Emulate Code
Emulate a raw code/shellcode blob on a virtual CPU (x86/x64/arm/arm64) with Unicorn and report the final register state, instruction count, and memory writes. Contained: the bytes run on an emulated CPU, not the host (memory-only; no host syscalls unless wired) — the safe way to 'run' shellcode or an isolated function.
Install
$ agentstack add skill-batteryshark-rekit-emulate-code ✓ scanned · ✓ verified, works with Claude Code, Cursor, and more.
Security review
✓ PassedNo issues found. Passed automated security review. · v0.1.0 How review works →
- ✓ Prompt-injection patterns
- ✓ Secret / credential exfiltration
- ✓ Dangerous shell & filesystem operations
- ✓ Untrusted network calls
- ✓ Known-malicious package signatures
What it can access
- ✓ Network access No
- ✓ Filesystem access No
- ✓ Shell / process execution No
- ✓ Environment & secrets No
- ✓ Dynamic code execution No
From automated source analysis of v0.1.0. “Used” means the capability is present in the source — more access means more to trust, not that it’s unsafe.
Verified badge
Passed review? Show it. Paste this badge into your README, it links to the public security report.
Links to your public security report.[](https://agentstack.voostack.com/security/report/skill-batteryshark-rekit-emulate-code) Reliability & compatibility
Declared compatibility
Compatibility is declared by the source manifest. End-to-end runtime verification is coming, see below.
We're building live execution health for every listing: tool-call success rate, median latency, uptime, and last-checked timestamps, measured, not self-reported. It isn't live yet, so we don't show numbers we can't stand behind.
How agent discovery & health will work →About
Code Emulator (Unicorn)
Emulate a raw code / shellcode blob on a virtual CPU and see what it computes — the contained member of the dynamic tier (the bytes run on Unicorn, not the host).
When to use
You have a chunk of machine code — shellcode carved out of a payload, an obfuscated decoder stub, an isolated function — and you want to know what it does without running it natively. Emulation gives you the register/memory effects safely.
What it does
Maps memory + a stack, writes the blob at a base address, and emulates it (x86/x64/ arm/arm64) with an instruction-count and timeout cap. Reports:
- final register state,
- instruction count and stop reason (completed / fault / instruction-limit),
- memory writes (address ← value).
- emulator/backend provenance (version, host/process architecture, native/Rosetta,
and library digest).
Contained: memory-only, no host syscalls unless explicitly wired. Because it can't touch the host, it is not behind the --allow-dynamic gate (unlike exec-observe and the tracer skills, which run the target natively).
Usage
rekit run emulate-code ./shellcode.bin --arch x64
rekit run emulate-code ./stub.bin --arch arm64 --base 0x400000 --format jsonPrerequisites
- python3 ≥ 3.8 — Unicorn is installed under
scripts/site(native; the local
tree is platform-specific — rebuild with scripts/build.sh on a new platform).
- On Apple Silicon, the build also vendors an x86_64 Unicorn runtime when Rosetta is
available. Doctor probes x87 execution and register access in crash-isolated child processes and selects this lane explicitly if native Unicorn is unsafe.
See [../../docs/UNICORN-X87.md](../../docs/UNICORN-X87.md) for the macOS ARM64 root cause, reproducer, fallback contract, and qualified environment.
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.
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Versions
- v0.1.0 Imported from the upstream source.