x86/build: convert function graph '-Os' error to warning (a5859c6d) · Commits · 戴 / test

For pre-4.6.0 versions of GCC, which don't have '-mfentry', the '-maccumulate-outgoing-args' option is required for function graph tracing in order to avoid GCC bug 42109. However, GCC ignores '-maccumulate-outgoing-args' when '-Os' is also set. Currently we force a build error to prevent that scenario, but that breaks randconfigs. So change the error to a warning which also disables CONFIG_CC_OPTIMIZE_FOR_SIZE. Reported-by:

Andi Kleen <andi@firstfloor.org> Signed-off-by:

Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kbuild test robot <fengguang.wu@intel.com> Cc: kbuild-all@01.org Link: http://lkml.kernel.org/r/20170418214429.o7fbwbmf4nqosezy@treble Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/Makefile

+8 −0

Original line number	Diff line number	Diff line
		@@ -154,6 +154,14 @@ ifdef CONFIG_FUNCTION_GRAPH_TRACER
		else
		ifeq ($(call cc-option-yn, -mfentry), n)
		ACCUMULATE_OUTGOING_ARGS := 1

		# GCC ignores '-maccumulate-outgoing-args' when used with '-Os'.
		# If '-Os' is enabled, disable it and print a warning.
		ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
		undefine CONFIG_CC_OPTIMIZE_FOR_SIZE
		$(warning Disabling CONFIG_CC_OPTIMIZE_FOR_SIZE. Your compiler does not have -mfentry so you cannot optimize for size with CONFIG_FUNCTION_GRAPH_TRACER.)
		endif

		endif
		endif
		endif

arch/x86/kernel/ftrace.c

+0 −6

Original line number	Diff line number	Diff line
		@@ -29,12 +29,6 @@
		#include <asm/ftrace.h>
		#include <asm/nops.h>

		#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && \
		!defined(CC_USING_FENTRY) && \
		!defined(CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE)
		# error The following combination is not supported: ((compiler missing -mfentry) \|\| (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE)) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE
		#endif

		#ifdef CONFIG_DYNAMIC_FTRACE

		int ftrace_arch_code_modify_prepare(void)

Admin message