How to correctly decode fun+X/Y

[andrej.skvortzov@gmail.com (Andrey Skvortsov)]

On 04 Dec, Daniel Baluta wrote:
> On Thu, Dec 3, 2015 at 8:14 PM, Matwey V. Kornilov
> <matwey.kornilov@gmail.com> wrote:
> > Hello,
> >
> > I have the following stack trace:
> >
> > [ 1351.381696] a.out           S c0afb050     0  1676   1658 0x00000000
> > [ 1351.387048] [<c0afb050>] (__schedule) from [<c0afb4d0>]
> > (schedule+0x58/0xcc)
> > [ 1351.392436] [<c0afb4d0>] (schedule) from [<c069369c>]
> > (tty_port_block_til_ready+0x1a8/0x35c)
> > [ 1351.396937] [<c069369c>] (tty_port_block_til_ready) from [<c06ab220>]
> > (uart_open+0x118/0x158)
> > [ 1351.402560] [<c06ab220>] (uart_open) from [<c068b768>]
> > (tty_open+0x11c/0x600)
> > [ 1351.407043] [<c068b768>] (tty_open) from [<c03e1ce4>]
> > (chrdev_open+0xb4/0x188)
> > [ 1351.412556] [<c03e1ce4>] (chrdev_open) from [<c03db3dc>]
> > (do_dentry_open+0x230/0x330)
> > [ 1351.417038] [<c03db3dc>] (do_dentry_open) from [<c03dc64c>]
> > (vfs_open+0x64/0x6c)
> > [ 1351.422470] [<c03dc64c>] (vfs_open) from [<c03eaf5c>]
> > (do_last+0x510/0xd94)
> > [ 1351.426909] [<c03eaf5c>] (do_last) from [<c03eb86c>]
> > (path_openat+0x8c/0x270)
> > [ 1351.432398] [<c03eb86c>] (path_openat) from [<c03ecd78>]
> > (do_filp_open+0x70/0xd4)
> > [ 1351.436815] [<c03ecd78>] (do_filp_open) from [<c03dc9cc>]
> > (do_sys_open+0x120/0x1e4)
> > [ 1351.442117] [<c03dc9cc>] (do_sys_open) from [<c03dcab8>]
> > (SyS_open+0x28/0x30)
> > [ 1351.447046] [<c03dcab8>] (SyS_open) from [<c021cd40>]
> > (ret_fast_syscall+0x0/0x34)
> >
> >
> > Could please explain, how to correctly decode
> > tty_port_block_til_ready+0x1a8/0x35c to the instruction or line of code
> > using gdb?
> 
> $ gdb ./vmlinux
> 
> list *(tty_port_block_til_ready+0x1a8)
> 

Or even easier using decode_stacktrace.sh from the linux
kernel tree (exists since 3.16).


Usage:
    
            ./decode_stacktrace.sh [vmlinux] [base path]
    
    Where vmlinux is the vmlinux to extract line numbers from and base path
    is the path that points to the root of the build tree, for example:
    
            ./decode_stacktrace.sh vmlinux /home/sasha/linux/ < input.log > output.log


Then stacktrace will include file and line number:

      [  635.148361]  dump_stack (lib/dump_stack.c:52)
      [  635.149127]  warn_slowpath_common (kernel/panic.c:418)
      [  635.150214]  warn_slowpath_null (kernel/panic.c:453)
      [  635.151031]  _oalloc_pages_slowpath+0x6a/0x7d0
      [  635.152171]  ? zone_watermark_ok (mm/page_alloc.c:1728)
      [  635.152988]  ? get_page_from_freelist (mm/page_alloc.c:1939)
      [  635.154766]  __alloc_pages_nodemask (mm/page_alloc.c:2766)


-- 
Best regards,
Andrey Skvortsov

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