On Sun, Feb 21, 2016 at 01:00:54PM +0530, Aneesh Kumar K.V wrote: > Paul Mackerras <pau...@samba.org> writes: > > > This moves the _PAGE_EXEC, _PAGE_RW and _PAGE_USER bits around in > > the Linux PTE on 64-bit Book 3S systems to correspond with the bit > > positions used in radix mode by PowerISA v3.0 CPUs. This also adds > > a _PAGE_READ bit corresponding to the read permission bit in the > > radix PTE. _PAGE_READ is currently unused but could possibly be used > > in future to improve pte_protnone(). > > > > Signed-off-by: Paul Mackerras <pau...@samba.org> > > --- > > arch/powerpc/include/asm/book3s/64/hash.h | 10 ++++++---- > > 1 file changed, 6 insertions(+), 4 deletions(-) > > > > diff --git a/arch/powerpc/include/asm/book3s/64/hash.h > > b/arch/powerpc/include/asm/book3s/64/hash.h > > index c8eba0e..0fc750c 100644 > > --- a/arch/powerpc/include/asm/book3s/64/hash.h > > +++ b/arch/powerpc/include/asm/book3s/64/hash.h > > @@ -13,9 +13,12 @@ > > * We could create separate kernel read-only if we used the 3 PP bits > > * combinations that newer processors provide but we currently don't. > > */ > > -#define _PAGE_BIT_SWAP_TYPE 2 > > -#define _PAGE_USER 0x00004 /* page may be accessed by userspace */ > > -#define _PAGE_EXEC 0x00008 /* execute permission */ > > +#define _PAGE_BIT_SWAP_TYPE 0 > > + > > +#define _PAGE_EXEC 0x00001 /* execute permission */ > > +#define _PAGE_RW 0x00002 /* read & write access allowed */ > > +#define _PAGE_READ 0x00004 /* read access allowed */ > > +#define _PAGE_USER 0x00008 /* page may be accessed by userspace */ > > #define _PAGE_GUARDED 0x00010 /* G: guarded (side-effect) > > page */ > > /* M (memory coherence) is always set in the HPTE, so we don't need it > > here */ > > #define _PAGE_COHERENT 0x0 > > @@ -23,7 +26,6 @@ > > #define _PAGE_WRITETHRU 0x00040 /* W: cache write-through */ > > #define _PAGE_DIRTY 0x00080 /* C: page changed */ > > #define _PAGE_ACCESSED 0x00100 /* R: page referenced */ > > -#define _PAGE_RW 0x00200 /* software: user write access allowed > > */ > > #define _PAGE_BUSY 0x00800 /* software: PTE & hash are busy */ > > #define _PAGE_SPECIAL 0x10000 /* software: special page */ > > > > > For radix, _PAGE_USER is the inverse of this right ?. Ie, we set that > bit position to 1 to indicate privileged access only.
Right, we'll need a follow-on patch that changes this to a _PAGE_PRIV bit and changes the logic that uses _PAGE_USER either that or a _PAGE_PRIV bit. But at least we have the bit position reserved now. > Also can you use constants like > #define _PAGE_USER PPC_BIT(60) I'd really rather not - that is harder for the casual reader to parse, because they then have to go off and find out what exactly PPC_BIT does. The only time that using PPC_BIT would help is when checking that the bit definitions match the Power ISA, and that's presumably done by intelligent people that can handle backwards bit numbering in their heads. :) Paul. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
