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
kmap_atomic(struct page * page,enum km_type type)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 idx = type + KM_TYPE_NR*smp_processor_id();
43 vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
44
45 /* XXX Fix - Anton */
46 #if 0
47 __flush_cache_one(vaddr);
48 #else
49 flush_cache_all();
50 #endif
51
52 #ifdef CONFIG_DEBUG_HIGHMEM
53 BUG_ON(!pte_none(*(kmap_pte-idx)));
54 #endif
55 set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
56 /* XXX Fix - Anton */
57 #if 0
58 __flush_tlb_one(vaddr);
59 #else
60 flush_tlb_all();
61 #endif
62
63 return (void*) vaddr;
64 }
65 EXPORT_SYMBOL(kmap_atomic);
66
kunmap_atomic(void * kvaddr,enum km_type type)67 void kunmap_atomic(void *kvaddr, enum km_type type)
68 {
69 #ifdef CONFIG_DEBUG_HIGHMEM
70 unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
71 unsigned long idx = type + KM_TYPE_NR*smp_processor_id();
72
73 if (vaddr < FIXADDR_START) { // FIXME
74 pagefault_enable();
75 return;
76 }
77
78 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
79
80 /* XXX Fix - Anton */
81 #if 0
82 __flush_cache_one(vaddr);
83 #else
84 flush_cache_all();
85 #endif
86
87 /*
88 * force other mappings to Oops if they'll try to access
89 * this pte without first remap it
90 */
91 pte_clear(&init_mm, vaddr, kmap_pte-idx);
92 /* XXX Fix - Anton */
93 #if 0
94 __flush_tlb_one(vaddr);
95 #else
96 flush_tlb_all();
97 #endif
98 #endif
99
100 pagefault_enable();
101 }
102 EXPORT_SYMBOL(kunmap_atomic);
103
104 /* We may be fed a pagetable here by ptep_to_xxx and others. */
kmap_atomic_to_page(void * ptr)105 struct page *kmap_atomic_to_page(void *ptr)
106 {
107 unsigned long idx, vaddr = (unsigned long)ptr;
108 pte_t *pte;
109
110 if (vaddr < SRMMU_NOCACHE_VADDR)
111 return virt_to_page(ptr);
112 if (vaddr < PKMAP_BASE)
113 return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
114 BUG_ON(vaddr < FIXADDR_START);
115 BUG_ON(vaddr > FIXADDR_TOP);
116
117 idx = virt_to_fix(vaddr);
118 pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
119 return pte_page(*pte);
120 }
121