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281 lines
7.9 KiB
281 lines
7.9 KiB
#include "../common.h" |
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static void |
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print_mov(u8 wide, u8 swap, struct rm dest, struct rm src) |
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{ |
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const char **regs = wide ? REGS_W1 : REGS_W0; |
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if (swap) { |
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struct rm buf = dest; |
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dest = src; |
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src = buf; |
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} |
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printf("mov "); |
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/* Dest can not be an immediate, so dest.imm indicates if there's a displacement */ |
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if (dest.reg1 == NO_REGISTER && dest.reg2 == NO_REGISTER && dest.disp != 0) { |
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printf("[%d]", dest.disp); |
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} else if (dest.reg2 == NO_REGISTER && dest.imm == 0) { |
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printf("%s", regs[dest.reg1]); |
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} else if (dest.reg2 != NO_REGISTER && dest.imm == 0) { |
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printf("[%s + %s]", REGS_W1[dest.reg1], REGS_W1[dest.reg2]); |
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} else if (dest.reg2 == NO_REGISTER && dest.imm != 0) { |
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printf("[%s + %d]", REGS_W1[dest.reg1], dest.disp); |
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} else if (dest.reg2 != NO_REGISTER && dest.imm != 0) { |
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printf("[%s + %s + %d]", REGS_W1[dest.reg1], REGS_W1[dest.reg2], dest.disp); |
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} |
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printf(", "); |
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if (src.reg1 == NO_REGISTER) { |
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if (src.disp == 0) { |
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printf("%s %d", wide ? "word" : "byte", src.imm); /* only the src can be an immediate */ |
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} else { |
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printf("[%d]", src.disp); |
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} |
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} else { |
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if (src.reg2 == NO_REGISTER && src.imm == 0) { |
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printf("%s", regs[src.reg1]); |
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} else if (src.reg2 != NO_REGISTER && src.imm == 0) { |
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printf("[%s + %s]", REGS_W1[src.reg1], REGS_W1[src.reg2]); |
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} else if (src.reg2 == NO_REGISTER && src.imm != 0) { |
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printf("[%s + %d]", REGS_W1[src.reg1], src.disp); |
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} else if (src.reg2 != NO_REGISTER && src.imm != 0) { |
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printf("[%s + %s + %d]", REGS_W1[src.reg1], REGS_W1[src.reg2], src.disp); |
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} |
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} |
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printf("\n"); |
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} |
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static int |
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decode_rm(u8 *data, int offset, struct rm *location) |
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{ |
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int advance = 0; |
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u8 b2 = data[offset + 1]; |
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u8 mod = (b2 & 0xC0) >> 6; |
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u8 rm_field = b2 & 0x7; |
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if (mod == MOD_REGISTER) { |
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location->reg1 = rm_field; |
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location->reg2 = -1; |
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location->disp = 0; |
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location->imm = 0; |
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advance = 2; |
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} else if (mod == MOD_MEMORY) { |
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s16 b3 = data[offset + 2]; |
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s16 b4 = data[offset + 3]; |
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if (rm_field == 0x6) { |
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location->reg1 = NO_REGISTER; |
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location->reg2 = NO_REGISTER; |
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location->disp = (b4 << 8) | b3; |
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location->imm = 0; |
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advance = 4; |
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} else { |
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location->reg1 = MOD_PAIRS_FIRST[rm_field]; |
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location->reg2 = MOD_PAIRS_SECOND[rm_field]; |
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location->disp = 0; |
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location->imm = 1; |
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advance = 2; |
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} |
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} else if (mod == MOD_MEMORY_8) { |
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s8 b3 = data[offset + 2]; |
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location->reg1 = MOD_PAIRS_FIRST[rm_field]; |
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location->reg2 = MOD_PAIRS_SECOND[rm_field]; |
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location->disp = b3; |
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location->imm = 1; |
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advance = 3; |
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} else if (mod == MOD_MEMORY_16) { |
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s16 b3 = data[offset + 2]; |
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s16 b4 = data[offset + 3]; |
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location->reg1 = MOD_PAIRS_FIRST[rm_field]; |
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location->reg2 = MOD_PAIRS_SECOND[rm_field]; |
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location->disp = (b4 << 8) | b3; |
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location->imm = 1; |
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advance = 4; |
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} |
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return(advance); |
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} |
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static void |
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decode_and_print_more_movs(u8 *data, u64 size) |
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{ |
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printf("bits 16\n\n"); |
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/* We still do not handle corrupt binaries */ |
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u64 offset = 0; |
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while (offset < size) { |
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u8 b1 = data[offset + 0]; |
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if ((b1 & MASK_REG_RM) == OPCODE_REG_RM) { |
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u8 b2 = data[offset + 1]; |
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u8 W_flag = b1 & 0x1; |
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u8 D_flag = (b1 & 0x2) >> 1; |
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u8 reg_field = (b2 & 0x38) >> 3; |
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struct rm dest = { 0 }; |
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struct rm src = { 0 }; |
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dest.reg1 = reg_field; |
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dest.reg2 = -1; |
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dest.disp = 0; |
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dest.imm = 0; |
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offset += decode_rm(data, offset, &src); |
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print_mov(W_flag, !D_flag, dest, src); |
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} else if ((b1 & MASK_IMM_RM) == OPCODE_IMM_RM) { |
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u8 W_flag = b1 & 0x1; |
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u8 D_flag = 1; /* Immediate to register-memory always has mod/rm as destination */ |
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struct rm dest = { 0 }; |
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struct rm src = { 0 }; |
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offset += decode_rm(data, offset, &dest); |
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s16 immediate = 0; |
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if (W_flag) { |
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s16 b5 = data[offset]; |
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s16 b6 = data[offset + 1]; |
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immediate = (b6 << 8) | b5; |
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offset += 2; |
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} else { |
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s16 b5 = data[offset]; |
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immediate = b5; |
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offset += 1; |
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} |
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src.reg1 = NO_REGISTER; |
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src.imm = immediate; |
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print_mov(W_flag, !D_flag, dest, src); |
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} else if ((b1 & MASK_IMM_REG) == OPCODE_IMM_REG) { |
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u8 W_flag = (b1 & 0x8) >> 3; |
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u16 b2 = data[offset + 1]; |
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u8 reg = b1 & 0x7; |
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struct rm dest = { 0 }; |
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struct rm src = { 0 }; |
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dest.reg1 = reg; |
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dest.reg2 = NO_REGISTER; |
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dest.disp = 0; |
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dest.imm = 0; |
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s16 immediate = 0; |
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if (W_flag) { |
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/* A 16-bit immediate follows */ |
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u16 b3 = data[offset + 2]; |
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immediate = (b3 << 8) | b2; |
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offset += 3; |
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} else { |
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/* An 8-bit immediate follows */ |
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immediate = b2; |
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offset += 2; |
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} |
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src.reg1 = NO_REGISTER; |
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src.reg2 = NO_REGISTER; |
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src.disp = 0; |
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src.imm = immediate; |
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print_mov(W_flag, 0, dest, src); |
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} else if ((b1 & MASK_MEM_ACC) == OPCODE_MEM_ACC) { |
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u8 W_flag = b1 & 0x1; |
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u8 b2 = data[offset + 1]; |
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struct rm dest = { 0 }; |
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struct rm src = { 0 }; |
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dest.reg1 = AX; |
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dest.reg2 = NO_REGISTER; |
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dest.disp = 0; |
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dest.imm = 0; |
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u16 address = 0; |
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if (W_flag) { |
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u16 b3 = data[offset + 2]; |
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address = (b3 << 8) | b2; |
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offset += 3; |
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} else { |
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address = b2; |
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offset += 2; |
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} |
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src.reg1 = NO_REGISTER; |
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src.reg2 = NO_REGISTER; |
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src.disp = address; |
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src.imm = 0; |
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print_mov(W_flag, 0, dest, src); |
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} else if ((b1 & MASK_ACC_MEM) == OPCODE_ACC_MEM) { |
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u8 W_flag = b1 & 0x1; |
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u8 b2 = data[offset + 1]; |
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struct rm dest = { 0 }; |
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struct rm src = { 0 }; |
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dest.reg1 = AX; |
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dest.reg2 = NO_REGISTER; |
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dest.disp = 0; |
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dest.imm = 0; |
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u16 address = 0; |
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if (W_flag) { |
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u16 b3 = data[offset + 2]; |
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address = (b3 << 8) | b2; |
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offset += 3; |
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} else { |
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address = b2; |
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offset += 2; |
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} |
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src.reg1 = NO_REGISTER; |
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src.reg2 = NO_REGISTER; |
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src.disp = address; |
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src.imm = 0; |
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print_mov(W_flag, 1, dest, src); |
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} |
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} |
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} |
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int |
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main(int argc, char **argv) |
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{ |
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if (argc != 2) { |
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fprintf(stderr, "Usage: %s binary_file\n", argv[0]); |
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return(1); |
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} |
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char *filename = argv[1]; |
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int fd = open(filename, O_RDONLY); |
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if (fd == -1) { |
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perror("open"); |
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return(1); |
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} |
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u64 size = file_size(fd); |
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u8 *data = read_file(fd, size); |
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decode_and_print_more_movs(data, size); |
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return(0); |
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}
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