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authorJason Baron <jbaron@redhat.com>2010-09-17 11:09:00 -0400
committerSteven Rostedt <rostedt@goodmis.org>2010-09-22 16:29:41 -0400
commitbf5438fca2950b03c21ad868090cc1a8fcd49536 (patch)
tree9fc5693763263704de8d8ba1c37a84172dbe5eb7 /arch
parentfa6f2cc77081792e4edca9168420a3422299ef15 (diff)
downloadlinux-bf5438fca2950b03c21ad868090cc1a8fcd49536.tar.bz2
jump label: Base patch for jump label
base patch to implement 'jump labeling'. Based on a new 'asm goto' inline assembly gcc mechanism, we can now branch to labels from an 'asm goto' statment. This allows us to create a 'no-op' fastpath, which can subsequently be patched with a jump to the slowpath code. This is useful for code which might be rarely used, but which we'd like to be able to call, if needed. Tracepoints are the current usecase that these are being implemented for. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jason Baron <jbaron@redhat.com> LKML-Reference: <ee8b3595967989fdaf84e698dc7447d315ce972a.1284733808.git.jbaron@redhat.com> [ cleaned up some formating ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/Kconfig3
-rw-r--r--arch/x86/include/asm/alternative.h3
-rw-r--r--arch/x86/kernel/alternative.c2
3 files changed, 6 insertions, 2 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 4877a8c8ee16..1462d8492d89 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -158,4 +158,7 @@ config HAVE_PERF_EVENTS_NMI
subsystem. Also has support for calculating CPU cycle events
to determine how many clock cycles in a given period.
+config HAVE_ARCH_JUMP_LABEL
+ bool
+
source "kernel/gcov/Kconfig"
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 634bf782dca5..76561d20ea2f 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -4,6 +4,7 @@
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/stringify.h>
+#include <linux/jump_label.h>
#include <asm/asm.h>
/*
@@ -182,7 +183,7 @@ extern void *text_poke_early(void *addr, const void *opcode, size_t len);
extern void *text_poke(void *addr, const void *opcode, size_t len);
extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
-#if defined(CONFIG_DYNAMIC_FTRACE)
+#if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)
#define IDEAL_NOP_SIZE_5 5
extern unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
extern void arch_init_ideal_nop5(void);
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 083bd010d92c..cb0e6d385f6d 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -641,7 +641,7 @@ void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
return addr;
}
-#if defined(CONFIG_DYNAMIC_FTRACE)
+#if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)
unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];