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 <linux/export.h>
 28#include <asm/pgalloc.h>
 29#include <asm/cacheflush.h>
 30#include <asm/tlbflush.h>
 31#include <asm/fixmap.h>
 32
 33void *kmap_atomic(struct page *page)
 34{
 35	unsigned long vaddr;
 36	long idx, type;
 37
 38	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
 39	pagefault_disable();
 40	if (!PageHighMem(page))
 41		return page_address(page);
 42
 43	type = kmap_atomic_idx_push();
 44	idx = type + KM_TYPE_NR*smp_processor_id();
 45	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 46
 47/* XXX Fix - Anton */
 48#if 0
 49	__flush_cache_one(vaddr);
 50#else
 51	flush_cache_all();
 52#endif
 53
 54#ifdef CONFIG_DEBUG_HIGHMEM
 55	BUG_ON(!pte_none(*(kmap_pte-idx)));
 56#endif
 57	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
 58/* XXX Fix - Anton */
 59#if 0
 60	__flush_tlb_one(vaddr);
 61#else
 62	flush_tlb_all();
 63#endif
 64
 65	return (void*) vaddr;
 66}
 67EXPORT_SYMBOL(kmap_atomic);
 68
 69void __kunmap_atomic(void *kvaddr)
 70{
 71	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
 72	int type;
 73
 74	if (vaddr < FIXADDR_START) { // FIXME
 75		pagefault_enable();
 76		return;
 77	}
 78
 79	type = kmap_atomic_idx();
 80
 81#ifdef CONFIG_DEBUG_HIGHMEM
 82	{
 83		unsigned long idx;
 84
 85		idx = type + KM_TYPE_NR * smp_processor_id();
 86		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 87
 88		/* XXX Fix - Anton */
 89#if 0
 90		__flush_cache_one(vaddr);
 91#else
 92		flush_cache_all();
 93#endif
 94
 95		/*
 96		 * force other mappings to Oops if they'll try to access
 97		 * this pte without first remap it
 98		 */
 99		pte_clear(&init_mm, vaddr, kmap_pte-idx);
100		/* XXX Fix - Anton */
101#if 0
102		__flush_tlb_one(vaddr);
103#else
104		flush_tlb_all();
105#endif
106	}
107#endif
108
109	kmap_atomic_idx_pop();
110	pagefault_enable();
111}
112EXPORT_SYMBOL(__kunmap_atomic);
113
114/* We may be fed a pagetable here by ptep_to_xxx and others. */
115struct page *kmap_atomic_to_page(void *ptr)
116{
117	unsigned long idx, vaddr = (unsigned long)ptr;
118	pte_t *pte;
119
120	if (vaddr < SRMMU_NOCACHE_VADDR)
121		return virt_to_page(ptr);
122	if (vaddr < PKMAP_BASE)
123		return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
124	BUG_ON(vaddr < FIXADDR_START);
125	BUG_ON(vaddr > FIXADDR_TOP);
126
127	idx = virt_to_fix(vaddr);
128	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
129	return pte_page(*pte);
130}