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/*
* Copyright 2013-2015, Michael Ellerman, IBM Corp.
* Licensed under GPLv2.
*/
#define _GNU_SOURCE /* For CPU_ZERO etc. */
#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <link.h>
#include <sched.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include "utils.h"
static char auxv[4096];
int read_auxv(char *buf, ssize_t buf_size)
{
ssize_t num;
int rc, fd;
fd = open("/proc/self/auxv", O_RDONLY);
if (fd == -1) {
perror("open");
return -errno;
}
num = read(fd, buf, buf_size);
if (num < 0) {
perror("read");
rc = -EIO;
goto out;
}
if (num > buf_size) {
printf("overflowed auxv buffer\n");
rc = -EOVERFLOW;
goto out;
}
rc = 0;
out:
close(fd);
return rc;
}
void *find_auxv_entry(int type, char *auxv)
{
ElfW(auxv_t) *p;
p = (ElfW(auxv_t) *)auxv;
while (p->a_type != AT_NULL) {
if (p->a_type == type)
return p;
p++;
}
return NULL;
}
void *get_auxv_entry(int type)
{
ElfW(auxv_t) *p;
if (read_auxv(auxv, sizeof(auxv)))
return NULL;
p = find_auxv_entry(type, auxv);
if (p)
return (void *)p->a_un.a_val;
return NULL;
}
int pick_online_cpu(void)
{
cpu_set_t mask;
int cpu;
CPU_ZERO(&mask);
if (sched_getaffinity(0, sizeof(mask), &mask)) {
perror("sched_getaffinity");
return -1;
}
/* We prefer a primary thread, but skip 0 */
for (cpu = 8; cpu < CPU_SETSIZE; cpu += 8)
if (CPU_ISSET(cpu, &mask))
return cpu;
/* Search for anything, but in reverse */
for (cpu = CPU_SETSIZE - 1; cpu >= 0; cpu--)
if (CPU_ISSET(cpu, &mask))
return cpu;
printf("No cpus in affinity mask?!\n");
return -1;
}
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