[PATCH AUTOSEL 4.19 122/177] perf probe: Skip overlapped location on searching variables

[Sasha Levin]

From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Link: http://lore.kernel.org/lkml/157241938927.32002.4026859017790562751.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 64d4837c8f821..946b027b45e8a 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1414,6 +1414,18 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
 	return DIE_FIND_CB_END;
 }
 
+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)
 {
@@ -1424,6 +1436,14 @@ 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