mm: allow arch code to control the user page table ceiling
On architectures where a pgd entry may be shared between user and kernel (e.g. ARM+LPAE), freeing page tables needs a ceiling other than 0. This patch introduces a generic USER_PGTABLES_CEILING that arch code can override. It is the responsibility of the arch code setting the ceiling to ensure the complete freeing of the page tables (usually in pgd_free()). [catalin.marinas@arm.com: commit log; shift_arg_pages(), asm-generic/pgtables.h changes] Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: <stable@vger.kernel.org> [3.3+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds
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commit
6ee8630e02
@ -613,7 +613,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
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* when the old and new regions overlap clear from new_end.
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*/
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free_pgd_range(&tlb, new_end, old_end, new_end,
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vma->vm_next ? vma->vm_next->vm_start : 0);
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vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
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} else {
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/*
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* otherwise, clean from old_start; this is done to not touch
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@ -622,7 +622,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
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* for the others its just a little faster.
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*/
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free_pgd_range(&tlb, old_start, old_end, new_end,
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vma->vm_next ? vma->vm_next->vm_start : 0);
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vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
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}
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tlb_finish_mmu(&tlb, new_end, old_end);
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