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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Christophe Leroy <christophe.leroy@c-s.fr>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/ftrace: Enable C Version of recordmcount
In-Reply-To: <4464516c0b6835b42acc65e088b6d7f88fe886f2.1557235811.git.christophe.leroy@c-s.fr>
References: <4464516c0b6835b42acc65e088b6d7f88fe886f2.1557235811.git.christophe.leroy@c-s.fr>
Date:   Wed, 08 May 2019 10:45:12 +1000
Message-ID: <87ef59wz8n.fsf@concordia.ellerman.id.au>
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Sender: linux-kernel-owner@vger.kernel.org
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Christophe Leroy <christophe.leroy@c-s.fr> writes:
> Selects HAVE_C_RECORDMCOUNT to use the C version of the recordmcount
> intead of the old Perl Version of recordmcount.
>
> This should improve build time. It also seems like the old Perl Version
> misses some calls to _mcount that the C version finds.

That would make this a bug fix possibly for stable even.

Any more details on what the difference is, is it just some random
subset of functions or some pattern?

cheers

> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 2711aac24621..d87de4f9da61 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -180,6 +180,7 @@ config PPC
>  	select HAVE_ARCH_NVRAM_OPS
>  	select HAVE_ARCH_SECCOMP_FILTER
>  	select HAVE_ARCH_TRACEHOOK
> +	select HAVE_C_RECORDMCOUNT
>  	select HAVE_CBPF_JIT			if !PPC64
>  	select HAVE_STACKPROTECTOR		if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
>  	select HAVE_STACKPROTECTOR		if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2)
> -- 
> 2.13.3