linux-kernel - Re: [PATCH 05/10] efi/libstub: distinguish between native/mixed not 32/64 bit

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Message-ID: <20191214221419.GA314531@rani.riverdale.lan>
Date:   Sat, 14 Dec 2019 17:14:20 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Ard Biesheuvel <ardb@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Matthew Garrett <matthewgarrett@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 05/10] efi/libstub: distinguish between native/mixed not
 32/64 bit

On Sat, Dec 14, 2019 at 09:30:08PM +0000, Ard Biesheuvel wrote:
> On Sat, 14 Dec 2019 at 22:17, Arvind Sankar <nivedita@...m.mit.edu> wrote:
> >
> > Maybe just do
> >         if (sizeof(at) < sizeof(__ret))
> >                 __ret = (__typeof__(__ret))(uintptr_t)at;
> >         else
> >                 __ret = (__typeof__(__ret))at;
> > That should cover most of the cases.
> 
> But the compiler will still be unhappy about the else clause if __ret
> is a pointer type, since we'll be casting an u32 to a pointer,

Ugh, yeah it complains even though it can tell at compile time that that
branch isn't taken.