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
34pgprot_t kmap_prot;
35
36static pte_t *kmap_pte;
37
38void __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
51void *kmap_atomic(struct page *page)
52{
53	unsigned long vaddr;
54	long idx, type;
55
56	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
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}
85EXPORT_SYMBOL(kmap_atomic);
86
87void __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		return;
95	}
96
97	type = kmap_atomic_idx();
98
99#ifdef CONFIG_DEBUG_HIGHMEM
100	{
101		unsigned long idx;
102
103		idx = type + KM_TYPE_NR * smp_processor_id();
104		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
105
106		/* XXX Fix - Anton */
107#if 0
108		__flush_cache_one(vaddr);
109#else
110		flush_cache_all();
111#endif
112
113		/*
114		 * force other mappings to Oops if they'll try to access
115		 * this pte without first remap it
116		 */
117		pte_clear(&init_mm, vaddr, kmap_pte-idx);
118		/* XXX Fix - Anton */
119#if 0
120		__flush_tlb_one(vaddr);
121#else
122		flush_tlb_all();
123#endif
124	}
125#endif
126
127	kmap_atomic_idx_pop();
128	pagefault_enable();
129}
130EXPORT_SYMBOL(__kunmap_atomic);
131