From: Vasily Gorbik <[email protected]> -mcount-nop gcc option generates the calls to the profiling functions as nops which allows to avoid patching mcount jump with NOP instructions initially.
-mcount-nop gcc option will be activated if platform selects HAVE_NOP_MCOUNT and gcc actually supports it. In addition to that CC_USING_NOP_MCOUNT is defined and could be used by architectures to adapt ftrace patching behavior. Link: http://lkml.kernel.org/r/patch-3.thread-aa7b8d.git-e02ed2dc082b.your-ad-here.call-01533557518-ext-9465@work.hours Signed-off-by: Vasily Gorbik <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- Makefile | 6 ++++++ kernel/trace/Kconfig | 5 +++++ kernel/trace/ftrace.c | 2 ++ 3 files changed, 13 insertions(+) diff --git a/Makefile b/Makefile index 2c92ebf59a34..c5b0cd7f3c2a 100644 --- a/Makefile +++ b/Makefile @@ -749,6 +749,12 @@ ifdef CONFIG_FTRACE_MCOUNT_RECORD CC_FLAGS_FTRACE += -mrecord-mcount export CC_USING_RECORD_MCOUNT := 1 endif + ifdef CONFIG_HAVE_NOP_MCOUNT + ifeq ($(call cc-option-yn, -mnop-mcount),y) + CC_FLAGS_FTRACE += -mnop-mcount + CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT + endif + endif endif ifdef CONFIG_HAVE_FENTRY ifeq ($(call cc-option-yn, -mfentry),y) diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 036cec1fcd24..fd6754b88f87 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -47,6 +47,11 @@ config HAVE_FENTRY help Arch supports the gcc options -pg with -mfentry +config HAVE_NOP_MCOUNT + bool + help + Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount + config HAVE_C_RECORDMCOUNT bool help diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 48b5b466ec7a..468e8527e979 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2950,12 +2950,14 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs) p = &pg->records[i]; p->flags = rec_flags; +#ifndef CC_USING_NOP_MCOUNT /* * Do the initial record conversion from mcount jump * to the NOP instructions. */ if (!ftrace_code_disable(mod, p)) break; +#endif update_cnt++; } -- 2.18.0
