mm/gup, x86/mm/pkeys: Check VMAs and PTEs for protection keys

Today, for normal faults and page table walks, we check the VMA
and/or PTE to ensure that it is compatible with the action.  For
instance, if we get a write fault on a non-writeable VMA, we
SIGSEGV.

We try to do the same thing for protection keys.  Basically, we
try to make sure that if a user does this:

	mprotect(ptr, size, PROT_NONE);
	*ptr = foo;

they see the same effects with protection keys when they do this:

	mprotect(ptr, size, PROT_READ|PROT_WRITE);
	set_pkey(ptr, size, 4);
	wrpkru(0xffffff3f); // access disable pkey 4
	*ptr = foo;

The state to do that checking is in the VMA, but we also
sometimes have to do it on the page tables only, like when doing
a get_user_pages_fast() where we have no VMA.

We add two functions and expose them to generic code:

	arch_pte_access_permitted(pte_flags, write)
	arch_vma_access_permitted(vma, write)

These are, of course, backed up in x86 arch code with checks
against the PTE or VMA's protection key.

But, there are also cases where we do not want to respect
protection keys.  When we ptrace(), for instance, we do not want
to apply the tracer's PKRU permissions to the PTEs from the
process being traced.

Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: Alexey Kardashevskiy <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Boaz Harrosh <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Gibson <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Vrabel <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Dominik Dingel <[email protected]>
Cc: Dominik Vogt <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jason Low <[email protected]>
Cc: Jerome Marchand <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Laurent Dufour <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mikulas Patocka <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Shachar Raindel <[email protected]>
Cc: Stephen Smalley <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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