[PULL REQ] Big Endian initial patch series

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Mon, Oct 28, 2013 at 08:44:55AM +0000, Will Deacon wrote:
> Hi Russell,
> 
> On Mon, Oct 28, 2013 at 12:47:36AM +0000, Russell King - ARM Linux wrote:
> > On Sat, Oct 19, 2013 at 08:51:35PM +0100, Ben Dooks wrote:
> > > On 19/10/13 18:09, Will Deacon wrote:
> > >> Do you think you could send another pull request please?
> > >
> > > Ok, sorted.
> > 
> > Pulled, but there was a conflict.  Please check this resolution (it's
> > copy'n'pasted).  I'll probably be in linux-next tomorrow in any case,
> > but any mistake here can be fixed.
> 
> This doesn't look quite right to me, but unfortunately I'm going be spending
> most (all?) of today trying to catch a flight out of the UK. Hopefully Dave
> or Ben can investigate further, but comments below.
> 
> > diff --cc arch/arm/kernel/head.S
> > index 54547947a4e9,a047acfa6b6d..000000000000
> > --- a/arch/arm/kernel/head.S
> > +++ b/arch/arm/kernel/head.S
> > @@@ -602,28 -586,26 +606,39 @@@ __fixup_a_pv_table
> >         b       2f
> >   1:    add     r7, r3
> >         ldrh    ip, [r7, #2]
> > + ARM_BE8(rev16 ip, ip)
> >  -      and     ip, 0x8f00
> >  -      orr     ip, r6  @ mask in offset bits 31-24
> >  +      tst     ip, #0x4000
> >  +      and     ip, #0x8f00
> >  +      orrne   ip, r6  @ mask in offset bits 31-24
> >  +      orreq   ip, r0  @ mask in offset bits 7-0
> > + ARM_BE8(rev16 ip, ip)
> >         strh    ip, [r7, #2]
> >  +      ldrheq  ip, [r7]
> >  +      biceq   ip, #0x20
> >  +      orreq   ip, ip, r0, lsr #16
> >  +      strheq  ip, [r7]
> 
> There are new halfword accesses here without any conditional revs.

Yes, I missed this one.

> > + #ifdef CONFIG_CPU_ENDIAN_BE8
> > +       @ in BE8, we load data in BE, but instructions still in LE
> > +       bic     ip, ip, #0xff000000
> >  -      orr     ip, ip, r6, lsl#24
> > ++      tst     ip, #0x000f0000 @ check the rotation field
> 
> Since that orr with shift has been removed, I think the masks for the BE
> case are now incorrect...
> 
> > ++      orrne   ip, ip, r6, lsl #24 @ mask in offset bits 31-24
> > ++      biceq   ip, ip, #0x00004000 @ clear bit 22
> > ++      orreq   ip, ip, r0, lsl #24 @ mask in offset bits 7-0

Actually, look closer.  It became the orrne here.

> > + #else
> >         bic     ip, ip, #0x000000ff
> >  -      orr     ip, ip, r6      @ mask in offset bits 31-24
> >  +      tst     ip, #0xf00      @ check the rotation field
> >  +      orrne   ip, ip, r6      @ mask in offset bits 31-24
> >  +      biceq   ip, ip, #0x400000       @ clear bit 22
> 
> ...which seems to be confirmed by the updated LE code (everything is off
> by a byte).

The LE code was left unaltered from Santosh's patch, so that should be
correct.  I just did an endian conversion to the BE case.

> Somebody should probably sit down with the conflicting patch and port the BE
> changes over. I think the relevant patch is "ARM: mm: Correct virt_to_phys
> patching for 64 bit physical addresses". In fact, looking at *that* patch,
> it's *also* broken for BE! It adds the following to head.S:
> 
> +#ifdef __ARMEB_
> +#define LOW_OFFSET     0x4
> +#define HIGH_OFFSET    0x0
> +#else
> +#define LOW_OFFSET     0x0
> +#define HIGH_OFFSET    0x4
> +#endif
> 
> (spot the missing underscore).

Yep, well spotted.

Well, we have some time to get this all fixed, so I'm going to drop
Ben's tree.  I think we need to first commit a patch to fix the error
in Santosh's patch.