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Commit e2cdef8c authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
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[PATCH] freepgt: free_pgtables from FIRST_USER_ADDRESS 



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: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 021740dc

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