721151d004
Some drivers have resources that they want to be able to map into userspace that are 4k in size. On a kernel configured with 64k pages we currently end up mapping the 4k we want plus another 60k of physical address space, which could contain anything. This can introduce security problems, for example in the case of an infiniband adaptor where the other 60k could contain registers that some other program is using for its communications. This patch adds a new function, remap_4k_pfn, which drivers can use to map a single 4k page to userspace regardless of whether the kernel is using a 4k or a 64k page size. Like remap_pfn_range, it would typically be called in a driver's mmap function. It only maps a single 4k page, which on a 64k page kernel appears replicated 16 times throughout a 64k page. On a 4k page kernel it reduces to a call to remap_pfn_range. The way this works on a 64k kernel is that a new bit, _PAGE_4K_PFN, gets set on the linux PTE. This alters the way that __hash_page_4K computes the real address to put in the HPTE. The RPN field of the linux PTE becomes the 4k RPN directly rather than being interpreted as a 64k RPN. Since the RPN field is 32 bits, this means that physical addresses being mapped with remap_4k_pfn have to be below 2^44, i.e. 0x100000000000. The patch also factors out the code in arch/powerpc/mm/hash_utils_64.c that deals with demoting a process to use 4k pages into one function that gets called in the various different places where we need to do that. There were some discrepancies between exactly what was done in the various places, such as a call to spu_flush_all_slbs in one case but not in others. Signed-off-by: Paul Mackerras <paulus@samba.org>
103 lines
3.5 KiB
C
103 lines
3.5 KiB
C
/*
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* Entries per page directory level. The PTE level must use a 64b record
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* for each page table entry. The PMD and PGD level use a 32b record for
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* each entry by assuming that each entry is page aligned.
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*/
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#define PTE_INDEX_SIZE 9
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#define PMD_INDEX_SIZE 7
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#define PUD_INDEX_SIZE 7
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#define PGD_INDEX_SIZE 9
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#define PTE_TABLE_SIZE (sizeof(pte_t) << PTE_INDEX_SIZE)
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#define PMD_TABLE_SIZE (sizeof(pmd_t) << PMD_INDEX_SIZE)
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#define PUD_TABLE_SIZE (sizeof(pud_t) << PUD_INDEX_SIZE)
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#define PGD_TABLE_SIZE (sizeof(pgd_t) << PGD_INDEX_SIZE)
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#define PTRS_PER_PTE (1 << PTE_INDEX_SIZE)
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#define PTRS_PER_PMD (1 << PMD_INDEX_SIZE)
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#define PTRS_PER_PUD (1 << PMD_INDEX_SIZE)
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#define PTRS_PER_PGD (1 << PGD_INDEX_SIZE)
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/* PMD_SHIFT determines what a second-level page table entry can map */
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#define PMD_SHIFT (PAGE_SHIFT + PTE_INDEX_SIZE)
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#define PMD_SIZE (1UL << PMD_SHIFT)
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#define PMD_MASK (~(PMD_SIZE-1))
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/* With 4k base page size, hugepage PTEs go at the PMD level */
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#define MIN_HUGEPTE_SHIFT PMD_SHIFT
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/* PUD_SHIFT determines what a third-level page table entry can map */
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#define PUD_SHIFT (PMD_SHIFT + PMD_INDEX_SIZE)
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#define PUD_SIZE (1UL << PUD_SHIFT)
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#define PUD_MASK (~(PUD_SIZE-1))
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/* PGDIR_SHIFT determines what a fourth-level page table entry can map */
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#define PGDIR_SHIFT (PUD_SHIFT + PUD_INDEX_SIZE)
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#define PGDIR_SIZE (1UL << PGDIR_SHIFT)
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#define PGDIR_MASK (~(PGDIR_SIZE-1))
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/* PTE bits */
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#define _PAGE_SECONDARY 0x8000 /* software: HPTE is in secondary group */
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#define _PAGE_GROUP_IX 0x7000 /* software: HPTE index within group */
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#define _PAGE_F_SECOND _PAGE_SECONDARY
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#define _PAGE_F_GIX _PAGE_GROUP_IX
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/* PTE flags to conserve for HPTE identification */
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#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | \
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_PAGE_SECONDARY | _PAGE_GROUP_IX)
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/* PAGE_MASK gives the right answer below, but only by accident */
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/* It should be preserving the high 48 bits and then specifically */
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/* preserving _PAGE_SECONDARY | _PAGE_GROUP_IX */
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#define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY | \
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_PAGE_HPTEFLAGS)
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/* Bits to mask out from a PMD to get to the PTE page */
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#define PMD_MASKED_BITS 0
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/* Bits to mask out from a PUD to get to the PMD page */
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#define PUD_MASKED_BITS 0
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/* Bits to mask out from a PGD to get to the PUD page */
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#define PGD_MASKED_BITS 0
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/* shift to put page number into pte */
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#define PTE_RPN_SHIFT (17)
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#ifdef STRICT_MM_TYPECHECKS
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#define __real_pte(e,p) ((real_pte_t){(e)})
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#define __rpte_to_pte(r) ((r).pte)
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#else
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#define __real_pte(e,p) (e)
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#define __rpte_to_pte(r) (__pte(r))
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#endif
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#define __rpte_to_hidx(r,index) (pte_val(__rpte_to_pte(r)) >> 12)
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#define pte_iterate_hashed_subpages(rpte, psize, va, index, shift) \
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do { \
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index = 0; \
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shift = mmu_psize_defs[psize].shift; \
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#define pte_iterate_hashed_end() } while(0)
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#define pte_pagesize_index(pte) MMU_PAGE_4K
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/*
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* 4-level page tables related bits
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*/
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#define pgd_none(pgd) (!pgd_val(pgd))
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#define pgd_bad(pgd) (pgd_val(pgd) == 0)
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#define pgd_present(pgd) (pgd_val(pgd) != 0)
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#define pgd_clear(pgdp) (pgd_val(*(pgdp)) = 0)
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#define pgd_page_vaddr(pgd) (pgd_val(pgd) & ~PGD_MASKED_BITS)
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#define pgd_page(pgd) virt_to_page(pgd_page_vaddr(pgd))
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#define pud_offset(pgdp, addr) \
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(((pud_t *) pgd_page_vaddr(*(pgdp))) + \
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(((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1)))
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#define pud_ERROR(e) \
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printk("%s:%d: bad pud %08lx.\n", __FILE__, __LINE__, pud_val(e))
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#define remap_4k_pfn(vma, addr, pfn, prot) \
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remap_pfn_range((vma), (addr), (pfn), PAGE_SIZE, (prot))
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