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