linux-kernel - Re: [PATCH v3 1/4] DYNAMIC_FTRACE configurable with and without REGS

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Message-ID: <CAKv+Gu9tvbM=tb-LJVJtGaq5wD0woX2gtdST+22xJnjZmc_SxQ@mail.gmail.com>
Date:   Mon, 1 Oct 2018 17:06:06 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Torsten Duwe <duwe@....de>
Cc:     Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Julien Thierry <julien.thierry@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        live-patching@...r.kernel.org
Subject: Re: [PATCH v3 1/4] DYNAMIC_FTRACE configurable with and without REGS

On 1 October 2018 at 17:03, Torsten Duwe <duwe@....de> wrote:
> On Mon, Oct 01, 2018 at 04:52:27PM +0200, Ard Biesheuvel wrote:
>>
>> I guess we now have Kbuild/Kconfig support for this, no? I mean, we
>> can now show/hide options depending on the capabilities of the
>> toolchain.
>
> Config options depending on flags availability?
>

Yes. Note that 'make menuconfig' now prints the compiler version at
the top, and kconfig options can now 'depend' on compiler features,
although I must admit I don't know how it works.

>> I am not saying it would be a better approach, though - I'd rather
>> have a warning than have things silently disabled, but other people
>> may think differently.
>
> Even then this switch has to be enabled, no matter who or what sets it.
> Note that this patch leaves everything as-is. Only arm64 users with
> "old" compilers would need to take action.
>
>         Torsten
>