kcsan: Start stack trace with explicit location if provided

If an explicit access address is set, as is done for scoped accesses,
always start the stack trace from that location. get_stack_skipnr() is
changed into sanitize_stack_entries(), which if given an address, scans
the stack trace for a matching function and then replaces that entry
with the explicitly provided address.

The previous reports for scoped accesses were all over the place, which
could be quite confusing. We now always point at the start of the scope.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 11 insertions, 8 deletions

diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index e282c1166373..a3b12429e1d3 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -338,7 +338,10 @@ static noinline void test_kernel_assert_bits_nochange(void)
 	ASSERT_EXCLUSIVE_BITS(test_var, ~TEST_CHANGE_BITS);
 }
 
-/* To check that scoped assertions do trigger anywhere in scope. */
+/*
+ * Scoped assertions do trigger anywhere in scope. However, the report should
+ * still only point at the start of the scope.
+ */
 static noinline void test_enter_scope(void)
 {
 	int x = 0;
@@ -845,22 +848,22 @@ static void test_assert_exclusive_writer_scoped(struct kunit *test)
 			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
 		},
 	};
-	const struct expect_report expect_anywhere = {
+	const struct expect_report expect_inscope = {
 		.access = {
 			{ test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED },
 			{ test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE },
 		},
 	};
 	bool match_expect_start = false;
-	bool match_expect_anywhere = false;
+	bool match_expect_inscope = false;
 
 	begin_test_checks(test_kernel_assert_writer_scoped, test_kernel_write_nochange);
 	do {
 		match_expect_start |= report_matches(&expect_start);
-		match_expect_anywhere |= report_matches(&expect_anywhere);
-	} while (!end_test_checks(match_expect_start && match_expect_anywhere));
+		match_expect_inscope |= report_matches(&expect_inscope);
+	} while (!end_test_checks(match_expect_inscope));
 	KUNIT_EXPECT_TRUE(test, match_expect_start);
-	KUNIT_EXPECT_TRUE(test, match_expect_anywhere);
+	KUNIT_EXPECT_FALSE(test, match_expect_inscope);
 }
 
 __no_kcsan
@@ -889,9 +892,9 @@ static void test_assert_exclusive_access_scoped(struct kunit *test)
 	do {
 		match_expect_start |= report_matches(&expect_start1) || report_matches(&expect_start2);
 		match_expect_inscope |= report_matches(&expect_inscope);
-	} while (!end_test_checks(match_expect_start && match_expect_inscope));
+	} while (!end_test_checks(match_expect_inscope));
 	KUNIT_EXPECT_TRUE(test, match_expect_start);
-	KUNIT_EXPECT_TRUE(test, match_expect_inscope);
+	KUNIT_EXPECT_FALSE(test, match_expect_inscope);
 }
 
 /*