text: #ifndef _ASM_X86_64_VSYSCALL_H_
  #define _ASM_X86_64_VSYSCALL_H_
  
  #include <linux/seqlock.h>
  
  enum vsyscall_num {
  	__NR_vgettimeofday,
  	__NR_vtime,
  };
  
  #define VSYSCALL_START (-10UL << 20)
  #define VSYSCALL_SIZE 1024
  #define VSYSCALL_END (-2UL << 20)
  #define VSYSCALL_ADDR(vsyscall_nr) (VSYSCALL_START+VSYSCALL_SIZE*(vsyscall_nr))
  
  #ifdef __KERNEL__
  
  #define __section_vxtime __attribute__ ((unused, __section__ (".vxtime"), aligned(16)))
  #define __section_wall_jiffies __attribute__ ((unused, __section__ (".wall_jiffies"), aligned(16)))
  #define __section_jiffies __attribute__ ((unused, __section__ (".jiffies"), aligned(16)))
  #define __section_sys_tz __attribute__ ((unused, __section__ (".sys_tz"), aligned(16)))
  #define __section_sysctl_vsyscall __attribute__ ((unused, __section__ (".sysctl_vsyscall"), aligned(16)))
  #define __section_xtime __attribute__ ((unused, __section__ (".xtime"), aligned(16)))
  #define __section_xtime_lock __attribute__ ((unused, __section__ (".xtime_lock"), aligned(L1_CACHE_BYTES)))
  
  #define VXTIME_TSC	1
  #define VXTIME_HPET	2
  
  struct vxtime_data {
  	long hpet_address;	/* HPET base address */
  	unsigned long hz;	/* HPET clocks / sec */
  	int last;
  	unsigned long last_tsc;
  	long quot;
  	long tsc_quot;
  	int mode;
  };
  
  #define hpet_readl(a)           readl(fix_to_virt(FIX_HPET_BASE) + a)
  #define hpet_writel(d,a)        writel(d, fix_to_virt(FIX_HPET_BASE) + a)
  
  /* vsyscall space (readonly) */
  extern struct vxtime_data __vxtime;
  extern struct timespec __xtime;
  extern volatile unsigned long __jiffies;
  extern unsigned long __wall_jiffies;
  extern struct timezone __sys_tz;
  extern seqlock_t __xtime_lock;
  
  /* kernel space (writeable) */
  extern struct vxtime_data vxtime;
  extern unsigned long wall_jiffies;
  extern struct timezone sys_tz;
  extern int sysctl_vsyscall;
  extern seqlock_t xtime_lock;
  
  #define ARCH_HAVE_XTIME_LOCK 1
  
  #endif /* __KERNEL__ */
  
  #endif /* _ASM_X86_64_VSYSCALL_H_ */
  