Re: [PATCH v2] powerpc/32s: fix BATs setting with CONFIG_STRICT_KERNEL_RWX

[christophe leroy]

Le 01/05/2019 Ã 02:55, Michael Ellerman a ÃcritÂ:
> Christophe Leroy <christophe.leroy@xxxxxx> writes:
> > Serge reported some crashes with CONFIG_STRICT_KERNEL_RWX enabled
> > on a book3s32 machine.
> >
> > Analysis shows two issues:
> > - BATs addresses and sizes are not properly aligned.
> > - There is a gap between the last address covered by BATs and the
> > first address covered by pages.
> >
> > Memory mapped with DBATs:
> > 0: 0xc0000000-0xc07fffff 0x00000000 Kernel RO coherent
> > 1: 0xc0800000-0xc0bfffff 0x00800000 Kernel RO coherent
> > 2: 0xc0c00000-0xc13fffff 0x00c00000 Kernel RW coherent
> > 3: 0xc1400000-0xc23fffff 0x01400000 Kernel RW coherent
> > 4: 0xc2400000-0xc43fffff 0x02400000 Kernel RW coherent
> > 5: 0xc4400000-0xc83fffff 0x04400000 Kernel RW coherent
> > 6: 0xc8400000-0xd03fffff 0x08400000 Kernel RW coherent
> > 7: 0xd0400000-0xe03fffff 0x10400000 Kernel RW coherent
> >
> > Memory mapped with pages:
> > 0xe1000000-0xefffffff  0x21000000       240M        rw       present           dirty  accessed
> >
> > This patch fixes both issues. With the patch, we get the following
> > which is as expected:
> >
> > Memory mapped with DBATs:
> > 0: 0xc0000000-0xc07fffff 0x00000000 Kernel RO coherent
> > 1: 0xc0800000-0xc0bfffff 0x00800000 Kernel RO coherent
> > 2: 0xc0c00000-0xc0ffffff 0x00c00000 Kernel RW coherent
> > 3: 0xc1000000-0xc1ffffff 0x01000000 Kernel RW coherent
> > 4: 0xc2000000-0xc3ffffff 0x02000000 Kernel RW coherent
> > 5: 0xc4000000-0xc7ffffff 0x04000000 Kernel RW coherent
> > 6: 0xc8000000-0xcfffffff 0x08000000 Kernel RW coherent
> > 7: 0xd0000000-0xdfffffff 0x10000000 Kernel RW coherent
> >
> > Memory mapped with pages:
> > 0xe0000000-0xefffffff  0x20000000       256M        rw       present           dirty  accessed
> >
> > Reported-by: Serge Belyshev <belyshev@xxxxxxxxxxxxxxxxx>
> > Fixes: 63b2bc619565 ("powerpc/mm/32s: Use BATs for STRICT_KERNEL_RWX")
> > Cc: stable@xxxxxxxxxxxxxxx
>
> I could probably still get this into v5.1 if you're confident it's a
> good fix.

If possible it would be great.

Yes I'm confident it is a good fix:
- The fix has no impact on the configurations I tested originally (they 
were lacking a trailing area not mapped with BATs and the boundarie 
between RW and RO was a power of 2 so ffs() returned the same as lfs())
- The fix was tested by myself on QEMU.
- The fix was tested by Serge.
- The fix was acked by Segher.
- The fix make sense (ie ffs() is the good one, fls() was definitly wrong)

Christophe

> cheers

---
L'absence de virus dans ce courrier Ãlectronique a Ãtà vÃrifiÃe par le logiciel antivirus Avast.
https://www.avast.com/antivirus