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()
---
b/arch/x86/include/asm/pgtable_types.h | 12 ++++++++++--
b/arch/x86/include/uapi/asm/mman.h | 16 ++++++++++++++++
b/include/linux/mm.h | 6 ++++++
3 files changed, 32 insertions(+), 2 deletions(-)
diff -puN arch/x86/include/asm/pgtable_types.h~pkeys-08-store-pkey-in-vma
arch/x86/include/asm/pgtable_types.h
--- a/arch/x86/include/asm/pgtable_types.h~pkeys-08-store-pkey-in-vma
2015-09-16 10:48:15.105140143 -0700
+++ b/arch/x86/include/asm/pgtable_types.h 2015-09-16 10:48:15.112140461
-0700
@@ -111,7 +111,12 @@
#define _KERNPG_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | \
_PAGE_DIRTY)
-/* Set of bits not changed in pte_modify */
+/*
+ * Set of bits not changed in pte_modify. The pte's
+ * protection key is treated like _PAGE_RW, for
+ * instance, and is *not* included in this mask since
+ * pte_modify() does modify it.
+ */
#define _PAGE_CHG_MASK (PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT | \
_PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY | \
_PAGE_SOFT_DIRTY)
@@ -227,7 +232,10 @@ enum page_cache_mode {
/* PTE_PFN_MASK extracts the PFN from a (pte|pmd|pud|pgd)val_t */
#define PTE_PFN_MASK ((pteval_t)PHYSICAL_PAGE_MASK)
-/* PTE_FLAGS_MASK extracts the flags from a (pte|pmd|pud|pgd)val_t */
+/*
+ * PTE_FLAGS_MASK extracts the flags from a (pte|pmd|pud|pgd)val_t
+ * This includes the protection key value.
+ */
#define PTE_FLAGS_MASK (~PTE_PFN_MASK)
typedef struct pgprot { pgprotval_t pgprot; } pgprot_t;
diff -puN arch/x86/include/uapi/asm/mman.h~pkeys-08-store-pkey-in-vma
arch/x86/include/uapi/asm/mman.h
--- a/arch/x86/include/uapi/asm/mman.h~pkeys-08-store-pkey-in-vma
2015-09-16 10:48:15.107140234 -0700
+++ b/arch/x86/include/uapi/asm/mman.h 2015-09-16 10:48:15.112140461 -0700
@@ -6,6 +6,22 @@
#define MAP_HUGE_2MB (21 << MAP_HUGE_SHIFT)
#define MAP_HUGE_1GB (30 << MAP_HUGE_SHIFT)
+#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
+/*
+ * Take the 4 protection key bits out of the vma->vm_flags
+ * value and turn them in to the bits that we can put in
+ * to a pte.
+ *
+ * Only override these if Protection Keys are available
+ * (which is only on 64-bit).
+ */
+#define arch_vm_get_page_prot(vm_flags) __pgprot( \
+ ((vm_flags) & VM_PKEY_BIT0 ? _PAGE_PKEY_BIT0 : 0) | \
+ ((vm_flags) & VM_PKEY_BIT1 ? _PAGE_PKEY_BIT1 : 0) | \
+ ((vm_flags) & VM_PKEY_BIT2 ? _PAGE_PKEY_BIT2 : 0) | \
+ ((vm_flags) & VM_PKEY_BIT3 ? _PAGE_PKEY_BIT3 : 0))
+#endif
+
#include <asm-generic/mman.h>
#endif /* _ASM_X86_MMAN_H */
diff -puN include/linux/mm.h~pkeys-08-store-pkey-in-vma include/linux/mm.h
--- a/include/linux/mm.h~pkeys-08-store-pkey-in-vma 2015-09-16
10:48:15.109140325 -0700
+++ b/include/linux/mm.h 2015-09-16 10:48:15.113140506 -0700
@@ -166,6 +166,12 @@ extern unsigned int kobjsize(const void
#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_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)
_
--
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