linux-kernel - Re: [PATCH] powerpc: avoid broken GCC __attribute_

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Date:   Wed, 25 Nov 2020 22:57:41 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Paul Mackerras <paulus@...ba.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...omium.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc: avoid broken GCC __attribute__((optimize))

On Wed, 28 Oct 2020 09:04:33 +0100, Ard Biesheuvel wrote:
> Commit 7053f80d9696 ("powerpc/64: Prevent stack protection in early boot")
> introduced a couple of uses of __attribute__((optimize)) with function
> scope, to disable the stack protector in some early boot code.
> 
> Unfortunately, and this is documented in the GCC man pages [0], overriding
> function attributes for optimization is broken, and is only supported for
> debug scenarios, not for production: the problem appears to be that
> setting GCC -f flags using this method will cause it to forget about some
> or all other optimization settings that have been applied.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc: Avoid broken GCC __attribute__((optimize))
      https://git.kernel.org/powerpc/c/a7223f5bfcaeade4a86d35263493bcda6c940891

cheers