From 22b31eec63e5f2e219a3ee15f456897272bc73e8 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 6 Jan 2009 14:40:09 -0800 Subject: [PATCH] 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 Cc: Nick Piggin Cc: Christoph Lameter Cc: Mel Gorman Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/internal.h | 1 + mm/memory.c | 20 ++++++++++---------- mm/page_alloc.c | 4 ++++ 3 files changed, 15 insertions(+), 10 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 13333bc2eb68..1981bc9454f3 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -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); /* diff --git a/mm/memory.c b/mm/memory.c index cda04b19f733..890095f5f36d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -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: diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3acb216e9a78..755c99a0ac71 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -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++) { /*