From mboxrd@z Thu Jan 1 00:00:00 1970 From: julien.thierry@arm.com (Julien Thierry) Date: Tue, 14 Aug 2018 09:33:52 +0100 Subject: [PATCH 1/3] arm64: implement ftrace with regs In-Reply-To: <20180813220315.6e8dfc9c@vmware.local.home> References: <20180810160043.9E45568C76@newverein.lst.de> <20180810160223.D360D68C76@newverein.lst.de> <2b5c1092-2cc0-00ec-ba3d-341dc61452b4@arm.com> <20180813220315.6e8dfc9c@vmware.local.home> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 14/08/18 03:03, Steven Rostedt wrote: > On Mon, 13 Aug 2018 11:54:06 +0100 > Julien Thierry wrote: > >>> --- a/arch/arm64/Makefile >>> +++ b/arch/arm64/Makefile >>> @@ -78,6 +78,15 @@ ifeq ($(CONFIG_ARM64_MODULE_PLTS),y) >>> KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/arm64/kernel/module.lds >>> endif >>> >>> +ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS >>> + CC_FLAGS_FTRACE := -fpatchable-function-entry=2 >>> + KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY >>> + ifeq ($(call cc-option,-fpatchable-function-entry=2),) >>> + $(warning Cannot use CONFIG_DYNAMIC_FTRACE_WITH_REGS: \ >>> + -fpatchable-function-entry not supported by compiler) >> >> Shouldn't this be an error? The option -fpatchable-function-entry has >> been added to the CC_FLAGS_FTRACE, so any call to the compiler is gonna >> break anyway. Or am I missing something? > > I'm guessing this adds a more informative message on that error. One > will know why -fpatchable-function-entry was added to the CFLAGS. I'm > for more informative error messages being a victim of poor error > messages causing me to dig deep into the guts of the build > infrastructure to figure out simple issues. > Yes, I agree it is better to have this message. My point was that we could have "$error" instead of "$warning" to stop the compilation right away since we know everything is gonna break (and on parallel builds this warning is gonna be drowned in compiler errors). -- Julien Thierry