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

From: Sathvika Vasireddy <sv@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Christophe Leroy <christophe.leroy@csgroup.eu>
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: Wed, 25 May 2022 16:30:34 +0530	[thread overview]
Message-ID: <cd006053-1bf2-eea0-dd82-9b0b997793df@linux.vnet.ibm.com> (raw)
In-Reply-To: <Yo03Flwa1s+o6wda@hirez.programming.kicks-ass.net>

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Hi Peter,

On 25/05/22 01:20, Peter Zijlstra wrote:
> On Tue, May 24, 2022 at 06:59:50PM +0000, Christophe Leroy wrote:
>>
>> 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
> So on x86 we have:
>
> arch/x86/entry/vdso/Makefile:OBJECT_FILES_NON_STANDARD       := y
>
> to kill objtool for the whole of the VDSO. When we run objtool on
> vmlinux it isn't a problem, because the VDSO ends up as a data section
> through linker scripts.
Right.. Like you and Christophe mentioned,
arch/powerpc/kernel/vdso/Makefile:OBJECT_FILES_NON_STANDARD := y
should solve it for powerpc as well.

I'll drop this patch and replace it with the above change as part of next
revision series.

Thanks for reviewing!

- Sathvika

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