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Commit a5859c6d authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

x86/build: convert function graph '-Os' error to warning 



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: default avatarAndi Kleen <andi@firstfloor.org>
Signed-off-by: default avatarJosh 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: default avatarIngo Molnar <mingo@kernel.org>
parent 34a477e5

arch/x86/Makefile

+8 −0
Original line number Original line Diff line number Diff line
@@ -154,6 +154,14 @@ ifdef CONFIG_FUNCTION_GRAPH_TRACER 
  else

  else

    ifeq ($(call cc-option-yn, -mfentry), n)

    ifeq ($(call cc-option-yn, -mfentry), n)

	ACCUMULATE_OUTGOING_ARGS := 1

	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

  endif

endif

endif

arch/x86/kernel/ftrace.c

+0 −6
Original line number Original line Diff line number Diff line
@@ -29,12 +29,6 @@ 
#include <asm/ftrace.h>

#include <asm/ftrace.h>

#include <asm/nops.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

#ifdef CONFIG_DYNAMIC_FTRACE





int ftrace_arch_code_modify_prepare(void)

int ftrace_arch_code_modify_prepare(void)