Re: [PATCH] ARM: fix alignement of __bug_table section entries

Russell King - ARM Linux
2015-09-06T19:48:33Z

On Sun, Sep 06, 2015 at 07:25:01PM +0200, Robert Jarzmik wrote:
> Russell King - ARM Linux <linux@arm.linux.org.uk> writes:
>
> > On Sat, Sep 05, 2015 at 07:10:49PM +0200, Robert Jarzmik wrote:
> >> Russell King - ARM Linux <linux@arm.linux.org.uk> writes:
> >> So the issue is around this SW_DOMAIN_PAN, at least on PXA.
> >
> > If so, you may need to add:
> >
> > mrc p15, 0, \rd, c2, c0, 0
> > mov \rd, \rd
> > sub pc, pc, #4
> >
> > to the places we update the domain access register to ensure that the
> > Xscale pipeline stalls to allow the CP15 DACR update to hit.
> Nope, that didn't work.
> I have tried 2 different patches :
> - in [1], your proposed solution
> - in [2], a PrefetchFlush as adviced by ARM Architecture Reference Manual
>
> None of them worked. I confirmed by disassembling __dabt_svc my changes hit the
> abort routine, and they did. I'll continue next week by trying to have a closer
> look at the SW_DOMAIN_PAN commit (a5e090acbf545), and take time to walk through
> the whole Oops for information I have missed.
>
> Cheers.
>
> --
> Robert
>
> [1] Approach 1 : translation table sync
> =======================================
> diff --cc arch/arm/include/asm/assembler.h
> index 7bbf325a4f31,7bbf325a4f31..6bb46198fd08
> --- a/arch/arm/include/asm/assembler.h
> +++ b/arch/arm/include/asm/assembler.h
> @@@ -449,6 -449,6 +449,12 @@@ THUMB( orr \reg , \reg , #PSR_T_BIT
> #endif
> .endm
>
> ++ .macro dacr_sync, rd
> ++ mrc p15, 0, \rd, c2, c0, 0
> ++ mov \rd, \rd
> ++ sub pc, pc, #4
> ++ .endm
> ++
> .macro uaccess_disable, tmp, isb=1
> #ifdef CONFIG_CPU_SW_DOMAIN_PAN
> /*
> @@@ -457,6 -457,6 +463,7 @@@
> */
> mov \tmp, #DACR_UACCESS_DISABLE
> mcr p15, 0, \tmp, c3, c0, 0 @ Set domain register
> ++ dacr_sync \tmp
> .if \isb
> instr_sync
> .endif
> @@@ -471,6 -471,6 +478,7 @@@
> */
> mov \tmp, #DACR_UACCESS_ENABLE
> mcr p15, 0, \tmp, c3, c0, 0
> ++ dacr_sync \tmp
> .if \isb
> instr_sync
> .endif
> @@@ -488,6 -488,6 +496,7 @@@
> #ifdef CONFIG_CPU_SW_DOMAIN_PAN
> ldr r0, [sp, #S_FRAME_SIZE]
> mcr p15, 0, r0, c3, c0, 0
> ++ dacr_sync r0
> #endif
> .endm

The important place is in arch/arm/include/asm/domain.h, which is where
we manipulate the DACR within probe_kernel_address().

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