x86/mm/pkeys: Add arch-specific VMA protection bits

Lots of things seem to do:

        vma->vm_page_prot = vm_get_page_prot(flags);

and the ptes get created right from things we pull out
of ->vm_page_prot.  So it is very convenient if we can
store the protection key in flags and vm_page_prot, just
like the existing permission bits (_PAGE_RW/PRESENT).  It
greatly reduces the amount of plumbing and arch-specific
hacking we have to do in generic code.

This also takes the new PROT_PKEY{0,1,2,3} flags and
turns *those* in to VM_ flags for vma->vm_flags.

The protection key values are stored in 4 places:
	1. "prot" argument to system calls
	2. vma->vm_flags, filled from the mmap "prot"
	3. vma->vm_page prot, filled from vma->vm_flags
	4. the PTE itself.

The pseudocode for these for steps are as follows:

	mmap(PROT_PKEY*)
	vma->vm_flags 	  = ... | arch_calc_vm_prot_bits(mmap_prot);
	vma->vm_page_prot = ... | arch_vm_get_page_prot(vma->vm_flags);
	pte = pfn | vma->vm_page_prot

Note that this provides a new definitions for x86:

	arch_vm_get_page_prot()

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160212210210.FE483A42@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 54d173bcc327..3056369bab1d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -183,6 +183,13 @@ extern unsigned int kobjsize(const void *objp);
 
 #if defined(CONFIG_X86)
 # define VM_PAT         VM_ARCH_1       /* PAT reserves whole VMA at once (x86) */
+#if defined (CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)
+# define VM_PKEY_SHIFT  VM_HIGH_ARCH_BIT_0
+# define VM_PKEY_BIT0   VM_HIGH_ARCH_0  /* A protection key is a 4-bit value */
+# define VM_PKEY_BIT1   VM_HIGH_ARCH_1
+# define VM_PKEY_BIT2   VM_HIGH_ARCH_2
+# define VM_PKEY_BIT3   VM_HIGH_ARCH_3
+#endif
 #elif defined(CONFIG_PPC)
 # define VM_SAO         VM_ARCH_1       /* Strong Access Ordering (powerpc) */
 #elif defined(CONFIG_PARISC)