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Linux/arch/sparc/mm/highmem.c

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  1 /*
  2  *  highmem.c: virtual kernel memory mappings for high memory
  3  *
  4  *  Provides kernel-static versions of atomic kmap functions originally
  5  *  found as inlines in include/asm-sparc/highmem.h.  These became
  6  *  needed as kmap_atomic() and kunmap_atomic() started getting
  7  *  called from within modules.
  8  *  -- Tomas Szepe <szepe@pinerecords.com>, September 2002
  9  *
 10  *  But kmap_atomic() and kunmap_atomic() cannot be inlined in
 11  *  modules because they are loaded with btfixup-ped functions.
 12  */
 13 
 14 /*
 15  * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
 16  * gives a more generic (and caching) interface. But kmap_atomic can
 17  * be used in IRQ contexts, so in some (very limited) cases we need it.
 18  *
 19  * XXX This is an old text. Actually, it's good to use atomic kmaps,
 20  * provided you remember that they are atomic and not try to sleep
 21  * with a kmap taken, much like a spinlock. Non-atomic kmaps are
 22  * shared by CPUs, and so precious, and establishing them requires IPI.
 23  * Atomic kmaps are lightweight and we may have NCPUS more of them.
 24  */
 25 #include <linux/mm.h>
 26 #include <linux/highmem.h>
 27 #include <asm/pgalloc.h>
 28 #include <asm/cacheflush.h>
 29 #include <asm/tlbflush.h>
 30 #include <asm/fixmap.h>
 31 
 32 void *kmap_atomic(struct page *page, enum km_type type)
 33 {
 34         unsigned long idx;
 35         unsigned long vaddr;
 36 
 37         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
 38         pagefault_disable();
 39         if (!PageHighMem(page))
 40                 return page_address(page);
 41 
 42         debug_kmap_atomic(type);
 43         idx = type + KM_TYPE_NR*smp_processor_id();
 44         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 45 
 46 /* XXX Fix - Anton */
 47 #if 0
 48         __flush_cache_one(vaddr);
 49 #else
 50         flush_cache_all();
 51 #endif
 52 
 53 #ifdef CONFIG_DEBUG_HIGHMEM
 54         BUG_ON(!pte_none(*(kmap_pte-idx)));
 55 #endif
 56         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
 57 /* XXX Fix - Anton */
 58 #if 0
 59         __flush_tlb_one(vaddr);
 60 #else
 61         flush_tlb_all();
 62 #endif
 63 
 64         return (void*) vaddr;
 65 }
 66 EXPORT_SYMBOL(kmap_atomic);
 67 
 68 void kunmap_atomic(void *kvaddr, enum km_type type)
 69 {
 70 #ifdef CONFIG_DEBUG_HIGHMEM
 71         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 72         unsigned long idx = type + KM_TYPE_NR*smp_processor_id();
 73 
 74         if (vaddr < FIXADDR_START) { // FIXME
 75                 pagefault_enable();
 76                 return;
 77         }
 78 
 79         BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 80 
 81 /* XXX Fix - Anton */
 82 #if 0
 83         __flush_cache_one(vaddr);
 84 #else
 85         flush_cache_all();
 86 #endif
 87 
 88         /*
 89          * force other mappings to Oops if they'll try to access
 90          * this pte without first remap it
 91          */
 92         pte_clear(&init_mm, vaddr, kmap_pte-idx);
 93 /* XXX Fix - Anton */
 94 #if 0
 95         __flush_tlb_one(vaddr);
 96 #else
 97         flush_tlb_all();
 98 #endif
 99 #endif
100 
101         pagefault_enable();
102 }
103 EXPORT_SYMBOL(kunmap_atomic);
104 
105 /* We may be fed a pagetable here by ptep_to_xxx and others. */
106 struct page *kmap_atomic_to_page(void *ptr)
107 {
108         unsigned long idx, vaddr = (unsigned long)ptr;
109         pte_t *pte;
110 
111         if (vaddr < SRMMU_NOCACHE_VADDR)
112                 return virt_to_page(ptr);
113         if (vaddr < PKMAP_BASE)
114                 return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
115         BUG_ON(vaddr < FIXADDR_START);
116         BUG_ON(vaddr > FIXADDR_TOP);
117 
118         idx = virt_to_fix(vaddr);
119         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
120         return pte_page(*pte);
121 }
122 

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