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 */ 61