656dad312f
Catch illegally nested kmap_atomic()s even if the page that is mapped by the 'inner' instance is from lowmem. This avoids spuriously zapped kmap-atomic ptes and turns hard to find crashes into clear asserts at the bug site. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
#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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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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/*
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* kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
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* no global lock is needed and because the kmap code must perform a global TLB
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* invalidation when the kmap pool wraps.
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*
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* However when holding an atomic kmap is is not legal to sleep, so atomic
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* kmaps are appropriate for short, tight code paths only.
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*/
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void *kmap_atomic(struct page *page, enum km_type type)
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{
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enum fixed_addresses idx;
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unsigned long vaddr;
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/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
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pagefault_disable();
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idx = type + KM_TYPE_NR*smp_processor_id();
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BUG_ON(!pte_none(*(kmap_pte-idx)));
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if (!PageHighMem(page))
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return page_address(page);
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vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
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set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
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return (void*) vaddr;
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}
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void kunmap_atomic(void *kvaddr, enum km_type type)
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{
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unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
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enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
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/*
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* Force other mappings to Oops if they'll try to access this pte
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* without first remap it. Keeping stale mappings around is a bad idea
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* also, in case the page changes cacheability attributes or becomes
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* a protected page in a hypervisor.
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*/
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if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
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kpte_clear_flush(kmap_pte-idx, vaddr);
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else {
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#ifdef CONFIG_DEBUG_HIGHMEM
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BUG_ON(vaddr < PAGE_OFFSET);
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BUG_ON(vaddr >= (unsigned long)high_memory);
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#endif
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}
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pagefault_enable();
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}
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/* This is the same as kmap_atomic() but can map memory that doesn't
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* have a struct page associated with it.
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*/
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void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
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{
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enum fixed_addresses idx;
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unsigned long vaddr;
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pagefault_disable();
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idx = type + KM_TYPE_NR*smp_processor_id();
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vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
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set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
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return (void*) vaddr;
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}
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struct page *kmap_atomic_to_page(void *ptr)
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{
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unsigned long idx, vaddr = (unsigned long)ptr;
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pte_t *pte;
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if (vaddr < FIXADDR_START)
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return virt_to_page(ptr);
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idx = virt_to_fix(vaddr);
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pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
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return pte_page(*pte);
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}
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EXPORT_SYMBOL(kmap);
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EXPORT_SYMBOL(kunmap);
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EXPORT_SYMBOL(kmap_atomic);
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EXPORT_SYMBOL(kunmap_atomic);
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EXPORT_SYMBOL(kmap_atomic_to_page);
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