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perf symbol: Do not fixup end address of labels

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When it loads symbols from an ELF file, it loads label symbols which is
0 size.  Sometimes it has the same address with other symbols and might
shadow the original symbols because it fixes up the size of the symbol.

For example, in my system __do_softirq is shadowed and only accepts the
__softirqentry_text_start instead.  But it should accept __do_softirq.

  $ readelf -sW vmlinux | grep -e __do_softirq -e __softirqentry_text_start
  105089: ffffffff82000000   814 FUNC    GLOBAL DEFAULT    1 __do_softirq
  111954: ffffffff82000000     0 NOTYPE  GLOBAL DEFAULT    1 __softirqentry_text_start

  $ perf annotate --stdio __do_softirq
  Error:
  The perf.data data has no samples!

  $ perf annotate --stdio __softirqentry_text_start | head
   Percent |	Source code & Disassembly of vmlinux for cycles (26 samples, percent: local period)
  ---------------------------------------------------------------------------------------------------
           : 0                0xffffffff82000000 <__softirqentry_text_start>:
      0.00 :   ffffffff82000000:        nopl    (%rax,%rax)
     30.77 :   ffffffff82000005:        pushq   %rbp
      3.85 :   ffffffff82000006:        movq    %rsp, %rbp
      0.00 :   ffffffff82000009:        pushq   %r15
      3.85 :   ffffffff8200000b:        pushq   %r14
      3.85 :   ffffffff8200000d:        pushq   %r13
      0.00 :   ffffffff8200000f:        pushq   %r12

We can ignore NOTYPE symbols in the symbols__fixup_end() so that it can
pick the __do_softirq() in choose_best_symbol().  This should be fine
since most symbols have either STT_FUNC or STT_OBJECT.

Link: https://lore.kernel.org/r/20240912224208.3360116-1-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Namhyung Kim
2024-09-12 15:42:08 -07:00
parent 235f0da327
commit 77b004f4c5
1 changed files with 1 additions and 1 deletions
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2
tools/perf/util/symbol.c
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@@ -257,7 +257,7 @@ void symbols__fixup_end(struct rb_root_cached *symbols, bool is_kallsyms)
* like in:
* ffffffffc1937000 T hdmi_driver_init [snd_hda_codec_hdmi]
*/
if (prev->end == prev->start) {
if (prev->end == prev->start && prev->type != STT_NOTYPE) {
const char *prev_mod;
const char *curr_mod;