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arm64: mm: introduce present, faulting entries for PAGE_NONE

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This is mostly a port of dbf62d5006 ("ARM: mm: introduce L_PTE_VALID
for page table entries") and 26ffd0d43b ("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 <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Will Deacon 2012-12-18 14:15:15 +00:00 committed by Catalin Marinas
parent 02522463c8
commit a6fadf7e67
1 changed files with 13 additions and 11 deletions
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24
arch/arm64/include/asm/pgtable.h
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@ -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;
}