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	preempt_disable();
 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		preempt_enable();
 95		return;
 96	}
 97
 98	type = kmap_atomic_idx();
 99
100#ifdef CONFIG_DEBUG_HIGHMEM
101	{
102		unsigned long idx;
103
104		idx = type + KM_TYPE_NR * smp_processor_id();
105		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
106
107		/* XXX Fix - Anton */
108#if 0
109		__flush_cache_one(vaddr);
110#else
111		flush_cache_all();
112#endif
113
114		/*
115		 * force other mappings to Oops if they'll try to access
116		 * this pte without first remap it
117		 */
118		pte_clear(&init_mm, vaddr, kmap_pte-idx);
119		/* XXX Fix - Anton */
120#if 0
121		__flush_tlb_one(vaddr);
122#else
123		flush_tlb_all();
124#endif
125	}
126#endif
127
128	kmap_atomic_idx_pop();
129	pagefault_enable();
130	preempt_enable();
131}
132EXPORT_SYMBOL(__kunmap_atomic);