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Date:   Tue, 24 May 2022 15:45:20 +0530
From:   "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 1/4] objtool: Add --mnop as an option to --mcount
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        Sathvika Vasireddy <sv@linux.ibm.com>
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        "jpoimboe@redhat.com" <jpoimboe@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "mbenes@suse.cz" <mbenes@suse.cz>,
        "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "rostedt@goodmis.org" <rostedt@goodmis.org>
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Christophe Leroy wrote:
>=20
>=20
> Le 23/05/2022 =C3=A0 19:55, Sathvika Vasireddy a =C3=A9crit=C2=A0:
>> Architectures can select HAVE_NOP_MCOUNT if they choose
>> to nop out mcount call sites. If that config option is
>> selected, then --mnop is passed as an option to objtool,
>> along with --mcount.
>>=20
>=20
> Is there a reason not to nop out mcount call sites on powerpc as well ?

Yes, if there are functions that are out of range of _mcount(), then the=20
linker would have inserted long branch trampolines. We detect such cases=20
during boot. But, if we nop out the _mcount call sites during build=20
time, we will need some other way to identify these.

- Naveen