1/*
2 * Copyright 2013-2015, Michael Ellerman, IBM Corp.
3 * Licensed under GPLv2.
4 */
5
6#define _GNU_SOURCE	/* For CPU_ZERO etc. */
7
8#include <elf.h>
9#include <errno.h>
10#include <fcntl.h>
11#include <link.h>
12#include <sched.h>
13#include <stdio.h>
14#include <sys/stat.h>
15#include <sys/types.h>
16#include <unistd.h>
17
18#include "utils.h"
19
20static char auxv[4096];
21
22void *get_auxv_entry(int type)
23{
24	ElfW(auxv_t) *p;
25	void *result;
26	ssize_t num;
27	int fd;
28
29	fd = open("/proc/self/auxv", O_RDONLY);
30	if (fd == -1) {
31		perror("open");
32		return NULL;
33	}
34
35	result = NULL;
36
37	num = read(fd, auxv, sizeof(auxv));
38	if (num < 0) {
39		perror("read");
40		goto out;
41	}
42
43	if (num > sizeof(auxv)) {
44		printf("Overflowed auxv buffer\n");
45		goto out;
46	}
47
48	p = (ElfW(auxv_t) *)auxv;
49
50	while (p->a_type != AT_NULL) {
51		if (p->a_type == type) {
52			result = (void *)p->a_un.a_val;
53			break;
54		}
55
56		p++;
57	}
58out:
59	close(fd);
60	return result;
61}
62
63int pick_online_cpu(void)
64{
65	cpu_set_t mask;
66	int cpu;
67
68	CPU_ZERO(&mask);
69
70	if (sched_getaffinity(0, sizeof(mask), &mask)) {
71		perror("sched_getaffinity");
72		return -1;
73	}
74
75	/* We prefer a primary thread, but skip 0 */
76	for (cpu = 8; cpu < CPU_SETSIZE; cpu += 8)
77		if (CPU_ISSET(cpu, &mask))
78			return cpu;
79
80	/* Search for anything, but in reverse */
81	for (cpu = CPU_SETSIZE - 1; cpu >= 0; cpu--)
82		if (CPU_ISSET(cpu, &mask))
83			return cpu;
84
85	printf("No cpus in affinity mask?!\n");
86	return -1;
87}
88