arch/xtensa/mm/highmem.c

   1 /*
   2  * High memory support for Xtensa architecture
   3  *
   4  * This file is subject to the terms and conditions of the GNU General
   5  * Public License.  See the file "COPYING" in the main directory of
   6  * this archive for more details.
   7  *
   8  * Copyright (C) 2014 Cadence Design Systems Inc.
   9  */
  10
  11 #include <linux/export.h>
  12 #include <linux/highmem.h>
  13 #include <asm/tlbflush.h>
  14
  15 static pte_t *kmap_pte;
  16
  17 void *kmap_atomic(struct page *page)
  18 {
  19         enum fixed_addresses idx;
  20         unsigned long vaddr;
  21         int type;
  22
  23         pagefault_disable();
  24         if (!PageHighMem(page))
  25                 return page_address(page);
  26
  27         type = kmap_atomic_idx_push();
  28         idx = type + KM_TYPE_NR * smp_processor_id();
  29         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  30 #ifdef CONFIG_DEBUG_HIGHMEM
  31         BUG_ON(!pte_none(*(kmap_pte - idx)));
  32 #endif
  33         set_pte(kmap_pte - idx, mk_pte(page, PAGE_KERNEL_EXEC));
  34
  35         return (void *)vaddr;
  36 }
  37 EXPORT_SYMBOL(kmap_atomic);
  38
  39 void __kunmap_atomic(void *kvaddr)
  40 {
  41         int idx, type;
  42
  43         if (kvaddr >= (void *)FIXADDR_START &&
  44             kvaddr < (void *)FIXADDR_TOP) {
  45                 type = kmap_atomic_idx();
  46                 idx = type + KM_TYPE_NR * smp_processor_id();
  47
  48                 /*
  49                  * Force other mappings to Oops if they'll try to access this
  50                  * pte without first remap it.  Keeping stale mappings around
  51                  * is a bad idea also, in case the page changes cacheability
  52                  * attributes or becomes a protected page in a hypervisor.
  53                  */
  54                 pte_clear(&init_mm, kvaddr, kmap_pte - idx);
  55                 local_flush_tlb_kernel_range((unsigned long)kvaddr,
  56                                              (unsigned long)kvaddr + PAGE_SIZE);
  57
  58                 kmap_atomic_idx_pop();
  59         }
  60
  61         pagefault_enable();
  62 }
  63 EXPORT_SYMBOL(__kunmap_atomic);
  64
  65 void __init kmap_init(void)
  66 {
  67         unsigned long kmap_vstart;
  68
  69         /* cache the first kmap pte */
  70         kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
  71         kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
  72 }