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/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
kmap_init(void)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
kmap_atomic(struct page * page)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
__kunmap_atomic(void * kvaddr)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);
131