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Subject[tip:perf/core] perf symbols: avoid SyS kernel syscall aliases
Commit-ID:  3445432b7b24665cf4693fc4794c62d4d768a978
Gitweb: http://git.kernel.org/tip/3445432b7b24665cf4693fc4794c62d4d768a978
Author: Adrian Hunter <adrian.hunter@intel.com>
AuthorDate: Wed, 7 Aug 2013 14:38:49 +0300
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 7 Aug 2013 17:35:30 -0300

perf symbols: avoid SyS kernel syscall aliases

When removing duplicate symbols, prefer to remove syscall aliases
starting with SyS or compat_SyS.

A side-effect of that is that it results in slightly improved results
for the "vmlinux symtab matches kallsyms" test.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1375875537-4509-6-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/symbol.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 02718e7..ea62ecd 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -87,6 +87,7 @@ static int choose_best_symbol(struct symbol *syma, struct symbol *symb)
{
s64 a;
s64 b;
+ size_t na, nb;

/* Prefer a symbol with non zero length */
a = syma->end - syma->start;
@@ -120,11 +121,21 @@ static int choose_best_symbol(struct symbol *syma, struct symbol *symb)
else if (a > b)
return SYMBOL_B;

- /* If all else fails, choose the symbol with the longest name */
- if (strlen(syma->name) >= strlen(symb->name))
+ /* Choose the symbol with the longest name */
+ na = strlen(syma->name);
+ nb = strlen(symb->name);
+ if (na > nb)
return SYMBOL_A;
- else
+ else if (na < nb)
+ return SYMBOL_B;
+
+ /* Avoid "SyS" kernel syscall aliases */
+ if (na >= 3 && !strncmp(syma->name, "SyS", 3))
return SYMBOL_B;
+ if (na >= 10 && !strncmp(syma->name, "compat_SyS", 10))
+ return SYMBOL_B;
+
+ return SYMBOL_A;
}

void symbols__fixup_duplicate(struct rb_root *symbols)

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