Subject: [PATCH] arm64: Clean up the default pgprot setting

From: [email-masked] (Catalin Marinas)
Date: Tue, 6 May 2014 15:08:59 +0100

On Fri, May 02, 2014 at 06:07:45PM +0100, Will Deacon wrote:
> On Fri, May 02, 2014 at 04:51:59PM +0100, Catalin Marinas wrote:
> > The primary aim of this patchset is to remove the pgprot_default and
> > prot_sect_default global variables and rely strictly on predefined
> > values. The original goal was to be able to run SMP kernels on UP
> > hardware by not setting the Shareability bit. However, it is unlikely to
> > see UP ARMv8 hardware and even if we do, the Shareability bit is no
> > longer assumed to disable cacheable accesses.
> > 
> > A side effect is that the device mappings now have the Shareability
> > attribute set. The hardware, however, should ignore it since Device
> > accesses are always Outer Shareable.
> > 
> > Following the removal of the two global variables, there is some PROT_*
> > macro reshuffling and cleanup, including the __PAGE_* macros (replaced
> > by PAGE_*).
> 
> [...]
> 
> > +#define PAGE_NONE		__pgprot(((_PAGE_DEFAULT) & ~PTE_TYPE_MASK) | PTE_PROT_NONE | PTE_PXN | PTE_UXN)
> > +#define PAGE_SHARED		__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
> > +#define PAGE_SHARED_EXEC	__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_WRITE)
> > +#define PAGE_COPY		__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
> > +#define PAGE_COPY_EXEC	__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN)
> > +#define PAGE_READONLY		__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN)
> > +#define PAGE_READONLY_EXEC	__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN)
> > +#define PAGE_EXECONLY		__pgprot(_PAGE_DEFAULT | PTE_NG | PTE_PXN)
> 
> Could you build the non-exec versions in terms of the exec versions? The
> difference is just the addition of PTE_UXN, and it would make this easier to
> read.

I think it still looks nicer this way. If we are writing one in terms of
the other we have to use pgprot_val() to decompose the __pgprot()
returned type.

-- 
Catalin