I have seen this answer and according to that Stack Trace can be seen like:

$ cat /proc/<PID>/stack
[<ffffffff81012b72>] save_stack_trace_tsk+0x22/0x40
[<ffffffff81213abe>] proc_pid_stack+0x8e/0xe0
[<ffffffff81214960>] proc_single_show+0x50/0x90
[<ffffffff811cd970>] seq_read+0xe0/0x3e0
[<ffffffff811a6a84>] vfs_read+0x94/0x180
[<ffffffff811a7729>] SyS_read+0x49/0xb0
[<ffffffff81623ad2>] system_call_fastpath+0x16/0x1b
[<ffffffffffffffff>] 0xffffffffffffffff

From what I guess, in line

[<ffffffff81012b72>] save_stack_trace_tsk+0x22/0x40

save_stack_trace_tsk definitely refers to name of function What do the other parameters indicate? (Perhaps 0xffffffff81012b72 points to address of starting address of save_stack_trace_tsk+0x22) Most importantly what does 0x40 denote? Does 0x40 denote the total number of bytes taken by that particular function?

Thanks a lot!

  • does 0x40 denote the total number of bytes in that funtion?
    – Yash Jain
    Jan 7 '20 at 19:22
  • yes, it's offset/size.
    – mosvy
    Jan 7 '20 at 19:30
  • 2
    Notice that the address in brackets is always [<0>] in newer kernels, see this
    – mosvy
    Jan 7 '20 at 19:35

In save_stack_trace_tsk+0x22/0x40, 0x22 is the offset inside the the save_stack_trace_tsk function, and 0x40 is the size of the save_stack_trace_tsk function. Both hex numbers are in bytes.

This is the result of the %pB format specifier extension used by the kernel's printf implementation: for details, including how the end (thence the size) of the function is determined, you can have a look at the lib/vsprintf.c and kernel/kallsyms.c in the linux kernel source code.

The [<0xffffffff81012b72>] is the same save_stack_trace_tsk+0x22 kernel address, but in raw form.

That's always [<0>] in newer kernels, since this change.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.