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 #include <limits.h>
  29
  30 #include "rseq.h"
  31
  32 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
  33
  34 __thread volatile struct rseq __rseq_abi = {
  35         .cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
  36 };
  37
  38 /*
  39  * Shared with other libraries. This library may take rseq ownership if it is
  40  * still 0 when executing the library constructor. Set to 1 by library
  41  * constructor when handling rseq. Set to 0 in destructor if handling rseq.
  42  */
  43 int __rseq_handled;
  44
  45 /* Whether this library have ownership of rseq registration. */
  46 static int rseq_ownership;
  47
  48 static __thread volatile uint32_t __rseq_refcount;
  49
  50 static void signal_off_save(sigset_t *oldset)
  51 {
  52         sigset_t set;
  53         int ret;
  54
  55         sigfillset(&set);
  56         ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
  57         if (ret)
  58                 abort();
  59 }
  60
  61 static void signal_restore(sigset_t oldset)
  62 {
  63         int ret;
  64
  65         ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
  66         if (ret)
  67                 abort();
  68 }
  69
  70 static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
  71                     int flags, uint32_t sig)
  72 {
  73         return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
  74 }
  75
  76 int rseq_register_current_thread(void)
  77 {
  78         int rc, ret = 0;
  79         sigset_t oldset;
  80
  81         if (!rseq_ownership)
  82                 return 0;
  83         signal_off_save(&oldset);
  84         if (__rseq_refcount == UINT_MAX) {
  85                 ret = -1;
  86                 goto end;
  87         }
  88         if (__rseq_refcount++)
  89                 goto end;
  90         rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
  91         if (!rc) {
  92                 assert(rseq_current_cpu_raw() >= 0);
  93                 goto end;
  94         }
  95         if (errno != EBUSY)
  96                 __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
  97         ret = -1;
  98         __rseq_refcount--;
  99 end:
 100         signal_restore(oldset);
 101         return ret;
 102 }
 103
 104 int rseq_unregister_current_thread(void)
 105 {
 106         int rc, ret = 0;
 107         sigset_t oldset;
 108
 109         if (!rseq_ownership)
 110                 return 0;
 111         signal_off_save(&oldset);
 112         if (!__rseq_refcount) {
 113                 ret = -1;
 114                 goto end;
 115         }
 116         if (--__rseq_refcount)
 117                 goto end;
 118         rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
 119                       RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
 120         if (!rc)
 121                 goto end;
 122         __rseq_refcount = 1;
 123         ret = -1;
 124 end:
 125         signal_restore(oldset);
 126         return ret;
 127 }
 128
 129 int32_t rseq_fallback_current_cpu(void)
 130 {
 131         int32_t cpu;
 132
 133         cpu = sched_getcpu();
 134         if (cpu < 0) {
 135                 perror("sched_getcpu()");
 136                 abort();
 137         }
 138         return cpu;
 139 }
 140
 141 void __attribute__((constructor)) rseq_init(void)
 142 {
 143         /* Check whether rseq is handled by another library. */
 144         if (__rseq_handled)
 145                 return;
 146         __rseq_handled = 1;
 147         rseq_ownership = 1;
 148 }
 149
 150 void __attribute__((destructor)) rseq_fini(void)
 151 {
 152         if (!rseq_ownership)
 153                 return;
 154         __rseq_handled = 0;
 155         rseq_ownership = 0;
 156 }