vgetcpu.c

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/*
 * Copyright 2006 Andi Kleen, SUSE Labs.
 * Subject to the GNU Public License, v.2
 *
 * Fast user context implementation of getcpu()
 */

#include <linux/kernel.h>
#include <linux/getcpu.h>
#include <linux/jiffies.h>
#include <linux/time.h>
#include <asm/vsyscall.h>
#include <asm/vgtod.h>

notrace long
__vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
{
    unsigned int p;

    if (VVAR(vgetcpu_mode) == VGETCPU_RDTSCP) {
        /* Load per CPU data from RDTSCP */
        native_read_tscp(&p);
    } else {
        /* Load per CPU data from GDT */
        asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
    }
    if (cpu)
        *cpu = p & 0xfff;
    if (node)
        *node = p >> 12;
    return 0;
}

long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
    __attribute__((weak, alias("__vdso_getcpu")));