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  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/mm.h>
 26#include <linux/highmem.h>
 27#include <asm/pgalloc.h>
 28#include <asm/cacheflush.h>
 29#include <asm/tlbflush.h>
 30#include <asm/fixmap.h>
 31
 32void *__kmap_atomic(struct page *page)
 33{
 34	unsigned long vaddr;
 35	long idx, type;
 36
 37	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
 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
 46/* XXX Fix - Anton */
 47#if 0
 48	__flush_cache_one(vaddr);
 49#else
 50	flush_cache_all();
 51#endif
 52
 53#ifdef CONFIG_DEBUG_HIGHMEM
 54	BUG_ON(!pte_none(*(kmap_pte-idx)));
 55#endif
 56	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
 57/* XXX Fix - Anton */
 58#if 0
 59	__flush_tlb_one(vaddr);
 60#else
 61	flush_tlb_all();
 62#endif
 63
 64	return (void*) vaddr;
 65}
 66EXPORT_SYMBOL(__kmap_atomic);
 67
 68void __kunmap_atomic(void *kvaddr)
 69{
 70	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 71	int type;
 72
 73	if (vaddr < FIXADDR_START) { // FIXME
 74		pagefault_enable();
 75		return;
 76	}
 77
 78	type = kmap_atomic_idx();
 79
 80#ifdef CONFIG_DEBUG_HIGHMEM
 81	{
 82		unsigned long idx;
 83
 84		idx = type + KM_TYPE_NR * smp_processor_id();
 85		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 86
 87		/* XXX Fix - Anton */
 88#if 0
 89		__flush_cache_one(vaddr);
 90#else
 91		flush_cache_all();
 92#endif
 93
 94		/*
 95		 * force other mappings to Oops if they'll try to access
 96		 * this pte without first remap it
 97		 */
 98		pte_clear(&init_mm, vaddr, kmap_pte-idx);
 99		/* XXX Fix - Anton */
100#if 0
101		__flush_tlb_one(vaddr);
102#else
103		flush_tlb_all();
104#endif
105	}
106#endif
107
108	kmap_atomic_idx_pop();
109	pagefault_enable();
110}
111EXPORT_SYMBOL(__kunmap_atomic);
112
113/* We may be fed a pagetable here by ptep_to_xxx and others. */
114struct page *kmap_atomic_to_page(void *ptr)
115{
116	unsigned long idx, vaddr = (unsigned long)ptr;
117	pte_t *pte;
118
119	if (vaddr < SRMMU_NOCACHE_VADDR)
120		return virt_to_page(ptr);
121	if (vaddr < PKMAP_BASE)
122		return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
123	BUG_ON(vaddr < FIXADDR_START);
124	BUG_ON(vaddr > FIXADDR_TOP);
125
126	idx = virt_to_fix(vaddr);
127	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
128	return pte_page(*pte);
129}