kfence: add function to mask address bits

s390 only reports the page address during a translation fault.
To make the kfence unit tests pass, add a function that might
be implemented by architectures to mask out address bits.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20210728190254.3921642-3-hca@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

mm/kfence/kfence_test.c

@@ -23,8 +23,15 @@
 #include <linux/tracepoint.h>
 #include <trace/events/printk.h>
 
+#include <asm/kfence.h>
+
 #include "kfence.h"
 
+/* May be overridden by <asm/kfence.h>. */
+#ifndef arch_kfence_test_address
+#define arch_kfence_test_address(addr) (addr)
+#endif
+
 /* Report as observed from console. */
 static struct {
 	spinlock_t lock;
@@ -82,6 +89,7 @@ static const char *get_access_type(const struct expect_report *r)
 /* Check observed report matches information in @r. */
 static bool report_matches(const struct expect_report *r)
 {
+	unsigned long addr = (unsigned long)r->addr;
 	bool ret = false;
 	unsigned long flags;
 	typeof(observed.lines) expect;
@@ -131,22 +139,25 @@ static bool report_matches(const struct expect_report *r)
 	switch (r->type) {
 	case KFENCE_ERROR_OOB:
 		cur += scnprintf(cur, end - cur, "Out-of-bounds %s at", get_access_type(r));
+		addr = arch_kfence_test_address(addr);
 		break;
 	case KFENCE_ERROR_UAF:
 		cur += scnprintf(cur, end - cur, "Use-after-free %s at", get_access_type(r));
+		addr = arch_kfence_test_address(addr);
 		break;
 	case KFENCE_ERROR_CORRUPTION:
 		cur += scnprintf(cur, end - cur, "Corrupted memory at");
 		break;
 	case KFENCE_ERROR_INVALID:
 		cur += scnprintf(cur, end - cur, "Invalid %s at", get_access_type(r));
+		addr = arch_kfence_test_address(addr);
 		break;
 	case KFENCE_ERROR_INVALID_FREE:
 		cur += scnprintf(cur, end - cur, "Invalid free of");
 		break;
 	}
 
-	cur += scnprintf(cur, end - cur, " 0x%p", (void *)r->addr);
+	cur += scnprintf(cur, end - cur, " 0x%p", (void *)addr);
 
 	spin_lock_irqsave(&observed.lock, flags);
 	if (!report_available())