1 /*
2 * highmem.c: virtual kernel memory mappings for high memory
3 *
4 * PowerPC version, stolen from the i386 version.
5 *
6 * Used in CONFIG_HIGHMEM systems for memory pages which
7 * are not addressable by direct kernel virtual addresses.
8 *
9 * Copyright (C) 1999 Gerhard Wichert, Siemens AG
10 * Gerhard.Wichert@pdb.siemens.de
11 *
12 *
13 * Redesigned the x86 32-bit VM architecture to deal with
14 * up to 16 Terrabyte physical memory. With current x86 CPUs
15 * we now support up to 64 Gigabytes physical RAM.
16 *
17 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
18 *
19 * Reworked for PowerPC by various contributors. Moved from
20 * highmem.h by Benjamin Herrenschmidt (c) 2009 IBM Corp.
21 */
22
23 #include <linux/highmem.h>
24 #include <linux/module.h>
25
26 /*
27 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
28 * gives a more generic (and caching) interface. But kmap_atomic can
29 * be used in IRQ contexts, so in some (very limited) cases we need
30 * it.
31 */
kmap_atomic_prot(struct page * page,pgprot_t prot)32 void *kmap_atomic_prot(struct page *page, pgprot_t prot)
33 {
34 unsigned long vaddr;
35 int idx, type;
36
37 preempt_disable();
38 pagefault_disable();
39 if (!PageHighMem(page))
40 return page_address(page);
41
42 type = kmap_atomic_idx_push();
43 idx = type + KM_TYPE_NR*smp_processor_id();
44 vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
45 #ifdef CONFIG_DEBUG_HIGHMEM
46 BUG_ON(!pte_none(*(kmap_pte-idx)));
47 #endif
48 __set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot), 1);
49 local_flush_tlb_page(NULL, vaddr);
50
51 return (void*) vaddr;
52 }
53 EXPORT_SYMBOL(kmap_atomic_prot);
54
__kunmap_atomic(void * kvaddr)55 void __kunmap_atomic(void *kvaddr)
56 {
57 unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
58 int type;
59
60 if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
61 pagefault_enable();
62 preempt_enable();
63 return;
64 }
65
66 type = kmap_atomic_idx();
67
68 #ifdef CONFIG_DEBUG_HIGHMEM
69 {
70 unsigned int idx;
71
72 idx = type + KM_TYPE_NR * smp_processor_id();
73 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
74
75 /*
76 * force other mappings to Oops if they'll try to access
77 * this pte without first remap it
78 */
79 pte_clear(&init_mm, vaddr, kmap_pte-idx);
80 local_flush_tlb_page(NULL, vaddr);
81 }
82 #endif
83
84 kmap_atomic_idx_pop();
85 pagefault_enable();
86 preempt_enable();
87 }
88 EXPORT_SYMBOL(__kunmap_atomic);
89