LoongArch: Add jump-label implementation

Add support for jump labels based on the ARM64 version.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Documentation/features/core/jump-labels/arch-support.txt

@@ -13,7 +13,7 @@
     |        csky: |  ok  |
     |     hexagon: | TODO |
     |        ia64: | TODO |
-    |   loongarch: | TODO |
+    |   loongarch: |  ok  |
     |        m68k: | TODO |
     |  microblaze: | TODO |
     |        mips: |  ok  |

arch/loongarch/Kconfig

@@ -87,6 +87,8 @@ config LOONGARCH
 	select GPIOLIB
 	select HAS_IOPORT
 	select HAVE_ARCH_AUDITSYSCALL
+	select HAVE_ARCH_JUMP_LABEL
+	select HAVE_ARCH_JUMP_LABEL_RELATIVE
 	select HAVE_ARCH_MMAP_RND_BITS if MMU
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK

arch/loongarch/include/asm/jump_label.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
+ *
+ * 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>
+
+#define JUMP_LABEL_NOP_SIZE	4
+
+#define JUMP_TABLE_ENTRY				\
+	 ".pushsection	__jump_table, \"aw\"	\n\t"	\
+	 ".align	3			\n\t"	\
+	 ".long		1b - ., %l[l_yes] - .	\n\t"	\
+	 ".quad		%0 - .			\n\t"	\
+	 ".popsection				\n\t"
+
+static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch)
+{
+	asm_volatile_goto(
+		"1:	nop			\n\t"
+		JUMP_TABLE_ENTRY
+		:  :  "i"(&((char *)key)[branch]) :  : l_yes);
+
+	return false;
+
+l_yes:
+	return true;
+}
+
+static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch)
+{
+	asm_volatile_goto(
+		"1:	b	%l[l_yes]	\n\t"
+		JUMP_TABLE_ENTRY
+		:  :  "i"(&((char *)key)[branch]) :  : l_yes);
+
+	return false;
+
+l_yes:
+	return true;
+}
+
+#endif  /* __ASSEMBLY__ */
+#endif	/* __ASM_JUMP_LABEL_H */

arch/loongarch/kernel/Makefile

@@ -54,4 +54,6 @@ obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
 
 obj-$(CONFIG_KPROBES)		+= kprobes.o kprobes_trampoline.o
 
+obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
+
 CPPFLAGS_vmlinux.lds		:= $(KBUILD_CFLAGS)

arch/loongarch/kernel/jump_label.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
+ *
+ * Based on arch/arm64/kernel/jump_label.c
+ */
+#include <linux/kernel.h>
+#include <linux/jump_label.h>
+#include <asm/inst.h>
+
+void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type type)
+{
+	u32 insn;
+	void *addr = (void *)jump_entry_code(entry);
+
+	if (type == JUMP_LABEL_JMP)
+		insn = larch_insn_gen_b(jump_entry_code(entry), jump_entry_target(entry));
+	else
+		insn = larch_insn_gen_nop();
+
+	larch_insn_patch_text(addr, insn);
+}