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Commit 694bf407 authored by Anton Blanchard's avatar Anton Blanchard Committed by Arnaldo Carvalho de Melo
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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: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 31877908

tools/perf/util/symbol.c

+88 −0
Original line number Diff line number Diff line
@@ -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 @@ static int dso__load_sym(struct dso *dso, struct map *map, const char *name, 
	 * 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) {

			/*