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-rw-r--r--arch/Kconfig14
-rw-r--r--arch/x86/Makefile_32.cpu13
2 files changed, 26 insertions, 1 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 53d7f619a1b9..8bf0fa652eb6 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 1255d953c65d..f2ee1abb1df9 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.
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