jump label: x86 support

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 archs.

Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <f838f49f40fbea0254036194be66dc48b598dcea.1284733808.git.jbaron@redhat.com>

[ cleaned up some formatting ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

5 files changed, 102 insertions, 1 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cea0cd9a316f..afcd6632c94f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -59,6 +59,7 @@ config X86
         select ANON_INODES
         select HAVE_ARCH_KMEMCHECK
         select HAVE_USER_RETURN_NOTIFIER
+        select HAVE_ARCH_JUMP_LABEL if !CC_OPTIMIZE_FOR_SIZE
 
 config INSTRUCTION_DECODER
         def_bool (KPROBES || PERF_EVENTS)
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
new file mode 100644
index 000000000000..b4a2cb403370
--- /dev/null
+++ b/arch/x86/include/asm/jump_label.h
@@ -0,0 +1,47 @@
+#ifndef _ASM_X86_JUMP_LABEL_H
+#define _ASM_X86_JUMP_LABEL_H
+
+#ifdef __KERNEL__
+
+#include <linux/types.h>
+#include <asm/nops.h>
+
+#define JUMP_LABEL_NOP_SIZE 5
+
+# define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"
+
+# define JUMP_LABEL(key, label)                                 \
+        do {                                                    \
+                asm goto("1:"                                   \
+                        JUMP_LABEL_INITIAL_NOP                  \
+                        ".pushsection __jump_table,  \"a\" \n\t"\
+                        _ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
+                        ".popsection \n\t"                      \
+                        : :  "i" (key) :  : label);             \
+        } while (0)
+
+#endif /* __KERNEL__ */
+
+#ifdef CONFIG_X86_64
+
+typedef u64 jump_label_t;
+
+struct jump_entry {
+        jump_label_t code;
+        jump_label_t target;
+        jump_label_t key;
+};
+
+#else
+
+typedef u32 jump_label_t;
+
+struct jump_entry {
+        jump_label_t code;
+        jump_label_t target;
+        jump_label_t key;
+};
+
+#endif
+
+#endif
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 0925676266bd..24fa1718ddb9 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 000000000000..961b6b30ba90
--- /dev/null
+++ b/arch/x86/kernel/jump_label.c
@@ -0,0 +1,50 @@
+/*
+ * jump label x86 support
+ *
+ * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
+ *
+ */
+#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>
+#include <asm/alternative.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
+                memcpy(&code, ideal_nop5, JUMP_LABEL_NOP_SIZE);
+        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();
+}
+
+void arch_jump_label_text_poke_early(jump_label_t addr)
+{
+        text_poke_early((void *)addr, ideal_nop5, JUMP_LABEL_NOP_SIZE);
+}
+
+#endif
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index e0bc186d7501..5399f58de7ed 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -239,6 +239,9 @@ int module_finalize(const Elf_Ehdr *hdr,
                 apply_paravirt(pseg, pseg + para->sh_size);
         }
 
+        /* make jump label nops */
+        jump_label_apply_nops(me);
+
         return module_bug_finalize(hdr, sechdrs, me);
 }