[PATCH 4.4 044/137] perf probe: Skip overlapped location on searching variables

Greg Kroah-Hartman
2020-01-02T22:35:34Z

From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit dee36a2abb67c175265d49b9a8c7dfa564463d9a ]

Since debuginfo__find_probes() callback function can be called with the
location which already passed, the callback function must filter out
such overlapped locations.

add_probe_trace_event() has already done it by commit 1a375ae7659a
("perf probe: Skip same probe address for a given line"), but
add_available_vars() doesn't. Thus perf probe -v shows same address
repeatedly as below:

# perf probe -V vfs_read:18
Available variables at vfs_read:18
@<vfs_read+217>
char* buf
loff_t* pos
ssize_t ret
struct file* file
@<vfs_read+217>
char* buf
loff_t* pos
ssize_t ret
struct file* file
@<vfs_read+226>
char* buf
loff_t* pos
ssize_t ret
struct file* file

With this fix, perf probe -V shows it correctly:

# perf probe -V vfs_read:18
Available variables at vfs_read:18
@<vfs_read+217>
char* buf
loff_t* pos
ssize_t ret
struct file* file
@<vfs_read+226>
char* buf
loff_t* pos
ssize_t ret
struct file* file

Fixes: cf6eb489e5c0 ("perf probe: Show accessible local variables")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/157241938927.32002.4026859017790562751.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/util/probe-finder.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 28a0f37b05c0..d917f83e8e85 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1331,6 +1331,18 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
return DIE_FIND_CB_SIBLING;
}

+static bool available_var_finder_overlap(struct available_var_finder *af)
+{
+ int i;
+
+ for (i = 0; i < af->nvls; i++) {
+ if (af->pf.addr == af->vls[i].point.address)
+ return true;
+ }
+ return false;
+
+}
+
/* Add a found vars into available variables list */
static int add_available_vars(Dwarf_Die *sc_die, struct probe_finder *pf)
{
@@ -1341,6 +1353,14 @@ static int add_available_vars(Dwarf_Die *sc_die, struct probe_finder *pf)
Dwarf_Die die_mem;
int ret;

+ /*
+ * For some reason (e.g. different column assigned to same address),
+ * this callback can be called with the address which already passed.
+ * Ignore it first.
+ */
+ if (available_var_finder_overlap(af))
+ return 0;
+
/* Check number of tevs */
if (af->nvls == af->max_vls) {
pr_warning("Too many( > %d) probe point found.\n", af->max_vls);
--
2.20.1