[PATCH] perf test record+probe_libc_inet_pton: Fix call chain match on powerpc

[Likhitha Korrapati]

The perf test "probe libc's inet_pton & backtrace it with ping" fails on
powerpc as below:

root at xxx perf]# perf test -v "probe libc's inet_pton & backtrace it with
ping"
 85: probe libc's inet_pton & backtrace it with ping                 :
--- start ---
test child forked, pid 96028
ping 96056 [002] 127271.101961: probe_libc:inet_pton: (7fffa1779a60)
7fffa1779a60 __GI___inet_pton+0x0
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
7fffa172a73c getaddrinfo+0x121c
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
FAIL: expected backtrace entry
"gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\(/usr/lib64/glibc-hwcaps/power10/libc.so.6\)$"
got "7fffa172a73c getaddrinfo+0x121c
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)"
test child finished with -1
---- end ----
probe libc's inet_pton & backtrace it with ping: FAILED!

This test installs a probe on libc's inet_pton function, which will use
uprobes and then uses perf trace on a ping to localhost. It gets 3
levels deep backtrace and checks whether it is what we expected or not.

The test started failing from RHEL 9.4 where as it works in previous
distro version (RHEL 9.2). Test expects gaih_inet function to be part of
backtrace. But in the glibc version (2.34-86) which is part of distro
where it fails, this function is missing and hence the test is failing.

>From nm and ping command output we can confirm that gaih_inet function
is not present in the expected backtrace for glibc version glibc-2.34-86

[root at xxx perf]# nm /usr/lib64/glibc-hwcaps/power10/libc.so.6 | grep gaih_inet
00000000001273e0 t gaih_inet_serv
00000000001cd8d8 r gaih_inet_typeproto

[root at xxx perf]# perf script -i /tmp/perf.data.6E8
ping  104048 [000] 128582.508976: probe_libc:inet_pton: (7fff83779a60)
            7fff83779a60 __GI___inet_pton+0x0
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
            7fff8372a73c getaddrinfo+0x121c
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
               11dc73534 [unknown] (/usr/bin/ping)
            7fff8362a8c4 __libc_start_call_main+0x84
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)

FAIL: expected backtrace entry
"gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\(/usr/lib64/glibc-hwcaps/power10/libc.so.6\)$"
got "7fff9d52a73c getaddrinfo+0x121c
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)"

With version glibc-2.34-60 gaih_inet function is present as part of the
expected backtrace. So we cannot just remove the gaih_inet function from
the backtrace.

[root at xxx perf]# nm /usr/lib64/glibc-hwcaps/power10/libc.so.6 | grep gaih_inet
0000000000130490 t gaih_inet.constprop.0
000000000012e830 t gaih_inet_serv
00000000001d45e4 r gaih_inet_typeproto

[root at xxx perf]# ./perf script -i /tmp/perf.data.b6S
ping   67906 [000] 22699.591699: probe_libc:inet_pton_3: (7fffbdd80820)
            7fffbdd80820 __GI___inet_pton+0x0
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
            7fffbdd31160 gaih_inet.constprop.0+0xcd0
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
            7fffbdd31c7c getaddrinfo+0x14c
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
               1140d3558 [unknown] (/usr/bin/ping)

This patch solves this issue by doing a conditional skip. If there is a
gaih_inet function present in the libc then it will be added to the
expected backtrace else the function will be skipped from being added
to the expected backtrace.

Output with the patch

[root at xxx perf]# ./perf test -v "probe libc's inet_pton & backtrace it
with ping"
 83: probe libc's inet_pton & backtrace it with ping                 :
--- start ---
test child forked, pid 102662
ping 102692 [000] 127935.549973: probe_libc:inet_pton: (7fff93379a60)
7fff93379a60 __GI___inet_pton+0x0
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
7fff9332a73c getaddrinfo+0x121c
(/usr/lib64/glibc-hwcaps/power10/libc.so.6)
11ef03534 [unknown] (/usr/bin/ping)
test child finished with 0
---- end ----
probe libc's inet_pton & backtrace it with ping: Ok

Signed-off-by: Likhitha Korrapati <likhitha at linux.ibm.com>
Reported-by: Disha Goel <disgoel at linux.ibm.com>
---
 tools/perf/tests/shell/record+probe_libc_inet_pton.sh | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/shell/record+probe_libc_inet_pton.sh b/tools/perf/tests/shell/record+probe_libc_inet_pton.sh
index eebeea6bdc76..72c65570db37 100755
--- a/tools/perf/tests/shell/record+probe_libc_inet_pton.sh
+++ b/tools/perf/tests/shell/record+probe_libc_inet_pton.sh
@@ -45,7 +45,10 @@ trace_libc_inet_pton_backtrace() {
 		;;
 	ppc64|ppc64le)
 		eventattr='max-stack=4'
-		echo "gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\($libc\)$" >> $expected
+		# Add gaih_inet to expected backtrace only if it is part of libc.
+		if nm $libc | grep -F -q gaih_inet.; then
+			echo "gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\($libc\)$" >> $expected
+		fi
 		echo "getaddrinfo\+0x[[:xdigit:]]+[[:space:]]\($libc\)$" >> $expected
 		echo ".*(\+0x[[:xdigit:]]+|\[unknown\])[[:space:]]\(.*/bin/ping.*\)$" >> $expected
 		;;
-- 
2.39.1