arch/x86_64/mm/ioremap.c

   1 /*
   2  * arch/x86_64/mm/ioremap.c
   3  *
   4  * Re-map IO memory to kernel address space so that we can access it.
   5  * This is needed for high PCI addresses that aren't mapped in the
   6  * 640k-1MB IO memory area on PC's
   7  *
   8  * (C) Copyright 1995 1996 Linus Torvalds
   9  */
  10
  11 #include <linux/vmalloc.h>
  12 #include <asm/io.h>
  13 #include <asm/pgalloc.h>
  14
  15 static inline void remap_area_pte(pte_t * pte, unsigned long address, unsigned long size,
  16         unsigned long phys_addr, unsigned long flags)
  17 {
  18         unsigned long end;
  19
  20         address &= ~PMD_MASK;
  21         end = address + size;
  22         if (end > PMD_SIZE)
  23                 end = PMD_SIZE;
  24         if (address >= end)
  25                 BUG();
  26         do {
  27                 if (!pte_none(*pte)) {
  28                         printk("remap_area_pte: page already exists\n");
  29                         BUG();
  30                 }
  31                 set_pte(pte, mk_pte_phys(phys_addr, __pgprot(_PAGE_PRESENT | _PAGE_RW |
  32                                         _PAGE_GLOBAL | _PAGE_DIRTY | _PAGE_ACCESSED | flags)));
  33                 address += PAGE_SIZE;
  34                 phys_addr += PAGE_SIZE;
  35                 pte++;
  36         } while (address && (address < end));
  37 }
  38
  39 static inline int remap_area_pmd(pmd_t * pmd, unsigned long address, unsigned long size,
  40         unsigned long phys_addr, unsigned long flags)
  41 {
  42         unsigned long end;
  43
  44         address &= ~PGDIR_MASK;
  45         end = address + size;
  46         if (end > PGDIR_SIZE)
  47                 end = PGDIR_SIZE;
  48         phys_addr -= address;
  49         if (address >= end)
  50                 BUG();
  51         do {
  52                 pte_t * pte = pte_alloc(&init_mm, pmd, address);
  53                 if (!pte)
  54                         return -ENOMEM;
  55                 remap_area_pte(pte, address, end - address, address + phys_addr, flags);
  56                 address = (address + PMD_SIZE) & PMD_MASK;
  57                 pmd++;
  58         } while (address && (address < end));
  59         return 0;
  60 }
  61
  62 static int remap_area_pages(unsigned long address, unsigned long phys_addr,
  63                                  unsigned long size, unsigned long flags)
  64 {
  65         int error;
  66         pgd_t * dir;
  67         unsigned long end = address + size;
  68
  69         phys_addr -= address;
  70         dir = pgd_offset_k(address);
  71         flush_cache_all();
  72         if (address >= end)
  73                 BUG();
  74         spin_lock(&init_mm.page_table_lock);
  75         do {
  76                 pmd_t *pmd;
  77                 pmd = pmd_alloc(&init_mm, dir, address);
  78                 error = -ENOMEM;
  79                 if (!pmd)
  80                         break;
  81                 if (remap_area_pmd(pmd, address, end - address,
  82                                          phys_addr + address, flags))
  83                         break;
  84                 error = 0;
  85                 address = (address + PGDIR_SIZE) & PGDIR_MASK;
  86                 dir++;
  87         } while (address && (address < end));
  88         spin_unlock(&init_mm.page_table_lock);
  89         flush_tlb_all();
  90         return error;
  91 }
  92
  93 /*
  94  * Generic mapping function (not visible outside):
  95  */
  96
  97 /*
  98  * Remap an arbitrary physical address space into the kernel virtual
  99  * address space. Needed when the kernel wants to access high addresses
 100  * directly.
 101  *
 102  * NOTE! We need to allow non-page-aligned mappings too: we will obviously
 103  * have to convert them into an offset in a page-aligned mapping, but the
 104  * caller shouldn't need to know that small detail.
 105  */
 106 void * __ioremap(unsigned long phys_addr, unsigned long size, unsigned long flags)
 107 {
 108         void * addr;
 109         struct vm_struct * area;
 110         unsigned long offset, last_addr;
 111
 112         /* Don't allow wraparound or zero size */
 113         last_addr = phys_addr + size - 1;
 114         if (!size || last_addr < phys_addr)
 115                 return NULL;
 116
 117         /*
 118          * Don't remap the low PCI/ISA area, it's always mapped..
 119          */
 120         if (phys_addr >= 0xA0000 && last_addr < 0x100000)
 121                 return phys_to_virt(phys_addr);
 122
 123         /*
 124          * Don't allow anybody to remap normal RAM that we're using..
 125          */
 126         if (phys_addr < virt_to_phys(high_memory)) {
 127                 char *t_addr, *t_end;
 128
 129                 t_addr = __va(phys_addr);
 130                 t_end = t_addr + (size - 1);
 131
 132 #ifndef CONFIG_DISCONTIGMEM
 133                 struct page *page;
 134                 for(page = virt_to_page(t_addr); page <= virt_to_page(t_end); page++)
 135                         if(!PageReserved(page))
 136                                 return NULL;
 137 #endif
 138         }
 139
 140         /*
 141          * Mappings have to be page-aligned
 142          */
 143         offset = phys_addr & ~PAGE_MASK;
 144         phys_addr &= PAGE_MASK;
 145         size = PAGE_ALIGN(last_addr + 1) - phys_addr;
 146
 147         /*
 148          * Ok, go for it..
 149          */
 150         area = get_vm_area(size, VM_IOREMAP);
 151         if (!area)
 152                 return NULL;
 153         addr = area->addr;
 154         if (remap_area_pages(VMALLOC_VMADDR(addr), phys_addr, size, flags)) {
 155                 vfree(addr);
 156                 return NULL;
 157         }
 158         return (void *) (offset + (char *)addr);
 159 }
 160
 161 void iounmap(void *addr)
 162 {
 163         if (addr > high_memory)
 164                 return vfree((void *) (PAGE_MASK & (unsigned long) addr));
 165 }