src/rseq.c

   1 // SPDX-License-Identifier: LGPL-2.1-only
   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 #ifndef _GNU_SOURCE
  18 #define _GNU_SOURCE
  19 #endif
  20 #include <errno.h>
  21 #include <sched.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <syscall.h>
  27 #include <assert.h>
  28 #include <signal.h>
  29 #include <limits.h>
  30
  31 #include <rseq/rseq.h>
  32
  33 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
  34
  35 __thread
  36 volatile struct rseq __rseq_abi = {
  37         .cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
  38 };
  39
  40 __thread
  41 volatile uint32_t __rseq_refcount;
  42
  43 static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
  44                     int flags, uint32_t sig)
  45 {
  46         return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
  47 }
  48
  49 int rseq_available(void)
  50 {
  51         int rc;
  52
  53         rc = sys_rseq(NULL, 0, 0, 0);
  54         if (rc != -1)
  55                 abort();
  56         switch (errno) {
  57         case ENOSYS:
  58                 return 0;
  59         case EINVAL:
  60                 return 1;
  61         default:
  62                 abort();
  63         }
  64 }
  65
  66 static void signal_off_save(sigset_t *oldset)
  67 {
  68         sigset_t set;
  69         int ret;
  70
  71         sigfillset(&set);
  72         ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
  73         if (ret)
  74                 abort();
  75 }
  76
  77 static void signal_restore(sigset_t oldset)
  78 {
  79         int ret;
  80
  81         ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
  82         if (ret)
  83                 abort();
  84 }
  85
  86 int rseq_register_current_thread(void)
  87 {
  88         int rc, ret = 0;
  89         sigset_t oldset;
  90
  91         signal_off_save(&oldset);
  92         if (__rseq_refcount == UINT_MAX) {
  93                 ret = -1;
  94                 goto end;
  95         }
  96         if (__rseq_refcount++)
  97                 goto end;
  98         rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
  99         if (!rc) {
 100                 assert(rseq_current_cpu_raw() >= 0);
 101                 goto end;
 102         }
 103         if (errno != EBUSY)
 104                 __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
 105         ret = -1;
 106         __rseq_refcount--;
 107 end:
 108         signal_restore(oldset);
 109         return ret;
 110 }
 111
 112 int rseq_unregister_current_thread(void)
 113 {
 114         int rc, ret = 0;
 115         sigset_t oldset;
 116
 117         signal_off_save(&oldset);
 118         if (!__rseq_refcount) {
 119                 ret = -1;
 120                 goto end;
 121         }
 122         if (--__rseq_refcount)
 123                 goto end;
 124         rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
 125                       RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
 126         if (!rc)
 127                 goto end;
 128         ret = -1;
 129 end:
 130         signal_restore(oldset);
 131         return ret;
 132 }
 133
 134 int32_t rseq_fallback_current_cpu(void)
 135 {
 136         int32_t cpu;
 137
 138         cpu = sched_getcpu();
 139         if (cpu < 0) {
 140                 perror("sched_getcpu()");
 141                 abort();
 142         }
 143         return cpu;
 144 }