arch/x86/vdso/vgetcpu.c

   1 /*
   2  * Copyright 2006 Andi Kleen, SUSE Labs.
   3  * Subject to the GNU Public License, v.2
   4  *
   5  * Fast user context implementation of getcpu()
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/getcpu.h>
  10 #include <linux/jiffies.h>
  11 #include <linux/time.h>
  12 #include <asm/vsyscall.h>
  13 #include <asm/vgtod.h>
  14 #include "vextern.h"
  15
  16 notrace long
  17 __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
  18 {
  19         unsigned int p;
  20
  21         if (*vdso_vgetcpu_mode == VGETCPU_RDTSCP) {
  22                 /* Load per CPU data from RDTSCP */
  23                 native_read_tscp(&p);
  24         } else {
  25                 /* Load per CPU data from GDT */
  26                 asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
  27         }
  28         if (cpu)
  29                 *cpu = p & 0xfff;
  30         if (node)
  31                 *node = p >> 12;
  32         return 0;
  33 }
  34
  35 long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
  36         __attribute__((weak, alias("__vdso_getcpu")));