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
15 notrace long
__vdso_getcpu(unsigned * cpu,unsigned * node,struct getcpu_cache * unused)16 __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
17 {
18 unsigned int p;
19
20 if (VVAR(vgetcpu_mode) == VGETCPU_RDTSCP) {
21 /* Load per CPU data from RDTSCP */
22 native_read_tscp(&p);
23 } else {
24 /* Load per CPU data from GDT */
25 asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
26 }
27 if (cpu)
28 *cpu = p & 0xfff;
29 if (node)
30 *node = p >> 12;
31 return 0;
32 }
33
34 long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
35 __attribute__((weak, alias("__vdso_getcpu")));
36