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/* arm_nrv2e_d8.S -- ARM decompressor for NRV2E
This file is part of the UPX executable compressor.
Copyright (C) 1996-2008 Markus Franz Xaver Johannes Oberhumer
Copyright (C) 1996-2008 Laszlo Molnar
Copyright (C) 2000-2008 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
<markus@oberhumer.com> <ml1050@users.sourceforge.net>
John F. Reiser
<jreiser@users.sourceforge.net>
*/
#define SAFE 0 /* 1 for src+dst bounds checking: cost 40 bytes */
#define src r0
#define len r1 /* overlaps 'cnt' */
#define dst r2
#define tmp r3
#define bits r4
#define off r5
#define wrnk r6 /* 0x500 M2_MAX_OFFSET before "wrinkle" */
#define srclim r7
#if 1==SAFE /*{*/
#define dstlim r12
#endif /*}*/
#define cnt r1 /* overlaps 'len' while reading an offset */
#if 1==SAFE /*{*/
#define CHECK_SRC cmp src,srclim; bhs bad_src_n2e
#define CHECK_DST cmp dst,dstlim; bhs bad_dst_n2e
#else /*}{*/
#define CHECK_SRC /*empty*/
#define CHECK_DST /*empty*/
#endif /*}*/
#if 0 /*{ DEBUG only: check newly-decompressed against original dst */
#define CHECK_BYTE \
push {wrnk}; \
ldrb wrnk,[dst]; \
cmp wrnk,tmp; beq 0f; bkpt; \
0: pop {wrnk}
#else /*}{*/
#define CHECK_BYTE /*empty*/
#endif /*}*/
/* "mov lr,pc; bxx ..." implements conditional subroutine call
*
* NOTE: the lsb will not be set, so you MUST NOT use 'bx lr' to return,
* else the T bit will be cleared and processor will go in ARM state */
#define GETBIT add bits,bits; mov lr,pc; beq get1_n2e
#define getnextb(reg) GETBIT; adc reg,reg
#define jnextb0 GETBIT; bcc
#define jnextb1 GETBIT; bcs
#ifndef PURE_THUMB
ucl_nrv2e_decompress_8: .globl ucl_nrv2e_decompress_8 @ ARM mode
.type ucl_nrv2e_decompress_8, %function
/* error = (*)(char const *src, int len_src, char *dst, int *plen_dst)
Actual decompressed length is stored through plen_dst.
For SAFE mode: at call, *plen_dst must be allowed length of output buffer.
*/
adr r12,1+.thumb_nrv2e_d8; bx r12 @ enter THUMB mode
#endif
.code 16 @ THUMB mode
.thumb_func
.thumb_nrv2e_d8:
#if 0
push {r2,r3, r4,r5,r6,r7, lr}
#define sp_DST0 0 /* stack offset of original dst */
#endif
add srclim,len,src @ srclim= eof_src;
#if 1==SAFE /*{*/
ldr tmp,[r3] @ len_dst
add tmp,dst
mov dstlim,tmp
#endif /*}*/
mov bits,#1; neg off,bits @ off= -1 initial condition
lsl bits,#31 @ 1<<31: refill next time
mov wrnk,#5
lsl wrnk,#8 @ 0x500 @ nrv2e M2_MAX_OFFSET
b top_n2e
#if 1==SAFE /*{*/
bad_dst_n2e: # return value will be 2
add src,srclim,#1
bad_src_n2e: # return value will be 1
add src,#1
#endif /*}*/
eof_n2e:
#if 0
pop {r3,r4} @ r3= orig_dst; r4= plen_dst
sub src,srclim @ 0 if actual src length equals expected length
sub dst,r3 @ actual dst length
str dst,[r4]
pop {r4,r5,r6,r7 /*,pc*/}
pop {r1}; bx r1 @ "pop {,pc}" fails return to ARM mode on ARMv4T
#else
mov r0, #0
bx r0 /* Branch to 0x0, switch to ARM mode */
#endif
get1_n2e: @ In: Carry set [from adding 0x80000000 (1<<31) to itself]
ldrb bits,[src] @ zero-extend next byte
adc bits,bits @ double and insert CarryIn as low bit
CHECK_SRC
add src,#1
lsl bits,#24 @ move to top byte, and set CarryOut from old bit 8
/* NOTE: the following instruction will not work on ARMv7+, because
* it will update the T bit and return into ARM state */
mov pc,lr @ return, stay in current (THUMB) mode
lit_n2e:
CHECK_SRC; ldrb tmp,[src]; add src,#1
CHECK_BYTE
CHECK_DST; strb tmp,[dst]; add dst,#1
top_n2e:
jnextb1 lit_n2e
mov cnt,#1; b getoff_n2e
off_n2e:
sub cnt,#1
getnextb(cnt)
getoff_n2e:
getnextb(cnt)
jnextb0 off_n2e
sub tmp,cnt,#3 @ set Carry
mov len,#0 @ Carry unaffected
blo offprev_n2e @ cnt was 2; tests Carry only
lsl tmp,#8
CHECK_SRC; ldrb off,[src]; add src,#1 @ low 7+1 bits
orr off,tmp
mvn off,off; beq eof_n2e @ off= ~off
asr off,#1; bcs lenlast_n2e
b lenmore_n2e
offprev_n2e:
jnextb1 lenlast_n2e
lenmore_n2e:
mov len,#1
jnextb1 lenlast_n2e
len_n2e:
getnextb(len)
jnextb0 len_n2e
add len,#6-2
b gotlen_n2e
lenlast_n2e:
getnextb(len) @ 0,1,2,3
add len,#2
gotlen_n2e: @ 'cmn': add the inputs, set condition codes, discard the sum
cmn wrnk,off; bcs near_n2e @ within M2_MAX_OFFSET
add len,#1 @ too far away, so minimum match length is 3
near_n2e:
#if 1==SAFE /*{*/
ldr tmp,[sp,#sp_DST0]
sub tmp,dst
sub tmp,off; bhi bad_dst_n2e @ reaching back too far
add tmp,dst,cnt
cmp tmp,dstlim; bhi bad_dst_n2e @ too much output
#endif /*}*/
ldrb tmp,[dst] @ force cacheline allocate
copy_n2e:
ldrb tmp,[dst,off]
CHECK_BYTE
strb tmp,[dst]; add dst,#1
sub len,#1; bne copy_n2e
b top_n2e
#ifndef PURE_THUMB
.size ucl_nrv2e_decompress_8, .-ucl_nrv2e_decompress_8
#endif
/*
vi:ts=8:et:nowrap
*/
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