PowerPC unfilter, decompress, and register definitions
Added Files: ppc_bxx.S ppc_d_nrv2e.S ppc_regs.h committer: jreiser <jreiser> 1108855959 +0000
This commit is contained in:
John Reiser
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/* ppc_d_nrv2e.S -- PowerPC decompressor for NRV2E
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This file is part of the UPX executable compressor.
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Copyright (C) 1996-2004 Markus Franz Xaver Johannes Oberhumer
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Copyright (C) 1996-2004 Laszlo Molnar
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Copyright (C) 2000-2005 John F. Reiser
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All Rights Reserved.
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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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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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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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Markus F.X.J. Oberhumer Laszlo Molnar
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<mfx@users.sourceforge.net> <ml1050@users.sourceforge.net>
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John F. Reiser
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<jreiser@users.sourceforge.net>
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*/
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#include "ppc_regs.h"
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/* Returns 0 on success; non-zero on failure. */
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decompress: # (uchar const *src, size_t lsrc, uchar *dst, size_t &ldst)
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/* PowerPC has no 'cmplis': compare logical [unsigned] immediate shifted [by 16] */
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#define hibit r0 /* holds 0x80000000 during decompress */
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#define src a0
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#define lsrc a1
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#define dst a2
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#define ldst a3 /* Out: actually a reference: &len_dst */
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#define off a4
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#define len a5
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#define bits a6
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#define disp a7
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stw dst,0(ldst) # original dst
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add lsrc,lsrc,src # input eof
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lis hibit,0x8000 # 0x80000000 for detecting next bit
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lis bits,0x8000 # prepare for first load
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addi src,src,-1 # prepare for 'lbzu'
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addi dst,dst,-1 # prepare for 'stbu'
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li disp,-1 # initial displacement
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mflr t3 # return address
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b top_n2e
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/* jump on next bit, with branch prediction: y==>likely; n==>unlikely
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cr0 is set by the cmpl ["compare logical"==>unsigned]:
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lt next bit is 0
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gt next bit is 1
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eq must load next 32 bits from memory
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beql-: branch and link [call subroutine] if cr0 is eq, unlikely
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*/
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#define jnextb0y cmpl 0,bits,hibit; add bits,bits,bits; beql- get32; blt+
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#define jnextb0n cmpl 0,bits,hibit; add bits,bits,bits; beql- get32; blt-
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#define jnextb1y cmpl 0,bits,hibit; add bits,bits,bits; beql- get32; bgt+
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#define jnextb1n cmpl 0,bits,hibit; add bits,bits,bits; beql- get32; bgt-
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/* rotate next bit into bottom bit of reg */
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#define getnextb(reg) addc. bits,bits,bits; beql- get32; adde reg,reg,reg
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get32:
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# fetch 4 bytes unaligned and LITTLE ENDIAN
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#if 0 /*{ clean; but 4 instr larger, and 3 cycles longer */
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lbz bits,1(src) # lo8
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lbz t0,2(src); rlwimi bits,t0, 8,16,23
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lbz t0,3(src); rlwimi bits,t0,16, 8,15
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lbzu t0,4(src); rlwimi bits,t0,24, 0, 7
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#else /*}{ pray for no unalignment trap or slowdown */
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li bits,1 # compensate for 'lbzu'
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lwbrx bits,bits,src # bits= fetch_le32(bits+src)
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addi src,src,4
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#endif /*}*/
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cmpl 0,bits,hibit # cr0 for jnextb
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addc bits,bits,bits # CArry for getnextb
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ori bits,bits,1 # the flag bit
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ret
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lit_n2e:
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#define tmp len
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lbzu tmp,1(src)
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stbu tmp,1(dst)
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#undef tmp
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top_n2e:
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jnextb1y lit_n2e
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li off,1
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b getoff_n2e
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off_n2e:
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addi off,off,-1
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getnextb(off)
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getoff_n2e:
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getnextb(off)
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jnextb0n off_n2e
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li len,0
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addic. off,off,-3 # CArry set [and ignored], but no 'addi.'
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rlwinm off,off,8,0,31-8 # off<<=8;
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blt- offprev_n2e
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lbzu t0,1(src)
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nor. disp,off,t0 # disp = -(1+ (off|t0));
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srawi disp,disp,1 # shift off low bit (sets CArry; ignored)
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beq- eof_n2e
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andi. t0,t0,1 # complement of low bit of unshifted disp
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beq+ lenlast_n2e # low bit was 1
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b lenmore_n2e # low bit was 0
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offprev_n2e:
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jnextb1y lenlast_n2e
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lenmore_n2e:
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li len,1 # 1: "the msb"
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jnextb1y lenlast_n2e
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len_n2e:
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getnextb(len)
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jnextb0n len_n2e
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addi len,len,6-2-2
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b gotlen_n2e
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lenlast_n2e:
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getnextb(len) # 0,1,2,3
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gotlen_n2e:
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#define tmp off
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subfic tmp,disp,(~0)+(-0x500) # want CArry only
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#undef tmp
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addi len,len,2
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addze len,len # len += (disp < -0x500);
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#define back off
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add back,disp,dst # point back to match in dst
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mtctr len
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short_n2e:
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#define tmp len
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lbzu tmp,1(back)
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stbu tmp,1(dst)
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#undef tmp
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bdnz+ short_n2e
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b top_n2e
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#undef back
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eof_n2e:
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#define tmp r0 /* hibit is dead */
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lwz tmp,0(ldst) # original dst
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mtlr t3 # return address
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addi dst,dst,1 # uncorrect for 'stbu'
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addi src,src,1 # uncorrect for 'lbzu'
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subf dst,tmp,dst # dst -= tmp; // dst length
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#undef tmp
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subf a0,lsrc,src # src -= eof; // return 0: good; else: bad
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stw dst,0(ldst)
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ret
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