perf test record+probe_libc_inet_pton: Make test resilient

The test failed back and forth due to the call chain being heavily
impacted by the libc, which varies across different architectures and
distros.

The libc contains the symbols for "gaih_inet" and "getaddrinfo" in some
cases, but not always. Moreover, these symbols can be either normal
symbols or dynamic symbols, making it difficult to decide the call chain
entries due to the symbols are inconsistent.

To fix the issue, this commit identifies three call chain entries are
always present. These entries are matched by iterating through the
lines in the "perf script" result. The recording attribute max-stack is
set to 4 for the possible maximum call chain depth.

After:

# perf test -vF pton
--- start ---
Pattern: ping[][0-9 \.:]+probe_libc:inet_pton: \([[:xdigit:]]+\)
Matching: ping 285058 [025] 1219802.466939: probe_libc:inet_pton: (ffffa14b7cf0)
Pattern: .*inet_pton\+0x[[:xdigit:]]+[[:space:]]\(/usr/lib/aarch64-linux-gnu/libc-2.31.so|inlined\)$
Matching: ping 285058 [025] 1219802.466939: probe_libc:inet_pton: (ffffa14b7cf0)
Matching: ffffa14b7cf0 __GI___inet_pton+0x0 (/usr/lib/aarch64-linux-gnu/libc-2.31.so)
Pattern: .*(\+0x[[:xdigit:]]+|\[unknown\])[[:space:]]\(.*/bin/ping.*\)$
Matching: ping 285058 [025] 1219802.466939: probe_libc:inet_pton: (ffffa14b7cf0)
Matching: ffffa14b7cf0 __GI___inet_pton+0x0 (/usr/lib/aarch64-linux-gnu/libc-2.31.so)
Matching: ffffa1488040 getaddrinfo+0xe8 (/usr/lib/aarch64-linux-gnu/libc-2.31.so)
Matching: aaaab8672da4 [unknown] (/usr/bin/ping)
---- end ----
82: probe libc's inet_pton & backtrace it with ping : Ok

Closes: https://lore.kernel.org/linux-perf-users/[e-mail]/
Closes: https://lore.kernel.org/linux-perf-users/Z0X3AYUWkAgfPpWj@x1/T/#m57327e135b156047e37d214a0d453af6ae1e02be
Reported-by: Guilherme Amadio <[e-mail]>
Reported-by: Jing Zhang <[e-mail]>
Reviewed-by: James Clark <[e-mail]>
Signed-off-by: Leo Yan <[e-mail]>
Tested-by: Thomas Richter <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Athira Rajeev <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/shell/record+probe_libc_inet_pton.sh

···
 		echo "((__GI_)?getaddrinfo|text_to_binary_address)\+0x[[:xdigit:]]+[[:space:]]\($libc|inlined\)$" >> $expected
 		echo "(gaih_inet|main)\+0x[[:xdigit:]]+[[:space:]]\(inlined|.*/bin/ping.*\)$" >> $expected
 		;;
-	ppc64|ppc64le)
-		eventattr='max-stack=4'
-		# 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
-		;;
 	*)
-		eventattr='max-stack=3'
+		eventattr='max-stack=4'
 		echo ".*(\+0x[[:xdigit:]]+|\[unknown\])[[:space:]]\(.*/bin/ping.*\)$" >> $expected
 		;;
 	esac
···
 	fi
 	perf script -i $perf_data | tac | grep -m1 ^ping -B9 | tac > $perf_script
 
-	exec 3<$perf_script
 	exec 4<$expected
-	while read line <&3 && read -r pattern <&4; do
+	while read -r pattern <&4; do
+		echo "Pattern: $pattern"
 		[ -z "$pattern" ] && break
-		echo $line
-		echo "$line" | grep -E -q "$pattern"
-		if [ $? -ne 0 ] ; then
-			printf "FAIL: expected backtrace entry \"%s\" got \"%s\"\n" "$pattern" "$line"
+
+		found=0
+
+		# Search lines in the perf script result
+		exec 3<$perf_script
+		while read line <&3; do
+			[ -z "$line" ] && break
+			echo "  Matching: $line"
+			! echo "$line" | grep -E -q "$pattern"
+			found=$?
+			[ $found -eq 1 ] && break
+		done
+
+		if [ $found -ne 1 ] ; then
+			printf "FAIL: Didn't find the expected backtrace entry \"%s\"\n" "$pattern"
 			return 1
 		fi
 	done