perf symbols: Add some heuristics for choosing the best duplicate symbol

Try and pick the best symbol based on a few heuristics:

-  Prefer a non weak symbol over a weak one
-  Prefer a global symbol over a non global one
-  Prefer a symbol with less underscores (idea taken from kallsyms.c)
-  If all else fails, choose the symbol with the longest name

Cc: Eric B Munson <emunson@mgebm.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110824065243.161953371@samba.org
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 0d94ddb55bd7903e15bfdd972889a2ce30bd73c1..870b3b8c649bfdc70f103203387482bd509d748b 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -86,6 +86,92 @@ bool symbol_type__is_a(char symbol_type, enum map_type map_type)
        }
 }
 
+static int prefix_underscores_count(const char *str)
+{
+       const char *tail = str;
+
+       while (*tail == '_')
+               tail++;
+
+       return tail - str;
+}
+
+#define SYMBOL_A 0
+#define SYMBOL_B 1
+
+static int choose_best_symbol(struct symbol *syma, struct symbol *symb)
+{
+       s64 a;
+       s64 b;
+
+       /* Prefer a symbol with non zero length */
+       a = syma->end - syma->start;
+       b = symb->end - symb->start;
+       if ((b == 0) && (a > 0))
+               return SYMBOL_A;
+       else if ((a == 0) && (b > 0))
+               return SYMBOL_B;
+
+       /* Prefer a non weak symbol over a weak one */
+       a = syma->binding == STB_WEAK;
+       b = symb->binding == STB_WEAK;
+       if (b && !a)
+               return SYMBOL_A;
+       if (a && !b)
+               return SYMBOL_B;
+
+       /* Prefer a global symbol over a non global one */
+       a = syma->binding == STB_GLOBAL;
+       b = symb->binding == STB_GLOBAL;
+       if (a && !b)
+               return SYMBOL_A;
+       if (b && !a)
+               return SYMBOL_B;
+
+       /* Prefer a symbol with less underscores */
+       a = prefix_underscores_count(syma->name);
+       b = prefix_underscores_count(symb->name);
+       if (b > a)
+               return SYMBOL_A;
+       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))
+               return SYMBOL_A;
+       else
+               return SYMBOL_B;
+}
+
+static void symbols__fixup_duplicate(struct rb_root *symbols)
+{
+       struct rb_node *nd;
+       struct symbol *curr, *next;
+
+       nd = rb_first(symbols);
+
+       while (nd) {
+               curr = rb_entry(nd, struct symbol, rb_node);
+again:
+               nd = rb_next(&curr->rb_node);
+               next = rb_entry(nd, struct symbol, rb_node);
+
+               if (!nd)
+                       break;
+
+               if (curr->start != next->start)
+                       continue;
+
+               if (choose_best_symbol(curr, next) == SYMBOL_A) {
+                       rb_erase(&next->rb_node, symbols);
+                       goto again;
+               } else {
+                       nd = rb_next(&curr->rb_node);
+                       rb_erase(&curr->rb_node, symbols);
+               }
+       }
+}
+
 static void symbols__fixup_end(struct rb_root *symbols)
 {
        struct rb_node *nd, *prevnd = rb_first(symbols);
@@ -692,6 +778,7 @@ int dso__load_kallsyms(struct dso *dso, const char *filename,
        if (dso__load_all_kallsyms(dso, filename, map) < 0)
                return -1;
 
+       symbols__fixup_duplicate(&dso->symbols[map->type]);
        symbols__fixup_end(&dso->symbols[map->type]);
 
        if (dso->kernel == DSO_TYPE_GUEST_KERNEL)
@@ -1269,6 +1356,7 @@ new_symbol:
         * For misannotated, zeroed, ASM function sizes.
         */
        if (nr > 0) {
+               symbols__fixup_duplicate(&dso->symbols[map->type]);
                symbols__fixup_end(&dso->symbols[map->type]);
                if (kmap) {
                        /*