fold_elf86.h: l_lx_elf.o fold_elf86.o l_lx_elf86.lds
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l_lx_exec.o: l_lx_exec.c
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$(CC_LINUX_I386) -c $<
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upx_itoa.o: upx_itoa.asm
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$(NASM) -f elf -o $@ $<
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fold_exec86.o: fold_exec86.asm
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$(NASM) -f elf -o $@ $<
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fold_exec86.h: l_lx_exec.o fold_exec86.o l_lx_exec86.lds
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ld -T $(srcdir)/l_lx_exec86.lds -Map $T.map -o $T.bin $T.o l_lx_exec.o
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fold_exec86.h: l_lx_exec.o upx_itoa.o fold_exec86.o l_lx_exec86.lds
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ld -T $(srcdir)/l_lx_exec86.lds -Map $T.map -o $T.bin $T.o l_lx_exec.o upx_itoa.o
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objcopy -S -R .comment -R .note $T.bin
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$(STRIPELF) $T.bin
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$(BRANDELF) $T.bin
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@ -73,33 +73,35 @@ static __inline__ int xwrite(int fd, const void *buf, int count)
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// util
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**************************************************************************/
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// FIXME: all code in this source file must be relocatible, so
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// we have to use `volatile' here.
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// FIXME: rewrite upx_itoa() in assembly
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static char *upx_itoa(char *buf, unsigned long v)
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{
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// const unsigned TEN = 10;
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volatile unsigned TEN = 10;
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char *p = buf;
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{
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unsigned long k = v;
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do {
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p++;
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k /= TEN;
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} while (k > 0);
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}
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buf = p;
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*p = 0;
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{
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unsigned long k = v;
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do {
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*--p = '0' + k % TEN;
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k /= TEN;
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} while (k > 0);
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}
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return buf;
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}
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extern char *
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__attribute__ ((regparm(2), stdcall)) // be ruthless
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upx_itoa(unsigned long v, char *buf);
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// Some versions of gcc optimize the division and/or remainder using
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// a multiplication by (2**32)/10, and use a relocatable 32-bit address
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// to reference the constant. We require no relocations because we move
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// the code at runtime. See upx_itoa.asm for replacement [also smaller.]
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//static char *upx_itoa(unsigned long v, char *buf)
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//{
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// volatile unsigned TEN = 10; // an ugly way to achieve no relocation
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// char *p = buf;
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// {
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// unsigned long k = v;
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// do {
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// p++;
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// k /= TEN;
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// } while (k > 0);
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// }
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// buf = p;
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// *p = 0;
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// {
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// unsigned long k = v;
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// do {
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// *--p = '0' + k % TEN;
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// k /= TEN;
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// } while (k > 0);
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// }
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// return buf;
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//}
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static uint32_t ascii5(char *p, uint32_t v, unsigned n)
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{
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@ -159,9 +161,9 @@ go_self(char const *tmpname, char *argv[], char *envp[])
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SET4(procself_buf + 0, '/', 'p', 'r', 'o');
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SET4(procself_buf + 4, 'c', '/', 0 , 0 );
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{
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char *const procself = upx_itoa(procself_buf + 6, getpid());
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char *const procself = upx_itoa(getpid(), procself_buf + 6);
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SET4(procself, '/', 'f', 'd', '/');
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upx_itoa(procself + 4, fdi);
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upx_itoa(fdi, procself + 4);
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}
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// Check for working /proc/self/fd/X by accessing the
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54
src/stub/upx_itoa.asm
Normal file
54
src/stub/upx_itoa.asm
Normal file
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@ -0,0 +1,54 @@
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; l_lx_itoa.asm -- decimal print; smaller than gcc, and no relocations
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;
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; This file is part of the UPX executable compressor.
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;
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; Copyright (C) 2002 John F. Reiser
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; All Rights Reserved.
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;
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; UPX and the UCL library are free software; you can redistribute them
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; and/or modify them under the terms of the GNU General Public License as
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; published by the Free Software Foundation; either version 2 of
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; the License, or (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program; see the file COPYING.
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; If not, write to the Free Software Foundation, Inc.,
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; 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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;
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; John F. Reiser
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; <jreiser@users.sourceforge.net>
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;
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BITS 32
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SECTION .text
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GLOBAL upx_itoa
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upx_itoa: ; char *upx_itoa(eax= unsigned v, edx= char *buf) /* 0<=(int)v */
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push edi ; save register
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mov edi,edx ; output ptr
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push byte 10
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cld
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pop ecx ; radix
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call recur
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mov [edi],ah ; NUL terminate
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xchg eax,edi ; eax= continuation point
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pop edi ; restore register
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ret
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recur:
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cdq ; zero extend eax into edx [use "sub edx,edx" if eax < 0 ]
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div ecx ; eax=quo, edx=rem; flags are undefined
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push edx
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test eax,eax
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je quo0
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call recur
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quo0:
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pop eax ; remainder
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add al, byte '0'
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stosb
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ret
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