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>

1 files changed, 14 insertions, 3 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 02718e728d59..ea62ecd191fa 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)