[PATCH] perf test: Handle perftool-testsuite_probe failure due to broken DWARF

[vmolnaro@redhat.com]

From: Veronika Molnarova <vmolnaro@redhat.com>

Test case test_adding_blacklisted ends in failure if the blacklisted
probe is of an assembler function with no DWARF available. At the same
time, probing the blacklisted function with ASM DWARF doesn't test the
blacklist itself as the failure is a result of the broken DWARF.

When the broken DWARF output is encountered, check if the probed
function was compiled by the assembler. If so, the broken DWARF message
is expected and does not report a perf issue, else report a failure.
If the ASM DWARF affected the probe, try the next probe on the blacklist.
If the first 5 probes are defective due to broken DWARF, skip the test
case.

Fixes: def5480d63c1e847 ("perf testsuite probe: Add test for blacklisted kprobes handling")
Signed-off-by: Veronika Molnarova <vmolnaro@redhat.com>
---
 .../base_probe/test_adding_blacklisted.sh     | 74 +++++++++++++++----
 1 file changed, 59 insertions(+), 15 deletions(-)

diff --git a/tools/perf/tests/shell/base_probe/test_adding_blacklisted.sh b/tools/perf/tests/shell/base_probe/test_adding_blacklisted.sh
index b5dc10b2a73810b3..f67b3b267ac55269 100755
--- a/tools/perf/tests/shell/base_probe/test_adding_blacklisted.sh
+++ b/tools/perf/tests/shell/base_probe/test_adding_blacklisted.sh
@@ -19,35 +19,79 @@
 TEST_RESULT=0
 
 # skip if not supported
-BLACKFUNC=`head -n 1 /sys/kernel/debug/kprobes/blacklist 2> /dev/null | cut -f2`
-if [ -z "$BLACKFUNC" ]; then
+BLACKFUNC_LIST=`head -n 5 /sys/kernel/debug/kprobes/blacklist 2> /dev/null | cut -f2`
+if [ -z "$BLACKFUNC_LIST" ]; then
 	print_overall_skipped
 	exit 0
 fi
 
+# chceck if locate is present to find vmlinux with DWARF debug info
+locate --help 2&> /dev/null
+if [ $? -eq 0 ]; then
+	VMLINUX_FILE=$(locate -r '/vmlinux$' | xargs -I{} sh -c 'test -f "{}" && echo "{}"' | grep "$(uname -r)")
+fi
+
 # remove all previously added probes
 clear_all_probes
 
 
 ### adding blacklisted function
-
-# functions from blacklist should be skipped by perf probe
-! $CMD_PERF probe $BLACKFUNC > $LOGS_DIR/adding_blacklisted.log 2> $LOGS_DIR/adding_blacklisted.err
-PERF_EXIT_CODE=$?
-
 REGEX_SCOPE_FAIL="Failed to find scope of probe point"
 REGEX_SKIP_MESSAGE=" is blacklisted function, skip it\."
-REGEX_NOT_FOUND_MESSAGE="Probe point \'$BLACKFUNC\' not found."
+REGEX_NOT_FOUND_MESSAGE="Probe point \'$RE_EVENT\' not found."
 REGEX_ERROR_MESSAGE="Error: Failed to add events."
 REGEX_INVALID_ARGUMENT="Failed to write event: Invalid argument"
 REGEX_SYMBOL_FAIL="Failed to find symbol at $RE_ADDRESS"
-REGEX_OUT_SECTION="$BLACKFUNC is out of \.\w+, skip it"
-../common/check_all_lines_matched.pl "$REGEX_SKIP_MESSAGE" "$REGEX_NOT_FOUND_MESSAGE" "$REGEX_ERROR_MESSAGE" "$REGEX_SCOPE_FAIL" "$REGEX_INVALID_ARGUMENT" "$REGEX_SYMBOL_FAIL" "$REGEX_OUT_SECTION" < $LOGS_DIR/adding_blacklisted.err
-CHECK_EXIT_CODE=$?
-
-print_results $PERF_EXIT_CODE $CHECK_EXIT_CODE "adding blacklisted function $BLACKFUNC"
-(( TEST_RESULT += $? ))
-
+REGEX_OUT_SECTION="$RE_EVENT is out of \.\w+, skip it"
+REGEX_MISSING_DECL_LINE="A function DIE doesn't have decl_line. Maybe broken DWARF?"
+
+BLACKFUNC=""
+SKIP_DWARF=0
+
+for BLACKFUNC in $BLACKFUNC_LIST; do
+	echo "Probing $BLACKFUNC"
+
+	# functions from blacklist should be skipped by perf probe
+	! $CMD_PERF probe $BLACKFUNC > $LOGS_DIR/adding_blacklisted.log 2> $LOGS_DIR/adding_blacklisted.err
+	PERF_EXIT_CODE=$?
+
+	# check for bad DWARF polluting the result
+	../common/check_all_patterns_found.pl "$REGEX_MISSING_DECL_LINE" >/dev/null < $LOGS_DIR/adding_blacklisted.err
+
+	if [ $? -eq 0 ]; then
+		SKIP_DWARF=1
+
+		# confirm that the broken DWARF comes from assembler
+		if [ -n "$VMLINUX_FILE" ]; then
+			readelf -wi "$VMLINUX_FILE" |
+			awk -v probe="$BLACKFUNC" '/DW_AT_language/ { comp_lang = $0 }
+										$0 ~ probe { if (comp_lang) { print comp_lang }; exit }' |
+			grep -q "MIPS assembler"
+
+			CHECK_EXIT_CODE=$?
+			if [ $CHECK_EXIT_CODE -ne 0 ]; then
+				SKIP_DWARF=0 # broken DWARF while available
+				break
+			fi
+		else
+			echo "Result polluted by broken DWARF, trying another probe"
+		fi
+
+	else
+		../common/check_all_lines_matched.pl "$REGEX_SKIP_MESSAGE" "$REGEX_NOT_FOUND_MESSAGE" "$REGEX_ERROR_MESSAGE" "$REGEX_SCOPE_FAIL" "$REGEX_INVALID_ARGUMENT" "$REGEX_SYMBOL_FAIL" "$REGEX_OUT_SECTION" < $LOGS_DIR/adding_blacklisted.err
+		CHECK_EXIT_CODE=$?
+
+		SKIP_DWARF=0
+		break
+	fi
+done
+
+if [ $SKIP_DWARF -eq 1 ]; then
+	print_testcase_skipped "adding blacklisted function $BLACKFUNC"
+else
+	print_results $PERF_EXIT_CODE $CHECK_EXIT_CODE "adding blacklisted function $BLACKFUNC"
+	(( TEST_RESULT += $? ))
+fi
 
 ### listing not-added probe
 
-- 
2.43.0