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Commit 926b2898 authored by Pekka Enberg's avatar Pekka Enberg Committed by Linus Torvalds
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Documentation: How to use GDB to decode OOPSes 



Adds instructions how to use GDB to figure out the exact location of
an OOPS to Documentation/BUG-HUNTING.

Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0a920b5b

Documentation/BUG-HUNTING

+24 −0
Original line number Diff line number Diff line
@@ -191,6 +191,30 @@ e.g. crash dump output as shown by Dave Miller. 
>        mov        0x8(%ebp), %ebx         ! %ebx = skb->sk

>        mov        0x13c(%ebx), %eax       ! %eax = inet_sk(sk)->opt



In addition, you can use GDB to figure out the exact file and line

number of the OOPS from the vmlinux file. If you have

CONFIG_DEBUG_INFO enabled, you can simply copy the EIP value from the

OOPS:



 EIP:    0060:[<c021e50e>]    Not tainted VLI



And use GDB to translate that to human-readable form:



  gdb vmlinux

  (gdb) l *0xc021e50e



If you don't have CONFIG_DEBUG_INFO enabled, you use the function

offset from the OOPS:



 EIP is at vt_ioctl+0xda8/0x1482



And recompile the kernel with CONFIG_DEBUG_INFO enabled:



  make vmlinux

  gdb vmlinux

  (gdb) p vt_ioctl

  (gdb) l *(0x<address of vt_ioctl> + 0xda8)



Another very useful option of the Kernel Hacking section in menuconfig is

Debug memory allocations. This will help you see whether data has been

initialised and not set before use etc. To see the values that get assigned