arch/x86/mm/init.c

   1 #include <linux/ioport.h>
   2 #include <linux/swap.h>
   3
   4 #include <asm/cacheflush.h>
   5 #include <asm/page.h>
   6 #include <asm/page_types.h>
   7 #include <asm/sections.h>
   8 #include <asm/system.h>
   9
  10 /*
  11  * devmem_is_allowed() checks to see if /dev/mem access to a certain address
  12  * is valid. The argument is a physical page number.
  13  *
  14  *
  15  * On x86, access has to be given to the first megabyte of ram because that area
  16  * contains bios code and data regions used by X and dosemu and similar apps.
  17  * Access has to be given to non-kernel-ram areas as well, these contain the PCI
  18  * mmio resources as well as potential bios/acpi data regions.
  19  */
  20 int devmem_is_allowed(unsigned long pagenr)
  21 {
  22         if (pagenr <= 256)
  23                 return 1;
  24         if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
  25                 return 0;
  26         if (!page_is_ram(pagenr))
  27                 return 1;
  28         return 0;
  29 }
  30
  31 void free_init_pages(char *what, unsigned long begin, unsigned long end)
  32 {
  33         unsigned long addr = begin;
  34
  35         if (addr >= end)
  36                 return;
  37
  38         /*
  39          * If debugging page accesses then do not free this memory but
  40          * mark them not present - any buggy init-section access will
  41          * create a kernel page fault:
  42          */
  43 #ifdef CONFIG_DEBUG_PAGEALLOC
  44         printk(KERN_INFO "debug: unmapping init memory %08lx..%08lx\n",
  45                 begin, PAGE_ALIGN(end));
  46         set_memory_np(begin, (end - begin) >> PAGE_SHIFT);
  47 #else
  48         /*
  49          * We just marked the kernel text read only above, now that
  50          * we are going to free part of that, we need to make that
  51          * writeable first.
  52          */
  53         set_memory_rw(begin, (end - begin) >> PAGE_SHIFT);
  54
  55         printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
  56
  57         for (; addr < end; addr += PAGE_SIZE) {
  58                 ClearPageReserved(virt_to_page(addr));
  59                 init_page_count(virt_to_page(addr));
  60                 memset((void *)(addr & ~(PAGE_SIZE-1)),
  61                         POISON_FREE_INITMEM, PAGE_SIZE);
  62                 free_page(addr);
  63                 totalram_pages++;
  64         }
  65 #endif
  66 }
  67
  68 void free_initmem(void)
  69 {
  70         free_init_pages("unused kernel memory",
  71                         (unsigned long)(&__init_begin),
  72                         (unsigned long)(&__init_end));
  73 }
  74
  75 #ifdef CONFIG_BLK_DEV_INITRD
  76 void free_initrd_mem(unsigned long start, unsigned long end)
  77 {
  78         free_init_pages("initrd memory", start, end);
  79 }
  80 #endif