From a6fadf7e67d3794aae40244f435d281a62736c93 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 18 Dec 2012 14:15:15 +0000 Subject: [PATCH] arm64: mm: introduce present, faulting entries for PAGE_NONE This is mostly a port of dbf62d50067e ("ARM: mm: introduce L_PTE_VALID for page table entries") and 26ffd0d43b18 ("ARM: mm: introduce present, faulting entries for PAGE_NONE") from ARM, which makes use of present, faulting page table entries for page table entries mapped as PROT_NONE. The main difference with this implementation is that we can make use of the two pte type bits in order to avoid allocating a software bit for identifying PROT_NONE pages, instead reserving the 10b suffix for these types of mappings. This is required to prevent users from accessing such pages via syscalls such as read/write over a pipe. Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/pgtable.h | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 7adf4142a85..e333a243bfc 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -24,7 +24,8 @@ /* * Software defined PTE bits definition. */ -#define PTE_VALID (_AT(pteval_t, 1) << 0) /* pte_present() check */ +#define PTE_VALID (_AT(pteval_t, 1) << 0) +#define PTE_PROT_NONE (_AT(pteval_t, 1) << 1) /* only when !PTE_VALID */ #define PTE_FILE (_AT(pteval_t, 1) << 2) /* only when !pte_present() */ #define PTE_DIRTY (_AT(pteval_t, 1) << 55) #define PTE_SPECIAL (_AT(pteval_t, 1) << 56) @@ -60,9 +61,12 @@ extern void __pgd_error(const char *file, int line, unsigned long val); extern pgprot_t pgprot_default; -#define _MOD_PROT(p, b) __pgprot(pgprot_val(p) | (b)) +#define __pgprot_modify(prot,mask,bits) \ + __pgprot((pgprot_val(prot) & ~(mask)) | (bits)) -#define PAGE_NONE _MOD_PROT(pgprot_default, PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY) +#define _MOD_PROT(p, b) __pgprot_modify(p, 0, b) + +#define PAGE_NONE __pgprot_modify(pgprot_default, PTE_TYPE_MASK, PTE_PROT_NONE) #define PAGE_SHARED _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN) #define PAGE_SHARED_EXEC _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN) #define PAGE_COPY _MOD_PROT(pgprot_default, PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY) @@ -72,7 +76,7 @@ extern pgprot_t pgprot_default; #define PAGE_KERNEL _MOD_PROT(pgprot_default, PTE_PXN | PTE_UXN | PTE_DIRTY) #define PAGE_KERNEL_EXEC _MOD_PROT(pgprot_default, PTE_UXN | PTE_DIRTY) -#define __PAGE_NONE __pgprot(_PAGE_DEFAULT | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY) +#define __PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_TYPE_MASK) | PTE_PROT_NONE) #define __PAGE_SHARED __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN) #define __PAGE_SHARED_EXEC __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN) #define __PAGE_COPY __pgprot(_PAGE_DEFAULT | PTE_USER | PTE_NG | PTE_PXN | PTE_UXN | PTE_RDONLY) @@ -125,14 +129,14 @@ extern struct page *empty_zero_page; /* * The following only work if pte_present(). Undefined behaviour otherwise. */ -#define pte_present(pte) (pte_val(pte) & PTE_VALID) +#define pte_present(pte) (pte_val(pte) & (PTE_VALID | PTE_PROT_NONE)) #define pte_dirty(pte) (pte_val(pte) & PTE_DIRTY) #define pte_young(pte) (pte_val(pte) & PTE_AF) #define pte_special(pte) (pte_val(pte) & PTE_SPECIAL) #define pte_write(pte) (!(pte_val(pte) & PTE_RDONLY)) #define pte_exec(pte) (!(pte_val(pte) & PTE_UXN)) -#define pte_present_user(pte) \ +#define pte_valid_user(pte) \ ((pte_val(pte) & (PTE_VALID | PTE_USER)) == (PTE_VALID | PTE_USER)) #define PTE_BIT_FUNC(fn,op) \ @@ -156,7 +160,7 @@ 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_present_user(pte)) { + if (pte_valid_user(pte)) { if (pte_exec(pte)) __sync_icache_dcache(pte, addr); if (!pte_dirty(pte)) @@ -172,9 +176,6 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, #define pte_huge(pte) ((pte_val(pte) & PTE_TYPE_MASK) == PTE_TYPE_HUGEPAGE) #define pte_mkhuge(pte) (__pte((pte_val(pte) & ~PTE_TYPE_MASK) | PTE_TYPE_HUGEPAGE)) -#define __pgprot_modify(prot,mask,bits) \ - __pgprot((pgprot_val(prot) & ~(mask)) | (bits)) - #define __HAVE_ARCH_PTE_SPECIAL /* @@ -266,7 +267,8 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr) static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) { - const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY; + const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY | + PTE_PROT_NONE | PTE_VALID; pte_val(pte) = (pte_val(pte) & ~mask) | (pgprot_val(newprot) & mask); return pte; }