139 lines
4.5 KiB
Markdown
139 lines
4.5 KiB
Markdown
# Kernel Debugging
|
|
|
|
## 1. Preparation
|
|
|
|
### Set up a development environment:
|
|
- Install a Linux distribution (e.g., Ubuntu, Fedora)
|
|
- Install essential development tools: gcc, make, binutils, etc.
|
|
- Download kernel source code from kernel.org
|
|
|
|
### Configure kernel for debugging:
|
|
- Enable CONFIG_DEBUG_INFO in kernel configuration
|
|
- Enable CONFIG_KGDB for remote debugging
|
|
- Enable other relevant debug options (e.g., CONFIG_DEBUG_KERNEL)
|
|
|
|
### Build the kernel with debug symbols:
|
|
```bash
|
|
make menuconfig
|
|
make -j$(nproc)
|
|
```
|
|
|
|
## 2. Kernel Debugging Techniques
|
|
|
|
### Printk Debugging:
|
|
- Use printk() function to add log messages
|
|
- Set appropriate log levels (KERN_INFO, KERN_DEBUG, etc.)
|
|
- View logs using dmesg or /var/log/kern.log
|
|
|
|
### Kernel Oops and Panic Analysis:
|
|
- Analyze oops messages in kernel logs
|
|
- Use addr2line to translate addresses to source code lines
|
|
- Examine call traces to identify the source of the problem
|
|
|
|
### KGDB (Kernel GNU Debugger):
|
|
- Configure a serial connection or network for remote debugging
|
|
- Set up a GDB client on the host machine
|
|
- Connect to the target machine running the kernel
|
|
- Set breakpoints, step through code, and examine variables
|
|
|
|
### Ftrace (Function Tracer):
|
|
- Enable Ftrace in kernel configuration
|
|
- Use trace-cmd tool to collect and analyze function call data
|
|
- Examine function graph to understand kernel execution flow
|
|
|
|
### Systemtap:
|
|
- Write custom scripts to instrument the kernel
|
|
- Collect detailed performance data and debug information
|
|
- Analyze complex scenarios without modifying kernel source
|
|
|
|
### Kernel Probes (Kprobes):
|
|
- Insert dynamic breakpoints in the kernel
|
|
- Gather debugging and performance information
|
|
- Use jprobes for function entry probing and kretprobes for return probes
|
|
|
|
## 3. Advanced Debugging Techniques
|
|
|
|
### Memory Debugging:
|
|
- Use KASAN (Kernel Address Sanitizer) to detect memory errors
|
|
- Enable CONFIG_DEBUG_PAGEALLOC to catch use-after-free bugs
|
|
- Utilize SLUB debug features for slab allocator issues
|
|
|
|
### Lockdep (Lock Dependency) Checker:
|
|
- Enable CONFIG_PROVE_LOCKING and CONFIG_DEBUG_LOCKDEP
|
|
- Detect potential deadlocks and incorrect locking behavior
|
|
- Analyze lock dependency graphs
|
|
|
|
### RCU (Read-Copy-Update) Debugging:
|
|
- Enable CONFIG_RCU_TRACE for RCU tracing
|
|
- Use rcutorture module to stress-test RCU implementations
|
|
- Analyze RCU grace period and callback execution
|
|
|
|
### Kernel Live Patching:
|
|
- Use kpatch or livepatch to apply runtime fixes
|
|
- Debug issues related to live patching mechanisms
|
|
- Verify patch consistency and function replacement
|
|
|
|
## 4. Tools and Utilities
|
|
|
|
### Crash utility:
|
|
- Analyze kernel core dumps
|
|
- Examine kernel data structures and memory
|
|
- Useful for post-mortem analysis of kernel panics
|
|
|
|
### Perf:
|
|
- Profile kernel and user space performance
|
|
- Identify hotspots and performance bottlenecks
|
|
- Analyze hardware events and software tracepoints
|
|
|
|
### eBPF (extended Berkeley Packet Filter):
|
|
- Write eBPF programs for advanced tracing and debugging
|
|
- Use bpftrace for one-liners and short scripts
|
|
- Develop custom eBPF tools for specific debugging needs
|
|
|
|
### Kdump:
|
|
- Configure and enable kernel crash dump mechanism
|
|
- Capture memory dumps on kernel panics
|
|
- Analyze dumps using crash utility or GDB
|
|
|
|
## 5. Best Practices
|
|
|
|
### Use git for version control:
|
|
- Maintain a clean development history
|
|
- Utilize git bisect for identifying problematic commits
|
|
|
|
### Maintain a test environment:
|
|
- Use virtual machines or dedicated hardware for testing
|
|
- Set up automated testing frameworks (e.g., KernelCI)
|
|
|
|
### Collaborate with the community:
|
|
- Subscribe to relevant mailing lists (e.g., LKML)
|
|
- Share and discuss issues on appropriate forums
|
|
- Submit well-formatted patch series for review
|
|
|
|
### Document your findings:
|
|
- Maintain detailed notes of debugging sessions
|
|
- Create reproducible test cases for bugs
|
|
- Write clear bug reports and patch descriptions
|
|
|
|
## 6. Debugging Real-world Scenarios
|
|
|
|
### Boot issues:
|
|
- Use early printk for early boot problems
|
|
- Analyze initcall debugging output
|
|
- Utilize kernel command line parameters for troubleshooting
|
|
|
|
### Device driver debugging:
|
|
- Use debugfs to expose driver information
|
|
- Implement IOCTL commands for debugging
|
|
- Utilize kernel's tracepoints in the driver code
|
|
|
|
### File system issues:
|
|
- Enable verbose mount options
|
|
- Use debugfs to examine file system internals
|
|
- Analyze block layer tracing for I/O related problems
|
|
|
|
### Network stack debugging:
|
|
- Use network sniffer tools (e.g., tcpdump, Wireshark)
|
|
- Enable netconsole for remote kernel debugging
|
|
- Analyze netfilter and netlink debugging information
|