Re: [RFC PATCH v2 5/7] objtool: Enable objtool to run only on files with ftrace enabled

From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "aik@ozlabs.ru" <aik@ozlabs.ru>,
	"jpoimboe@redhat.com" <jpoimboe@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"sv@linux.ibm.com" <sv@linux.ibm.com>,
	Paul Mackerras <paulus@samba.org>,
	"naveen.n.rao@linux.vnet.ibm.com"
	<naveen.n.rao@linux.vnet.ibm.com>,
	"mbenes@suse.cz" <mbenes@suse.cz>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [RFC PATCH v2 5/7] objtool: Enable objtool to run only on files with ftrace enabled
Date: Tue, 24 May 2022 18:59:50 +0000	[thread overview]
Message-ID: <5cb959a2-7e88-5aff-2f8e-be8fdecd002c@csgroup.eu> (raw)
In-Reply-To: <Yo0dpDuK3ilphNAA@hirez.programming.kicks-ass.net>


Le 24/05/2022 à 20:02, Peter Zijlstra a écrit :
> On Tue, May 24, 2022 at 08:01:39PM +0200, Peter Zijlstra wrote:
>> On Tue, May 24, 2022 at 03:17:45PM +0200, Christophe Leroy wrote:
>>> From: Sathvika Vasireddy <sv@linux.ibm.com>
>>>
>>> This patch makes sure objtool runs only on the object files
>>> that have ftrace enabled, instead of running on all the object
>>> files.
>>>
>>> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
>>> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>> ---
>>>   scripts/Makefile.build | 4 ++--
>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
>>> index 2e0c3f9c1459..06ceffd92921 100644
>>> --- a/scripts/Makefile.build
>>> +++ b/scripts/Makefile.build
>>> @@ -258,8 +258,8 @@ else
>>>   # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
>>>   # 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
>>>   
>>> -$(obj)/%.o: objtool-enabled = $(if $(filter-out y%, \
>>> -	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y)
>>> +$(obj)/%.o: objtool-enabled = $(and $(if $(filter-out y%, $(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n),y),        \
>>> +        $(if $(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),y),y)
>>
>> I think this breaks x86, quite a bit of files have ftrace disabled but
>> very much must run objtool anyway.
> 
> Also; since the Changelog gives 0 clue as to what problem it's trying to
> solve, I can't suggest anything.

I asked Sathvika on the previous series, see 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220523175548.922671-3-sv@linux.ibm.com/

He says it is to solve the problem I reported at 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20220318105140.43914-4-sv@linux.ibm.com/#2861128

Christophe