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    SubjectRe: [PATCH 3/3] perf: parse the .debug_frame section in case .eh_frame is not present
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    Hi Will,


    On Thu, Sep 5, 2013 at 2:45 PM, Will Deacon <will.deacon@arm.com> wrote:
    > Hi Jean,
    >
    > [adding Michael, since I know he was interested in this]
    >
    > On Wed, Sep 04, 2013 at 07:04:14PM +0100, Jean Pihet wrote:
    >> On ARM the debug info is not present in the .eh_frame sections but
    >> instead in .debug_frame.
    >> Use libunwind to load and parse the debug info.
    >
    > How have you tested this? Regardless of whether or not I apply this patch, I
    > get the same (broken/truncated) callchains for userspace in perf report.
    Here are the commands I have been using:
    perf record -g dwarf -- <binary to profile>
    perf report --sort symbol --call-graph --stdio

    >
    > E.g. the following stupid program (built with -O0 -g):
    >
    > --->8
    >
    > void bar(void)
    > {
    > int i;
    > for (i = 0; i < 1000000; ++i)
    > asm volatile("nop" ::: "memory");
    > }
    >
    > void foo(void)
    > {
    > bar();
    > }
    >
    >
    > int main(void)
    > {
    > foo();
    > return 0;
    > }
    >
    > 8<---
    >
    > Gives me an incomplete callchain:
    >
    > # Overhead Command Shared Object Symbol
    > # ........ ........ ................. ...............................
    > #
    > 0.00% unwindme unwindme [.] bar
    > |
    > --- bar
    I get the following with a simple stupid program with a long call chain:
    0.57% stress_bt stress_bt [.] foo_115
    |
    --- foo_115
    foo_114
    foo_113
    ...
    foo_92
    bar
    doit
    main
    __libc_start_main

    Things to check:
    - compile the binaries and libraries with -g (-dbg flavor of libs are
    usually ok),
    - use -g dwarf in perf record


    > This is the same with or without your patch.
    >
    > Will

    Thanks for testing!
    Jean

    >
    > _______________________________________________
    > linux-arm-kernel mailing list
    > linux-arm-kernel@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel


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