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 */
9static 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 */
23static 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
41void 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 */
48void check_for_bios_corruption(void);
49void start_periodic_check_for_corruption(void);
50#else
51static inline void check_for_bios_corruption(void)
52{
53}
54
55static inline void start_periodic_check_for_corruption(void)
56{
57}
58#endif
59
60#endif /* _ASM_X86_BIOS_EBDA_H */
61