LXR linux/tools/testing/selftests/rseq/rseq.c

   1// SPDX-License-Identifier: LGPL-2.1
   2/*
   3 * rseq.c
   4 *
   5 * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6 *
   7 * This library is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU Lesser General Public
   9 * License as published by the Free Software Foundation; only
  10 * version 2.1 of the License.
  11 *
  12 * This library is distributed in the hope that it will be useful,
  13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15 * Lesser General Public License for more details.
  16 */
  17
  18#define _GNU_SOURCE
  19#include <errno.h>
  20#include <sched.h>
  21#include <stdio.h>
  22#include <stdlib.h>
  23#include <string.h>
  24#include <unistd.h>
  25#include <syscall.h>
  26#include <assert.h>
  27#include <signal.h>
  28
  29#include "rseq.h"
  30
  31#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
  32
  33__attribute__((tls_model("initial-exec"))) __thread
  34volatile struct rseq __rseq_abi = {
  35        .cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
  36};
  37
  38static __attribute__((tls_model("initial-exec"))) __thread
  39volatile int refcount;
  40
  41static void signal_off_save(sigset_t *oldset)
  42{
  43        sigset_t set;
  44        int ret;
  45
  46        sigfillset(&set);
  47        ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
  48        if (ret)
  49                abort();
  50}
  51
  52static void signal_restore(sigset_t oldset)
  53{
  54        int ret;
  55
  56        ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
  57        if (ret)
  58                abort();
  59}
  60
  61static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
  62                    int flags, uint32_t sig)
  63{
  64        return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
  65}
  66
  67int rseq_register_current_thread(void)
  68{
  69        int rc, ret = 0;
  70        sigset_t oldset;
  71
  72        signal_off_save(&oldset);
  73        if (refcount++)
  74                goto end;
  75        rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
  76        if (!rc) {
  77                assert(rseq_current_cpu_raw() >= 0);
  78                goto end;
  79        }
  80        if (errno != EBUSY)
  81                __rseq_abi.cpu_id = -2;
  82        ret = -1;
  83        refcount--;
  84end:
  85        signal_restore(oldset);
  86        return ret;
  87}
  88
  89int rseq_unregister_current_thread(void)
  90{
  91        int rc, ret = 0;
  92        sigset_t oldset;
  93
  94        signal_off_save(&oldset);
  95        if (--refcount)
  96                goto end;
  97        rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
  98                      RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
  99        if (!rc)
 100                goto end;
 101        ret = -1;
 102end:
 103        signal_restore(oldset);
 104        return ret;
 105}
 106
 107int32_t rseq_fallback_current_cpu(void)
 108{
 109        int32_t cpu;
 110
 111        cpu = sched_getcpu();
 112        if (cpu < 0) {
 113                perror("sched_getcpu()");
 114                abort();
 115        }
 116        return cpu;
 117}
 118