1 files changed, 102 insertions, 0 deletions
diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c
new file mode 100644
index 000000000..10009a0cd
--- /dev/null
+++ b/arch/s390/kernel/jump_label.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Jump label s390 support
+ *
+ * Copyright IBM Corp. 2011
+ * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
+ */
+#include <linux/uaccess.h>
+#include <linux/stop_machine.h>
+#include <linux/jump_label.h>
+#include <asm/ipl.h>
+
+struct insn {
+	u16 opcode;
+	s32 offset;
+} __packed;
+
+struct insn_args {
+	struct jump_entry *entry;
+	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 *expected,
+			   struct insn *new)
+{
+	unsigned char *ipc = (unsigned char *)entry->code;
+	unsigned char *ipe = (unsigned char *)expected;
+	unsigned char *ipn = (unsigned char *)new;
+
+	pr_emerg("Jump label code mismatch at %pS [%px]\n", ipc, ipc);
+	pr_emerg("Found:    %6ph\n", ipc);
+	pr_emerg("Expected: %6ph\n", ipe);
+	pr_emerg("New:      %6ph\n", ipn);
+	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,
+				   int init)
+{
+	struct insn old, new;
+
+	if (type == JUMP_LABEL_JMP) {
+		jump_label_make_nop(entry, &old);
+		jump_label_make_branch(entry, &new);
+	} else {
+		jump_label_make_branch(entry, &old);
+		jump_label_make_nop(entry, &new);
+	}
+	if (init) {
+		if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
+			jump_label_bug(entry, &orignop, &new);
+	} else {
+		if (memcmp((void *)entry->code, &old, sizeof(old)))
+			jump_label_bug(entry, &old, &new);
+	}
+	s390_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, 0);
+	return 0;
+}
+
+void arch_jump_label_transform(struct jump_entry *entry,
+			       enum jump_label_type type)
+{
+	struct insn_args args;
+
+	args.entry = entry;
+	args.type = type;
+
+	stop_machine_cpuslocked(__sm_arch_jump_label_transform, &args, NULL);
+}
+
+void arch_jump_label_transform_static(struct jump_entry *entry,
+				      enum jump_label_type type)
+{
+	__jump_label_transform(entry, type, 1);
+}