1 files changed, 82 insertions, 0 deletions
diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c
new file mode 100644
index 0000000000..e808bb8bc0
--- /dev/null
+++ b/arch/s390/kernel/jump_label.c
@@ -0,0 +1,82 @@
+// 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/jump_label.h>
+#include <linux/module.h>
+#include <asm/text-patching.h>
+#include <asm/ipl.h>
+
+struct insn {
+	u16 opcode;
+	s32 offset;
+} __packed;
+
+static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)
+{
+	/* brcl 0,offset */
+	insn->opcode = 0xc004;
+	insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
+}
+
+static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
+{
+	/* brcl 15,offset */
+	insn->opcode = 0xc0f4;
+	insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
+}
+
+static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
+			   struct insn *new)
+{
+	unsigned char *ipc = (unsigned char *)jump_entry_code(entry);
+	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 void jump_label_transform(struct jump_entry *entry,
+				 enum jump_label_type type)
+{
+	void *code = (void *)jump_entry_code(entry);
+	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 (memcmp(code, &old, sizeof(old)))
+		jump_label_bug(entry, &old, &new);
+	s390_kernel_write(code, &new, sizeof(new));
+}
+
+void arch_jump_label_transform(struct jump_entry *entry,
+			       enum jump_label_type type)
+{
+	jump_label_transform(entry, type);
+	text_poke_sync();
+}
+
+bool arch_jump_label_transform_queue(struct jump_entry *entry,
+				     enum jump_label_type type)
+{
+	jump_label_transform(entry, type);
+	return true;
+}
+
+void arch_jump_label_transform_apply(void)
+{
+	text_poke_sync();
+}