1. 根目录:
2. arch
3. x86
4. include
5. asm
6. vgtod.h

#ifndef _ASM_X86_VGTOD_H
#define _ASM_X86_VGTOD_H

#include <asm/vsyscall.h>
#include <linux/clocksource.h>

struct vsyscall_gtod_data {
	seqlock_t	lock;

	/* open coded 'struct timespec' */
	time_t		wall_time_sec;
	u32		wall_time_nsec;

	int		sysctl_enabled;
	struct timezone sys_tz;
	struct { /* extract of a clocksource struct */
		cycle_t (*vread)(void);
		cycle_t	cycle_last;
		cycle_t	mask;
		u32	mult;
		u32	shift;
	} clock;
	struct timespec wall_to_monotonic;
	struct timespec wall_time_coarse;
};
extern struct vsyscall_gtod_data __vsyscall_gtod_data
__section_vsyscall_gtod_data;
extern struct vsyscall_gtod_data vsyscall_gtod_data;

#endif /* _ASM_X86_VGTOD_H */