linux-kernel - [PATCH 1/2] tools/perf: Fix the string match for "/tmp/perf-$PID.map" files in dso_

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Date: Fri, 14 Jun 2024 22:57:41 +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 1/2] 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 regex of form "/tmp/perf-*.map"

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>
---
 tools/perf/util/symbol.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 9e5940b5bc59..bfb88a4b0987 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -41,6 +41,7 @@
 #include <limits.h>
 #include <symbol/kallsyms.h>
 #include <sys/utsname.h>
+#include <regex.h>
 
 static int dso__load_kernel_sym(struct dso *dso, struct map *map);
 static int dso__load_guest_kernel_sym(struct dso *dso, struct map *map);
@@ -1797,9 +1798,18 @@ int dso__load(struct dso *dso, struct map *map)
 	struct nscookie nsc;
 	char newmapname[PATH_MAX];
 	const char *map_path = dso__long_name(dso);
+	regex_t    regex;
+	const char *pattern =  "(^/tmp/perf-).*(map)";
 
 	mutex_lock(dso__lock(dso));
-	perfmap = strncmp(dso__name(dso), "/tmp/perf-", 10) == 0;
+	if (regcomp(&regex, pattern, REG_EXTENDED)) {
+		pr_debug("regcomp() failed in dso__load\n");
+		ret = -1;
+		goto out;
+	}
+
+	perfmap = !regexec(&regex, dso__name(dso), 0, NULL, 0);
+
 	if (perfmap) {
 		if (dso__nsinfo(dso) &&
 		    (dso__find_perf_map(newmapname, sizeof(newmapname),
-- 
2.35.3