GNU Linux-libre 4.9.296-gnu1
[releases.git] / arch / sparc / mm / highmem.c
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
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         preempt_disable();
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                 preempt_enable();
95                 return;
96         }
97
98         type = kmap_atomic_idx();
99
100 #ifdef CONFIG_DEBUG_HIGHMEM
101         {
102                 unsigned long idx;
103
104                 idx = type + KM_TYPE_NR * smp_processor_id();
105                 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
106
107                 /* XXX Fix - Anton */
108 #if 0
109                 __flush_cache_one(vaddr);
110 #else
111                 flush_cache_all();
112 #endif
113
114                 /*
115                  * force other mappings to Oops if they'll try to access
116                  * this pte without first remap it
117                  */
118                 pte_clear(&init_mm, vaddr, kmap_pte-idx);
119                 /* XXX Fix - Anton */
120 #if 0
121                 __flush_tlb_one(vaddr);
122 #else
123                 flush_tlb_all();
124 #endif
125         }
126 #endif
127
128         kmap_atomic_idx_pop();
129         pagefault_enable();
130         preempt_enable();
131 }
132 EXPORT_SYMBOL(__kunmap_atomic);