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authorCatalin Marinas <catalin.marinas@arm.com>2014-04-03 16:17:32 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2014-05-09 15:53:36 +0100
commitbc07c2c6e9ed125d362af0214b6313dca180cb08 (patch)
treea5a63f1272c11e321999145b8b7e8135b094aaaa /arch/arm64/include
parent15af1942dd61ee236a48b3de14d6f31c0b9e8116 (diff)
arm64: Introduce execute-only page access permissions
The ARMv8 architecture allows execute-only user permissions by clearing the PTE_UXN and PTE_USER bits. The kernel, however, 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 implement/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_valid_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_valid_ng() macro. VM_READ is also checked now for page faults. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include')
-rw-r--r--arch/arm64/include/asm/pgtable.h11
1 files changed, 6 insertions, 5 deletions
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 90c811f05a2..e50bb3cbd8f 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -90,6 +90,7 @@ extern pgprot_t pgprot_default;
#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)
#endif /* __ASSEMBLY__ */
@@ -97,7 +98,7 @@ extern pgprot_t pgprot_default;
#define __P001 __PAGE_READONLY
#define __P010 __PAGE_COPY
#define __P011 __PAGE_COPY
-#define __P100 __PAGE_READONLY_EXEC
+#define __P100 __PAGE_EXECONLY
#define __P101 __PAGE_READONLY_EXEC
#define __P110 __PAGE_COPY_EXEC
#define __P111 __PAGE_COPY_EXEC
@@ -106,7 +107,7 @@ extern pgprot_t pgprot_default;
#define __S001 __PAGE_READONLY
#define __S010 __PAGE_SHARED
#define __S011 __PAGE_SHARED
-#define __S100 __PAGE_READONLY_EXEC
+#define __S100 __PAGE_EXECONLY
#define __S101 __PAGE_READONLY_EXEC
#define __S110 __PAGE_SHARED_EXEC
#define __S111 __PAGE_SHARED_EXEC
@@ -143,8 +144,8 @@ extern struct page *empty_zero_page;
#define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE))
#define pte_exec(pte) (!(pte_val(pte) & PTE_UXN))
-#define pte_valid_user(pte) \
- ((pte_val(pte) & (PTE_VALID | PTE_USER)) == (PTE_VALID | PTE_USER))
+#define pte_valid_ng(pte) \
+ ((pte_val(pte) & (PTE_VALID | PTE_NG)) == (PTE_VALID | PTE_NG))
static inline pte_t pte_wrprotect(pte_t pte)
{
@@ -198,7 +199,7 @@ extern void __sync_icache_dcache(pte_t pteval, unsigned long addr);
static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pte)
{
- if (pte_valid_user(pte)) {
+ if (pte_valid_ng(pte)) {
if (!pte_special(pte) && pte_exec(pte))
__sync_icache_dcache(pte, addr);
if (pte_dirty(pte) && pte_write(pte))