arch/x86/include/asm/vgtod.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_X86_VGTOD_H
   3 #define _ASM_X86_VGTOD_H
   4
   5 #include <linux/compiler.h>
   6 #include <linux/clocksource.h>
   7
   8 #ifdef BUILD_VDSO32_64
   9 typedef u64 gtod_long_t;
  10 #else
  11 typedef unsigned long gtod_long_t;
  12 #endif
  13 /*
  14  * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time
  15  * so be carefull by modifying this structure.
  16  */
  17 struct vsyscall_gtod_data {
  18         unsigned seq;
  19
  20         int vclock_mode;
  21         u64     cycle_last;
  22         u64     mask;
  23         u32     mult;
  24         u32     shift;
  25
  26         /* open coded 'struct timespec' */
  27         u64             wall_time_snsec;
  28         gtod_long_t     wall_time_sec;
  29         gtod_long_t     monotonic_time_sec;
  30         u64             monotonic_time_snsec;
  31         gtod_long_t     wall_time_coarse_sec;
  32         gtod_long_t     wall_time_coarse_nsec;
  33         gtod_long_t     monotonic_time_coarse_sec;
  34         gtod_long_t     monotonic_time_coarse_nsec;
  35
  36         int             tz_minuteswest;
  37         int             tz_dsttime;
  38 };
  39 extern struct vsyscall_gtod_data vsyscall_gtod_data;
  40
  41 extern int vclocks_used;
  42 static inline bool vclock_was_used(int vclock)
  43 {
  44         return READ_ONCE(vclocks_used) & (1 << vclock);
  45 }
  46
  47 static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s)
  48 {
  49         unsigned ret;
  50
  51 repeat:
  52         ret = READ_ONCE(s->seq);
  53         if (unlikely(ret & 1)) {
  54                 cpu_relax();
  55                 goto repeat;
  56         }
  57         smp_rmb();
  58         return ret;
  59 }
  60
  61 static inline int gtod_read_retry(const struct vsyscall_gtod_data *s,
  62                                         unsigned start)
  63 {
  64         smp_rmb();
  65         return unlikely(s->seq != start);
  66 }
  67
  68 static inline void gtod_write_begin(struct vsyscall_gtod_data *s)
  69 {
  70         ++s->seq;
  71         smp_wmb();
  72 }
  73
  74 static inline void gtod_write_end(struct vsyscall_gtod_data *s)
  75 {
  76         smp_wmb();
  77         ++s->seq;
  78 }
  79
  80 #ifdef CONFIG_X86_64
  81
  82 #define VGETCPU_CPU_MASK 0xfff
  83
  84 static inline unsigned int __getcpu(void)
  85 {
  86         unsigned int p;
  87
  88         /*
  89          * Load per CPU data from GDT.  LSL is faster than RDTSCP and
  90          * works on all CPUs.  This is volatile so that it orders
  91          * correctly wrt barrier() and to keep gcc from cleverly
  92          * hoisting it out of the calling function.
  93          *
  94          * If RDPID is available, use it.
  95          */
  96         alternative_io ("lsl %[p],%[seg]",
  97                         ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
  98                         X86_FEATURE_RDPID,
  99                         [p] "=a" (p), [seg] "r" (__PER_CPU_SEG));
 100
 101         return p;
 102 }
 103
 104 #endif /* CONFIG_X86_64 */
 105
 106 #endif /* _ASM_X86_VGTOD_H */