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
signal_off_save(sigset_t * oldset)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
signal_restore(sigset_t oldset)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
sys_rseq(volatile struct rseq * rseq_abi,uint32_t rseq_len,int flags,uint32_t sig)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
rseq_register_current_thread(void)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
rseq_unregister_current_thread(void)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
rseq_fallback_current_cpu(void)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 }
118