What is syzkaller-build-loop?

A build workflow for adding new system-call descriptions to syzkaller, a Linux kernel fuzzing tool. It covers compiling the descriptions, building syzkaller, and checking common errors.

Use it to rebuild syzkaller after editing syscall description files or their companion constant files.

It helps catch invalid types, missing constants, and broken references before the descriptions are used for fuzzing.

syzkaller-build-loop — Skill for Claude Code and Codex by xuansenpa1

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add xuansenpa1/skillrevise --skill syzkaller-build-loop

Clone the repo

git clone --depth 1 https://github.com/xuansenpa1/skillrevise

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/xuansenpa1/skillrevise/syzkaller-build-loop/github.svg)](https://agentmods.dev/skills/xuansenpa1/skillrevise/syzkaller-build-loop)

Your own site

<a href="https://agentmods.dev/skills/xuansenpa1/skillrevise/syzkaller-build-loop"><img src="https://agentmods.dev/badge/skills/xuansenpa1/skillrevise/syzkaller-build-loop/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/xuansenpa1/skillrevise/syzkaller-build-loop"><img src="https://agentmods.dev/badge/skills/xuansenpa1/skillrevise/syzkaller-build-loop.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 18 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 458 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin 100% copy Near-identical to another mod in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00018	$0.00458
Opus 5	$0.00009	$0.00229
Sonnet 5	$0.00004	$0.00092
Haiku 4.5	$0.00002	$0.00046

Measured 9d ago against content hash 36d455ae98e5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

syzkaller-build-loop scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to syzkaller-build-loop — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

data/skillsbench/tasks/syzkaller-ppdev-syzlang/environment/skills/syzkaller-build-loop/SKILL.md · 79 lines

What it actually says

Syzkaller Description Workflow

Full Build Loop for New Descriptions

When adding new syscall descriptions, follow this workflow:

cd /opt/syzkaller

# 1. Write/edit your .txt file in sys/linux/

# 2. Create a .const file with constant values (see syz-extract-constants skill)
#    The .const file should be named: sys/linux/your_file.txt.const

# 3. Compile descriptions
make descriptions

# 4. Build syzkaller
make all

Quick Rebuild (After Minor Edits)

If you only changed descriptions (not constants):

cd /opt/syzkaller
make descriptions   # Runs syz-sysgen to compile descriptions

If you add new constants, update the .const file first.

Common Errors

Unknown type

unknown type foo_bar

Type not defined, or defined after first use
Define all types before using them

Constant not available / defined for none of the arches

SOME_CONST is defined for none of the arches

The constant isn't in the .const file
Add it to sys/linux/your_file.txt.const with the correct value

Missing reference

undefined reference to 'some_type'

Type defined in another file not being found
Check includes or existing type definitions

Exploring Existing Code

Find examples of patterns:

grep -r "pattern" /opt/syzkaller/sys/linux/

Useful searches:

resource fd_ - How other fd resources are defined
ioctl\$ - Ioctl definition patterns
read\$ / write\$ - Read/write specializations
struct.*{ - Struct definition patterns

Files to Reference

sys/linux/socket.txt - Network types (ifreq_t, sockaddr, etc.)
sys/linux/sys.txt - Basic syscall patterns
sys/linux/fs.txt - File operations

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

9d ago First seen · 79 lines · 18 tokens per session scan A 36d455ae98e5

Subscribe to this mod's changes

syzkaller-build-loop is a skill published in the GitHub repository xuansenpa1/skillrevise (56 stars, last pushed 7d ago), licensed MIT. It adds 18 tokens to every session and 458 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to syzkaller-build-loop, differing in 0 lines, and is treated as a copy.

Security Testing

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syzkaller-build-loop