Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 28 Apr 2022 22:54:38 +0530
From:   "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [PATCH 2/2] recordmcount: Handle sections with no non-weak
 symbols
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        llvm@lists.linux.dev, Michael Ellerman <mpe@ellerman.id.au>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>
References: <cover.1651047542.git.naveen.n.rao@linux.vnet.ibm.com>
        <1b9566f0e7185fb8fd8ef2535add7a081501ccc8.1651047542.git.naveen.n.rao@linux.vnet.ibm.com>
        <20220427095415.594e5120@gandalf.local.home>
        <1651129169.fpixr00hgx.naveen@linux.ibm.com>
        <20220428100602.7b215e52@gandalf.local.home>
In-Reply-To: <20220428100602.7b215e52@gandalf.local.home>
MIME-Version: 1.0
User-Agent: astroid/4d6b06ad (https://github.com/astroidmail/astroid)
Message-Id: <1651166416.afl3n7tts7.naveen@linux.ibm.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Steven Rostedt wrote:
> On Thu, 28 Apr 2022 13:15:22 +0530
> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
>=20
>> Indeed, plain old -pg will be a problem. I'm not sure there is a generic=
=20
>> way to address this. I suppose architectures will have to validate the=20
>> mcount locations, something like this?
>=20
> Perhaps another solution is to make the mcount locations after the linkin=
g
> is done. The main downside to that is that it takes time to go over the
> entire vmlinux, and will slow down a compile that only modified a couple =
of
> files.

Yes, and I think that is also very useful with LTO. So, that would be a=20
good one to consider in the longer term.

For now, I have posted a v2 of this series with your comments addressed. =20
It is working well in my tests on powerpc in the different=20
configurations, including the older elf abi v1 that uses -pg. If it=20
looks ok to you, we can use this approach for now.


Thanks,
Naveen