[PATCH blktests] check: add kmemleak support to blktests

[Nilay Shroff <nilay@linux.ibm.com>]

Running blktests can also help uncover kernel memory leaks when the
kernel is built with CONFIG_DEBUG_KMEMLEAK. However, until now the
blktests framework had no way to automatically detect or report such
leaks. Users typically had to manually setup kmemleak and trigger
scans after running tests[1][2].

This change integrates kmemleak support directly into the blktests
framework. Before running each test, the framework checks for the
presence of /sys/kernel/debug/kmemleak to determine whether kmemleak
is enabled for the running kernel. If available, before running a test,
any existing kmemleak reports are cleared to avoid false positives
from previous tests. After the test completes, the framework explicitly
triggers a kmemleak scan. If memory leaks are detected, they are written
to a per-test file at, "results/.../.../<test>.kmemleak" and the
corresponding test is marked as FAIL. Users can then inspect the
<test>.kmemleak file to analyze the reported leaks.

With this enhancement, blktests can automatically detect kernel memory
leaks (if kerel is configured with CONFIG_DEBUG_KMEMLEAK support)  on
a per-test basis, removing the need for manual kmemleak setup and scans.
This should make it easier and faster to identify memory leaks
introduced by individual tests.

[1] https://lore.kernel.org/all/CAHj4cs8oJFvz=daCvjHM5dYCNQH4UXwSySPPU4v-WHce_kZXZA@mail.gmail.com/
[2] https://lore.kernel.org/all/CAHj4cs9wv3SdPo+N01Fw2SHBYDs9tj2M_e1-GdQOkRy=DsBB1w@mail.gmail.com/

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 check | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/check b/check
index 6d77d8e..3a6e837 100755
--- a/check
+++ b/check
@@ -183,6 +183,36 @@ _check_dmesg() {
 	fi
 }
 
+_setup_kmemleak() {
+	local f="/sys/kernel/debug/kmemleak"
+
+	if [[ ! -e $f || ! -r $f ]]; then
+		return 0
+	fi
+
+	echo clear > "$f"
+}
+
+_check_kmemleak() {
+	local kmemleak
+	local f="/sys/kernel/debug/kmemleak"
+
+	if [[ ! -e $f || ! -r $f ]]; then
+		return 0
+	fi
+
+	echo scan > "$f"
+	sleep 1
+	kmemleak=$(cat "$f")
+
+	if [[ -z $kmemleak ]]; then
+		return 0
+	fi
+
+	printf '%s\n' "$kmemleak" > "${seqres}.kmemleak"
+	return 1
+}
+
 _read_last_test_run() {
 	local seqres="${RESULTS_DIR}/${TEST_NAME}"
 
@@ -377,6 +407,8 @@ _call_test() {
 	if [[ -v SKIP_REASONS ]]; then
 		TEST_RUN["status"]="not run"
 	else
+		_setup_kmemleak
+
 		if [[ -w /dev/kmsg ]]; then
 			local dmesg_marker="run blktests $TEST_NAME at ${TEST_RUN["date"]}"
 			echo "$dmesg_marker" >> /dev/kmsg
@@ -414,6 +446,9 @@ _call_test() {
 		elif ! _check_dmesg "$dmesg_marker"; then
 			TEST_RUN["status"]=fail
 			TEST_RUN["reason"]=dmesg
+		elif ! _check_kmemleak; then
+			TEST_RUN["status"]=fail
+			TEST_RUN["reason"]=kmemleak
 		else
 			TEST_RUN["status"]=pass
 		fi
@@ -451,6 +486,18 @@ _call_test() {
 				print \"    \" \$0
 			}" "${seqres}.dmesg"
 			;;
+		kmemleak)
+			echo "    kmemleak detected:"
+                        awk "
+                        {
+                                if (NR > 10) {
+                                        print \"    ...\"
+                                        print \"    (See '${seqres}.kmemleak' for the entire message)\"
+                                        exit
+                                }
+                                print \"    \" \$0
+                        }" "${seqres}.kmemleak"
+                        ;;
 		esac
 		return 1
 	else
-- 
2.52.0