kasan: switch kunit tests to console tracepoints

Switch KUnit-compatible KASAN tests from using per-task KUnit resources to
console tracepoints.

This allows for two things:

1. Migrating tests that trigger a KASAN report in the context of a task
   other than current to KUnit framework.
   This is implemented in the patches that follow.

2. Parsing and matching the contents of KASAN reports.
   This is not yet implemented.

Link: https://lkml.kernel.org/r/9345acdd11e953b207b0ed4724ff780e63afeb36.1664298455.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 62 insertions, 23 deletions

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 0d59098f0876..0ff20bfa3376 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -5,8 +5,12 @@
  * Author: Andrey Ryabinin <a.ryabinin@samsung.com>
  */
 
+#define pr_fmt(fmt) "kasan_test: " fmt
+
+#include <kunit/test.h>
 #include <linux/bitops.h>
 #include <linux/delay.h>
+#include <linux/io.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
@@ -14,21 +18,28 @@
 #include <linux/module.h>
 #include <linux/printk.h>
 #include <linux/random.h>
+#include <linux/set_memory.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/tracepoint.h>
 #include <linux/uaccess.h>
-#include <linux/io.h>
 #include <linux/vmalloc.h>
-#include <linux/set_memory.h>
+#include <trace/events/printk.h>
 
 #include <asm/page.h>
 
-#include <kunit/test.h>
-
 #include "kasan.h"
 
 #define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : KASAN_GRANULE_SIZE)
 
+static bool multishot;
+
+/* Fields set based on lines observed in the console. */
+static struct {
+	bool report_found;
+	bool async_fault;
+} test_status;
+
 /*
  * Some tests use these global variables to store return values from function
  * calls that could otherwise be eliminated by the compiler as dead code.
@@ -36,35 +47,61 @@
 void *kasan_ptr_result;
 int kasan_int_result;
 
-static struct kunit_resource resource;
-static struct kunit_kasan_status test_status;
-static bool multishot;
+/* Probe for console output: obtains test_status lines of interest. */
+static void probe_console(void *ignore, const char *buf, size_t len)
+{
+	if (strnstr(buf, "BUG: KASAN: ", len))
+		WRITE_ONCE(test_status.report_found, true);
+	else if (strnstr(buf, "Asynchronous fault: ", len))
+		WRITE_ONCE(test_status.async_fault, true);
+}
 
-/*
- * Temporarily enable multi-shot mode. Otherwise, KASAN would only report the
- * first detected bug and panic the kernel if panic_on_warn is enabled. For
- * hardware tag-based KASAN also allow tag checking to be reenabled for each
- * test, see the comment for KUNIT_EXPECT_KASAN_FAIL().
- */
-static int kasan_test_init(struct kunit *test)
+static void register_tracepoints(struct tracepoint *tp, void *ignore)
+{
+	check_trace_callback_type_console(probe_console);
+	if (!strcmp(tp->name, "console"))
+		WARN_ON(tracepoint_probe_register(tp, probe_console, NULL));
+}
+
+static void unregister_tracepoints(struct tracepoint *tp, void *ignore)
+{
+	if (!strcmp(tp->name, "console"))
+		tracepoint_probe_unregister(tp, probe_console, NULL);
+}
+
+static int kasan_suite_init(struct kunit_suite *suite)
 {
 	if (!kasan_enabled()) {
-		kunit_err(test, "can't run KASAN tests with KASAN disabled");
+		pr_err("Can't run KASAN tests with KASAN disabled");
 		return -1;
 	}
 
+	/*
+	 * Temporarily enable multi-shot mode. Otherwise, KASAN would only
+	 * report the first detected bug and panic the kernel if panic_on_warn
+	 * is enabled.
+	 */
 	multishot = kasan_save_enable_multi_shot();
-	test_status.report_found = false;
-	test_status.sync_fault = false;
-	kunit_add_named_resource(test, NULL, NULL, &resource,
-					"kasan_status", &test_status);
+
+	/*
+	 * Because we want to be able to build the test as a module, we need to
+	 * iterate through all known tracepoints, since the static registration
+	 * won't work here.
+	 */
+	for_each_kernel_tracepoint(register_tracepoints, NULL);
 	return 0;
 }
 
-static void kasan_test_exit(struct kunit *test)
+static void kasan_suite_exit(struct kunit_suite *suite)
 {
 	kasan_restore_multi_shot(multishot);
-	KUNIT_EXPECT_FALSE(test, test_status.report_found);
+	for_each_kernel_tracepoint(unregister_tracepoints, NULL);
+	tracepoint_synchronize_unregister();
+}
+
+static void kasan_test_exit(struct kunit *test)
+{
+	KUNIT_EXPECT_FALSE(test, READ_ONCE(test_status.report_found));
 }
 
 /**
@@ -106,11 +143,12 @@ static void kasan_test_exit(struct kunit *test)
 	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS) &&				\
 	    kasan_sync_fault_possible()) {				\
 		if (READ_ONCE(test_status.report_found) &&		\
-		    READ_ONCE(test_status.sync_fault))			\
+		    !READ_ONCE(test_status.async_fault))		\
 			kasan_enable_tagging();				\
 		migrate_enable();					\
 	}								\
 	WRITE_ONCE(test_status.report_found, false);			\
+	WRITE_ONCE(test_status.async_fault, false);			\
 } while (0)
 
 #define KASAN_TEST_NEEDS_CONFIG_ON(test, config) do {			\
@@ -1447,9 +1485,10 @@ static struct kunit_case kasan_kunit_test_cases[] = {
 
 static struct kunit_suite kasan_kunit_test_suite = {
 	.name = "kasan",
-	.init = kasan_test_init,
 	.test_cases = kasan_kunit_test_cases,
 	.exit = kasan_test_exit,
+	.suite_init = kasan_suite_init,
+	.suite_exit = kasan_suite_exit,
 };
 
 kunit_test_suite(kasan_kunit_test_suite);