arch/x86/include/asm/bios_ebda.h

   1 #ifndef _ASM_X86_BIOS_EBDA_H
   2 #define _ASM_X86_BIOS_EBDA_H
   3
   4 #include <asm/io.h>
   5
   6 /*
   7  * Returns physical address of EBDA.  Returns 0 if there is no EBDA.
   8  */
   9 static inline unsigned int get_bios_ebda(void)
  10 {
  11         /*
  12          * There is a real-mode segmented pointer pointing to the
  13          * 4K EBDA area at 0x40E.
  14          */
  15         unsigned int address = *(unsigned short *)phys_to_virt(0x40E);
  16         address <<= 4;
  17         return address; /* 0 means none */
  18 }
  19
  20 /*
  21  * Return the sanitized length of the EBDA in bytes, if it exists.
  22  */
  23 static inline unsigned int get_bios_ebda_length(void)
  24 {
  25         unsigned int address;
  26         unsigned int length;
  27
  28         address = get_bios_ebda();
  29         if (!address)
  30                 return 0;
  31
  32         /* EBDA length is byte 0 of the EBDA (stored in KiB) */
  33         length = *(unsigned char *)phys_to_virt(address);
  34         length <<= 10;
  35
  36         /* Trim the length if it extends beyond 640KiB */
  37         length = min_t(unsigned int, (640 * 1024) - address, length);
  38         return length;
  39 }
  40
  41 void reserve_ebda_region(void);
  42
  43 #ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION
  44 /*
  45  * This is obviously not a great place for this, but we want to be
  46  * able to scatter it around anywhere in the kernel.
  47  */
  48 void check_for_bios_corruption(void);
  49 void start_periodic_check_for_corruption(void);
  50 #else
  51 static inline void check_for_bios_corruption(void)
  52 {
  53 }
  54
  55 static inline void start_periodic_check_for_corruption(void)
  56 {
  57 }
  58 #endif
  59
  60 #endif /* _ASM_X86_BIOS_EBDA_H */