From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 6 Aug 2018 15:17:46 +0200 From: Vasily Gorbik Subject: [PATCH 3/4] trace: add -mcount-nop option support References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Message-Id: Sender: linux-kbuild-owner@vger.kernel.org List-Archive: List-Post: To: Masahiro Yamada , Michal Marek , Martin Schwidefsky , Heiko Carstens , Steven Rostedt , Ingo Molnar Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Andi Kleen List-ID: -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. Signed-off-by: Vasily Gorbik --- Makefile | 6 ++++++ kernel/trace/Kconfig | 5 +++++ kernel/trace/ftrace.c | 2 ++ 3 files changed, 13 insertions(+) diff --git a/Makefile b/Makefile index 621ebdbfbf89..281f4ededf3a 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 dcc0166d1997..855109214e3d 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 caf9cbf35816..310dfcb20d5b 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2981,12 +2981,14 @@ 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++; } -- 2.18.0.13.gd42ae10