1/* arm_nrv2e_d8.S -- ARM decompressor for NRV2E 2 3 This file is part of the UPX executable compressor. 4 5 Copyright (C) 1996-2020 Markus Franz Xaver Johannes Oberhumer 6 Copyright (C) 1996-2020 Laszlo Molnar 7 Copyright (C) 2000-2020 John F. Reiser 8 All Rights Reserved. 9 10 UPX and the UCL library are free software; you can redistribute them 11 and/or modify them under the terms of the GNU General Public License as 12 published by the Free Software Foundation; either version 2 of 13 the License, or (at your option) any later version. 14 15 This program is distributed in the hope that it will be useful, 16 but WITHOUT ANY WARRANTY; without even the implied warranty of 17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18 GNU General Public License for more details. 19 20 You should have received a copy of the GNU General Public License 21 along with this program; see the file COPYING. 22 If not, write to the Free Software Foundation, Inc., 23 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 24 25 Markus F.X.J. Oberhumer Laszlo Molnar 26 <markus@oberhumer.com> <ezerotven+github@gmail.com> 27 28 John F. Reiser 29 <jreiser@users.sourceforge.net> 30*/ 31#define SAFE 0 /* 1 for src+dst bounds checking: cost 40 bytes */ 32 33#define src r0 34#define len r1 /* overlaps 'cnt' */ 35#define dst r2 36#define tmp r3 37#define bits r4 38#define off r5 39#define wrnk r6 /* 0x500 M2_MAX_OFFSET before "wrinkle" */ 40#define srclim r7 41#if 1==SAFE /*{*/ 42#define dstlim r12 43#endif /*}*/ 44 45#define cnt r1 /* overlaps 'len' while reading an offset */ 46 47#if 1==SAFE /*{*/ 48#define CHECK_SRC cmp src,srclim; bhs bad_src_n2e 49#define CHECK_DST cmp dst,dstlim; bhs bad_dst_n2e 50#else /*}{*/ 51#define CHECK_SRC /*empty*/ 52#define CHECK_DST /*empty*/ 53#endif /*}*/ 54 55#if 0 /*{ DEBUG only: check newly-decompressed against original dst */ 56#define CHECK_BYTE \ 57 push {wrnk}; \ 58 ldrb wrnk,[dst]; \ 59 cmp wrnk,tmp; beq 0f; bkpt; \ 600: pop {wrnk} 61#else /*}{*/ 62#define CHECK_BYTE /*empty*/ 63#endif /*}*/ 64 65/* "mov lr,pc; bxx ..." implements conditional subroutine call */ 66#define GETBIT add bits,bits; mov lr,pc; beq get1_n2e 67 68#define getnextb(reg) GETBIT; adc reg,reg 69#define jnextb0 GETBIT; bcc 70#define jnextb1 GETBIT; bcs 71 72#ifndef PURE_THUMB 73ucl_nrv2e_decompress_8: .globl ucl_nrv2e_decompress_8 @ ARM mode 74 .type ucl_nrv2e_decompress_8, %function 75/* error = (*)(char const *src, int len_src, char *dst, int *plen_dst) 76 Actual decompressed length is stored through plen_dst. 77 For SAFE mode: at call, *plen_dst must be allowed length of output buffer. 78*/ 79 adr r12,1+.thumb_nrv2e_d8; bx r12 @ enter THUMB mode 80 .code 16 @ THUMB mode 81 .thumb_func 82#endif 83 84.thumb_nrv2e_d8: 85 push {r2,r3, r4,r5,r6,r7, lr} 86#define sp_DST0 0 /* stack offset of original dst */ 87 add srclim,len,src @ srclim= eof_src; 88#if 1==SAFE /*{*/ 89 ldr tmp,[r3] @ len_dst 90 add tmp,dst 91 mov dstlim,tmp 92#endif /*}*/ 93 mov bits,#1; neg off,bits @ off= -1 initial condition 94 lsl bits,#31 @ 1<<31: refill next time 95 mov wrnk,#5 96 lsl wrnk,#8 @ 0x500 @ nrv2e M2_MAX_OFFSET 97 b top_n2e 98 99#if 1==SAFE /*{*/ 100bad_dst_n2e: # return value will be 2 101 add src,srclim,#1 102bad_src_n2e: # return value will be 1 103 add src,#1 104#endif /*}*/ 105eof_n2e: 106 pop {r3,r4} @ r3= orig_dst; r4= plen_dst 107 sub src,srclim @ 0 if actual src length equals expected length 108 sub dst,r3 @ actual dst length 109 str dst,[r4] 110 pop {r4,r5,r6,r7 /*,pc*/} 111 pop {r1}; bx r1 @ "pop {,pc}" fails return to ARM mode on ARMv4T 112 113get1_n2e: @ In: Carry set [from adding 0x80000000 (1<<31) to itself] 114 ldrb bits,[src] @ zero-extend next byte 115 adc bits,bits @ double and insert CarryIn as low bit 116 CHECK_SRC 117 add src,#1 118 lsl bits,#24 @ move to top byte, and set CarryOut from old bit 8 119 mov pc,lr @ return, stay in current (THUMB) mode 120 121lit_n2e: 122 CHECK_SRC; ldrb tmp,[src]; add src,#1 123 CHECK_BYTE 124 CHECK_DST; strb tmp,[dst]; add dst,#1 125top_n2e: 126 jnextb1 lit_n2e 127 mov cnt,#1; b getoff_n2e 128 129off_n2e: 130 sub cnt,#1 131 getnextb(cnt) 132getoff_n2e: 133 getnextb(cnt) 134 jnextb0 off_n2e 135 136 sub tmp,cnt,#3 @ set Carry 137 mov len,#0 @ Carry unaffected 138 blo offprev_n2e @ cnt was 2; tests Carry only 139 lsl tmp,#8 140 CHECK_SRC; ldrb off,[src]; add src,#1 @ low 7+1 bits 141 orr off,tmp 142 mvn off,off; beq eof_n2e @ off= ~off 143 asr off,#1; bcs lenlast_n2e 144 b lenmore_n2e 145 146offprev_n2e: 147 jnextb1 lenlast_n2e 148lenmore_n2e: 149 mov len,#1 150 jnextb1 lenlast_n2e 151len_n2e: 152 getnextb(len) 153 jnextb0 len_n2e 154 add len,#6-2 155 b gotlen_n2e 156 157lenlast_n2e: 158 getnextb(len) @ 0,1,2,3 159 add len,#2 160gotlen_n2e: @ 'cmn': add the inputs, set condition codes, discard the sum 161 cmn wrnk,off; bcs near_n2e @ within M2_MAX_OFFSET 162 add len,#1 @ too far away, so minimum match length is 3 163near_n2e: 164#if 1==SAFE /*{*/ 165 ldr tmp,[sp,#sp_DST0] 166 sub tmp,dst 167 sub tmp,off; bhi bad_dst_n2e @ reaching back too far 168 169 add tmp,dst,cnt 170 cmp tmp,dstlim; bhi bad_dst_n2e @ too much output 171#endif /*}*/ 172 ldrb tmp,[dst] @ force cacheline allocate 173copy_n2e: 174 ldrb tmp,[dst,off] 175 CHECK_BYTE 176 strb tmp,[dst]; add dst,#1 177 sub len,#1; bne copy_n2e 178 b top_n2e 179 180#ifndef PURE_THUMB 181 .size ucl_nrv2e_decompress_8, .-ucl_nrv2e_decompress_8 182#endif 183 184/* 185vi:ts=8:et:nowrap 186 */ 187 188