[PATCH] freepgt: free_pgtables from FIRST_USER_ADDRESS (e2cdef8c) · Commits · 戴 / test

The patches to free_pgtables by vma left problems on any architectures which leave some user address page table entries unencapsulated by vma. Andi has fixed the 32-bit vDSO on x86_64 to use a vma. Now fix arm (and arm26), whose first PAGE_SIZE is reserved (perhaps) for machine vectors. Our calls to free_pgtables must not touch that area, and exit_mmap's BUG_ON(nr_ptes) must allow that arm's get_pgd_slow may (or may not) have allocated an extra page table, which its free_pgd_slow would free later. FIRST_USER_PGD_NR has misled me and others: until all the arches define FIRST_USER_ADDRESS instead, a hack in mmap.c to derive one from t'other. This patch fixes the bugs, the remaining patches just clean it up. Signed-off-by:

Hugh Dickins <hugh@veritas.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

mm/mmap.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -1612,6 +1612,11 @@ static void unmap_vma_list(struct mm_struct mm, struct vm_area_struct vma)
		validate_mm(mm);
		}

		#ifndef FIRST_USER_ADDRESS /* temporary hack */
		#define THIS_IS_ARM FIRST_USER_PGD_NR
		#define FIRST_USER_ADDRESS (THIS_IS_ARM * PAGE_SIZE)
		#endif

		/*
		* Get rid of page table information in the indicated region.
		*
		@@ -1630,7 +1635,7 @@ static void unmap_region(struct mm_struct *mm,
		tlb = tlb_gather_mmu(mm, 0);
		unmap_vmas(&tlb, mm, vma, start, end, &nr_accounted, NULL);
		vm_unacct_memory(nr_accounted);
		free_pgtables(&tlb, vma, prev? prev->vm_end: 0,
		free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
		next? next->vm_start: 0);
		tlb_finish_mmu(tlb, start, end);
		spin_unlock(&mm->page_table_lock);
		@@ -1910,7 +1915,7 @@ void exit_mmap(struct mm_struct *mm)
		/* Use -1 here to ensure all VMAs in the mm are unmapped */
		end = unmap_vmas(&tlb, mm, vma, 0, -1, &nr_accounted, NULL);
		vm_unacct_memory(nr_accounted);
		free_pgtables(&tlb, vma, 0, 0);
		free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
		tlb_finish_mmu(tlb, 0, end);

		mm->mmap = mm->mmap_cache = NULL;
		@@ -1931,7 +1936,7 @@ void exit_mmap(struct mm_struct *mm)
		vma = next;
		}

		BUG_ON(mm->nr_ptes); /* This is just debugging */
		BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
		}

		/* Insert vm structure into process list sorted by address

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