2024-06-14 19:57:03

by Athira Rajeev

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<[email protected]>
---
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