cargo-disassemble

Easily disassemble your Rust project

Usage

cargo-disassemble attempts to emulate the command-line interface of other cargo subcommands. Notice that the function argument is optional - not including it will disassemble all functions in the current crate.

USAGE:
    cargo-disassemble [FLAGS] [OPTIONS] [function]

FLAGS:
        --all-features           Enable all features
        --everything             Include functions not defined by the current crate
    -h, --help                   Prints help information
        --intel                  Emit intel-flavored x86 ASM
        --no-default-features    Enable no_default features
        --optimize               Optimize the binary as much as possible
        --release                Compile in release mode
    -V, --version                Prints version information

OPTIONS:
        --features <features>    Features to enable, if any

ARGS:
    <function>    The name of the function to be decompiled

Example

Given the function:

#[inline(never)]
fn is_branch_label(line: &str) -> bool {
    line.starts_with(".LBB")
}

we can disassemble the optimized version of is_branch_label with the following command:

$ cargo disassemble is_branch_label --release --optimize --intel

which will yield this result:

cargo_disassemble::is_branch_label
        cmp	rsi, 4
        je	.LBB66_4
        cmp	rsi, 5
        jb	.LBB66_3
        cmp	byte ptr [rdi + 4], -65
        jle	.LBB66_3
.LBB66_4:
        push	rbp
        mov	rbp, rsp
        sub	rsp, 16
        mov	qword ptr [rbp - 16], rdi
        mov	qword ptr [rbp - 8], rsi
        mov	al, 1
        lea	rcx, [rip + .Lbyte_str.1e]
        cmp	rdi, rcx
        lea	rsp, [rsp + 16]
        pop	rbp
        je	.LBB66_6
        cmp	dword ptr [rdi], 1111641134
        je	.LBB66_6
.LBB66_3:
        xor	eax, eax
        ret

Caveats

When compiling in release mode, rustc will often aggressively inline smaller functions. Because inlined functions typically don’t have a freestanding copy in the final binary, they may not be disassembled. Adding the #[inline(never)] attribute to a function will ensure it’s included, but may also change the code within the function.