Asm Assemble

Assembler (LLVM/clang)

🔨 Construct tier — produces bytes, runs nothing.

Role in the workflow

The write-side partner of emulate-code. Where that skill runs bytes on a virtual CPU, this one makes them: assemble a snippet, then emulate it — a tight write-shellcode → observe-behavior loop with no host execution at any point.

What it does

Assembles asm text (a file or --code "…") with the LLVM/clang integrated assembler for x64 / x86 / arm64 / arm, then extracts the raw .text bytes, emitted as:

• hex (default) — a hex string
• c — a ready-to-paste unsigned char shellcode[] = { … }; array (drop into a cc-build stub)
• raw — the raw bytes (to --out, or stdout)
• json — {ok, arch, triple, length, hex, out?}

x86/x64 default to Intel syntax (--att for AT&T/GAS); ARM uses GAS syntax.

Toolchain choice

The LLVM assembler supports the target architectures anywhere clang runs. keystone-engine has no arm64 macOS wheel, which would make that alternative platform-dependent.

Prerequisites

• clang — xcode-select --install (macOS) or install clang/LLVM (Linux).
• A section extractor — otool (ships with Xcode CLT) on macOS, or

objcopy/llvm-objcopy/objdump on Linux. Checked flexibly; absent → honest hint.

Usage — the shellcode loop

rekit run asm-assemble --code "mov rax, 0x1337; mov [rsp], rax" --out sc.bin
rekit run emulate-code sc.bin            # ← run what you just assembled, contained
rekit run asm-assemble --code "mov x0, #0x1337" --arch arm64 --format hex
rekit run asm-assemble --code "xor eax,eax; ret" --arch x86 --format c   # C array for a stub

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: batteryshark
• Source: batteryshark/rekit
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.