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>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cea0cd9a316fb987bfa611a1dffa06cdba1f0332..afcd6632c94f5d08d3fb2206c9feb644c5b4a376 100644 (file)
--- 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 (file)
index 0000000..b4a2cb4
--- /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 0925676266bdbc9cbcf03811916b9f8b9b9e627e..24fa1718ddb964e03f13f0c5319d1ddfcd0ec29b 100644 (file)
--- 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 (file)
index 0000000..961b6b3
--- /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 e0bc186d7501f123265ae288ae071e772016e89b..5399f58de7ed356098a8d408a9c4d0acc7809b30 100644 (file)
--- 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);
 }