arch/x86//kernel/ftrace.c:35:3: error: #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

arch/x86//kernel/ftrace.c:35:3: error: #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

[kbuild test robot]

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Hi Josh,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   d5ff0814fda50f0306e102f39640cf5bb76af08e
commit: 3f135e57a4f76d24ae8d8a490314331f0ced40c5 x86/build: Mostly disable '-maccumulate-outgoing-args'
date:   2 weeks ago
config: x86_64-randconfig-s1-04160822 (attached as .config)
compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
reproduce:
        git checkout 3f135e57a4f76d24ae8d8a490314331f0ced40c5
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

>> arch/x86//kernel/ftrace.c:35:3: error: #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

vim +35 arch/x86//kernel/ftrace.c

    29	#include <asm/ftrace.h>
    30	#include <asm/nops.h>
    31	
    32	#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && \
    33		!defined(CC_USING_FENTRY) && \
    34		!defined(CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE)
  > 35	# 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
    36	#endif
    37	
    38	#ifdef CONFIG_DYNAMIC_FTRACE

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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Re: arch/x86//kernel/ftrace.c:35:3: error: #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

[Josh Poimboeuf]

On Sun, Apr 16, 2017 at 09:20:50AM +0800, kbuild test robot wrote:
> Hi Josh,
> 
> FYI, the error/warning still remains.
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   d5ff0814fda50f0306e102f39640cf5bb76af08e
> commit: 3f135e57a4f76d24ae8d8a490314331f0ced40c5 x86/build: Mostly disable '-maccumulate-outgoing-args'
> date:   2 weeks ago
> config: x86_64-randconfig-s1-04160822 (attached as .config)
> compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
> reproduce:
>         git checkout 3f135e57a4f76d24ae8d8a490314331f0ced40c5
>         # save the attached .config to linux build tree
>         make ARCH=x86_64 
> 
> All errors (new ones prefixed by >>):
> 
> >> arch/x86//kernel/ftrace.c:35:3: error: #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

Hi Fengguang,

The error is working as designed.  gcc < 4.6.0 doesn't have -mfentry, so
it fails the above check on x86.  Can you add a skip rule?  It should
skip building the following case:

  x86 && ((gcc < 4.6.0) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE)) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE

-- 
Josh

Re: arch/x86//kernel/ftrace.c:35:3: error: #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

[Andi Kleen]

Josh Poimboeuf <jpoimboe@redhat.com> writes:
>
> The error is working as designed.  gcc < 4.6.0 doesn't have -mfentry, so
> it fails the above check on x86.  Can you add a skip rule?  It should
> skip building the following case:
>
>   x86 && ((gcc < 4.6.0) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE))
> && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE

This will also break everyone's randconfig builds. The better way
would be to check this in the Makefile and disable one of the options

-Andi

Re: arch/x86//kernel/ftrace.c:35:3: error: #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

[Josh Poimboeuf]

On Tue, Apr 18, 2017 at 11:52:41AM -0700, Andi Kleen wrote:
> Josh Poimboeuf <jpoimboe@redhat.com> writes:
> >
> > The error is working as designed.  gcc < 4.6.0 doesn't have -mfentry, so
> > it fails the above check on x86.  Can you add a skip rule?  It should
> > skip building the following case:
> >
> >   x86 && ((gcc < 4.6.0) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE))
> > && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE
> 
> This will also break everyone's randconfig builds. The better way
> would be to check this in the Makefile and disable one of the options

I don't know how to disable a config option from the Makefile like that.
Any ideas?

BTW, I think it will only break randconfigs for old versions of gcc,
before 4.6.0.  The error message isn't quite right.  I just noticed the
FUNCTION_GRAPH_TRACER config has:

  depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE

which means that X86_32 and CC_OPTIMIZE_FOR_SIZE can never be set with
FUNCTION_GRAPH_TRACER.  So the error message could be simplified to:

  #error The following combination is not supported: (compiler missing -mfentry) && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE

-- 
Josh

Re: arch/x86//kernel/ftrace.c:35:3: error: #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

[Andi Kleen]

On Tue, Apr 18, 2017 at 03:19:42PM -0500, Josh Poimboeuf wrote:
> On Tue, Apr 18, 2017 at 11:52:41AM -0700, Andi Kleen wrote:
> > Josh Poimboeuf <jpoimboe@redhat.com> writes:
> > >
> > > The error is working as designed.  gcc < 4.6.0 doesn't have -mfentry, so
> > > it fails the above check on x86.  Can you add a skip rule?  It should
> > > skip building the following case:
> > >
> > >   x86 && ((gcc < 4.6.0) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE))
> > > && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE
> > 
> > This will also break everyone's randconfig builds. The better way
> > would be to check this in the Makefile and disable one of the options
> 
> I don't know how to disable a config option from the Makefile like that.

You just don't do something in the Makefile, e.g. don't set the -Os 

For an example see the LTO Makefile here

https://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git/tree/scripts/Makefile.lto?h=lto-411-1


-Andi

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

[Josh Poimboeuf]

On Tue, Apr 18, 2017 at 01:25:19PM -0700, Andi Kleen wrote:
> On Tue, Apr 18, 2017 at 03:19:42PM -0500, Josh Poimboeuf wrote:
> > On Tue, Apr 18, 2017 at 11:52:41AM -0700, Andi Kleen wrote:
> > > Josh Poimboeuf <jpoimboe@redhat.com> writes:
> > > >
> > > > The error is working as designed.  gcc < 4.6.0 doesn't have -mfentry, so
> > > > it fails the above check on x86.  Can you add a skip rule?  It should
> > > > skip building the following case:
> > > >
> > > >   x86 && ((gcc < 4.6.0) || (CONFIG_X86_32 and !CONFIG_DYNAMIC_FTRACE))
> > > > && CONFIG_FUNCTION_GRAPH_TRACER && CONFIG_CC_OPTIMIZE_FOR_SIZE
> > > 
> > > This will also break everyone's randconfig builds. The better way
> > > would be to check this in the Makefile and disable one of the options
> > 
> > I don't know how to disable a config option from the Makefile like that.
> 
> You just don't do something in the Makefile, e.g. don't set the -Os 
> 
> For an example see the LTO Makefile here
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc.git/tree/scripts/Makefile.lto?h=lto-411-1

This seems to work:

----

From: Josh Poimboeuf <jpoimboe@redhat.com>
Subject: [PATCH] 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: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/Makefile        | 8 ++++++++
 arch/x86/kernel/ftrace.c | 6 ------
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 73604e1..4430dd4 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -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
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 0e5ceac..5b71535 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -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)
-- 
2.7.4

[tip:x86/urgent] x86/build: convert function graph '-Os' error to warning

[tip-bot for Josh Poimboeuf]

Commit-ID:  a5859c6d7b6114fc0e52be40f7b0f5451c4aba93
Gitweb:     http://git.kernel.org/tip/a5859c6d7b6114fc0e52be40f7b0f5451c4aba93
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Tue, 18 Apr 2017 16:44:29 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 19 Apr 2017 09:57:23 +0200

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: 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 ++++++++
 arch/x86/kernel/ftrace.c | 6 ------
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index a94a4d1..49d160b 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -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
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 0e5ceac..5b71535 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -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)