linux-kernel - Re: [PATCH] efi/x86: use naked RET on mixed mode call wrapper

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Message-ID: <Ytbr52VKK6aQT259@zn.tnic>
Date:   Tue, 19 Jul 2022 19:37:43 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        stable <stable@...r.kernel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>
Subject: Re: [PATCH] efi/x86: use naked RET on mixed mode call wrapper

On Tue, Jul 19, 2022 at 05:22:28PM +0200, Ard Biesheuvel wrote:
> The code in question is a little trampoline that executes from the EFI
> mixed mode 1:1 mapping of the kernel text, and never via the kernel
> mapping, so we should just move it into .rodata instead (and fix up
> the mixed mode virtual address map logic accordingly). I don't think
> mapping the kernel text and rodata into the 1;1 EFI map is needed at
> all, tbh, and the only thing we ever access via that mapping is that
> little trampoline.
> 
> Something like

I'm obviously always for simplifications like that. I'm guessing this
should be tested for a full next release before it goes to Linus?

Thx.

-- 
Regards/Gruss,
    Boris.

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