lkml.org 
[lkml]   [2010]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH -tip 6/7] perf bts trace: print function+offset
    On Fri, Dec 03, 2010 at 01:00:15PM +0900, Akihiro Nagai wrote:
    > Provide the function to print function+offset.
    > And, set it as the default behavior of 'perf bts trace'.
    > To use this function, users can also specify the option '-s' or '--symbol'.
    >
    > Example: 'perf bts -as trace'
    > This command prints address and function+offset.
    >
    > Output sample:
    > address function+offset
    > 0xffffffff8146fe0e irq_return+0x0 => 0x00007fd4038e3b20 _start+0x0
    > ...
    > 0x000000380661ee79 __libc_start_main+0xf9 => 0x00000000004035c3 main+0x0
    > 0xffffffff8146ef4e irq_return+0x0 => 0x00000000004035c3 main+0x0
    > 0x00000000004035e8 main+0x25 => 0x000000000040bca0 set_program_name+0x0
    > 0xffffffff8146ef4e irq_return+0x0 => 0x000000000040bca0 set_program_name+0x0
    > 0x000000000040bcae set_program_name+0xe => 0x00000000004023d0 strrchr@plt+0x0
    > 0x00000000004023d0 strrchr@plt+0x0 => 0x00000000004023d6 strrchr@plt+0x6
    > ...
    > 0x0000000000403e0c main+0x849 => 0x00000000004021f0 exit@plt+0x0
    > 0x00000000004021f0 exit@plt+0x0 => 0x00000000004021f6 exit@plt+0x6
    > 0x00000000004021fb exit@plt+0xb => 0x00000000004020d0 _init+0x18
    > 0x00000000004020d6 _init+0x1e => 0x00000038062149d0 _dl_runtime_resolve+0x0
    > ...

    There is another kind of mode that I suspect would be very useful: something like
    a userspace function graph tracer (you can have a look into the kernel function
    graph tracer we have in ftrace to get an overview).

    So, the idea would be to rebuild the whole function call flow:

    main() {
    func1()
    func2() {
    func3()
    }
    }


    This would require to deref the instructions into the dso addresses from
    the bts trace, keep only the "call" and the "ret" (there would be a small arch
    backend for this mode) and rebuild the whole tree of calls.
    We already have all the dso address mapping API in place with perf.

    I really think this could be a very useful tool. Also we can even later
    expand this to the branches, as Peter suggested. But starting with calls
    would a very great start already.

    Thanks.


    \
     
     \ /
      Last update: 2010-12-06 03:45    [W:0.023 / U:0.092 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site