129 lines
2.8 KiB
C
129 lines
2.8 KiB
C
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/*
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* xlat.c
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*
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* Translate
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*/
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#include "decoder.h"
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void NEAR init_decoder_translation(t_decoder_context *context)
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{
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context->dec_instr_pos = 0;
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}
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#ifdef ASM_TRANSLATE_E8
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ulong asm_decoder_translate_e8(ulong instr_pos, ulong file_size, byte *mem, long bytes);
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void NEAR decoder_translate_e8(t_decoder_context *context, byte *mem, long bytes)
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{
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/*
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* We don't want the ASM code to have to worry about where in the
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* context structure a particular element is
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*/
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context->dec_instr_pos = asm_decoder_translate_e8(
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context->dec_instr_pos,
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context->dec_current_file_size,
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mem,
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bytes
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);
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}
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#else /* !ASM_TRANSLATE_E8 */
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void NEAR decoder_translate_e8(t_decoder_context *context, byte *mem, long bytes)
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{
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ulong end_instr_pos;
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byte temp[6];
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byte *mem_backup;
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if (bytes <= 6)
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{
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context->dec_instr_pos += bytes;
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return;
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}
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mem_backup = mem;
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/* backup these bytes */
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memcpy(temp, &mem[bytes-6], 6);
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/* overwrite them with 0xE8 */
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memset(&mem[bytes-6], 0xE8, 6);
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end_instr_pos = context->dec_instr_pos + bytes - 6;
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while (1)
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{
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unsigned long absolute;
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#if !defined(_X86_)
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unsigned long offset;
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#endif
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/*
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* We are guaranteed to hit one of the 6 0xE8's we stuck at the
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* end of the buffer, even if we ran into some corrupted data
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* that resulted in our jumping over 5 bytes due to a translation
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*/
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while (*mem++ != 0xE8)
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context->dec_instr_pos++;
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if (context->dec_instr_pos >= end_instr_pos)
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break;
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/*
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* There are 5 or more bytes in the buffer
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* (i.e. E8 xx xx xx xx)
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*
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* We have a complete offset available to (potentially) translate
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*/
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#if defined(_X86_)
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absolute = *(ulong *) mem;
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#else
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absolute = ( (ulong)mem[0]) |
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(((ulong)mem[1])<<8) |
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(((ulong)mem[2])<<16)|
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(((ulong)mem[3])<<24);
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#endif
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if (absolute < context->dec_current_file_size)
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{
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/* absolute >= 0 && absolute < dec_current_file_size */
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#if defined(_X86_)
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*(ulong *) mem = absolute - context->dec_instr_pos;
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#else
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offset = absolute - context->dec_instr_pos;
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mem[0] = (byte) (offset & 255);
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mem[1] = (byte) ((offset >> 8) & 255);
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mem[2] = (byte) ((offset >> 16) & 255);
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mem[3] = (byte) ((offset >> 24) & 255);
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#endif
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}
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else if ((ulong) (-(long) absolute) <= context->dec_instr_pos)
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{
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/* absolute >= -instr_pos && absolute < 0 */
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#if defined(_X86_)
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*(ulong *) mem = absolute + context->dec_current_file_size;
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#else
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offset = absolute + context->dec_current_file_size;
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mem[0] = (byte) (offset & 255);
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mem[1] = (byte) (offset >> 8) & 255;
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mem[2] = (byte) (offset >> 16) & 255;
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mem[3] = (byte) (offset >> 24) & 255;
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#endif
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}
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mem += 4;
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context->dec_instr_pos += 5;
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}
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context->dec_instr_pos = end_instr_pos + 6;
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/* restore these bytes */
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memcpy(&mem_backup[bytes-6], temp, 6);
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}
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#endif
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