lkml.org 
[lkml]   [2012]   [Feb]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH] perf annotate: Numeric assembly labels cause incorrect annotation

    A perf annotate of a kernel function written in assembly shows
    very strange percentages:

    : _GLOBAL(__copy_tofrom_user_base)

    ...

    : addi r3,r3,1
    99.67 : c00000000004d78c: addi r3,r3,1
    :
    0.00 : 1: bf cr7*4+2,2f
    0.07 : c00000000004d790: bne- cr7,c00000000004d7a4
    : err1; lhz r0,0(r4)
    0.00 : c00000000004d794: lhz r0,0(r4)
    : addi r4,r4,2
    0.00 : c00000000004d798: addi r4,r4,2
    : err1; sth r0,0(r3)
    0.00 : c00000000004d79c: sth r0,0(r3)
    : addi r3,r3,2
    99.60 : c00000000004d7a0: addi r3,r3,2
    :
    0.00 : 2: bf cr7*4+1,3f
    0.12 : c00000000004d7a4: ble- cr7,c00000000004d7b8
    : err1; lwz r0,0(r4)
    0.00 : c00000000004d7a8: lwz r0,0(r4)
    : addi r4,r4,4
    0.00 : c00000000004d7ac: addi r4,r4,4
    : err1; stw r0,0(r3)
    0.00 : c00000000004d7b0: stw r0,0(r3)
    : addi r3,r3,4
    99.48 : c00000000004d7b4: addi r3,r3,4

    ~300% in one function. Urgh.

    This is caused by the way we parse objdump -S output, eg:

    addi r3,r3,1
    c00000000004d78c: addi r3,r3,1

    1: bf cr7*4+2,2f
    c00000000004d790: bne- cr7,c00000000004d7a4

    We assume the asm label (1:) is an address, compute a bogus offset
    into the function and then screw up the matching of samples to lines.
    I notice this also fails with c inline assembly in a similar
    manner.

    We already have a sanity check that the address is not beyond the end
    of the function, so add a check against the start too.

    Signed-off-by: Anton Blanchard <anton@samba.org>
    ---
    Cc: <stable@kernel.org>

    Index: linux-tip/tools/perf/util/annotate.c
    ===================================================================
    --- linux-tip.orig/tools/perf/util/annotate.c 2012-01-09 17:45:09.056373433 +1100
    +++ linux-tip/tools/perf/util/annotate.c 2012-02-07 13:53:01.610970209 +1100
    @@ -244,7 +244,7 @@ static int symbol__parse_objdump_line(st
    end = map__rip_2objdump(map, sym->end);

    offset = line_ip - start;
    - if (offset < 0 || (u64)line_ip > end)
    + if (offset < 0 || (u64)line_ip < start || (u64)line_ip > end)
    offset = -1;
    }


    \
     
     \ /
      Last update: 2012-02-07 04:59    [W:0.020 / U:208.332 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site