diff options
| -rw-r--r-- | arch/Kconfig | 14 | ||||
| -rw-r--r-- | arch/x86/Makefile_32.cpu | 13 | ||||
| -rw-r--r-- | include/linux/jump_label.h | 2 |
3 files changed, 27 insertions, 2 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 53d7f619a1b..8bf0fa652eb 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -42,6 +42,20 @@ config KPROBES for kernel debugging, non-intrusive instrumentation and testing. If in doubt, say "N". +config JUMP_LABEL + bool "Optimize trace point call sites" + depends on HAVE_ARCH_JUMP_LABEL + help + If it is detected that the compiler has support for "asm goto", + the kernel will compile trace point locations with just a + nop instruction. When trace points are enabled, the nop will + be converted to a jump to the trace function. This technique + lowers overhead and stress on the branch prediction of the + processor. + + On i386, options added to the compiler flags may increase + the size of the kernel slightly. + config OPTPROBES def_bool y depends on KPROBES && HAVE_OPTPROBES diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu index 1255d953c65..f2ee1abb1df 100644 --- a/arch/x86/Makefile_32.cpu +++ b/arch/x86/Makefile_32.cpu @@ -51,7 +51,18 @@ cflags-$(CONFIG_X86_GENERIC) += $(call tune,generic,$(call tune,i686)) # prologue (push %ebp, mov %esp, %ebp) which breaks the function graph # tracer assumptions. For i686, generic, core2 this is set by the # compiler anyway -cflags-$(CONFIG_FUNCTION_GRAPH_TRACER) += $(call cc-option,-maccumulate-outgoing-args) +ifeq ($(CONFIG_FUNCTION_GRAPH_TRACER), y) +ADD_ACCUMULATE_OUTGOING_ARGS := y +endif + +# Work around to a bug with asm goto with first implementations of it +# in gcc causing gcc to mess up the push and pop of the stack in some +# uses of asm goto. +ifeq ($(CONFIG_JUMP_LABEL), y) +ADD_ACCUMULATE_OUTGOING_ARGS := y +endif + +cflags-$(ADD_ACCUMULATE_OUTGOING_ARGS) += $(call cc-option,-maccumulate-outgoing-args) # Bug fix for binutils: this option is required in order to keep # binutils from generating NOPL instructions against our will. diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h index 1947a121267..7880f18e4b8 100644 --- a/include/linux/jump_label.h +++ b/include/linux/jump_label.h @@ -1,7 +1,7 @@ #ifndef _LINUX_JUMP_LABEL_H #define _LINUX_JUMP_LABEL_H -#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_HAVE_ARCH_JUMP_LABEL) +#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL) # include <asm/jump_label.h> # define HAVE_JUMP_LABEL #endif |