1 files changed, 42 insertions, 14 deletions

diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c
index b987ab2c1541..25aef40584f7 100644
--- a/arch/s390/kernel/jump_label.c
+++ b/arch/s390/kernel/jump_label.c
@@ -22,31 +22,59 @@ 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 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;
+                if (init)
+                        jump_label_make_nop(entry, &old);
+                else
+                        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 (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 +92,7 @@ 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