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authorCatalin Marinas <catalin.marinas@arm.com>2016-08-11 18:44:50 +0100
committerWill Deacon <will.deacon@arm.com>2016-08-25 18:00:29 +0100
commitcab15ce604e550020bb7115b779013b91bcdbc21 (patch)
tree0ba025b8ad16505532aaa6e1b4cc665473f026fa /mm
parent7419333fa15ec958d12845fcc79b7bdd16de06ec (diff)
downloadlinux-cab15ce604e550020bb7115b779013b91bcdbc21.tar.bz2
arm64: Introduce execute-only page access permissions
The ARMv8 architecture allows execute-only user permissions by clearing the PTE_UXN and PTE_USER bits. However, the kernel running on a CPU implementation without User Access Override (ARMv8.2 onwards) can still access such page, so execute-only page permission does not protect against read(2)/write(2) etc. accesses. Systems requiring such protection must enable features like SECCOMP. This patch changes the arm64 __P100 and __S100 protection_map[] macros to the new __PAGE_EXECONLY attributes. A side effect is that pte_user() no longer triggers for __PAGE_EXECONLY since PTE_USER isn't set. To work around this, the check is done on the PTE_NG bit via the pte_ng() macro. VM_READ is also checked now for page faults. Reviewed-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'mm')
-rw-r--r--mm/mmap.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index ca9d91bca0d6..69cad562cd00 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -88,6 +88,11 @@ static void unmap_region(struct mm_struct *mm,
* w: (no) no w: (no) no w: (copy) copy w: (no) no
* x: (no) no x: (no) yes x: (no) yes x: (yes) yes
*
+ * On arm64, PROT_EXEC has the following behaviour for both MAP_SHARED and
+ * MAP_PRIVATE:
+ * r: (no) no
+ * w: (no) no
+ * x: (yes) yes
*/
pgprot_t protection_map[16] = {
__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,