src/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 #include <limits.h>
  29
  30 #include <rseq/rseq.h>
  31
  32 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
  33
  34 __attribute__((weak)) __thread
  35 volatile struct rseq __rseq_abi = {
  36         .cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
  37 };
  38
  39 __attribute__((weak)) __thread
  40 volatile uint32_t __rseq_refcount;
  41
  42 static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
  43                     int flags, uint32_t sig)
  44 {
  45         return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
  46 }
  47
  48 int rseq_available(void)
  49 {
  50         int rc;
  51
  52         rc = sys_rseq(NULL, 0, 0, 0);
  53         if (rc != -1)
  54                 abort();
  55         switch (errno) {
  56         case ENOSYS:
  57                 return 0;
  58         case EINVAL:
  59                 return 1;
  60         default:
  61                 abort();
  62         }
  63 }
  64
  65 static void signal_off_save(sigset_t *oldset)
  66 {
  67         sigset_t set;
  68         int ret;
  69
  70         sigfillset(&set);
  71         ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
  72         if (ret)
  73                 abort();
  74 }
  75
  76 static void signal_restore(sigset_t oldset)
  77 {
  78         int ret;
  79
  80         ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
  81         if (ret)
  82                 abort();
  83 }
  84
  85 int rseq_register_current_thread(void)
  86 {
  87         int rc, ret = 0;
  88         sigset_t oldset;
  89
  90         signal_off_save(&oldset);
  91         if (__rseq_refcount == UINT_MAX) {
  92                 ret = -1;
  93                 goto end;
  94         }
  95         if (__rseq_refcount++)
  96                 goto end;
  97         rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
  98         if (!rc) {
  99                 assert(rseq_current_cpu_raw() >= 0);
 100                 goto end;
 101         }
 102         if (errno != EBUSY)
 103                 __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
 104         ret = -1;
 105         __rseq_refcount--;
 106 end:
 107         signal_restore(oldset);
 108         return ret;
 109 }
 110
 111 int rseq_unregister_current_thread(void)
 112 {
 113         int rc, ret = 0;
 114         sigset_t oldset;
 115
 116         signal_off_save(&oldset);
 117         if (!__rseq_refcount) {
 118                 ret = -1;
 119                 goto end;
 120         }
 121         if (--__rseq_refcount)
 122                 goto end;
 123         rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
 124                       RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
 125         if (!rc)
 126                 goto end;
 127         ret = -1;
 128 end:
 129         signal_restore(oldset);
 130         return ret;
 131 }
 132
 133 int32_t rseq_fallback_current_cpu(void)
 134 {
 135         int32_t cpu;
 136
 137         cpu = sched_getcpu();
 138         if (cpu < 0) {
 139                 perror("sched_getcpu()");
 140                 abort();
 141         }
 142         return cpu;
 143 }