csky: Add jump-label implementation

Add jump-label implementation for static branch

Signed-off-by: Guo Ren <[e-mail]>
Signed-off-by: Guo Ren <[e-mail]>

arch/csky/Kconfig

···
 	select GX6605S_TIMER if CPU_CK610
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_AUDITSYSCALL
+	select HAVE_ARCH_JUMP_LABEL if !CPU_CK610
+	select HAVE_ARCH_JUMP_LABEL_RELATIVE
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_CONTEXT_TRACKING

arch/csky/include/asm/jump_label.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_CSKY_JUMP_LABEL_H
+#define __ASM_CSKY_JUMP_LABEL_H
+
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+#define JUMP_LABEL_NOP_SIZE 4
+
+static __always_inline bool arch_static_branch(struct static_key *key,
+					       bool branch)
+{
+	asm_volatile_goto(
+		"1:	nop32					\n"
+		"	.pushsection	__jump_table, \"aw\"	\n"
+		"	.align		2			\n"
+		"	.long		1b - ., %l[label] - .	\n"
+		"	.long		%0 - .			\n"
+		"	.popsection				\n"
+		:  :  "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(
+		"1:	bsr32		%l[label]		\n"
+		"	.pushsection	__jump_table, \"aw\"	\n"
+		"	.align		2			\n"
+		"	.long		1b - ., %l[label] - .	\n"
+		"	.long		%0 - .			\n"
+		"	.popsection				\n"
+		:  :  "i"(&((char *)key)[branch]) :  : label);
+
+	return false;
+label:
+	return true;
+}
+
+#endif  /* __ASSEMBLY__ */
+#endif	/* __ASM_CSKY_JUMP_LABEL_H */

arch/csky/kernel/Makefile

···
 obj-$(CONFIG_CSKY_PMU_V1)		+= perf_event.o
 obj-$(CONFIG_PERF_EVENTS)		+= perf_callchain.o
 obj-$(CONFIG_HAVE_PERF_REGS)            += perf_regs.o
+obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o
 
 ifdef CONFIG_FUNCTION_TRACER
 CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)

arch/csky/kernel/jump_label.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/jump_label.h>
+#include <linux/kernel.h>
+#include <linux/memory.h>
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+
+#define NOP32_HI	0xc400
+#define NOP32_LO	0x4820
+#define BSR_LINK	0xe000
+
+void arch_jump_label_transform(struct jump_entry *entry,
+			       enum jump_label_type type)
+{
+	unsigned long addr = jump_entry_code(entry);
+	u16 insn[2];
+	int ret = 0;
+
+	if (type == JUMP_LABEL_JMP) {
+		long offset = jump_entry_target(entry) - jump_entry_code(entry);
+
+		if (WARN_ON(offset & 1 || offset < -67108864 || offset >= 67108864))
+			return;
+
+		offset = offset >> 1;
+
+		insn[0] = BSR_LINK |
+			((uint16_t)((unsigned long) offset >> 16) & 0x3ff);
+		insn[1] = (uint16_t)((unsigned long) offset & 0xffff);
+	} else {
+		insn[0] = NOP32_HI;
+		insn[1] = NOP32_LO;
+	}
+
+	ret = copy_to_kernel_nofault((void *)addr, insn, 4);
+	WARN_ON(ret);
+
+	flush_icache_range(addr, addr + 4);
+}
+
+void arch_jump_label_transform_static(struct jump_entry *entry,
+				      enum jump_label_type type)
+{
+	/*
+	 * We use the same instructions in the arch_static_branch and
+	 * arch_static_branch_jump inline functions, so there's no
+	 * need to patch them up here.
+	 * The core will call arch_jump_label_transform  when those
+	 * instructions need to be replaced.
+	 */
+	arch_jump_label_transform(entry, type);
+}