riscv: Add jump-label implementation

Add jump-label implementation based on the ARM64 version
and add CONFIG_JUMP_LABEL=y to the defconfigs.

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Tested-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h
new file mode 100644
index 000000000000..38af2ec7b9bf
--- /dev/null
+++ b/arch/riscv/include/asm/jump_label.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Emil Renner Berthing
+ *
+ * Based on arch/arm64/include/asm/jump_label.h
+ */
+#ifndef __ASM_JUMP_LABEL_H
+#define __ASM_JUMP_LABEL_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+#include <asm/asm.h>
+
+#define JUMP_LABEL_NOP_SIZE 4
+
+static __always_inline bool arch_static_branch(struct static_key *key,
+					       bool branch)
+{
+	asm_volatile_goto(
+		"	.option push				\n\t"
+		"	.option norelax				\n\t"
+		"	.option norvc				\n\t"
+		"1:	nop					\n\t"
+		"	.option pop				\n\t"
+		"	.pushsection	__jump_table, \"aw\"	\n\t"
+		"	.align		" RISCV_LGPTR "		\n\t"
+		"	.long		1b - ., %l[label] - .	\n\t"
+		"	" RISCV_PTR "	%0 - .			\n\t"
+		"	.popsection				\n\t"
+		:  :  "i"(&((char *)key)[branch]) :  : label);
+
+	return false;
+label:
+	return true;
+}
+
+static __always_inline bool arch_static_branch_jump(struct static_key *key,
+						    bool branch)
+{
+	asm_volatile_goto(
+		"	.option push				\n\t"
+		"	.option norelax				\n\t"
+		"	.option norvc				\n\t"
+		"1:	jal		zero, %l[label]		\n\t"
+		"	.option pop				\n\t"
+		"	.pushsection	__jump_table, \"aw\"	\n\t"
+		"	.align		" RISCV_LGPTR "		\n\t"
+		"	.long		1b - ., %l[label] - .	\n\t"
+		"	" RISCV_PTR "	%0 - .			\n\t"
+		"	.popsection				\n\t"
+		:  :  "i"(&((char *)key)[branch]) :  : label);
+
+	return false;
+label:
+	return true;
+}
+
+#endif  /* __ASSEMBLY__ */
+#endif	/* __ASM_JUMP_LABEL_H */