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Date:   Mon, 05 Sep 2022 16:07:55 +0530
From:   "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [PATCH v2 15/16] objtool/powerpc: Enable objtool to be built on
 ppc
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        Sathvika Vasireddy <sv@linux.ibm.com>
Cc:     "aik@ozlabs.ru" <aik@ozlabs.ru>,
        "chenzhongjin@huawei.com" <chenzhongjin@huawei.com>,
        "Elliott, Robert (Servers)" <elliott@hpe.com>,
        "jpoimboe@redhat.com" <jpoimboe@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "mbenes@suse.cz" <mbenes@suse.cz>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
        "npiggin@gmail.com" <npiggin@gmail.com>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "rostedt@goodmis.org" <rostedt@goodmis.org>
References: <20220829055223.24767-1-sv@linux.ibm.com>
        <20220829055223.24767-16-sv@linux.ibm.com>
        <33924523-5437-eb9a-116a-8e249ce99bd2@csgroup.eu>
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Christophe Leroy wrote:
>=20
>=20
> Le 29/08/2022 =C3=A0 07:52, Sathvika Vasireddy a =C3=A9crit=C2=A0:
>>=20
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index 4c466acdc70d..dc05cd23c233 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -237,6 +237,7 @@ config PPC
>>   	select HAVE_MOD_ARCH_SPECIFIC
>>   	select HAVE_NMI				if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
>>   	select HAVE_OPTPROBES
>> +	select HAVE_OBJTOOL			if PPC32 || MPROFILE_KERNEL
>=20
> Why restrict it to MPROFILE_KERNEL ? In your RFC it was for all PPC64.
>=20
> Recent discussion on the list shows new problem with recordmcount, see=20
> https://lore.kernel.org/all/MW5PR84MB184250EA1CAE04497C1E7CE9AB769@MW5PR8=
4MB1842.NAMPRD84.PROD.OUTLOOK.COM/
>=20
> Those ones are with ppc64 big endian, so objtool would be welcome here=20
> as well.

I don't think adding support for objtool on ppc64 elfv1 is a good idea.=20
While it might solve the immediate issue with recordmcount, I worry that=20
the function descriptors and dot symbols in ppc64 elfv1 might throw up=20
issues in the future causing maintenance overhead.


- Naveen