linux-kernel - Re: [PATCH 04/11] Define the virtual space of KASan's shadow region

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: <20171019124149.GX20805@n2100.armlinux.org.uk>
Date:   Thu, 19 Oct 2017 13:41:49 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     "Liuwenliang (Lamb)" <liuwenliang@...wei.com>,
        "tixy@...aro.org" <tixy@...aro.org>,
        "mhocko@...e.com" <mhocko@...e.com>,
        "grygorii.strashko@...aro.org" <grygorii.strashko@...aro.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "glider@...gle.com" <glider@...gle.com>,
        "afzal.mohd.ma@...il.com" <afzal.mohd.ma@...il.com>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "cdall@...aro.org" <cdall@...aro.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        kbuild test robot <lkp@...el.com>,
        "mawilcox@...rosoft.com" <mawilcox@...rosoft.com>,
        "kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
        Dailei <dylix.dailei@...wei.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "aryabinin@...tuozzo.com" <aryabinin@...tuozzo.com>,
        "labbott@...hat.com" <labbott@...hat.com>,
        "vladimir.murzin@....com" <vladimir.murzin@....com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        Zengweilin <zengweilin@...wei.com>,
        "opendmb@...il.com" <opendmb@...il.com>,
        Heshaoliang <heshaoliang@...wei.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kbuild-all@...org" <kbuild-all@...org>,
        Jiazhenghua <jiazhenghua@...wei.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "thgarnie@...gle.com" <thgarnie@...gle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH 04/11] Define the virtual space of KASan's shadow region

On Mon, Oct 16, 2017 at 01:14:54PM +0100, Ard Biesheuvel wrote:
> On 16 October 2017 at 12:42, Liuwenliang (Lamb) <liuwenliang@...wei.com> wrote:
> > On 10/16/2017 07:03 PM, Abbott Liu wrote:
> >>arch/arm/kernel/entry-armv.S:348: Error: selected processor does not support `movw r1,
> >   #:lower16:((((0xC0000000-0x01000000)>>3)+((0xC0000000-0x01000000)-(1<<29))))' in ARM mode
> >>arch/arm/kernel/entry-armv.S:348: Error: selected processor does not support `movt r1,
> >   #:upper16:((((0xC0000000-0x01000000)>>3)+((0xC0000000-0x01000000)-(1<<29))))' in ARM mode
> >
> > Thanks for building test. This error can be solved by following code:
> > --- a/arch/arm/kernel/entry-armv.S
> > +++ b/arch/arm/kernel/entry-armv.S
> > @@ -188,8 +188,7 @@ ENDPROC(__und_invalid)
> >         get_thread_info tsk
> >         ldr     r0, [tsk, #TI_ADDR_LIMIT]
> >  #ifdef CONFIG_KASAN
> > -   movw r1, #:lower16:TASK_SIZE
> > -   movt r1, #:upper16:TASK_SIZE
> > + ldr r1, =TASK_SIZE
> >  #else
> >         mov r1, #TASK_SIZE
> >  #endif
> 
> This is unnecessary:
> 
> ldr r1, =TASK_SIZE
> 
> will be converted to a mov instruction by the assembler if the value
> of TASK_SIZE fits its 12-bit immediate field.

It's an 8-bit immediate field for ARM.

What it won't do is expand it to a pair of movw/movt instructions if it
doesn't fit.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up