Commit 22b31eec authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

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: default avatarHugh 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3dc14741

mm/internal.h

+1 −0
Original line number Diff line number Diff line
@@ -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);



/*

mm/memory.c

+10 −10
Original line number Diff line number Diff line
@@ -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:

mm/page_alloc.c

+4 −0
Original line number Diff line number Diff line
@@ -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++) {

		/*

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