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
  34 volatile struct rseq __rseq_abi = {
  35         .cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
  36 };
  37
  38 static __attribute__((tls_model("initial-exec"))) __thread
  39 volatile int refcount;
  40
  41 static 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
  52 static 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
  61 static 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
  67 int 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--;
  84 end:
  85         signal_restore(oldset);
  86         return ret;
  87 }
  88
  89 int 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;
 102 end:
 103         signal_restore(oldset);
 104         return ret;
 105 }
 106
 107 int32_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 }