linux-kernel - Re: [PATCH 1/3] arm64: implement ftrace with regs

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Message-ID: <20180815134710.GA27854@lst.de>
Date:   Wed, 15 Aug 2018 15:47:10 +0200
From:   Torsten Duwe <duwe@....de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Julien Thierry <julien.thierry@....com>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        live-patching@...r.kernel.org
Subject: Re: [PATCH 1/3] arm64: implement ftrace with regs

[working on V2 with your feedback]

On Tue, Aug 14, 2018 at 12:04:33PM -0400, Steven Rostedt wrote:
> On Tue, 14 Aug 2018 09:33:52 +0100
> Julien Thierry <julien.thierry@....com> wrote:
> > >> Shouldn't this be an error? The option -fpatchable-function-entry has
> > >> been added to the CC_FLAGS_FTRACE, so any call to the compiler is gonna
> > >> break anyway. Or am I missing something?  

This should be the case.

> OK, I see what you mean. If the resulting build wont boot, then yes
> this should be an error and not a warning.

No, there won't be a binary because the first gcc invocation with
CC_FLAGS_FTRACE will error out.

The alternatives are a makefile-warning followed by a gcc-error or just
a makefile-error. The makefile warning or error should hint at the causing
config option, that's the key point. Beyond that I don't have any preference.

	Torsten