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https://github.com/torvalds/linux
synced 2024-09-26 14:28:29 +00:00
20273941f2
Christoph reported a nice splat which illustrated a race in the new stack based kmap_atomic implementation. The problem is that we pop our stack slot before we're completely done resetting its state -- in particular clearing the PTE (sometimes that's CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear the PTE used for the last slot, that interrupt can reuse the slot in a dirty state, which triggers a BUG in kmap_atomic(). Fix this by introducing kmap_atomic_idx() which reports the current slot index without actually releasing it and use that to find the PTE and delay the _pop() until after we're completely done. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reported-by: Christoph Hellwig <hch@infradead.org> Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
90 lines
2 KiB
C
90 lines
2 KiB
C
/* highmem.c: arch-specific highmem stuff
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/highmem.h>
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#include <linux/module.h>
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void *kmap(struct page *page)
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{
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might_sleep();
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if (!PageHighMem(page))
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return page_address(page);
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return kmap_high(page);
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}
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EXPORT_SYMBOL(kmap);
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void kunmap(struct page *page)
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{
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if (in_interrupt())
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BUG();
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if (!PageHighMem(page))
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return;
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kunmap_high(page);
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}
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EXPORT_SYMBOL(kunmap);
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struct page *kmap_atomic_to_page(void *ptr)
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{
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return virt_to_page(ptr);
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}
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void *__kmap_atomic(struct page *page)
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{
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unsigned long paddr;
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int type;
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pagefault_disable();
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type = kmap_atomic_idx_push();
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paddr = page_to_phys(page);
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switch (type) {
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/*
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* The first 4 primary maps are reserved for architecture code
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*/
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case 0: return __kmap_atomic_primary(4, paddr, 6);
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case 1: return __kmap_atomic_primary(5, paddr, 7);
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case 2: return __kmap_atomic_primary(6, paddr, 8);
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case 3: return __kmap_atomic_primary(7, paddr, 9);
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case 4: return __kmap_atomic_primary(8, paddr, 10);
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case 5 ... 5 + NR_TLB_LINES - 1:
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return __kmap_atomic_secondary(type - 5, paddr);
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default:
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BUG();
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return NULL;
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}
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}
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EXPORT_SYMBOL(__kmap_atomic);
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void __kunmap_atomic(void *kvaddr)
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{
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int type = kmap_atomic_idx();
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switch (type) {
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case 0: __kunmap_atomic_primary(4, 6); break;
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case 1: __kunmap_atomic_primary(5, 7); break;
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case 2: __kunmap_atomic_primary(6, 8); break;
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case 3: __kunmap_atomic_primary(7, 9); break;
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case 4: __kunmap_atomic_primary(8, 10); break;
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case 5 ... 5 + NR_TLB_LINES - 1:
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__kunmap_atomic_secondary(type - 5, kvaddr);
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break;
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default:
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BUG();
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}
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kmap_atomic_idx_pop();
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pagefault_enable();
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}
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EXPORT_SYMBOL(__kunmap_atomic);
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