[PATCH perf/core 3/4] perf-probe: Fix --line to handle aliased symbols in glibc

Masami Hiramatsu
2015-03-02T12:51:18Z

Fix perf probe --line to handle aliased symbols correctly
in glibc.

This makes line_range search failing back to address-based
alternative search as same as --add and --vars.

Without this patch;
-----
# ./perf probe -x /usr/lib64/libc-2.17.so -L malloc
Specified source line is not found.
Error: Failed to show lines.
-----

With this patch;
-----
# ./perf probe -x /usr/lib64/libc-2.17.so -L malloc
<__libc_malloc@/usr/src/debug/glibc-2.17-c758a686/malloc/malloc.c:0>
0 __libc_malloc(size_t bytes)
1 {
mstate ar_ptr;
void *victim;

__malloc_ptr_t (*hook) (size_t, const __malloc_ptr_t)
6 = force_reg (__malloc_hook);
7 if (__builtin_expect (hook != NULL, 0))
8 return (*hook)(bytes, RETURN_ADDRESS (0));

10 arena_lookup(ar_ptr);

12 arena_lock(ar_ptr, bytes);
-----

Note that this actually shows __libc_malloc, since it is
the real instance of malloc. User can use both __libc_malloc
and malloc for --line.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
tools/perf/util/probe-event.c | 35 +++++++++++++++++++++++++++++++++--
1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index b8f4578..4cfd121 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -353,6 +353,31 @@ static int get_alternative_probe_event(struct debuginfo *dinfo,
return ret;
}

+static int get_alternative_line_range(struct debuginfo *dinfo,
+ struct line_range *lr,
+ const char *target, bool user)
+{
+ struct perf_probe_point pp = { 0 }, result = { 0 };
+ int ret, len = 0;
+
+ pp.function = lr->function;
+ pp.file = lr->file;
+ pp.line = lr->start;
+ if (lr->end != INT_MAX)
+ len = lr->end - lr->start;
+ ret = find_alternative_probe_point(dinfo, &pp, &result,
+ target, user);
+ if (!ret) {
+ lr->function = result.function;
+ lr->file = result.file;
+ lr->start = result.line;
+ if (lr->end != INT_MAX)
+ lr->end = lr->start + len;
+ clear_perf_probe_point(&pp);
+ }
+ return ret;
+}
+
/* Open new debuginfo of given module */
static struct debuginfo *open_debuginfo(const char *module, bool silent)
{
@@ -734,7 +759,8 @@ static int _show_one_line(FILE *fp, int l, bool skip, bool show_num)
* Show line-range always requires debuginfo to find source file and
* line number.
*/
-static int __show_line_range(struct line_range *lr, const char *module)
+static int __show_line_range(struct line_range *lr, const char *module,
+ bool user)
{
int l = 1;
struct int_node *ln;
@@ -750,6 +776,11 @@ static int __show_line_range(struct line_range *lr, const char *module)
return -ENOENT;

ret = debuginfo__find_line_range(dinfo, lr);
+ if (!ret) { /* Not found, retry with an alternative */
+ ret = get_alternative_line_range(dinfo, lr, module, user);
+ if (!ret)
+ ret = debuginfo__find_line_range(dinfo, lr);
+ }
debuginfo__delete(dinfo);
if (ret == 0 || ret == -ENOENT) {
pr_warning("Specified source line is not found.\n");
@@ -819,7 +850,7 @@ int show_line_range(struct line_range *lr, const char *module, bool user)
ret = init_symbol_maps(user);
if (ret < 0)
return ret;
- ret = __show_line_range(lr, module);
+ ret = __show_line_range(lr, module, user);
exit_symbol_maps();

return ret;