arch/sparc/mm/highmem.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  highmem.c: virtual kernel memory mappings for high memory
   4  *
   5  *  Provides kernel-static versions of atomic kmap functions originally
   6  *  found as inlines in include/asm-sparc/highmem.h.  These became
   7  *  needed as kmap_atomic() and kunmap_atomic() started getting
   8  *  called from within modules.
   9  *  -- Tomas Szepe <szepe@pinerecords.com>, September 2002
  10  *
  11  *  But kmap_atomic() and kunmap_atomic() cannot be inlined in
  12  *  modules because they are loaded with btfixup-ped functions.
  13  */
  14
  15 /*
  16  * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
  17  * gives a more generic (and caching) interface. But kmap_atomic can
  18  * be used in IRQ contexts, so in some (very limited) cases we need it.
  19  *
  20  * XXX This is an old text. Actually, it's good to use atomic kmaps,
  21  * provided you remember that they are atomic and not try to sleep
  22  * with a kmap taken, much like a spinlock. Non-atomic kmaps are
  23  * shared by CPUs, and so precious, and establishing them requires IPI.
  24  * Atomic kmaps are lightweight and we may have NCPUS more of them.
  25  */
  26 #include <linux/highmem.h>
  27 #include <linux/export.h>
  28 #include <linux/mm.h>
  29
  30 #include <asm/cacheflush.h>
  31 #include <asm/tlbflush.h>
  32 #include <asm/vaddrs.h>
  33
  34 static pte_t *kmap_pte;
  35
  36 void __init kmap_init(void)
  37 {
  38         unsigned long address = __fix_to_virt(FIX_KMAP_BEGIN);
  39
  40         /* cache the first kmap pte */
  41         kmap_pte = virt_to_kpte(address);
  42 }
  43
  44 void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
  45 {
  46         unsigned long vaddr;
  47         long idx, type;
  48
  49         type = kmap_atomic_idx_push();
  50         idx = type + KM_TYPE_NR*smp_processor_id();
  51         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  52
  53 /* XXX Fix - Anton */
  54 #if 0
  55         __flush_cache_one(vaddr);
  56 #else
  57         flush_cache_all();
  58 #endif
  59
  60 #ifdef CONFIG_DEBUG_HIGHMEM
  61         BUG_ON(!pte_none(*(kmap_pte-idx)));
  62 #endif
  63         set_pte(kmap_pte-idx, mk_pte(page, prot));
  64 /* XXX Fix - Anton */
  65 #if 0
  66         __flush_tlb_one(vaddr);
  67 #else
  68         flush_tlb_all();
  69 #endif
  70
  71         return (void*) vaddr;
  72 }
  73 EXPORT_SYMBOL(kmap_atomic_high_prot);
  74
  75 void kunmap_atomic_high(void *kvaddr)
  76 {
  77         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  78         int type;
  79
  80         if (vaddr < FIXADDR_START)
  81                 return;
  82
  83         type = kmap_atomic_idx();
  84
  85 #ifdef CONFIG_DEBUG_HIGHMEM
  86         {
  87                 unsigned long idx;
  88
  89                 idx = type + KM_TYPE_NR * smp_processor_id();
  90                 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
  91
  92                 /* XXX Fix - Anton */
  93 #if 0
  94                 __flush_cache_one(vaddr);
  95 #else
  96                 flush_cache_all();
  97 #endif
  98
  99                 /*
 100                  * force other mappings to Oops if they'll try to access
 101                  * this pte without first remap it
 102                  */
 103                 pte_clear(&init_mm, vaddr, kmap_pte-idx);
 104                 /* XXX Fix - Anton */
 105 #if 0
 106                 __flush_tlb_one(vaddr);
 107 #else
 108                 flush_tlb_all();
 109 #endif
 110         }
 111 #endif
 112
 113         kmap_atomic_idx_pop();
 114 }
 115 EXPORT_SYMBOL(kunmap_atomic_high);