tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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/export.h>
24#include <linux/highmem.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 */
32#include <asm/tlbflush.h>
33
34void *kmap_atomic_prot(struct page *page, pgprot_t prot)
35{
36
37 unsigned long vaddr;
38 int idx, type;
39
40 preempt_disable();
41 pagefault_disable();
42 if (!PageHighMem(page))
43 return page_address(page);
44
45
46 type = kmap_atomic_idx_push();
47 idx = type + KM_TYPE_NR*smp_processor_id();
48 vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
49#ifdef CONFIG_DEBUG_HIGHMEM
50 BUG_ON(!pte_none(*(kmap_pte-idx)));
51#endif
52 set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
53 local_flush_tlb_page(NULL, vaddr);
54
55 return (void *) vaddr;
56}
57EXPORT_SYMBOL(kmap_atomic_prot);
58
59void __kunmap_atomic(void *kvaddr)
60{
61 unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
62 int type;
63
64 if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
65 pagefault_enable();
66 preempt_enable();
67 return;
68 }
69
70 type = kmap_atomic_idx();
71#ifdef CONFIG_DEBUG_HIGHMEM
72 {
73 unsigned int idx;
74
75 idx = type + KM_TYPE_NR * smp_processor_id();
76 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
77
78 /*
79 * force other mappings to Oops if they'll try to access
80 * this pte without first remap it
81 */
82 pte_clear(&init_mm, vaddr, kmap_pte-idx);
83 local_flush_tlb_page(NULL, vaddr);
84 }
85#endif
86 kmap_atomic_idx_pop();
87 pagefault_enable();
88 preempt_enable();
89}
90EXPORT_SYMBOL(__kunmap_atomic);