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badpage: vm_normal_page use print_bad_pte 

print_bad_pte() is so far being called only when zap_pte_range() finds
negative page_mapcount, or there's a fault on a pte_file where it does not
belong.  That's weak coverage when we suspect pagetable corruption.

Originally, it was called when vm_normal_page() found an invalid pfn: but
pfn_valid is expensive on some architectures and configurations, so 2.6.24
put that under CONFIG_DEBUG_VM (which doesn't help in the field), then
2.6.26 replaced it by a VM_BUG_ON (likewise).

Reinstate the print_bad_pte() in vm_normal_page(), but use a cheaper test
than pfn_valid(): memmap_init_zone() (used in bootup and hotplug) keep a
__read_mostly note of the highest_memmap_pfn, vm_normal_page() then check
pfn against that.  We could call this pfn_plausible() or pfn_sane(), but I
doubt we'll need it elsewhere: of course it's not reliable, but gives much
stronger pagetable validation on many boxes.

Also use print_bad_pte() when the pte_special bit is found outside a
VM_PFNMAP or VM_MIXEDMAP area, instead of VM_BUG_ON.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2009-01-06 14:40:09 -08:00 committed by Linus Torvalds
parent 3dc147414c
commit 22b31eec63
3 changed files with 15 additions and 10 deletions
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1
mm/internal.h
View File

@ -49,6 +49,7 @@ extern void putback_lru_page(struct page *page);
/*
* in mm/page_alloc.c
*/
extern unsigned long highest_memmap_pfn;
extern void __free_pages_bootmem(struct page *page, unsigned int order);
/*

20
mm/memory.c
View File

@ -467,21 +467,18 @@ static inline int is_cow_mapping(unsigned int flags)
struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
pte_t pte)
{
unsigned long pfn;
unsigned long pfn = pte_pfn(pte);
if (HAVE_PTE_SPECIAL) {
if (likely(!pte_special(pte))) {
VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
return pte_page(pte);
}
VM_BUG_ON(!(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)));
if (likely(!pte_special(pte)))
goto check_pfn;
if (!(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)))
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
/* !HAVE_PTE_SPECIAL case follows: */
pfn = pte_pfn(pte);
if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
if (vma->vm_flags & VM_MIXEDMAP) {
if (!pfn_valid(pfn))
@ -497,11 +494,14 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
}
}
VM_BUG_ON(!pfn_valid(pfn));
check_pfn:
if (unlikely(pfn > highest_memmap_pfn)) {
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
/*
* NOTE! We still have PageReserved() pages in the page tables.
*
* eg. VDSO mappings can cause them to exist.
*/
out:

4
mm/page_alloc.c
View File

@ -69,6 +69,7 @@ EXPORT_SYMBOL(node_states);
unsigned long totalram_pages __read_mostly;
unsigned long totalreserve_pages __read_mostly;
unsigned long highest_memmap_pfn __read_mostly;
int percpu_pagelist_fraction;
#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
@ -2597,6 +2598,9 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
unsigned long pfn;
struct zone *z;
if (highest_memmap_pfn < end_pfn - 1)
highest_memmap_pfn = end_pfn - 1;
z = &NODE_DATA(nid)->node_zones[zone];
for (pfn = start_pfn; pfn < end_pfn; pfn++) {
/*