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Subject[PATCH 1/6] freepgt2: 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: Hugh Dickins <hugh@veritas.com>
---

mm/mmap.c | 11 ++++++++---
1 files changed, 8 insertions(+), 3 deletions(-)

--- 2.6.12-rc2-mm1/mm/mmap.c 2005-04-05 15:23:00.000000000 +0100
+++ linux/mm/mmap.c 2005-04-05 18:59:01.000000000 +0100
@@ -1608,6 +1608,11 @@ static void unmap_vma_list(struct mm_str
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.
*
@@ -1626,7 +1631,7 @@ static void unmap_region(struct mm_struc
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);
@@ -1906,7 +1911,7 @@ 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;
@@ -1927,7 +1932,7 @@ 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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