README.md

qx86

x86 assembler, disassembler and emulator in Q

Loading

Requires KDB 3.5 for the enhanced lambda metadata

\l path/to/qx86/x86.q

Usage

Disassembler

.x86das.disasm[addr;bytecode]

The address is used for jumps and calls.

Example:

q).x86das.disasm[0;0x0FB70C4F]
0i
0x0fb70c4f
"MOVZX ECX, WORD PTR DS:[EDI+2*ECX]"
`MOVZX
(`reg`ECX;(`mem;2;`DS;`EDI;2;`ECX;0))

The return value has the following elements:

1. Address
2. Bytecode (if the input had more bytes after the instruction, only the actual bytes belonging to the instruction are returned)
3. String representation of the instruction
4. Instruction type
5. Arguments as a list

• Immediate operand is (`imm;number)
• Register operand is (`reg;regname)
• Memory operand is (`mem;size;segment;basereg;multiplier;indexreg;offset)

Assembler

.x86asm.asm[addr;instruction]
.x86asm.asmAll[addr;instructions]

Example:

q).x86asm.asm[0;"MOVZX ECX, WORD PTR DS:[EDI+2*ECX]"]
0x0fb70c4f

q).x86asm.asmAll[0;("JMP L1";"DATA:";"DB 0x90909090";"L1:";"MOV DWORD PTR [DATA],0x01020304")]
0xe90400000090909090c7050500000004030201

Notes:

• Memory operands always need size (e.g. DWORD PTR)
• Max. 32-bit ints. Make sure to cast to int before using .x86util.shex on the number.
• Only DB supported for literal data.
• Only .x86asm.asmAll supports labels. Label definition is "LABEL:" on its own line. Labels are dumb search-and-replace, so don't make labels that may appear in other places than derefrences.

Emulator

.x86emu.blankState[]
.x86emu.run[st;inst]

inst must be the output from .x86das.disasm.

Example:

q)st:.x86emu.blankState[];
q)st:.x86emu.run[st;.x86das.disasm[0;0xB804030201]]
q)st`EAX
16909060i

Use .x86emu.smv[state;addr;bytes] to initialize memory and .x86emu.gmv[state;addr;size] to extract bytes from memory.