1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * highmem.c: virtual kernel memory mappings for high memory
4 *
5 * Provides kernel-static versions of atomic kmap functions originally
6 * found as inlines in include/asm-sparc/highmem.h. These became
7 * needed as kmap_atomic() and kunmap_atomic() started getting
8 * called from within modules.
9 * -- Tomas Szepe <szepe@pinerecords.com>, September 2002
10 *
11 * But kmap_atomic() and kunmap_atomic() cannot be inlined in
12 * modules because they are loaded with btfixup-ped functions.
13 */
14
15 /*
16 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
17 * gives a more generic (and caching) interface. But kmap_atomic can
18 * be used in IRQ contexts, so in some (very limited) cases we need it.
19 *
20 * XXX This is an old text. Actually, it's good to use atomic kmaps,
21 * provided you remember that they are atomic and not try to sleep
22 * with a kmap taken, much like a spinlock. Non-atomic kmaps are
23 * shared by CPUs, and so precious, and establishing them requires IPI.
24 * Atomic kmaps are lightweight and we may have NCPUS more of them.
25 */
26 #include <linux/highmem.h>
27 #include <linux/export.h>
28 #include <linux/mm.h>
29
30 #include <asm/cacheflush.h>
31 #include <asm/tlbflush.h>
32 #include <asm/pgalloc.h>
33 #include <asm/vaddrs.h>
34
35 pgprot_t kmap_prot;
36
37 static pte_t *kmap_pte;
38
kmap_init(void)39 void __init kmap_init(void)
40 {
41 unsigned long address;
42 pmd_t *dir;
43
44 address = __fix_to_virt(FIX_KMAP_BEGIN);
45 dir = pmd_offset(pgd_offset_k(address), address);
46
47 /* cache the first kmap pte */
48 kmap_pte = pte_offset_kernel(dir, address);
49 kmap_prot = __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE);
50 }
51
kmap_atomic(struct page * page)52 void *kmap_atomic(struct page *page)
53 {
54 unsigned long vaddr;
55 long idx, type;
56
57 preempt_disable();
58 pagefault_disable();
59 if (!PageHighMem(page))
60 return page_address(page);
61
62 type = kmap_atomic_idx_push();
63 idx = type + KM_TYPE_NR*smp_processor_id();
64 vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
65
66 /* XXX Fix - Anton */
67 #if 0
68 __flush_cache_one(vaddr);
69 #else
70 flush_cache_all();
71 #endif
72
73 #ifdef CONFIG_DEBUG_HIGHMEM
74 BUG_ON(!pte_none(*(kmap_pte-idx)));
75 #endif
76 set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
77 /* XXX Fix - Anton */
78 #if 0
79 __flush_tlb_one(vaddr);
80 #else
81 flush_tlb_all();
82 #endif
83
84 return (void*) vaddr;
85 }
86 EXPORT_SYMBOL(kmap_atomic);
87
__kunmap_atomic(void * kvaddr)88 void __kunmap_atomic(void *kvaddr)
89 {
90 unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
91 int type;
92
93 if (vaddr < FIXADDR_START) { // FIXME
94 pagefault_enable();
95 preempt_enable();
96 return;
97 }
98
99 type = kmap_atomic_idx();
100
101 #ifdef CONFIG_DEBUG_HIGHMEM
102 {
103 unsigned long idx;
104
105 idx = type + KM_TYPE_NR * smp_processor_id();
106 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
107
108 /* XXX Fix - Anton */
109 #if 0
110 __flush_cache_one(vaddr);
111 #else
112 flush_cache_all();
113 #endif
114
115 /*
116 * force other mappings to Oops if they'll try to access
117 * this pte without first remap it
118 */
119 pte_clear(&init_mm, vaddr, kmap_pte-idx);
120 /* XXX Fix - Anton */
121 #if 0
122 __flush_tlb_one(vaddr);
123 #else
124 flush_tlb_all();
125 #endif
126 }
127 #endif
128
129 kmap_atomic_idx_pop();
130 pagefault_enable();
131 preempt_enable();
132 }
133 EXPORT_SYMBOL(__kunmap_atomic);
134
