linux-kernel - [PATCH V2 1/3] tools/perf: Fix the string match for "/tmp/perf-$PID.map" files in dso_

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Message-Id: <20240617130332.13427-1-atrajeev@linux.vnet.ibm.com>
Date: Mon, 17 Jun 2024 18:33:30 +0530
From: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
To: acme@...nel.org, jolsa@...nel.org, adrian.hunter@...el.com,
        irogers@...gle.com, namhyung@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, akanksha@...ux.ibm.com,
        maddy@...ux.ibm.com, atrajeev@...ux.vnet.ibm.com, kjain@...ux.ibm.com,
        disgoel@...ux.vnet.ibm.com
Subject: [PATCH V2 1/3] tools/perf: Fix the string match for "/tmp/perf-$PID.map" files in dso__load

Perf test for perf probe of function from different CU fails
as below:

	./perf test -vv "test perf probe of function from different CU"
	116: test perf probe of function from different CU:
	--- start ---
	test child forked, pid 2679
	Failed to find symbol foo in /tmp/perf-uprobe-different-cu-sh.Msa7iy89bx/testfile
	  Error: Failed to add events.
	--- Cleaning up ---
	"foo" does not hit any event.
	  Error: Failed to delete events.
	---- end(-1) ----
	116: test perf probe of function from different CU                   : FAILED!

The test does below to probe function "foo" :

	# gcc -g -Og -flto -c /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-foo.c
	-o /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-foo.o
	# gcc -g -Og -c /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-main.c
	-o /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-main.o
	# gcc -g -Og -o /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile
	/tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-foo.o
	/tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile-main.o

	# ./perf probe -x /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile foo
	Failed to find symbol foo in /tmp/perf-uprobe-different-cu-sh.XniNxNEVT7/testfile
	   Error: Failed to add events.

Perf probe fails to find symbol foo in the executable placed in
/tmp/perf-uprobe-different-cu-sh.XniNxNEVT7

Simple reproduce:

 # mktemp -d /tmp/perf-checkXXXXXXXXXX
   /tmp/perf-checkcWpuLRQI8j

 # gcc -g -o test test.c
 # cp test /tmp/perf-checkcWpuLRQI8j/
 # nm /tmp/perf-checkcWpuLRQI8j/test | grep foo
   00000000100006bc T foo

 # ./perf probe -x /tmp/perf-checkcWpuLRQI8j/test foo
   Failed to find symbol foo in /tmp/perf-checkcWpuLRQI8j/test
      Error: Failed to add events.

But it works with any files like /tmp/perf/test. Only for
patterns with "/tmp/perf-", this fails.

Further debugging, commit 80d496be89ed ("perf report: Add support
for profiling JIT generated code") added support for profiling JIT
generated code. This patch handles dso's of form
"/tmp/perf-$PID.map" .

The check used "if (strncmp(self->name, "/tmp/perf-", 10) == 0)"
to match "/tmp/perf-$PID.map". With this commit, any dso in
/tmp/perf- folder will be considered separately for processing
(not only JIT created map files ). Fix this by changing the
string pattern to check for "/tmp/perf-%d.map". Add a helper
function is_perf_pid_map_name to do this check.

With the fix,
	# ./perf test "test perf probe of function from different CU"
	117: test perf probe of function from different CU                   : Ok

Signed-off-by: Athira Rajeev<atrajeev@...ux.vnet.ibm.com>
---
Changelog:
v2 -> v2:
 Addressed review comments from Adrian.
 Added helper function is_perf_pid_map_name to check
 dso name of form "/tmp/perf-%d.map". Used sscanf
 instead of regex comparison.

 tools/perf/util/dso.c    | 7 +++++++
 tools/perf/util/dso.h    | 3 +++
 tools/perf/util/symbol.c | 3 ++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index dde706b71da7..4dabb82d8018 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1652,3 +1652,10 @@ int dso__strerror_load(struct dso *dso, char *buf, size_t buflen)
 	scnprintf(buf, buflen, "%s", dso_load__error_str[idx]);
 	return 0;
 }
+
+bool is_perf_pid_map_name(const char *dso_name)
+{
+	int tid;
+
+	return sscanf(dso_name, "/tmp/perf-%d.map", &tid) == 1;
+}
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index df2c98402af3..44a3a5c97daf 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -809,4 +809,7 @@ void reset_fd_limit(void);
 u64 dso__find_global_type(struct dso *dso, u64 addr);
 u64 dso__findnew_global_type(struct dso *dso, u64 addr, u64 offset);
 
+/* Check if dso name is of format "/tmp/perf-%d.map" */
+bool is_perf_pid_map_name(const char *dso_name);
+
 #endif /* __PERF_DSO */
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 9e5940b5bc59..aee0a4cfb383 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1799,7 +1799,8 @@ int dso__load(struct dso *dso, struct map *map)
 	const char *map_path = dso__long_name(dso);
 
 	mutex_lock(dso__lock(dso));
-	perfmap = strncmp(dso__name(dso), "/tmp/perf-", 10) == 0;
+	perfmap = is_perf_pid_map_name(map_path);
+
 	if (perfmap) {
 		if (dso__nsinfo(dso) &&
 		    (dso__find_perf_map(newmapname, sizeof(newmapname),
-- 
2.35.3