linux-kernel - Re: [PATCH v7 14/22] x86/decompressor: Merge trampoline cleanup with switching code

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Date:   Tue, 1 Aug 2023 14:46:16 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Evgeniy Baskov <baskov@...ras.ru>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Peter Jones <pjones@...hat.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Dave Young <dyoung@...hat.com>,
        Mario Limonciello <mario.limonciello@....com>,
        Kees Cook <keescook@...omium.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v7 14/22] x86/decompressor: Merge trampoline cleanup with
 switching code

On Tue, 1 Aug 2023 at 14:41, Borislav Petkov <bp@...en8.de> wrote:
>
> On Tue, Aug 01, 2023 at 02:11:21PM +0200, Ard Biesheuvel wrote:
> > Removing it breaks the build for !CONFIG_X86_5LEVEL
>
> How come?
>

Because a label cannot be at the end of a block. There needs to be at
least one statement.

> $ grep 5LEVEL .config
> # CONFIG_X86_5LEVEL is not set
>
> and it builds fine here.
>

I guess it depends on the compiler version. GCC 10 gives me this

<source>: In function 'foo':
<source>:4:5: error: label at end of compound statement
    4 |     bar:
      |     ^~~

but GCC 13 seems to be fine with it.

https://godbolt.org/z/KnWbY8vEY