diff options
Diffstat (limited to 'contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/unnrv2b.S')
| -rw-r--r-- | contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/unnrv2b.S | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/unnrv2b.S b/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/unnrv2b.S new file mode 100644 index 0000000..f5724c1 --- /dev/null +++ b/contrib/syslinux-4.02/gpxe/src/arch/i386/prefix/unnrv2b.S @@ -0,0 +1,184 @@ +/* + * 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 + * + * - Modified to be compilable as either 16-bit or 32-bit code. + * Michael Brown 9 Mar 2005 + */ + +FILE_LICENCE ( GPL2_OR_LATER ) + +/**************************************************************************** + * This file provides the decompress() and decompress16() functions + * which can be called in order to decompress an image compressed with + * the nrv2b utility in src/util. + * + * These functions are designed to be called by the prefix. They are + * position-independent code. + * + * The same basic assembly code is used to compile both + * decompress() and decompress16(). + **************************************************************************** + */ + + .text + .arch i386 + .section ".prefix.lib", "ax", @progbits + +#ifdef CODE16 +/**************************************************************************** + * decompress16 (real-mode near call, position independent) + * + * Decompress data in 16-bit mode + * + * Parameters (passed via registers): + * %ds:%esi - Start of compressed input data + * %es:%edi - Start of output buffer + * Returns: + * %ds:%esi - End of compressed input data + * %es:%edi - End of decompressed output data + * All other registers are preserved + * + * NOTE: It would be possible to build a smaller version of the + * decompression code for -DKEEP_IT_REAL by using + * #define REG(x) x + * to use 16-bit registers where possible. This would impose limits + * that the compressed data size must be in the range [1,65533-%si] + * and the uncompressed data size must be in the range [1,65536-%di] + * (where %si and %di are the input values for those registers). Note + * particularly that the lower limit is 1, not 0, and that the upper + * limit on the input (compressed) data really is 65533, since the + * algorithm may read up to three bytes beyond the end of the input + * data, since it reads dwords. + **************************************************************************** + */ + +#define REG(x) e ## x +#define ADDR32 addr32 + + .code16 + .globl decompress16 +decompress16: + +#else /* CODE16 */ + +/**************************************************************************** + * decompress (32-bit protected-mode near call, position independent) + * + * Parameters (passed via registers): + * %ds:%esi - Start of compressed input data + * %es:%edi - Start of output buffer + * Returns: + * %ds:%esi - End of compressed input data + * %es:%edi - End of decompressed output data + * All other registers are preserved + **************************************************************************** + */ + +#define REG(x) e ## x +#define ADDR32 + + .code32 + .globl decompress +decompress: + +#endif /* CODE16 */ + +#define xAX REG(ax) +#define xCX REG(cx) +#define xBP REG(bp) +#define xSI REG(si) +#define xDI REG(di) + + /* Save registers */ + push %xAX + pushl %ebx + push %xCX + push %xBP + /* Do the decompression */ + cld + xor %xBP, %xBP + dec %xBP /* last_m_off = -1 */ + jmp dcl1_n2b + +decompr_literals_n2b: + ADDR32 movsb +decompr_loop_n2b: + addl %ebx, %ebx + jnz dcl2_n2b +dcl1_n2b: + call getbit32 +dcl2_n2b: + jc decompr_literals_n2b + xor %xAX, %xAX + inc %xAX /* m_off = 1 */ +loop1_n2b: + call getbit1 + adc %xAX, %xAX /* m_off = m_off*2 + getbit() */ + call getbit1 + jnc loop1_n2b /* while(!getbit()) */ + sub $3, %xAX + jb decompr_ebpeax_n2b /* if (m_off == 2) goto decompr_ebpeax_n2b ? */ + shl $8, %xAX + ADDR32 movb (%xSI), %al /* m_off = (m_off - 3)*256 + src[ilen++] */ + inc %xSI + xor $-1, %xAX + jz decompr_end_n2b /* if (m_off == 0xffffffff) goto decomp_end_n2b */ + mov %xAX, %xBP /* last_m_off = m_off ?*/ +decompr_ebpeax_n2b: + xor %xCX, %xCX + call getbit1 + adc %xCX, %xCX /* m_len = getbit() */ + call getbit1 + adc %xCX, %xCX /* m_len = m_len*2 + getbit()) */ + jnz decompr_got_mlen_n2b /* if (m_len == 0) goto decompr_got_mlen_n2b */ + inc %xCX /* m_len++ */ +loop2_n2b: + call getbit1 + adc %xCX, %xCX /* m_len = m_len*2 + getbit() */ + call getbit1 + jnc loop2_n2b /* while(!getbit()) */ + inc %xCX + inc %xCX /* m_len += 2 */ +decompr_got_mlen_n2b: + cmp $-0xd00, %xBP + adc $1, %xCX /* m_len = m_len + 1 + (last_m_off > 0xd00) */ + push %xSI + ADDR32 lea (%xBP,%xDI), %xSI /* m_pos = dst + olen + -m_off */ + rep + es ADDR32 movsb /* dst[olen++] = *m_pos++ while(m_len > 0) */ + pop %xSI + jmp decompr_loop_n2b + + +getbit1: + addl %ebx, %ebx + jnz 1f +getbit32: + ADDR32 movl (%xSI), %ebx + sub $-4, %xSI /* sets carry flag */ + adcl %ebx, %ebx +1: + ret + +decompr_end_n2b: + /* Restore registers and return */ + pop %xBP + pop %xCX + popl %ebx + pop %xAX + ret |