[PATCH 03/11] jump label: x86 support

[Jason Baron]

add x86 support for jump label. I'm keeping this patch separate so its clear to
arch maintainers what was required for x86 support this new feature. hopefully,
it wouldn't be too painful for other arches.

Signed-off-by: Jason Baron <jbaron@xxxxxxxxxx>
---
 arch/x86/Kconfig                  |    1 +
 arch/x86/include/asm/jump_entry.h |   28 +++++++++++++++++
 arch/x86/include/asm/jump_label.h |   27 ++++++++++++++++
 arch/x86/kernel/Makefile          |    2 +-
 arch/x86/kernel/jump_label.c      |   60 +++++++++++++++++++++++++++++++++++++
 5 files changed, 117 insertions(+), 1 deletions(-)
 create mode 100644 arch/x86/include/asm/jump_entry.h
 create mode 100644 arch/x86/include/asm/jump_label.h
 create mode 100644 arch/x86/kernel/jump_label.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d3b7bb3..802b91b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -58,6 +58,7 @@ config X86
 	select ANON_INODES
 	select HAVE_ARCH_KMEMCHECK
 	select HAVE_USER_RETURN_NOTIFIER
+	select HAVE_ARCH_JUMP_LABEL
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS)
diff --git a/arch/x86/include/asm/jump_entry.h b/arch/x86/include/asm/jump_entry.h
new file mode 100644
index 0000000..9b32696
--- /dev/null
+++ b/arch/x86/include/asm/jump_entry.h
@@ -0,0 +1,28 @@
+#ifndef _LINUX_JUMP_ENTRY_H
+#define _LINUX_JUMP_ENTRY_H
+
+/* Defined in a separate file, so that it can be used by user program modpost.c
+ * This file is included by include/asm/jump_label.h, in turn included by
+ * include/linux/jump_label.h. Kernel sources should only include
+ * include/linux/jump_label.h.
+ **/
+
+#ifdef CONFIG_X86_64
+
+struct jump_entry {
+	__u64 code;
+	__u64 target;
+	__u64 name;
+};
+
+#else
+
+struct jump_entry {
+	__u32 code;
+	__u32 target;
+	__u32 name;
+};
+
+#endif
+
+#endif
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
new file mode 100644
index 0000000..70da737
--- /dev/null
+++ b/arch/x86/include/asm/jump_label.h
@@ -0,0 +1,27 @@
+#ifndef _ASM_X86_JUMP_LABEL_H
+#define _ASM_X86_JUMP_LABEL_H
+
+#include <linux/types.h>
+#include <asm/nops.h>
+#include <asm/jump_entry.h>
+
+#define JUMP_LABEL_NOP_SIZE 5
+
+#ifdef CONFIG_X86_64
+# define JUMP_LABEL_NOP P6_NOP5
+#else
+# define JUMP_LABEL_NOP ".byte 0xe9 \n\t .long 0\n\t"
+#endif
+
+#define JUMP_LABEL(tag, label, cond)				\
+	do {							\
+		extern const char __jlstrtab_##tag[];		\
+		asm goto("1:"					\
+			JUMP_LABEL_NOP				\
+			".pushsection __jump_table,  \"a\" \n\t"\
+			_ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
+			".popsection \n\t"			\
+			: :  "i" (__jlstrtab_##tag) :  : label);\
+	} while (0)
+
+#endif
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index e77b220..44f6bea 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -32,7 +32,7 @@ GCOV_PROFILE_paravirt.o		:= n
 obj-y			:= process_$(BITS).o signal.o entry_$(BITS).o
 obj-y			+= traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
 obj-y			+= time.o ioport.o ldt.o dumpstack.o
-obj-y			+= setup.o x86_init.o i8259.o irqinit.o
+obj-y			+= setup.o x86_init.o i8259.o irqinit.o jump_label.o
 obj-$(CONFIG_X86_VISWS)	+= visws_quirks.o
 obj-$(CONFIG_X86_32)	+= probe_roms_32.o
 obj-$(CONFIG_X86_32)	+= sys_i386_32.o i386_ksyms_32.o
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
new file mode 100644
index 0000000..c347431
--- /dev/null
+++ b/arch/x86/kernel/jump_label.c
@@ -0,0 +1,60 @@
+/*
+ * jump label x86 support
+ *
+ * Copyright (C) 2009 Jason Baron <jbaron@xxxxxxxxxx>
+ *
+ */
+#include <linux/jump_label.h>
+#include <linux/memory.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/jhash.h>
+#include <linux/cpu.h>
+#include <asm/kprobes.h>
+
+#ifdef HAVE_JUMP_LABEL
+
+union jump_code_union {
+	char code[JUMP_LABEL_NOP_SIZE];
+	struct {
+		char jump;
+		int offset;
+	} __attribute__((packed));
+};
+
+void arch_jump_label_transform(struct jump_entry *entry, enum jump_label_type type)
+{
+	union jump_code_union code;
+
+	if (type == JUMP_LABEL_ENABLE) {
+		code.jump = 0xe9;
+		code.offset = entry->target - (entry->code + JUMP_LABEL_NOP_SIZE);
+	} else {
+#ifdef CONFIG_X86_64
+		/* opcode for P6_NOP5 */
+		code.code[0] = 0x0f;
+		code.code[1] = 0x1f;
+		code.code[2] = 0x44;
+		code.code[3] = 0x00;
+		code.code[4] = 0x00;
+#else
+		code.jump = 0xe9;
+		code.offset = 0;
+#endif
+	}
+	get_online_cpus();
+	mutex_lock(&text_mutex);
+	text_poke_smp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
+	mutex_unlock(&text_mutex);
+	put_online_cpus();
+}
+
+static const u8 jump_label_nop[JUMP_LABEL_NOP_SIZE] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
+
+const u8 *arch_get_jump_label_nop()
+{
+	return jump_label_nop;
+}
+
+#endif
-- 
1.7.0.1

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