[PATCH v2 2/2] vsprintf: Add test for restricted kernel pointers

["Thomas Weißschuh" <thomas.weissschuh@linutronix.de>]

Fill out the tests for restricted kernel pointers, using the %pK format.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

---
Please note that changes to the kptr_restrict sysctl from the kernel
commandline are only applied *after* the boot-time KUnit tests run.
---
 lib/tests/printf_kunit.c | 22 +++++++++++++++++++++-
 lib/vsprintf.c           |  3 +++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/tests/printf_kunit.c b/lib/tests/printf_kunit.c
index bb70b9cddadd..58e639b01e83 100644
--- a/lib/tests/printf_kunit.c
+++ b/lib/tests/printf_kunit.c
@@ -319,7 +319,27 @@ symbol_ptr(struct kunit *kunittest)
 static void
 kernel_ptr(struct kunit *kunittest)
 {
-	/* We can't test this without access to kptr_restrict. */
+	switch (kptr_restrict) {
+	case 0:
+		if (no_hash_pointers) {
+			test(PTR_STR, "%pK", PTR);
+		} else {
+			char buf[PLAIN_BUF_SIZE];
+
+			plain_hash_to_buffer(kunittest, PTR, buf, PLAIN_BUF_SIZE);
+			/* %pK behaves the same as hashing */
+			test(buf, "%pK", PTR);
+		}
+		break;
+	case 1:
+		/* The KUnit kthread has all capabilities, including CAP_SYSLOG */
+		test(PTR_STR, "%pK", PTR);
+		break;
+	case 2:
+	default:
+		test(ZEROS "00000000", "%pK", PTR);
+		break;
+	}
 }
 
 static void
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index f70d240a394c..dc7e012a6ed7 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -859,6 +859,9 @@ static char *default_pointer(char *buf, char *end, const void *ptr,
 }
 
 int kptr_restrict __read_mostly;
+#if IS_MODULE(CONFIG_PRINTF_KUNIT_TEST)
+EXPORT_SYMBOL_FOR_MODULES(kptr_restrict, "printf_kunit");
+#endif
 
 static noinline_for_stack
 char *restricted_pointer(char *buf, char *end, const void *ptr,

-- 
2.53.0