使用 kernel 中调试工具

KASLR

/*
 * See Documentation/x86/x86_64/mm.txt for a description of the memory map.
 *
 * Be very careful vs. KASLR when changing anything here. The KASLR address
 * range must not overlap with anything except the KASAN shadow area, which
 * is correct as KASAN disables KASLR.
 */
#define MAXMEM      (1UL << MAX_PHYSMEM_BITS)

debug

从内核的选项来看，对于 debug 一无所知啊 !

• Extend memmap on extra space for more information on page
• Debug page memory allocations
• Track page owner
• Poison pages after freeing
• Enable tracepoint to track down page reference manipulation
• Testcase for the marking rodata read-only
• Export kernel pagetable layout to userspace via debugfs
• Debug object operations
• SLUB debugging on by default
• Enable SLUB performance statistics
• Kernel memory leak detector
• Stack utilization instrumentation
• Detect stack corruption on calls to schedule()
• Debug VM
• Debug VM translations
• Debug access to per_cpu maps

page owner

page owner is for the tracking about who allocated each page.

Kernel 调试

基本按照这个操作

• https://sergioprado.blog/how-is-the-linux-kernel-tested/

• disassemble with code and line
• 如何增大 dmesg buffer 的大小

通过插入预防错误的方法实现

dump_page(page, "VM_BUG_ON_PAGE(" __stringify(cond)")");\

void dump_page(struct page *page, const char *reason)
{
	__dump_page(page, reason);
	dump_page_owner(page);
}
EXPORT_SYMBOL(dump_page);

以后再去慢慢跟踪吧!

kernel hacking

• pr_info
  • 注意 %px 来输出指针

• dump_stack

• 这个没有测试过啊 调试内核模块

  cat /proc/modules
  objdump -dS --adjust-vma=0xffffffff85037434 vmlinux
  

• 如何 hacking 内核的官方文档:
  • https://www.kernel.org/doc/html/latest/kernel-hacking/index.html
  • https://www.kernel.org/doc/html/latest/trace/index.html#
  • https://www.kernel.org/doc/html/latest/dev-tools/index.html

memtest

• https://github.com/memtest86plus/memtest86plus

• journalctl -t kernel 展示所有的的内核日志。

还有其他的，参考 : /Documentation/dev-tools/

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