linux-kernel - Re: [PATCH v2 05/16] powerpc: Skip objtool from running on drivers/crypto/vmx/aesp8-ppc.o

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Message-Id: <1662374747.rv53oucl9s.naveen@linux.ibm.com>
Date:   Mon, 05 Sep 2022 16:17:39 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Sathvika Vasireddy <sv@...ux.ibm.com>
Cc:     aik@...abs.ru, chenzhongjin@...wei.com,
        christophe.leroy@...roup.eu, jpoimboe@...hat.com,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        mbenes@...e.cz, mingo@...hat.com, mpe@...erman.id.au,
        npiggin@...il.com, rostedt@...dmis.org
Subject: Re: [PATCH v2 05/16] powerpc: Skip objtool from running on
 drivers/crypto/vmx/aesp8-ppc.o

Peter Zijlstra wrote:
> On Mon, Aug 29, 2022 at 11:22:12AM +0530, Sathvika Vasireddy wrote:
>> With objtool enabled, below warnings are seen when trying to build:
>> 
>> drivers/crypto/vmx/aesp8-ppc.o: warning: objtool: aes_p8_set_encrypt_key+0x44: unannotated intra-function call
>> 
>> drivers/crypto/vmx/aesp8-ppc.o: warning: objtool: .text+0x2448: unannotated intra-function call
>> 
>> drivers/crypto/vmx/aesp8-ppc.o: warning: objtool: .text+0x2d68: unannotated intra-function call
>> 
>> Skip objtool from running on this file, for two main reasons:
>> 
>> Since this file comes from OpenSSL, and since it is a perl file
>> which generates a .S file, it may not be the best choice to
>> make too many code changes to such files, unless absolutely
>> necessary.
>> 
>> Second reason is that, at least as far as the objtool --mcount
>> functionality is concerned, we do not have to run objtool on
>> that file because that file does not have any calls to _mcount.
>> 
>> Signed-off-by: Sathvika Vasireddy <sv@...ux.ibm.com>
>> ---
>>  drivers/crypto/vmx/Makefile | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/drivers/crypto/vmx/Makefile b/drivers/crypto/vmx/Makefile
>> index 2560cfea1dec..7b41f0da6807 100644
>> --- a/drivers/crypto/vmx/Makefile
>> +++ b/drivers/crypto/vmx/Makefile
>> @@ -9,3 +9,5 @@ targets += aesp8-ppc.S ghashp8-ppc.S
>>  
>>  $(obj)/aesp8-ppc.S $(obj)/ghashp8-ppc.S: $(obj)/%.S: $(src)/%.pl FORCE
>>  	$(call if_changed,perl)
>> +
>> +OBJECT_FILES_NON_STANDARD_aesp8-ppc.o := y
> 
> Just be aware that the moment you start to run objtool on vmlinux.o this
> annotation becomes unstuck.
> 
> Specifically things like LTO builds require this because there simply
> isn't an object file before that.

Good point. LTO isn't supported today with ftrace on powerpc, so I guess 
we are ok with this patch for now.

To add LTO support, I guess we will need to add some annotations to this 
file later on.


- Naveen