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/pgalloc.h>
  33 #include <asm/vaddrs.h>
  34
  35 pgprot_t kmap_prot;
  36
  37 static pte_t *kmap_pte;
  38
  39 void __init kmap_init(void)
  40 {
  41         unsigned long address;
  42         p4d_t *p4d;
  43         pud_t *pud;
  44         pmd_t *dir;
  45
  46         address = __fix_to_virt(FIX_KMAP_BEGIN);
  47         p4d = p4d_offset(pgd_offset_k(address), address);
  48         pud = pud_offset(p4d, address);
  49         dir = pmd_offset(pud, address);
  50
  51         /* cache the first kmap pte */
  52         kmap_pte = pte_offset_kernel(dir, address);
  53         kmap_prot = __pgprot(SRMMU_ET_PTE | SRMMU_PRIV | SRMMU_CACHE);
  54 }
  55
  56 void *kmap_atomic(struct page *page)
  57 {
  58         unsigned long vaddr;
  59         long idx, type;
  60
  61         preempt_disable();
  62         pagefault_disable();
  63         if (!PageHighMem(page))
  64                 return page_address(page);
  65
  66         type = kmap_atomic_idx_push();
  67         idx = type + KM_TYPE_NR*smp_processor_id();
  68         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  69
  70 /* XXX Fix - Anton */
  71 #if 0
  72         __flush_cache_one(vaddr);
  73 #else
  74         flush_cache_all();
  75 #endif
  76
  77 #ifdef CONFIG_DEBUG_HIGHMEM
  78         BUG_ON(!pte_none(*(kmap_pte-idx)));
  79 #endif
  80         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
  81 /* XXX Fix - Anton */
  82 #if 0
  83         __flush_tlb_one(vaddr);
  84 #else
  85         flush_tlb_all();
  86 #endif
  87
  88         return (void*) vaddr;
  89 }
  90 EXPORT_SYMBOL(kmap_atomic);
  91
  92 void __kunmap_atomic(void *kvaddr)
  93 {
  94         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  95         int type;
  96
  97         if (vaddr < FIXADDR_START) { // FIXME
  98                 pagefault_enable();
  99                 preempt_enable();
 100                 return;
 101         }
 102
 103         type = kmap_atomic_idx();
 104
 105 #ifdef CONFIG_DEBUG_HIGHMEM
 106         {
 107                 unsigned long idx;
 108
 109                 idx = type + KM_TYPE_NR * smp_processor_id();
 110                 BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
 111
 112                 /* XXX Fix - Anton */
 113 #if 0
 114                 __flush_cache_one(vaddr);
 115 #else
 116                 flush_cache_all();
 117 #endif
 118
 119                 /*
 120                  * force other mappings to Oops if they'll try to access
 121                  * this pte without first remap it
 122                  */
 123                 pte_clear(&init_mm, vaddr, kmap_pte-idx);
 124                 /* XXX Fix - Anton */
 125 #if 0
 126                 __flush_tlb_one(vaddr);
 127 #else
 128                 flush_tlb_all();
 129 #endif
 130         }
 131 #endif
 132
 133         kmap_atomic_idx_pop();
 134         pagefault_enable();
 135         preempt_enable();
 136 }
 137 EXPORT_SYMBOL(__kunmap_atomic);