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