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riscv: Add pte bit to distinguish swap from invalid 

Previously, invalid PTEs and swap PTEs had the same binary
representation, causing errors when attempting to unmap PROT_NONE
mappings, including implicit unmap on exit.

Typical error:

swap_info_get: Bad swap file entry 40000000007a9879
BUG: Bad page map in process a.out  pte:3d4c3cc0 pmd:3e521401

Cc: stable@vger.kernel.org
Signed-off-by: Stefan O'Rear <sorear2@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
This commit is contained in:
Stefan O'Rear 2018-12-16 13:03:36 -05:00 committed by Palmer Dabbelt
parent d13937116f
commit e3613bb8af
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GPG Key ID: EF4CA1502CCBAB41
2 changed files with 10 additions and 4 deletions
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6
arch/riscv/include/asm/pgtable-bits.h
View File

@ -35,6 +35,12 @@
#define _PAGE_SPECIAL _PAGE_SOFT
#define _PAGE_TABLE _PAGE_PRESENT
/*
* _PAGE_PROT_NONE is set on not-present pages (and ignored by the hardware) to
* distinguish them from swapped out pages
*/
#define _PAGE_PROT_NONE _PAGE_READ
#define _PAGE_PFN_SHIFT 10
/* Set of bits to preserve across pte_modify() */

8
arch/riscv/include/asm/pgtable.h
View File

@ -44,7 +44,7 @@
/* Page protection bits */
#define _PAGE_BASE (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER)
#define PAGE_NONE __pgprot(0)
#define PAGE_NONE __pgprot(_PAGE_PROT_NONE)
#define PAGE_READ __pgprot(_PAGE_BASE | _PAGE_READ)
#define PAGE_WRITE __pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_WRITE)
#define PAGE_EXEC __pgprot(_PAGE_BASE | _PAGE_EXEC)
@ -98,7 +98,7 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
static inline int pmd_present(pmd_t pmd)
{
return (pmd_val(pmd) & _PAGE_PRESENT);
return (pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROT_NONE));
}
static inline int pmd_none(pmd_t pmd)
@ -178,7 +178,7 @@ static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long addr)
static inline int pte_present(pte_t pte)
{
return (pte_val(pte) & _PAGE_PRESENT);
return (pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROT_NONE));
}
static inline int pte_none(pte_t pte)
@ -380,7 +380,7 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
*
* Format of swap PTE:
* bit 0: _PAGE_PRESENT (zero)
* bit 1: reserved for future use (zero)
* bit 1: _PAGE_PROT_NONE (zero)
* bits 2 to 6: swap type
* bits 7 to XLEN-1: swap offset
*/