printing kernel backtrace

[Nikolay Borisov]

Hello,

I've started experimenting with systemtamp and I'd like to print the
callstack leading to the probed function. To that effect I have created
the following very simple tapset:

probe module("dm_thin_pool").function("do_waker") {
    print_syms(callers(-1))
    printf("finished backtrace\n");
}

However the output I get is something like that:

 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffff810a5025 : 0xffffffff810a5025
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c80 : do_waker+0x0/0x40 [dm_thin_pool]
 0xffffffffa0152c8 : 0xffffffffa0152c8
finished backtrace


It seems that systemtap is unable to unwind the debug information? I
believe I have compiled systemtap with the necessary unwidn libraries
but how do I check that for sure?