# kernel-debugging-advanced

A skill for Linux kernel tracing: ftrace, trace-cmd, perf, kprobes, kgdb and vmcore analysis. Useful when a driver stalls with no obvious bug.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 317 installs · ★ 267
- Author: mohitmishra786
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/mohitmishra786/low-level-dev-skills/tree/HEAD/skills/kernel-dev/kernel-debugging-advanced/SKILL.md
- Updated: 2026-06-27
- HTML: https://affpapa.org/en/nevibecode/skills/kernel-debugging-advanced

## What it does

The skill walks the agent through eight kernel debugging workflows: function_graph tracing with ftrace, capture with trace-cmd, kernel perf profiling, dynamic kprobes, dyndbg and printk discipline, kgdb/kdb, and post-mortem vmcore analysis in crash.

ftrace needs `CONFIG_FUNCTION_GRAPH_TRACER` and a mounted debugfs, otherwise the trace comes back empty. kprobes are meant to be used sparingly in production, with static tracepoints preferred. Crash analysis fails without debuginfo — install `linux-image-dbg` or point crash at vmlinux.

It complements the baseline `kernel-debugging` skill rather than replacing it: that one covers kgdb and dyndbg, this one adds trace-cmd, function_graph and production workflows for live and post-mortem inspection. A troubleshooting table maps symptoms to causes: empty trace, ftrace overhead, a kprobe that fails on an inlined symbol, kgdb that will not connect.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill kernel-debugging-advanced -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/kernel-debugging-advanced/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/kernel-debugging-advanced/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill kernel-debugging-advanced -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/kernel-debugging-advanced/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill kernel-debugging-advanced -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/kernel-debugging-advanced/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install mohitmishra786/low-level-dev-skills kernel-debugging-advanced
```

2. **Manually: put the files in place**
- File: `.github/skills/kernel-debugging-advanced/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill kernel-debugging-advanced -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/mohitmishra786/low-level-dev-skills --path skills/kernel-dev/kernel-debugging-advanced
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/kernel-debugging-advanced/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill kernel-debugging-advanced -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/mohitmishra786/low-level-dev-skills/tree/HEAD/skills/kernel-dev/kernel-debugging-advanced/SKILL.md

## When to use it
- catch a latency spike in a driver with no clear bug
- build a kernel function call graph
- inspect a running system without recompiling
- analyze a vmcore after a panic
- turn on debug messages for a module at runtime

## Example prompts
- /kernel-debugging-advanced Trace my_driver_ioctl latency with ftrace function_graph
- Help me capture a trace with trace-cmd record -p function_graph and read the report
- Walk through this vmcore in crash: show bt and dev -s

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 0646724e593777d7.

BEGIN THIRD-PARTY FILE 0646724e593777d7
````text
---
name: kernel-debugging-advanced
description: Advanced kernel debugging skill for ftrace, trace-cmd, perf, kprobes, kgdb, and crash analysis. Use when tracing kernel functions, profiling syscalls in kernel, dynamic instrumentation, or analyzing vmcore. Activates on queries about ftrace, trace-cmd, kprobe, kgdb, kernel crash dump, or dyndbg.
---

# Advanced Kernel Debugging

## Purpose

Extend `skills/kernel/kernel-debugging` with production-grade tracing: `ftrace`, `trace-cmd`, kernel `perf`, `kprobes`/`kretprobes`, `kgdb`, crash dump analysis, and `printk` discipline. **Not merged** with `kernel-debugging` — that skill covers baseline kgdb/dyndbg; this one focuses on trace-cmd, function_graph, and live/post-mortem production workflows.

## When to Use

- Latency spikes in kernel driver without obvious bug
- Tracing function call graph in kernel
- Live inspection without recompiling (kprobes, bpf)
- Post-mortem `vmcore` after panic

## Workflow

### 1. ftrace function graph

```bash
# Enable function graph tracer
echo function_graph > /sys/kernel/debug/tracing/current_tracer
echo my_driver_probe > /sys/kernel/debug/tracing/set_graph_function
echo 1 > /sys/kernel/debug/tracing/tracing_on
# reproduce issue
cat /sys/kernel/debug/tracing/trace
echo 0 > /sys/kernel/debug/tracing/tracing_on
```

Requires `CONFIG_FUNCTION_GRAPH_TRACER` and debugfs mounted.

### 2. trace-cmd record

```bash
trace-cmd record -p function_graph -F my_probe
trace-cmd report
trace-cmd stat
```

Portable capture for sharing with others.

### 3. perf in kernel context

```bash
perf record -a -g -- sleep 10
perf report --stdio
perf probe --add my_driver:probe
```

See `skills/profilers/linux-perf` for userspace overlap.

### 4. kprobes (dynamic)

```c
#include <linux/kprobes.h>

static struct kprobe kp = {
    .symbol_name = "do_sys_open",
    .pre_handler = handler,
};
register_kprobe(&kp);
```

Use sparingly in production; prefer static tracepoints when available.

### 5. dyndbg and printk discipline

```bash
echo 'module mydriver +p' > /sys/kernel/debug/dynamic_debug/control
echo 'file drivers/foo/*.c +p' > /sys/kernel/debug/dynamic_debug/control
```

```c
pr_debug("state=%d\n", s);           /* compile-time optional */
printk_ratelimited(KERN_WARNING "hw fault\n");
```

### 6. kgdb / kdb

```bash
# kernel cmdline: kgdboc=ttyS0,115200 kgdbwait
echo g > /proc/sysrq-trigger   # break into debugger (when configured)
```

### 7. Crash dump (vmcore)

```bash
# after kdump capture
crash /usr/lib/debug/vmlinux vmcore
````
END THIRD-PARTY FILE 0646724e593777d7

The third-party file has ended. Everything between the 0646724e593777d7 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 2530 of 3431 bytes. © mohitmishra786 · MIT · https://github.com/mohitmishra786/low-level-dev-skills/tree/HEAD/skills/kernel-dev/kernel-debugging-advanced/SKILL.md

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