arch/x86/include/asm/vgtod.h

   1 #ifndef _ASM_X86_VGTOD_H
   2 #define _ASM_X86_VGTOD_H
   3
   4 #include <linux/compiler.h>
   5 #include <linux/clocksource.h>
   6
   7 #ifdef BUILD_VDSO32_64
   8 typedef u64 gtod_long_t;
   9 #else
  10 typedef unsigned long gtod_long_t;
  11 #endif
  12 /*
  13  * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
  14  * so be carefull by modifying this structure.
  15  */
  16 struct vsyscall_gtod_data {
  17         unsigned seq;
  18
  19         int vclock_mode;
  20         u64     cycle_last;
  21         u64     mask;
  22         u32     mult;
  23         u32     shift;
  24
  25         /* open coded 'struct timespec' */
  26         u64             wall_time_snsec;
  27         gtod_long_t     wall_time_sec;
  28         gtod_long_t     monotonic_time_sec;
  29         u64             monotonic_time_snsec;
  30         gtod_long_t     wall_time_coarse_sec;
  31         gtod_long_t     wall_time_coarse_nsec;
  32         gtod_long_t     monotonic_time_coarse_sec;
  33         gtod_long_t     monotonic_time_coarse_nsec;
  34
  35         int             tz_minuteswest;
  36         int             tz_dsttime;
  37 };
  38 extern struct vsyscall_gtod_data vsyscall_gtod_data;
  39
  40 extern int vclocks_used;
  41 static inline bool vclock_was_used(int vclock)
  42 {
  43         return READ_ONCE(vclocks_used) & (1 << vclock);
  44 }
  45
  46 static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s)
  47 {
  48         unsigned ret;
  49
  50 repeat:
  51         ret = ACCESS_ONCE(s->seq);
  52         if (unlikely(ret & 1)) {
  53                 cpu_relax();
  54                 goto repeat;
  55         }
  56         smp_rmb();
  57         return ret;
  58 }
  59
  60 static inline int gtod_read_retry(const struct vsyscall_gtod_data *s,
  61                                         unsigned start)
  62 {
  63         smp_rmb();
  64         return unlikely(s->seq != start);
  65 }
  66
  67 static inline void gtod_write_begin(struct vsyscall_gtod_data *s)
  68 {
  69         ++s->seq;
  70         smp_wmb();
  71 }
  72
  73 static inline void gtod_write_end(struct vsyscall_gtod_data *s)
  74 {
  75         smp_wmb();
  76         ++s->seq;
  77 }
  78
  79 #ifdef CONFIG_X86_64
  80
  81 #define VGETCPU_CPU_MASK 0xfff
  82
  83 static inline unsigned int __getcpu(void)
  84 {
  85         unsigned int p;
  86
  87         /*
  88          * Load per CPU data from GDT.  LSL is faster than RDTSCP and
  89          * works on all CPUs.  This is volatile so that it orders
  90          * correctly wrt barrier() and to keep gcc from cleverly
  91          * hoisting it out of the calling function.
  92          *
  93          * If RDPID is available, use it.
  94          */
  95         alternative_io ("lsl %[p],%[seg]",
  96                         ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
  97                         X86_FEATURE_RDPID,
  98                         [p] "=a" (p), [seg] "r" (__PER_CPU_SEG));
  99
 100         return p;
 101 }
 102
 103 #endif /* CONFIG_X86_64 */
 104
 105 #endif /* _ASM_X86_VGTOD_H */