1 files changed, 49 insertions, 14 deletions

diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c
index b987ab2c1541..cb2d51e779df 100644
--- a/arch/s390/kernel/jump_label.c
+++ b/arch/s390/kernel/jump_label.c
@@ -22,31 +22,66 @@ struct insn_args {
 	enum jump_label_type type;
 };
 
+static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
+{
+	/* brcl 0,0 */
+	insn->opcode = 0xc004;
+	insn->offset = 0;
+}
+
+static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
+{
+	/* brcl 15,offset */
+	insn->opcode = 0xc0f4;
+	insn->offset = (entry->target - entry->code) >> 1;
+}
+
+static void jump_label_bug(struct jump_entry *entry, struct insn *insn)
+{
+	unsigned char *ipc = (unsigned char *)entry->code;
+	unsigned char *ipe = (unsigned char *)insn;
+
+	pr_emerg("Jump label code mismatch at %pS [%p]\n", ipc, ipc);
+	pr_emerg("Found:    %02x %02x %02x %02x %02x %02x\n",
+		 ipc[0], ipc[1], ipc[2], ipc[3], ipc[4], ipc[5]);
+	pr_emerg("Expected: %02x %02x %02x %02x %02x %02x\n",
+		 ipe[0], ipe[1], ipe[2], ipe[3], ipe[4], ipe[5]);
+	panic("Corrupted kernel text");
+}
+
+static struct insn orignop = {
+	.opcode = 0xc004,
+	.offset = JUMP_LABEL_NOP_OFFSET >> 1,
+};
+
 static void __jump_label_transform(struct jump_entry *entry,
-				   enum jump_label_type type)
+				   enum jump_label_type type,
+				   int init)
 {
-	struct insn insn;
-	int rc;
+	struct insn old, new;
 
 	if (type == JUMP_LABEL_ENABLE) {
-		/* brcl 15,offset */
-		insn.opcode = 0xc0f4;
-		insn.offset = (entry->target - entry->code) >> 1;
+		jump_label_make_nop(entry, &old);
+		jump_label_make_branch(entry, &new);
 	} else {
-		/* brcl 0,0 */
-		insn.opcode = 0xc004;
-		insn.offset = 0;
+		jump_label_make_branch(entry, &old);
+		jump_label_make_nop(entry, &new);
 	}
-
-	rc = probe_kernel_write((void *)entry->code, &insn, JUMP_LABEL_NOP_SIZE);
-	WARN_ON_ONCE(rc < 0);
+	if (init) {
+		if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
+			jump_label_bug(entry, &old);
+	} else {
+		if (memcmp((void *)entry->code, &old, sizeof(old)))
+			jump_label_bug(entry, &old);
+	}
+	probe_kernel_write((void *)entry->code, &new, sizeof(new));
 }
 
 static int __sm_arch_jump_label_transform(void *data)
 {
 	struct insn_args *args = data;
 
-	__jump_label_transform(args->entry, args->type);
+	__jump_label_transform(args->entry, args->type, 0);
 	return 0;
 }
 
@@ -64,7 +99,7 @@ void arch_jump_label_transform(struct jump_entry *entry,
 void arch_jump_label_transform_static(struct jump_entry *entry,
 				      enum jump_label_type type)
 {
-	__jump_label_transform(entry, type);
+	__jump_label_transform(entry, type, 1);
 }
 
 #endif