linux-kernel - RE: [PATCH] x86: bitops: fix build regression

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ef7d077424554abebbd0d46738c90163@AcuMS.aculab.com>
Date:   Thu, 7 May 2020 08:35:01 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'hpa@...or.com'" <hpa@...or.com>,
        'Brian Gerst' <brgerst@...il.com>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Sedat Dilek <sedat.dilek@...il.com>,
        stable <stable@...r.kernel.org>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "kernelci . org bot" <bot@...nelci.org>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Ilie Halip <ilie.halip@...il.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Marco Elver <elver@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Daniel Axtens <dja@...ens.net>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>
Subject: RE: [PATCH] x86: bitops: fix build regression

From: hpa@...or.com
> Sent: 07 May 2020 08:59
> On May 7, 2020 12:44:44 AM PDT, David Laight <David.Laight@...LAB.COM> wrote:
> >From: Brian Gerst
> >> Sent: 07 May 2020 07:18
> >...
> >> > --- a/arch/x86/include/asm/bitops.h
> >> > +++ b/arch/x86/include/asm/bitops.h
> >> > @@ -54,7 +54,7 @@ arch_set_bit(long nr, volatile unsigned long
> >*addr)
> >> >         if (__builtin_constant_p(nr)) {
> >> >                 asm volatile(LOCK_PREFIX "orb %1,%0"
> >> >                         : CONST_MASK_ADDR(nr, addr)
> >> > -                       : "iq" (CONST_MASK(nr) & 0xff)
> >> > +                       : "iq" ((u8)(CONST_MASK(nr) & 0xff))
> >>
> >> I think a better fix would be to make CONST_MASK() return a u8 value
> >> rather than have to cast on every use.
> >
> >Or assign to a local variable - then it doesn't matter how
> >the value is actually calculated. So:
> >			u8 mask = CONST_MASK(nr);
> >			asm volatile(LOCK_PREFIX "orb %1,%0"
> >				: CONST_MASK_ADDR(nr, addr)
> >				: "iq" mask
> >
> >	David
> >
> >-
> >Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes,
> >MK1 1PT, UK
> >Registration No: 1397386 (Wales)
> 
> "const u8" please...

Why, just a waste of disk space.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)