linux-kernel - Re: A bug about system call on ARM

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Message-ID: <20130529094826.GD13095@mudshark.cambridge.arm.com>
Date:	Wed, 29 May 2013 10:48:27 +0100
From:	Will Deacon <will.deacon@....com>
To:	richard -rw- weinberger <richard.weinberger@...il.com>
Cc:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: A bug about system call on ARM

Hello,

On Wed, May 29, 2013 at 09:46:42AM +0100, richard -rw- weinberger wrote:
> On Wed, May 29, 2013 at 10:24 AM, Wang, Yalin <Yalin.Wang@...ymobile.com> wrote:
> > I have download the latest linux kernel code  3.9.4
> > And Compare with  3.4.0 kernel .
> >
> > It seems there is no change for this part ,
> > So it will still happen .
> > Does anyone know who is responsible for  arm arch part kernel code ?
> 
> See MAINTAINERS file.
> CC'ing linux-arm-kernel@...ts.infradead.org

Cheers for adding us to CC.

> >> #ifdef CONFIG_ARM_THUMB
> >>         tst     r8, #PSR_T_BIT
> >>         movne   r10, #0                         @ no thumb OABI emulation
> >>         ldreq   r10, [lr, #-4]                  @ get SWI instruction          // crash at this instruction, when get SWI instruction

Do you have the panic log please? Also, which SoC are you using and how are
you reproducing this?

> >>         ldr     r10, [lr, #-4]                  @ get SWI instruction
> >>   A710( and     ip, r10, #0x0f000000            @ check for SWI         )
> >>   A710( teq     ip, #0x0f000000                                         )
> >>   A710( bne     .Larm710bug                                             )
> >> #endif
> >> #ifdef CONFIG_CPU_ENDIAN_BE8
> >>         rev     r10, r10                        @ little endian instruction
> >> #endif
> >>
> >> /*********************************************************************
> >> ******************************/
> >>
> >> Then reason why it will crash when get SWI instruction is maybe This
> >> page is clear to aged by kernel, But this MMU fault happpened in
> >> kernel, So the kernel do_page_fault function will not clear this page
> >> to young, So that  will crash .

Sounds like we might need some USER annotations around the instruction
loads, but we should also rework the code so that we re-enable interrupts
first.

Will
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