Linux Kernel  3.7.1
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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 <[email protected]>, 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/highmem.h>
26 #include <linux/export.h>
27 #include <linux/mm.h>
28 
29 #include <asm/cacheflush.h>
30 #include <asm/tlbflush.h>
31 #include <asm/pgalloc.h>
32 #include <asm/vaddrs.h>
33 
34 pgprot_t kmap_prot;
35 
36 static pte_t *kmap_pte;
37 
38 void __init kmap_init(void)
39 {
40  unsigned long address;
41  pmd_t *dir;
42 
43  address = __fix_to_virt(FIX_KMAP_BEGIN);
44  dir = pmd_offset(pgd_offset_k(address), address);
45 
46  /* cache the first kmap pte */
47  kmap_pte = pte_offset_kernel(dir, address);
48  kmap_prot = __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE);
49 }
50 
51 void *kmap_atomic(struct page *page)
52 {
53  unsigned long vaddr;
54  long idx, type;
55 
56  /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
57  pagefault_disable();
58  if (!PageHighMem(page))
59  return page_address(page);
60 
61  type = kmap_atomic_idx_push();
62  idx = type + KM_TYPE_NR*smp_processor_id();
63  vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
64 
65 /* XXX Fix - Anton */
66 #if 0
67  __flush_cache_one(vaddr);
68 #else
69  flush_cache_all();
70 #endif
71 
72 #ifdef CONFIG_DEBUG_HIGHMEM
73  BUG_ON(!pte_none(*(kmap_pte-idx)));
74 #endif
75  set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
76 /* XXX Fix - Anton */
77 #if 0
78  __flush_tlb_one(vaddr);
79 #else
80  flush_tlb_all();
81 #endif
82 
83  return (void*) vaddr;
84 }
85 EXPORT_SYMBOL(kmap_atomic);
86 
87 void __kunmap_atomic(void *kvaddr)
88 {
89  unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
90  int type;
91 
92  if (vaddr < FIXADDR_START) { // FIXME
93  pagefault_enable();
94  return;
95  }
96 
97  type = kmap_atomic_idx();
98 
99 #ifdef CONFIG_DEBUG_HIGHMEM
100  {
101  unsigned long idx;
102 
103  idx = type + KM_TYPE_NR * smp_processor_id();
104  BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
105 
106  /* XXX Fix - Anton */
107 #if 0
108  __flush_cache_one(vaddr);
109 #else
110  flush_cache_all();
111 #endif
112 
113  /*
114  * force other mappings to Oops if they'll try to access
115  * this pte without first remap it
116  */
117  pte_clear(&init_mm, vaddr, kmap_pte-idx);
118  /* XXX Fix - Anton */
119 #if 0
120  __flush_tlb_one(vaddr);
121 #else
122  flush_tlb_all();
123 #endif
124  }
125 #endif
126 
127  kmap_atomic_idx_pop();
128  pagefault_enable();
129 }
130 EXPORT_SYMBOL(__kunmap_atomic);
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