linux-kernel - [PATCH v3] LoongArch: Add jump-label implementation

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Date:   Mon, 15 May 2023 10:42:54 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     Jonathan Corbet <corbet@....net>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jason Baron <jbaron@...mai.com>,
        WANG Xuerui <kernel@...0n.name>,
        Zhangjin Wu <falcon@...ylab.org>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev
Subject: [PATCH v3] LoongArch: Add jump-label implementation

Add support for jump labels based on the ARM64 version.

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
---
Changes in v3:
- Define the JUMP_TABLE_ENTRY macro so that arch_static_branch
  and arch_static_branch_jump can be shared.
- Modify commit message.

Changes in v2:
- Fix build errors.
- fix comment.

 .../core/jump-labels/arch-support.txt         |  2 +-
 arch/loongarch/Kconfig                        |  2 +
 arch/loongarch/configs/loongson3_defconfig    |  1 +
 arch/loongarch/include/asm/jump_label.h       | 50 +++++++++++++++++++
 arch/loongarch/kernel/Makefile                |  2 +
 arch/loongarch/kernel/jump_label.c            | 23 +++++++++
 6 files changed, 79 insertions(+), 1 deletion(-)
 create mode 100644 arch/loongarch/include/asm/jump_label.h
 create mode 100644 arch/loongarch/kernel/jump_label.c

diff --git a/Documentation/features/core/jump-labels/arch-support.txt b/Documentation/features/core/jump-labels/arch-support.txt
index 2328eada3a49..94d9dece580f 100644
--- a/Documentation/features/core/jump-labels/arch-support.txt
+++ b/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  |
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index d38b066fc931..193a959a5611 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -83,6 +83,8 @@ 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
diff --git a/arch/loongarch/configs/loongson3_defconfig b/arch/loongarch/configs/loongson3_defconfig
index 6cd26dd3c134..33a0f5f742f6 100644
--- a/arch/loongarch/configs/loongson3_defconfig
+++ b/arch/loongarch/configs/loongson3_defconfig
@@ -63,6 +63,7 @@ CONFIG_EFI_ZBOOT=y
 CONFIG_EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER=y
 CONFIG_EFI_CAPSULE_LOADER=m
 CONFIG_EFI_TEST=m
+CONFIG_JUMP_LABEL=y
 CONFIG_MODULES=y
 CONFIG_MODULE_FORCE_LOAD=y
 CONFIG_MODULE_UNLOAD=y
diff --git a/arch/loongarch/include/asm/jump_label.h b/arch/loongarch/include/asm/jump_label.h
new file mode 100644
index 000000000000..4d8cbd5a8221
--- /dev/null
+++ b/arch/loongarch/include/asm/jump_label.h
@@ -0,0 +1,50 @@
+/* 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 */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 9a72d91cd104..64ea76f60e2c 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/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)
diff --git a/arch/loongarch/kernel/jump_label.c b/arch/loongarch/kernel/jump_label.c
new file mode 100644
index 000000000000..b06245955f7a
--- /dev/null
+++ b/arch/loongarch/kernel/jump_label.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
+ *
+ * Based on arch/arm64/kernel/jump_label.c
+ */
+#include <linux/jump_label.h>
+#include <linux/kernel.h>
+#include <asm/inst.h>
+
+void arch_jump_label_transform(struct jump_entry *entry,
+			       enum jump_label_type type)
+{
+	void *addr = (void *)jump_entry_code(entry);
+	u32 insn;
+
+	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);
+}
-- 
2.37.1