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Is Kernel Debugging Advanced free to use?

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Who published Kernel Debugging Advanced?

mohitmishra786 (@mohitmishra786) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Kernel Debugging Advanced by mohitmishra786

Name: Kernel Debugging Advanced
Rating: 4.666666666666667 (3 reviews)
Author: mohitmishra786

Kernel Debugging Advanced

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.

File contents

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

# 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

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

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)

#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

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

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

6. kgdb / kdb

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

7. Crash dump (vmcore)

# after kdump capture
crash /usr/lib/debug/vmlinux vmcore
crash> bt
crash> dev -s

8. Agent usage

/kernel-debugging-advanced Trace my_driver_ioctl latency with ftrace function_graph

Common Problems

Symptom	Cause	Fix
Empty trace	Tracer not enabled	`tracing_on`; check `current_tracer`
ftrace overhead	Graph all functions	Filter with `set_graph_function`
kprobe fail	Inlined symbol	Try nearby symbol or static key
kgdb no connect	Wrong `kgdboc` tty	Match serial/USB gadget
crash no symbols	Missing debuginfo	Install `linux-image-dbg` / vmlinux

Related Skills

skills/kernel/kernel-debugging — baseline kgdb, dyndbg
skills/profilers/linux-perf — perf record/report
skills/observability/ebpf — BPF kprobe alternative
skills/kernel-dev/writing-char-drivers — ioctl trace targets
skills/debuggers/core-dumps — userspace core parallels

---name: kernel-debugging-advanceddescription: 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 crash> bt crash> dev -s ``` ### 8. Agent usage ``` /kernel-debugging-advanced Trace my_driver_ioctl latency with ftrace function_graph ``` ## Common Problems | Symptom | Cause | Fix | |---------|-------|-----| | Empty trace | Tracer not enabled | `tracing_on`; check `current_tracer` | | ftrace overhead | Graph all functions | Filter with `set_graph_function` | | kprobe fail | Inlined symbol | Try nearby symbol or static key | | kgdb no connect | Wrong `kgdboc` tty | Match serial/USB gadget | | crash no symbols | Missing debuginfo | Install `linux-image-dbg` / vmlinux | ## Related Skills - `skills/kernel/kernel-debugging` — baseline kgdb, dyndbg - `skills/profilers/linux-perf` — perf record/report - `skills/observability/ebpf` — BPF kprobe alternative - `skills/kernel-dev/writing-char-drivers` — ioctl trace targets - `skills/debuggers/core-dumps` — userspace core parallels

Frequently asked questions