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Commit dcc85cb6 authored by Richard Kennedy's avatar Richard Kennedy Committed by Linus Torvalds
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Documentation: add hint about call traces & module symbols to BUG-HUNTING 



Here's a couple of small additions to BUG-HUNTING.

1. point out that you can list code in gdb with only one command
	(gdb) l *(<symbol> + offset)

2. give a very brief hint how to decode module symbols in call traces

Signed-off-by: default avatarRichard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 844fcc53

Documentation/BUG-HUNTING

+17 −0
Original line number Diff line number Diff line
@@ -214,6 +214,23 @@ And recompile the kernel with CONFIG_DEBUG_INFO enabled: 
  gdb vmlinux

  (gdb) p vt_ioctl

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

or, as one command

  (gdb) l *(vt_ioctl + 0xda8)



If you have a call trace, such as :-

>Call Trace:

> [<ffffffff8802c8e9>] :jbd:log_wait_commit+0xa3/0xf5

> [<ffffffff810482d9>] autoremove_wake_function+0x0/0x2e

> [<ffffffff8802770b>] :jbd:journal_stop+0x1be/0x1ee

> ...

this shows the problem in the :jbd: module. You can load that module in gdb

and list the relevant code.

  gdb fs/jbd/jbd.ko

  (gdb) p log_wait_commit

  (gdb) l *(0x<address> + 0xa3)

or

  (gdb) l *(log_wait_commit + 0xa3)





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

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