iced-x86
[](https://crates.io/crates/iced-x86)
[](https://docs.rs/iced-x86)
[](#minimum-supported-rustc-version)
iced-x86 is a high performance and correct x86 (16/32/64-bit) instruction decoder, disassembler and assembler written in Rust.
It can be used for static analysis of x86/x64 binaries, to rewrite code (eg. remove garbage instructions), to relocate code or as a disassembler.
- ✔️Supports all Intel and AMD instructions
- ✔️Correct: All instructions are tested and iced has been tested against other disassemblers/assemblers (xed, gas, objdump, masm, dumpbin, nasm, ndisasm) and fuzzed
- ✔️100% Rust code
- ✔️The formatter supports masm, nasm, gas (AT&T), Intel (XED) and there are many options to customize the output
- ✔️The decoder is 4x+ faster than other similar libraries and doesn't allocate any memory
- ✔️Small decoded instructions, only 32 bytes
- ✔️The encoder can be used to re-encode decoded instructions at any address
- ✔️API to get instruction info, eg. read/written registers, memory and rflags bits; CPUID feature flag, flow control info, etc
- ✔️Supports `#![no_std]` and `WebAssembly`
- ✔️Supports `rustc` `1.20.0` or later
- ✔️Few dependencies (`static_assertions` and `lazy_static`)
- ✔️License: MIT
## Usage
Add this to your `Cargo.toml`:
```toml
[dependencies]
iced-x86 = "1.9.0"
```
Or to customize which features to use:
```toml
[dependencies.iced-x86]
version = "1.9.0"
default-features = false
# See below for all features
features = ["std", "decoder", "masm"]
```
If you're using Rust 2015 edition you must also add this to your `lib.rs` or `main.rs`:
```rust
extern crate iced_x86;
```
## Crate feature flags
You can enable/disable these in your `Cargo.toml` file.
- `decoder`: (✔️Enabled by default) Enables the decoder
- `encoder`: (✔️Enabled by default) Enables the encoder
- `block_encoder`: (✔️Enabled by default) Enables the [`BlockEncoder`]. This feature enables `encoder`
- `op_code_info`: (✔️Enabled by default) Enables getting instruction metadata ([`OpCodeInfo`]). This feature enables `encoder`
- `instr_info`: (✔️Enabled by default) Enables the instruction info code
- `gas`: (✔️Enabled by default) Enables the GNU Assembler (AT&T) formatter
- `intel`: (✔️Enabled by default) Enables the Intel (XED) formatter
- `masm`: (✔️Enabled by default) Enables the masm formatter
- `nasm`: (✔️Enabled by default) Enables the nasm formatter
- `fast_fmt`: (✔️Enabled by default) Enables `FastFormatter` (masm syntax) which is ~1.9x faster than the other formatters (the time includes decoding + formatting). Use it if formatting speed is more important than being able to re-assemble formatted instructions or if targeting wasm (this formatter uses less code).
- `db`: Enables creating `db`, `dw`, `dd`, `dq` instructions. It's not enabled by default because it's possible to store up to 16 bytes in the instruction and then use another method to read an enum value.
- `std`: (✔️Enabled by default) Enables the `std` crate. `std` or `no_std` must be defined, but not both.
- `no_std`: Enables `#![no_std]`. `std` or `no_std` must be defined, but not both. This feature uses the `alloc` crate (`rustc` `1.36.0+`) and the `hashbrown` crate.
- `exhaustive_enums`: Enables exhaustive enums, i.e., no enum has the `#[non_exhaustive]` attribute
- `no_vex`: Disables all `VEX` instructions. See below for more info.
- `no_evex`: Disables all `EVEX` instructions. See below for more info.
- `no_xop`: Disables all `XOP` instructions. See below for more info.
- `no_d3now`: Disables all `3DNow!` instructions. See below for more info.
If you use `no_vex`, `no_evex`, `no_xop` or `no_d3now`, you should run the generator again (before building iced) to generate even smaller output.
[`BlockEncoder`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.BlockEncoder.html
[`OpCodeInfo`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.OpCodeInfo.html
## How-tos
- [Disassemble (decode and format instructions)](#disassemble-decode-and-format-instructions)
- [Create and encode instructions](#create-and-encode-instructions)
- [Disassemble with a symbol resolver](#disassemble-with-a-symbol-resolver)
- [Disassemble with colorized text](#disassemble-with-colorized-text)
- [Move code in memory (eg. hook a function)](#move-code-in-memory-eg-hook-a-function)
- [Get instruction info, eg. read/written regs/mem, control flow info, etc](#get-instruction-info-eg-readwritten-regsmem-control-flow-info-etc)
- [Get the virtual address of a memory operand](#get-the-virtual-address-of-a-memory-operand)
- [Disassemble old/deprecated CPU instructions](#disassemble-olddeprecated-cpu-instructions)
## Disassemble (decode and format instructions)
This example uses a [`Decoder`] and one of the [`Formatter`]s to decode and format the code,
eg. [`GasFormatter`], [`IntelFormatter`], [`MasmFormatter`], [`NasmFormatter`], [`FastFormatter`].
[`Decoder`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.Decoder.html
[`Formatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/trait.Formatter.html
[`GasFormatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.GasFormatter.html
[`IntelFormatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.IntelFormatter.html
[`MasmFormatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.MasmFormatter.html
[`NasmFormatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.NasmFormatter.html
[`FastFormatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.FastFormatter.html
```rust
use iced_x86::{Decoder, DecoderOptions, Formatter, Instruction, NasmFormatter};
/*
This method produces the following output:
00007FFAC46ACDA4 48895C2410 mov [rsp+10h],rbx
00007FFAC46ACDA9 4889742418 mov [rsp+18h],rsi
00007FFAC46ACDAE 55 push rbp
00007FFAC46ACDAF 57 push rdi
00007FFAC46ACDB0 4156 push r14
00007FFAC46ACDB2 488DAC2400FFFFFF lea rbp,[rsp-100h]
00007FFAC46ACDBA 4881EC00020000 sub rsp,200h
00007FFAC46ACDC1 488B0518570A00 mov rax,[rel 7FFA`C475`24E0h]
00007FFAC46ACDC8 4833C4 xor rax,rsp
00007FFAC46ACDCB 488985F0000000 mov [rbp+0F0h],rax
00007FFAC46ACDD2 4C8B052F240A00 mov r8,[rel 7FFA`C474`F208h]
00007FFAC46ACDD9 488D05787C0400 lea rax,[rel 7FFA`C46F`4A58h]
00007FFAC46ACDE0 33FF xor edi,edi
*/
pub(crate) fn how_to_disassemble() {
let bytes = EXAMPLE_CODE;
let mut decoder = Decoder::new(EXAMPLE_CODE_BITNESS, bytes, DecoderOptions::NONE);
decoder.set_ip(EXAMPLE_CODE_RIP);
// Formatters: Masm*, Nasm*, Gas* (AT&T) and Intel* (XED).
// There's also `FastFormatter` which is ~1.9x faster. Use it if formatting speed is more
// important than being able to re-assemble formatted instructions.
let mut formatter = NasmFormatter::new();
// Change some options, there are many more
formatter.options_mut().set_digit_separator("`");
formatter.options_mut().set_first_operand_char_index(10);
// String implements FormatterOutput
let mut output = String::new();
// Initialize this outside the loop because decode_out() writes to every field
let mut instruction = Instruction::default();
// The decoder also implements Iterator/IntoIterator so you could use a for loop:
// for instruction in &mut decoder { /* ... */ }
// or collect():
// let instructions: Vec<_> = decoder.into_iter().collect();
// but can_decode()/decode_out() is a little faster:
while decoder.can_decode() {
// There's also a decode() method that returns an instruction but that also
// means it copies an instruction (32 bytes):
// instruction = decoder.decode();
decoder.decode_out(&mut instruction);
// Format the instruction ("disassemble" it)
output.clear();
formatter.format(&instruction, &mut output);
// Eg. "00007FFAC46ACDB2 488DAC2400FFFFFF lea rbp,[rsp-100h]"
print!("{:016X} ", instruction.ip());
let start_index = (instruction.ip() - EXAMPLE_CODE_RIP) as usize;
let instr_bytes = &bytes[start_index..start_index + instruction.len()];
for b in instr_bytes.iter() {
print!("{:02X}", b);
}
if instr_bytes.len() < HEXBYTES_COLUMN_BYTE_LENGTH {
for _ in 0..HEXBYTES_COLUMN_BYTE_LENGTH - instr_bytes.len() {
print!(" ");
}
}
println!(" {}", output);
}
}
const HEXBYTES_COLUMN_BYTE_LENGTH: usize = 10;
const EXAMPLE_CODE_BITNESS: u32 = 64;
const EXAMPLE_CODE_RIP: u64 = 0x0000_7FFA_C46A_CDA4;
static EXAMPLE_CODE: &[u8] = &[
0x48, 0x89, 0x5C, 0x24, 0x10, 0x48, 0x89, 0x74, 0x24, 0x18, 0x55, 0x57, 0x41, 0x56, 0x48, 0x8D,
0xAC, 0x24, 0x00, 0xFF, 0xFF, 0xFF, 0x48, 0x81, 0xEC, 0x00, 0x02, 0x00, 0x00, 0x48, 0x8B, 0x05,
0x18, 0x57, 0x0A, 0x00, 0x48, 0x33, 0xC4, 0x48, 0x89, 0x85, 0xF0, 0x00, 0x00, 0x00, 0x4C, 0x8B,
0x05, 0x2F, 0x24, 0x0A, 0x00, 0x48, 0x8D, 0x05, 0x78, 0x7C, 0x04, 0x00, 0x33, 0xFF,
];
```
## Create and encode instructions
This example uses a [`BlockEncoder`] to encode created [`Instruction`]s. This example needs the `db` feature because it creates `db` "instructions".
[`BlockEncoder`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.BlockEncoder.html
[`Instruction`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.Instruction.html
```rust
use iced_x86::{
BlockEncoder, BlockEncoderOptions, Code, Decoder, DecoderOptions, Formatter, GasFormatter,
Instruction, InstructionBlock, MemoryOperand, Register,
};
pub(crate) fn how_to_encode_instructions() {
let bitness = 64;
// All created instructions get an IP of 0. The label id is just an IP.
// The branch instruction's *target* IP should be equal to the IP of the
// target instruction.
let mut label_id: u64 = 1;
let mut create_label = || {
let id = label_id;
label_id += 1;
id
};
fn add_label(id: u64, mut instruction: Instruction) -> Instruction {
instruction.set_ip(id);
instruction
}
let label1 = create_label();
let mut instructions: Vec<Instruction> = Vec::new();
instructions.push(Instruction::with_reg(Code::Push_r64, Register::RBP));
instructions.push(Instruction::with_reg(Code::Push_r64, Register::RDI));
instructions.push(Instruction::with_reg(Code::Push_r64, Register::RSI));
instructions.push(Instruction::with_reg_u32(Code::Sub_rm64_imm32, Register::RSP, 0x50));
instructions.push(Instruction::with(Code::VEX_Vzeroupper));
instructions.push(Instruction::with_reg_mem(
Code::Lea_r64_m,
Register::RBP,
MemoryOperand::with_base_displ(Register::RSP, 0x60),
));
instructions.push(Instruction::with_reg_reg(Code::Mov_r64_rm64, Register::RSI, Register::RCX));
instructions.push(Instruction::with_reg_mem(
Code::Lea_r64_m,
Register::RDI,
MemoryOperand::with_base_displ(Register::RBP, -0x38),
));
instructions.push(Instruction::with_reg_i32(Code::Mov_r32_imm32, Register::ECX, 0x0A));
instructions.push(Instruction::with_reg_reg(Code::Xor_r32_rm32, Register::EAX, Register::EAX));
instructions.push(Instruction::with_rep_stosd(bitness));
instructions.push(Instruction::with_reg_u64(Code::Cmp_rm64_imm32, Register::RSI, 0x1234_5678));
// Create a branch instruction that references label1
instructions.push(Instruction::with_branch(Code::Jne_rel32_64, label1));
instructions.push(Instruction::with(Code::Nopd));
// Add the instruction that is the target of the branch
instructions.push(add_label(
label1,
Instruction::with_reg_reg(Code::Xor_r32_rm32, Register::R15D, Register::R15D),
));
// Create an instruction that accesses some data using an RIP relative memory operand
let data1 = create_label();
instructions.push(Instruction::with_reg_mem(
Code::Lea_r64_m,
Register::R14,
MemoryOperand::with_base_displ(Register::RIP, data1 as i32),
));
instructions.push(Instruction::with(Code::Nopd));
let raw_data: &[u8] = &[0x12, 0x34, 0x56, 0x78];
// Creating db/dw/dd/dq instructions requires the `db` feature or it will panic!()
instructions.push(add_label(data1, Instruction::with_declare_byte(raw_data)));
// Use BlockEncoder to encode a block of instructions. This block can contain any
// number of branches and any number of instructions. It does support encoding more
// than one block but it's rarely needed.
// It uses Encoder to encode all instructions.
// If the target of a branch is too far away, it can fix it to use a longer branch.
// This can be disabled by enabling some BlockEncoderOptions flags.
let target_rip = 0x0000_1248_FC84_0000;
let block = InstructionBlock::new(&instructions, target_rip);
let result = match BlockEncoder::encode(bitness, block, BlockEncoderOptions::NONE) {
Err(error) => panic!("Failed to encode it: {}", error),
Ok(result) => result,
};
// Now disassemble the encoded instructions. Note that the 'jmp near'
// instruction was turned into a 'jmp short' instruction because we
// didn't disable branch optimizations.
let bytes = result.code_buffer;
let mut output = String::new();
let bytes_code = &bytes[0..bytes.len() - raw_data.len()];
let bytes_data = &bytes[bytes.len() - raw_data.len()..];
let mut decoder = Decoder::new(bitness, bytes_code, DecoderOptions::NONE);
decoder.set_ip(target_rip);
let mut formatter = GasFormatter::new();
formatter.options_mut().set_first_operand_char_index(8);
for instruction in &mut decoder {
output.clear();
formatter.format(&instruction, &mut output);
println!("{:016X} {}", instruction.ip(), output);
}
// Creating db/dw/dd/dq instructions requires the `db` feature or it will panic!()
let db = Instruction::with_declare_byte(bytes_data);
output.clear();
formatter.format(&db, &mut output);
println!("{:016X} {}", decoder.ip(), output);
}
/*
Output:
00001248FC840000 push %rbp
00001248FC840001 push %rdi
00001248FC840002 push %rsi
00001248FC840003 sub $0x50,%rsp
00001248FC84000A vzeroupper
00001248FC84000D lea 0x60(%rsp),%rbp
00001248FC840012 mov %rcx,%rsi
00001248FC840015 lea -0x38(%rbp),%rdi
00001248FC840019 mov $0xA,%ecx
00001248FC84001E xor %eax,%eax
00001248FC840020 rep stos %eax,(%rdi)
00001248FC840022 cmp $0x12345678,%rsi
00001248FC840029 jne 0x00001248FC84002C
00001248FC84002B nop
00001248FC84002C xor %r15d,%r15d
00001248FC84002F lea 0x1248FC840037,%r14
00001248FC840036 nop
00001248FC840037 .byte 0x12,0x34,0x56,0x78
*/
```
## Disassemble with a symbol resolver
Creates a custom [`SymbolResolver`] that is called by a [`Formatter`].
[`SymbolResolver`]: https://docs.rs/iced-x86/1.9.0/iced_x86/trait.SymbolResolver.html
[`Formatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/trait.Formatter.html
```rust
use iced_x86::{
Decoder, DecoderOptions, Formatter, Instruction, MasmFormatter, SymbolResolver, SymbolResult,
};
use std::collections::HashMap;
struct MySymbolResolver {
map: HashMap<u64, String>,
}
impl SymbolResolver for MySymbolResolver {
fn symbol(
&mut self, _instruction: &Instruction, _operand: u32, _instruction_operand: Option<u32>,
address: u64, _address_size: u32,
) -> Option<SymbolResult> {
if let Some(symbol_string) = self.map.get(&address) {
// The 'address' arg is the address of the symbol and doesn't have to be identical
// to the 'address' arg passed to symbol(). If it's different from the input
// address, the formatter will add +N or -N, eg. '[rax+symbol+123]'
Some(SymbolResult::with_str(address, symbol_string.as_str()))
} else {
None
}
}
}
pub(crate) fn how_to_resolve_symbols() {
let bytes = b"\x48\x8B\x8A\xA5\x5A\xA5\x5A";
let mut decoder = Decoder::new(64, bytes, DecoderOptions::NONE);
let instr = decoder.decode();
let mut sym_map: HashMap<u64, String> = HashMap::new();
sym_map.insert(0x5AA5_5AA5, String::from("my_data"));
let mut output = String::new();
let resolver = Box::new(MySymbolResolver { map: sym_map });
// Create a formatter that uses our symbol resolver
let mut formatter = MasmFormatter::with_options(Some(resolver), None);
// This will call the symbol resolver for each immediate / displacement
// it finds in the instruction.
formatter.format(&instr, &mut output);
// Prints: mov rcx,[rdx+my_data]
println!("{}", output);
}
```
## Disassemble with colorized text
Creates a custom [`FormatterOutput`] that is called by a [`Formatter`].
This example will fail to compile unless you install the `colored` crate, see below.
[`FormatterOutput`]: https://docs.rs/iced-x86/1.9.0/iced_x86/trait.FormatterOutput.html
[`Formatter`]: https://docs.rs/iced-x86/1.9.0/iced_x86/trait.Formatter.html
```rust compile_fail
// This example uses crate colored = "2.0.0"
use colored::{ColoredString, Colorize};
use iced_x86::{
Decoder, DecoderOptions, Formatter, FormatterOutput, FormatterTextKind, IntelFormatter,
};
// Custom formatter output that stores the output in a vector.
struct MyFormatterOutput {
vec: Vec<(String, FormatterTextKind)>,
}
impl MyFormatterOutput {
pub fn new() -> Self {
Self { vec: Vec::new() }
}
}
impl FormatterOutput for MyFormatterOutput {
fn write(&mut self, text: &str, kind: FormatterTextKind) {
// This allocates a string. If that's a problem, just call print!() here
// instead of storing the result in a vector.
self.vec.push((String::from(text), kind));
}
}
pub(crate) fn how_to_colorize_text() {
let bytes = EXAMPLE_CODE;
let mut decoder = Decoder::new(EXAMPLE_CODE_BITNESS, bytes, DecoderOptions::NONE);
decoder.set_ip(EXAMPLE_CODE_RIP);
let mut formatter = IntelFormatter::new();
formatter.options_mut().set_first_operand_char_index(8);
let mut output = MyFormatterOutput::new();
for instruction in &mut decoder {
output.vec.clear();
// The formatter calls output.write() which will update vec with text/colors
formatter.format(&instruction, &mut output);
for (text, kind) in output.vec.iter() {
print!("{}", get_color(text.as_str(), *kind));
}
println!();
}
}
fn get_color(s: &str, kind: FormatterTextKind) -> ColoredString {
match kind {
FormatterTextKind::Directive | FormatterTextKind::Keyword => s.bright_yellow(),
FormatterTextKind::Prefix | FormatterTextKind::Mnemonic => s.bright_red(),
FormatterTextKind::Register => s.bright_blue(),
FormatterTextKind::Number => s.bright_cyan(),
_ => s.white(),
}
}
const EXAMPLE_CODE_BITNESS: u32 = 64;
const EXAMPLE_CODE_RIP: u64 = 0x0000_7FFA_C46A_CDA4;
static EXAMPLE_CODE: &[u8] = &[
0x48, 0x89, 0x5C, 0x24, 0x10, 0x48, 0x89, 0x74, 0x24, 0x18, 0x55, 0x57, 0x41, 0x56, 0x48, 0x8D,
0xAC, 0x24, 0x00, 0xFF, 0xFF, 0xFF, 0x48, 0x81, 0xEC, 0x00, 0x02, 0x00, 0x00, 0x48, 0x8B, 0x05,
0x18, 0x57, 0x0A, 0x00, 0x48, 0x33, 0xC4, 0x48, 0x89, 0x85, 0xF0, 0x00, 0x00, 0x00, 0x4C, 0x8B,
0x05, 0x2F, 0x24, 0x0A, 0x00, 0x48, 0x8D, 0x05, 0x78, 0x7C, 0x04, 0x00, 0x33, 0xFF,
];
```
## Move code in memory (eg. hook a function)
Uses instruction info API and the encoder to patch a function to jump to the programmer's function.
```rust
use iced_x86::{
BlockEncoder, BlockEncoderOptions, Code, Decoder, DecoderOptions, FlowControl, Formatter,
Instruction, InstructionBlock, NasmFormatter, OpKind,
};
// Decodes instructions from some address, then encodes them starting at some
// other address. This can be used to hook a function. You decode enough instructions
// until you have enough bytes to add a JMP instruction that jumps to your code.
// Your code will then conditionally jump to the original code that you re-encoded.
//
// This code uses the BlockEncoder which will help with some things, eg. converting
// short branches to longer branches if the target is too far away.
//
// 64-bit mode also supports RIP relative addressing, but the encoder can't rewrite
// those to use a longer displacement. If any of the moved instructions have RIP
// relative addressing and it tries to access data too far away, the encoder will fail.
// The easiest solution is to use OS alloc functions that allocate memory close to the
// original code (+/-2GB).
/*
This method produces the following output:
Original code:
00007FFAC46ACDA4 mov [rsp+10h],rbx
00007FFAC46ACDA9 mov [rsp+18h],rsi
00007FFAC46ACDAE push rbp
00007FFAC46ACDAF push rdi
00007FFAC46ACDB0 push r14
00007FFAC46ACDB2 lea rbp,[rsp-100h]
00007FFAC46ACDBA sub rsp,200h
00007FFAC46ACDC1 mov rax,[rel 7FFAC47524E0h]
00007FFAC46ACDC8 xor rax,rsp
00007FFAC46ACDCB mov [rbp+0F0h],rax
00007FFAC46ACDD2 mov r8,[rel 7FFAC474F208h]
00007FFAC46ACDD9 lea rax,[rel 7FFAC46F4A58h]
00007FFAC46ACDE0 xor edi,edi
Original + patched code:
00007FFAC46ACDA4 mov rax,123456789ABCDEF0h
00007FFAC46ACDAE jmp rax
00007FFAC46ACDB0 push r14
00007FFAC46ACDB2 lea rbp,[rsp-100h]
00007FFAC46ACDBA sub rsp,200h
00007FFAC46ACDC1 mov rax,[rel 7FFAC47524E0h]
00007FFAC46ACDC8 xor rax,rsp
00007FFAC46ACDCB mov [rbp+0F0h],rax
00007FFAC46ACDD2 mov r8,[rel 7FFAC474F208h]
00007FFAC46ACDD9 lea rax,[rel 7FFAC46F4A58h]
00007FFAC46ACDE0 xor edi,edi
Moved code:
00007FFAC48ACDA4 mov [rsp+10h],rbx
00007FFAC48ACDA9 mov [rsp+18h],rsi
00007FFAC48ACDAE push rbp
00007FFAC48ACDAF push rdi
00007FFAC48ACDB0 jmp 00007FFAC46ACDB0h
*/
pub(crate) fn how_to_move_code() {
let example_code = EXAMPLE_CODE.to_vec();
println!("Original code:");
disassemble(&example_code, EXAMPLE_CODE_RIP);
let mut decoder = Decoder::new(EXAMPLE_CODE_BITNESS, &example_code, DecoderOptions::NONE);
decoder.set_ip(EXAMPLE_CODE_RIP);
// In 64-bit mode, we need 12 bytes to jump to any address:
// mov rax,imm64 // 10
// jmp rax // 2
// We overwrite rax because it's probably not used by the called function.
// In 32-bit mode, a normal JMP is just 5 bytes
let required_bytes = 10 + 2;
let mut total_bytes = 0;
let mut orig_instructions: Vec<Instruction> = Vec::new();
for instr in &mut decoder {
orig_instructions.push(instr);
total_bytes += instr.len() as u32;
if instr.is_invalid() {
panic!("Found garbage");
}
if total_bytes >= required_bytes {
break;
}
match instr.flow_control() {
FlowControl::Next => {}
FlowControl::UnconditionalBranch => {
if instr.op0_kind() == OpKind::NearBranch64 {
let _target = instr.near_branch_target();
// You could check if it's just jumping forward a few bytes and follow it
// but this is a simple example so we'll fail.
}
panic!("Not supported by this simple example");
}
FlowControl::IndirectBranch
| FlowControl::ConditionalBranch
| FlowControl::Return
| FlowControl::Call
| FlowControl::IndirectCall
| FlowControl::Interrupt
| FlowControl::XbeginXabortXend
| FlowControl::Exception => panic!("Not supported by this simple example"),
}
}
if total_bytes < required_bytes {
panic!("Not enough bytes!");
}
assert!(!orig_instructions.is_empty());
// Create a JMP instruction that branches to the original code, except those instructions
// that we'll re-encode. We don't need to do it if it already ends in 'ret'
let (jmp_back_addr, add) = {
let last_instr = orig_instructions.last().unwrap();
if last_instr.flow_control() != FlowControl::Return {
(last_instr.next_ip(), true)
} else {
(last_instr.next_ip(), false)
}
};
if add {
orig_instructions.push(Instruction::with_branch(Code::Jmp_rel32_64, jmp_back_addr));
}
// Relocate the code to some new location. It can fix short/near branches and
// convert them to short/near/long forms if needed. This also works even if it's a
// jrcxz/loop/loopcc instruction which only have short forms.
//
// It can currently only fix RIP relative operands if the new location is within 2GB
// of the target data location.
//
// Note that a block is not the same thing as a basic block. A block can contain any
// number of instructions, including any number of branch instructions. One block
// should be enough unless you must relocate different blocks to different locations.
let relocated_base_address = EXAMPLE_CODE_RIP + 0x20_0000;
let block = InstructionBlock::new(&orig_instructions, relocated_base_address);
// This method can also encode more than one block but that's rarely needed, see above comment.
let result = match BlockEncoder::encode(decoder.bitness(), block, BlockEncoderOptions::NONE) {
Err(err) => panic!("{}", err),
Ok(result) => result,
};
let new_code = result.code_buffer;
// Patch the original code. Pretend that we use some OS API to write to memory...
// We could use the BlockEncoder/Encoder for this but it's easy to do yourself too.
// This is 'mov rax,imm64; jmp rax'
const YOUR_FUNC: u64 = 0x1234_5678_9ABC_DEF0; // Address of your code
let mut example_code = example_code.to_vec();
example_code[0] = 0x48; // \ 'MOV RAX,imm64'
example_code[1] = 0xB8; // /
let mut v = YOUR_FUNC;
for p in &mut example_code[2..10] {
*p = v as u8;
v >>= 8;
}
example_code[10] = 0xFF; // \ JMP RAX
example_code[11] = 0xE0; // /
// Disassemble it
println!("Original + patched code:");
disassemble(&example_code, EXAMPLE_CODE_RIP);
// Disassemble the moved code
println!("Moved code:");
disassemble(&new_code, relocated_base_address);
}
fn disassemble(data: &[u8], ip: u64) {
let mut formatter = NasmFormatter::new();
let mut output = String::new();
let mut decoder = Decoder::new(EXAMPLE_CODE_BITNESS, data, DecoderOptions::NONE);
decoder.set_ip(ip);
for instruction in &mut decoder {
output.clear();
formatter.format(&instruction, &mut output);
println!("{:016X} {}", instruction.ip(), output);
}
println!();
}
const EXAMPLE_CODE_BITNESS: u32 = 64;
const EXAMPLE_CODE_RIP: u64 = 0x0000_7FFA_C46A_CDA4;
static EXAMPLE_CODE: &[u8] = &[
0x48, 0x89, 0x5C, 0x24, 0x10, 0x48, 0x89, 0x74, 0x24, 0x18, 0x55, 0x57, 0x41, 0x56, 0x48, 0x8D,
0xAC, 0x24, 0x00, 0xFF, 0xFF, 0xFF, 0x48, 0x81, 0xEC, 0x00, 0x02, 0x00, 0x00, 0x48, 0x8B, 0x05,
0x18, 0x57, 0x0A, 0x00, 0x48, 0x33, 0xC4, 0x48, 0x89, 0x85, 0xF0, 0x00, 0x00, 0x00, 0x4C, 0x8B,
0x05, 0x2F, 0x24, 0x0A, 0x00, 0x48, 0x8D, 0x05, 0x78, 0x7C, 0x04, 0x00, 0x33, 0xFF,
];
```
## Get instruction info, eg. read/written regs/mem, control flow info, etc
Shows how to get used registers/memory and other info. It uses [`Instruction`] methods
and an [`InstructionInfoFactory`] to get this info.
[`Instruction`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.Instruction.html
[`InstructionInfoFactory`]: https://docs.rs/iced-x86/1.9.0/iced_x86/struct.InstructionInfoFactory.html
```rust
use iced_x86::{
ConditionCode, Decoder, DecoderOptions, Instruction, InstructionInfoFactory, OpKind, RflagsBits,
};
/*
This method produces the following output:
00007FFAC46ACDA4 mov [rsp+10h],rbx
OpCode: o64 89 /r
Instruction: MOV r/m64, r64
Encoding: Legacy
Mnemonic: Mov
Code: Mov_rm64_r64
CpuidFeature: X64
FlowControl: Next
Displacement offset = 4, size = 1
Memory size: 8
Op0Access: Write
Op1Access: Read
Op0: r64_or_mem
Op1: r64_reg
Used reg: RSP:Read
Used reg: RBX:Read
Used mem: [SS:RSP+0x10;UInt64;Write]
00007FFAC46ACDA9 mov [rsp+18h],rsi
OpCode: o64 89 /r
Instruction: MOV r/m64, r64
Encoding: Legacy
Mnemonic: Mov
Code: Mov_rm64_r64
CpuidFeature: X64
FlowControl: Next
Displacement offset = 4, size = 1
Memory size: 8
Op0Access: Write
Op1Access: Read
Op0: r64_or_mem
Op1: r64_reg
Used reg: RSP:Read
Used reg: RSI:Read
Used mem: [SS:RSP+0x18;UInt64;Write]
00007FFAC46ACDAE push rbp
OpCode: o64 50+ro
Instruction: PUSH r64
Encoding: Legacy
Mnemonic: Push
Code: Push_r64
CpuidFeature: X64
FlowControl: Next
SP Increment: -8
Op0Access: Read
Op0: r64_opcode
Used reg: RBP:Read
Used reg: RSP:ReadWrite
Used mem: [SS:RSP+0xFFFFFFFFFFFFFFF8;UInt64;Write]
00007FFAC46ACDAF push rdi
OpCode: o64 50+ro
Instruction: PUSH r64
Encoding: Legacy
Mnemonic: Push
Code: Push_r64
CpuidFeature: X64
FlowControl: Next
SP Increment: -8
Op0Access: Read
Op0: r64_opcode
Used reg: RDI:Read
Used reg: RSP:ReadWrite
Used mem: [SS:RSP+0xFFFFFFFFFFFFFFF8;UInt64;Write]
00007FFAC46ACDB0 push r14
OpCode: o64 50+ro
Instruction: PUSH r64
Encoding: Legacy
Mnemonic: Push
Code: Push_r64
CpuidFeature: X64
FlowControl: Next
SP Increment: -8
Op0Access: Read
Op0: r64_opcode
Used reg: R14:Read
Used reg: RSP:ReadWrite
Used mem: [SS:RSP+0xFFFFFFFFFFFFFFF8;UInt64;Write]
00007FFAC46ACDB2 lea rbp,[rsp-100h]
OpCode: o64 8D /r
Instruction: LEA r64, m
Encoding: Legacy
Mnemonic: Lea
Code: Lea_r64_m
CpuidFeature: X64
FlowControl: Next
Displacement offset = 4, size = 4
Op0Access: Write
Op1Access: NoMemAccess
Op0: r64_reg
Op1: mem
Used reg: RBP:Write
Used reg: RSP:Read
00007FFAC46ACDBA sub rsp,200h
OpCode: o64 81 /5 id
Instruction: SUB r/m64, imm32
Encoding: Legacy
Mnemonic: Sub
Code: Sub_rm64_imm32
CpuidFeature: X64
FlowControl: Next
Immediate offset = 3, size = 4
RFLAGS Written: OF, SF, ZF, AF, CF, PF
RFLAGS Modified: OF, SF, ZF, AF, CF, PF
Op0Access: ReadWrite
Op1Access: Read
Op0: r64_or_mem
Op1: imm32sex64
Used reg: RSP:ReadWrite
00007FFAC46ACDC1 mov rax,[7FFAC47524E0h]
OpCode: o64 8B /r
Instruction: MOV r64, r/m64
Encoding: Legacy
Mnemonic: Mov
Code: Mov_r64_rm64
CpuidFeature: X64
FlowControl: Next
Displacement offset = 3, size = 4
Memory size: 8
Op0Access: Write
Op1Access: Read
Op0: r64_reg
Op1: r64_or_mem
Used reg: RAX:Write
Used mem: [DS:0x7FFAC47524E0;UInt64;Read]
00007FFAC46ACDC8 xor rax,rsp
OpCode: o64 33 /r
Instruction: XOR r64, r/m64
Encoding: Legacy
Mnemonic: Xor
Code: Xor_r64_rm64
CpuidFeature: X64
FlowControl: Next
RFLAGS Written: SF, ZF, PF
RFLAGS Cleared: OF, CF
RFLAGS Undefined: AF
RFLAGS Modified: OF, SF, ZF, AF, CF, PF
Op0Access: ReadWrite
Op1Access: Read
Op0: r64_reg
Op1: r64_or_mem
Used reg: RAX:ReadWrite
Used reg: RSP:Read
00007FFAC46ACDCB mov [rbp+0F0h],rax
OpCode: o64 89 /r
Instruction: MOV r/m64, r64
Encoding: Legacy
Mnemonic: Mov
Code: Mov_rm64_r64
CpuidFeature: X64
FlowControl: Next
Displacement offset = 3, size = 4
Memory size: 8
Op0Access: Write
Op1Access: Read
Op0: r64_or_mem
Op1: r64_reg
Used reg: RBP:Read
Used reg: RAX:Read
Used mem: [SS:RBP+0xF0;UInt64;Write]
00007FFAC46ACDD2 mov r8,[7FFAC474F208h]
OpCode: o64 8B /r
Instruction: MOV r64, r/m64
Encoding: Legacy
Mnemonic: Mov
Code: Mov_r64_rm64
CpuidFeature: X64
FlowControl: Next
Displacement offset = 3, size = 4
Memory size: 8
Op0Access: Write
Op1Access: Read
Op0: r64_reg
Op1: r64_or_mem
Used reg: R8:Write
Used mem: [DS:0x7FFAC474F208;UInt64;Read]
00007FFAC46ACDD9 lea rax,[7FFAC46F4A58h]
OpCode: o64 8D /r
Instruction: LEA r64, m
Encoding: Legacy
Mnemonic: Lea
Code: Lea_r64_m
CpuidFeature: X64
FlowControl: Next
Displacement offset = 3, size = 4
Op0Access: Write
Op1Access: NoMemAccess
Op0: r64_reg
Op1: mem
Used reg: RAX:Write
00007FFAC46ACDE0 xor edi,edi
OpCode: o32 33 /r
Instruction: XOR r32, r/m32
Encoding: Legacy
Mnemonic: Xor
Code: Xor_r32_rm32
CpuidFeature: INTEL386
FlowControl: Next
RFLAGS Cleared: OF, SF, CF
RFLAGS Set: ZF, PF
RFLAGS Undefined: AF
RFLAGS Modified: OF, SF, ZF, AF, CF, PF
Op0Access: Write
Op1Access: None
Op0: r32_reg
Op1: r32_or_mem
Used reg: RDI:Write
*/
pub(crate) fn how_to_get_instruction_info() {
let mut decoder = Decoder::new(EXAMPLE_CODE_BITNESS, EXAMPLE_CODE, DecoderOptions::NONE);
decoder.set_ip(EXAMPLE_CODE_RIP);
// Use a factory to create the instruction info if you need register and
// memory usage. If it's something else, eg. encoding, flags, etc, there
// are Instruction methods that can be used instead.
let mut info_factory = InstructionInfoFactory::new();
let mut instr = Instruction::default();
while decoder.can_decode() {
decoder.decode_out(&mut instr);
// Gets offsets in the instruction of the displacement and immediates and their sizes.
// This can be useful if there are relocations in the binary. The encoder has a similar
// method. This method must be called after decode() and you must pass in the last
// instruction decode() returned.
let offsets = decoder.get_constant_offsets(&instr);
// For quick hacks, it's fine to use the Display trait to format an instruction,
// but for real code, use a formatter, eg. MasmFormatter. See other examples.
println!("{:016X} {}", instr.ip(), instr);
let op_code = instr.op_code();
let info = info_factory.info(&instr);
println!(" OpCode: {}", op_code.op_code_string());
println!(" Instruction: {}", op_code.instruction_string());
println!(" Encoding: {:?}", instr.encoding());
println!(" Mnemonic: {:?}", instr.mnemonic());
println!(" Code: {:?}", instr.code());
println!(
" CpuidFeature: {}",
instr
.cpuid_features()
.iter()
.map(|&a| format!("{:?}", a))
.collect::<Vec<String>>()
.join(" and ")
);
println!(" FlowControl: {:?}", instr.flow_control());
if offsets.has_displacement() {
println!(
" Displacement offset = {}, size = {}",
offsets.displacement_offset(),
offsets.displacement_size()
);
}
if offsets.has_immediate() {
println!(
" Immediate offset = {}, size = {}",
offsets.immediate_offset(),
offsets.immediate_size()
);
}
if offsets.has_immediate2() {
println!(
" Immediate #2 offset = {}, size = {}",
offsets.immediate_offset2(),
offsets.immediate_size2()
);
}
if instr.is_stack_instruction() {
println!(" SP Increment: {}", instr.stack_pointer_increment());
}
if instr.condition_code() != ConditionCode::None {
println!(" Condition code: {:?}", instr.condition_code());
}
if instr.rflags_read() != RflagsBits::NONE {
println!(" RFLAGS Read: {}", flags(instr.rflags_read()));
}
if instr.rflags_written() != RflagsBits::NONE {
println!(" RFLAGS Written: {}", flags(instr.rflags_written()));
}
if instr.rflags_cleared() != RflagsBits::NONE {
println!(" RFLAGS Cleared: {}", flags(instr.rflags_cleared()));
}
if instr.rflags_set() != RflagsBits::NONE {
println!(" RFLAGS Set: {}", flags(instr.rflags_set()));
}
if instr.rflags_undefined() != RflagsBits::NONE {
println!(" RFLAGS Undefined: {}", flags(instr.rflags_undefined()));
}
if instr.rflags_modified() != RflagsBits::NONE {
println!(" RFLAGS Modified: {}", flags(instr.rflags_modified()));
}
for i in 0..instr.op_count() {
let op_kind = instr.op_kind(i);
if op_kind == OpKind::Memory || op_kind == OpKind::Memory64 {
let size = instr.memory_size().size();
if size != 0 {
println!(" Memory size: {}", size);
}
break;
}
}
for i in 0..instr.op_count() {
println!(" Op{}Access: {:?}", i, info.op_access(i));
}
for i in 0..op_code.op_count() {
println!(" Op{}: {:?}", i, op_code.op_kind(i));
}
for reg_info in info.used_registers() {
println!(" Used reg: {:?}", reg_info);
}
for mem_info in info.used_memory() {
println!(" Used mem: {:?}", mem_info);
}
}
}
fn flags(rf: u32) -> String {
fn append(sb: &mut String, s: &str) {
if !sb.is_empty() {
sb.push_str(", ");
}
sb.push_str(s);
}
let mut sb = String::new();
if (rf & RflagsBits::OF) != 0 {
append(&mut sb, "OF");
}
if (rf & RflagsBits::SF) != 0 {
append(&mut sb, "SF");
}
if (rf & RflagsBits::ZF) != 0 {
append(&mut sb, "ZF");
}
if (rf & RflagsBits::AF) != 0 {
append(&mut sb, "AF");
}
if (rf & RflagsBits::CF) != 0 {
append(&mut sb, "CF");
}
if (rf & RflagsBits::PF) != 0 {
append(&mut sb, "PF");
}
if (rf & RflagsBits::DF) != 0 {
append(&mut sb, "DF");
}
if (rf & RflagsBits::IF) != 0 {
append(&mut sb, "IF");
}
if (rf & RflagsBits::AC) != 0 {
append(&mut sb, "AC");
}
if sb.is_empty() {
sb.push_str("<empty>");
}
sb
}
const EXAMPLE_CODE_BITNESS: u32 = 64;
const EXAMPLE_CODE_RIP: u64 = 0x0000_7FFA_C46A_CDA4;
static EXAMPLE_CODE: &[u8] = &[
0x48, 0x89, 0x5C, 0x24, 0x10, 0x48, 0x89, 0x74, 0x24, 0x18, 0x55, 0x57, 0x41, 0x56, 0x48, 0x8D,
0xAC, 0x24, 0x00, 0xFF, 0xFF, 0xFF, 0x48, 0x81, 0xEC, 0x00, 0x02, 0x00, 0x00, 0x48, 0x8B, 0x05,
0x18, 0x57, 0x0A, 0x00, 0x48, 0x33, 0xC4, 0x48, 0x89, 0x85, 0xF0, 0x00, 0x00, 0x00, 0x4C, 0x8B,
0x05, 0x2F, 0x24, 0x0A, 0x00, 0x48, 0x8D, 0x05, 0x78, 0x7C, 0x04, 0x00, 0x33, 0xFF,
];
```
## Get the virtual address of a memory operand
```rust
use iced_x86::{Decoder, DecoderOptions, Register};
pub(crate) fn how_to_get_virtual_address() {
// add [rdi+r12*8-5AA5EDCCh],esi
let bytes = b"\x42\x01\xB4\xE7\x34\x12\x5A\xA5";
let mut decoder = Decoder::new(64, bytes, DecoderOptions::NONE);
let instr = decoder.decode();
// There's also try_virtual_address() which returns an Option<u64>
let va = instr.virtual_address(0, 0, |register, _element_index, _element_size| {
match register {
// The base address of ES, CS, SS and DS is always 0 in 64-bit mode
Register::ES | Register::CS | Register::SS | Register::DS => 0,
Register::RDI => 0x0000_0000_1000_0000,
Register::R12 => 0x0000_0004_0000_0000,
_ => unimplemented!(),
}
});
assert_eq!(0x0000_001F_B55A_1234, va);
}
```
## Disassemble old/deprecated CPU instructions
```rust
use iced_x86::{Decoder, DecoderOptions, Formatter, Instruction, NasmFormatter};
/*
This method produces the following output:
731E0A03 bndmov bnd1, [eax]
731E0A07 mov tr3, esi
731E0A0A rdshr [eax]
731E0A0D dmint
731E0A0F svdc [eax], cs
731E0A12 cpu_read
731E0A14 pmvzb mm1, [eax]
731E0A17 frinear
731E0A19 altinst
*/
pub(crate) fn how_to_disassemble_old_instrs() {
#[rustfmt::skip]
let bytes = &[
// bndmov bnd1,[eax]
0x66, 0x0F, 0x1A, 0x08,
// mov tr3,esi
0x0F, 0x26, 0xDE,
// rdshr [eax]
0x0F, 0x36, 0x00,
// dmint
0x0F, 0x39,
// svdc [eax],cs
0x0F, 0x78, 0x08,
// cpu_read
0x0F, 0x3D,
// pmvzb mm1,[eax]
0x0F, 0x58, 0x08,
// frinear
0xDF, 0xFC,
// altinst
0x0F, 0x3F,
];
// Enable decoding of Cyrix/Geode instructions, Centaur ALTINST, MOV to/from TR
// and MPX instructions.
// There are other options to enable other instructions such as UMOV, etc.
// These are deprecated instructions or only used by old CPUs so they're not
// enabled by default. Some newer instructions also use the same opcodes as
// some of these old instructions.
const DECODER_OPTIONS: u32 = DecoderOptions::MPX
| DecoderOptions::MOV_TR
| DecoderOptions::CYRIX
| DecoderOptions::CYRIX_DMI
| DecoderOptions::ALTINST;
let mut decoder = Decoder::new(32, bytes, DECODER_OPTIONS);
decoder.set_ip(0x731E0A03);
let mut formatter = NasmFormatter::new();
formatter.options_mut().set_space_after_operand_separator(true);
let mut output = String::new();
let mut instruction = Instruction::default();
while decoder.can_decode() {
decoder.decode_out(&mut instruction);
output.clear();
formatter.format(&instruction, &mut output);
println!("{:08X} {}", instruction.ip(), &output);
}
}
```
## Minimum supported `rustc` version
iced-x86 supports `rustc` `1.20.0` or later.
This is checked in CI builds where the minimum supported version and the latest stable version are used to build the source code and run tests.
If you use an older version of `rustc`, you may need to update the versions of some iced-x86 dependencies because `cargo` prefers to use the latest version which may not support your `rustc`.
Eg. iced-x86 needs `lazy_static` `1.1.1` (or later), but `cargo` wants to use the latest version which is currently `1.4.0` and it doesn't support the minimum supported `rustc` version.
Here's how you can force a compatible version of any iced-x86 dependency without updating iced-x86's `Cargo.toml`:
```sh
cargo generate-lockfile
cargo update --package lazy_static --precise 1.1.1
```
Bumping the minimum supported version of `rustc` is considered a minor breaking change. The minor version of iced-x86 will be incremented.