linux-kernel - Re: [PATCH v3] x86/entry: emit a symbol for register restoring thunk

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Date:   Tue, 12 Jan 2021 02:00:10 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Fāng-ruì Sòng <maskray@...gle.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH v3] x86/entry: emit a symbol for register restoring thunk

On Mon, Jan 11, 2021 at 04:41:52PM -0800, Fāng-ruì Sòng wrote:
> To be fair: we cannot use

Who's "we"?

> .L-prefixed local because of the objtool limitation.

What objtool limitation? I thought clang's assembler removes .text which
objtool uses. It worked fine with GNU as so far.

> The LLVM integrated assembler behavior is a good one

Please explain what "good one" means in that particular context.

> and binutils global maintainers have agreed so H.J. went ahead and
> implemented it for GNU as x86.

But they don't break old behavior, do they? Or are they removing .text
unconditionally now too?

> --generate-unused-section-symbols=[yes|no] as an assembler option has
> been rejected.

Meaning what exactly? There's no way for clang's integrated assembler to
even get a cmdline option to not strip .text?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette