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Date:   Wed, 31 Oct 2018 18:58:00 +0100
From:   Torsten Duwe <duwe@lst.de>
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Jiri Kosina <jikos@kernel.org>, Will Deacon <will.deacon@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Julien Thierry <julien.thierry@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        AKASHI Takahiro <takahiro.akashi@linaro.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        live-patching@vger.kernel.org, kristina.martsenko@arm.com
Subject: Re: [PATCH v4 1/3] arm64: implement ftrace with regs
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On Wed, 31 Oct 2018 14:18:19 +0000
Mark Rutland <mark.rutland@arm.com> wrote:

> On Wed, Oct 31, 2018 at 02:19:07PM +0100, Jiri Kosina wrote:

> > Other architectures do rely on that. That's exactly for example why
> > on x86 we use '-pg -mfentry', to make sure we hook the function
> > *before* prologue.  
> 
> Ah, I'd missed -mfentry for x86. I now see that's also the case with
> __gnu_mcount_nc on arch/arm, so that covers my confusion.

Yes, fentry used to be the prerequisite, but it's everything but
portable. PPC64 already had the profile-kernel switch, which was
becoming just usable as we got at live patching.

I'm hoping that the patchable-function-entry will become the future
de-facto standard.

	Torsten