diff options
Diffstat (limited to 'src/arch/i386/prefix/unnrv2b.S')
| -rw-r--r-- | src/arch/i386/prefix/unnrv2b.S | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/src/arch/i386/prefix/unnrv2b.S b/src/arch/i386/prefix/unnrv2b.S new file mode 100644 index 00000000..1836fa71 --- /dev/null +++ b/src/arch/i386/prefix/unnrv2b.S @@ -0,0 +1,129 @@ +/* + * Copyright (C) 1996-2002 Markus Franz Xaver Johannes Oberhumer + * + * This file is free software; you can redistribute it and/or + * modify it 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. + * + * Originally this code was part of ucl the data compression library + * for upx the ``Ultimate Packer of eXecutables''. + * + * - Converted to gas assembly, and refitted to work with etherboot. + * Eric Biederman 20 Aug 2002 + * + * - Structure modified to be a subroutine call rather than an + * executable prefix. + * Michael Brown 30 Mar 2004 + */ + + + .text + .arch i386 + .section ".prefix", "ax", @progbits + .code32 + + .globl decompress +decompress: + /* Save the initial register values */ + pushal + + /* + * See where I am running, and compute %ebp + * %ebp holds delta between physical and virtual addresses. + */ + call 1f +1: popl %ebp + subl $1b, %ebp + + /* "compressed" and "decompress_to" defined by linker script */ + /* move compressed image up to temporary area before decompressing */ + std + movl $_compressed_size, %ecx + leal _compressed+4-1(%ebp, %ecx), %esi + leal _compressed_copy-1(%ebp, %ecx), %edi + rep movsb + /* Setup to run the decompressor */ + cld + leal _compressed_copy(%ebp), %esi + leal decompress_to(%ebp), %edi + movl $-1, %ebp /* last_m_off = -1 */ + jmp dcl1_n2b + +/* ------------- DECOMPRESSION ------------- + + Input: + %esi - source + %edi - dest + %ebp - -1 + cld + + Output: + %eax - 0 + %ecx - 0 +*/ + +.macro getbit bits +.if \bits == 1 + addl %ebx, %ebx + jnz 1f +.endif + movl (%esi), %ebx + subl $-4, %esi /* sets carry flag */ + adcl %ebx, %ebx +1: +.endm + +decompr_literals_n2b: + movsb + +decompr_loop_n2b: + addl %ebx, %ebx + jnz dcl2_n2b +dcl1_n2b: + getbit 32 +dcl2_n2b: + jc decompr_literals_n2b + xorl %eax, %eax + incl %eax /* m_off = 1 */ +loop1_n2b: + getbit 1 + adcl %eax, %eax /* m_off = m_off*2 + getbit() */ + getbit 1 + jnc loop1_n2b /* while(!getbit()) */ + xorl %ecx, %ecx + subl $3, %eax + jb decompr_ebpeax_n2b /* if (m_off == 2) goto decompr_ebpeax_n2b ? */ + shll $8, %eax + movb (%esi), %al /* m_off = (m_off - 3)*256 + src[ilen++] */ + incl %esi + xorl $-1, %eax + jz decompr_end_n2b /* if (m_off == 0xffffffff) goto decomp_end_n2b */ + movl %eax, %ebp /* last_m_off = m_off ?*/ +decompr_ebpeax_n2b: + getbit 1 + adcl %ecx, %ecx /* m_len = getbit() */ + getbit 1 + adcl %ecx, %ecx /* m_len = m_len*2 + getbit()) */ + jnz decompr_got_mlen_n2b /* if (m_len == 0) goto decompr_got_mlen_n2b */ + incl %ecx /* m_len++ */ +loop2_n2b: + getbit 1 + adcl %ecx, %ecx /* m_len = m_len*2 + getbit() */ + getbit 1 + jnc loop2_n2b /* while(!getbit()) */ + incl %ecx + incl %ecx /* m_len += 2 */ +decompr_got_mlen_n2b: + cmpl $-0xd00, %ebp + adcl $1, %ecx /* m_len = m_len + 1 + (last_m_off > 0xd00) */ + pushl %esi + leal (%edi,%ebp), %esi /* m_pos = dst + olen + -m_off */ + rep + movsb /* dst[olen++] = *m_pos++ while(m_len > 0) */ + popl %esi + jmp decompr_loop_n2b +decompr_end_n2b: + /* Restore the initial register values */ + popal + ret |