1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
2 /*
3 * rseq.h
4 *
5 * (C) Copyright 2016-2018 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 */
7
8 #ifndef RSEQ_H
9 #define RSEQ_H
10
11 #include <stdint.h>
12 #include <stdbool.h>
13 #include <pthread.h>
14 #include <signal.h>
15 #include <sched.h>
16 #include <errno.h>
17 #include <stdio.h>
18 #include <stdlib.h>
19 #include <linux/rseq.h>
20
21 /*
22 * Empty code injection macros, override when testing.
23 * It is important to consider that the ASM injection macros need to be
24 * fully reentrant (e.g. do not modify the stack).
25 */
26 #ifndef RSEQ_INJECT_ASM
27 #define RSEQ_INJECT_ASM(n)
28 #endif
29
30 #ifndef RSEQ_INJECT_C
31 #define RSEQ_INJECT_C(n)
32 #endif
33
34 #ifndef RSEQ_INJECT_INPUT
35 #define RSEQ_INJECT_INPUT
36 #endif
37
38 #ifndef RSEQ_INJECT_CLOBBER
39 #define RSEQ_INJECT_CLOBBER
40 #endif
41
42 #ifndef RSEQ_INJECT_FAILED
43 #define RSEQ_INJECT_FAILED
44 #endif
45
46 extern __thread volatile struct rseq __rseq_abi;
47 extern int __rseq_handled;
48
49 #define rseq_likely(x) __builtin_expect(!!(x), 1)
50 #define rseq_unlikely(x) __builtin_expect(!!(x), 0)
51 #define rseq_barrier() __asm__ __volatile__("" : : : "memory")
52
53 #define RSEQ_ACCESS_ONCE(x) (*(__volatile__ __typeof__(x) *)&(x))
54 #define RSEQ_WRITE_ONCE(x, v) __extension__ ({ RSEQ_ACCESS_ONCE(x) = (v); })
55 #define RSEQ_READ_ONCE(x) RSEQ_ACCESS_ONCE(x)
56
57 #define __rseq_str_1(x) #x
58 #define __rseq_str(x) __rseq_str_1(x)
59
60 #define rseq_log(fmt, args...) \
61 fprintf(stderr, fmt "(in %s() at " __FILE__ ":" __rseq_str(__LINE__)"\n", \
62 ## args, __func__)
63
64 #define rseq_bug(fmt, args...) \
65 do { \
66 rseq_log(fmt, ##args); \
67 abort(); \
68 } while (0)
69
70 #if defined(__x86_64__) || defined(__i386__)
71 #include <rseq-x86.h>
72 #elif defined(__ARMEL__)
73 #include <rseq-arm.h>
74 #elif defined (__AARCH64EL__)
75 #include <rseq-arm64.h>
76 #elif defined(__PPC__)
77 #include <rseq-ppc.h>
78 #elif defined(__mips__)
79 #include <rseq-mips.h>
80 #elif defined(__s390__)
81 #include <rseq-s390.h>
82 #else
83 #error unsupported target
84 #endif
85
86 /*
87 * Register rseq for the current thread. This needs to be called once
88 * by any thread which uses restartable sequences, before they start
89 * using restartable sequences, to ensure restartable sequences
90 * succeed. A restartable sequence executed from a non-registered
91 * thread will always fail.
92 */
93 int rseq_register_current_thread(void);
94
95 /*
96 * Unregister rseq for current thread.
97 */
98 int rseq_unregister_current_thread(void);
99
100 /*
101 * Restartable sequence fallback for reading the current CPU number.
102 */
103 int32_t rseq_fallback_current_cpu(void);
104
105 /*
106 * Values returned can be either the current CPU number, -1 (rseq is
107 * uninitialized), or -2 (rseq initialization has failed).
108 */
rseq_current_cpu_raw(void)109 static inline int32_t rseq_current_cpu_raw(void)
110 {
111 return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id);
112 }
113
114 /*
115 * Returns a possible CPU number, which is typically the current CPU.
116 * The returned CPU number can be used to prepare for an rseq critical
117 * section, which will confirm whether the cpu number is indeed the
118 * current one, and whether rseq is initialized.
119 *
120 * The CPU number returned by rseq_cpu_start should always be validated
121 * by passing it to a rseq asm sequence, or by comparing it to the
122 * return value of rseq_current_cpu_raw() if the rseq asm sequence
123 * does not need to be invoked.
124 */
rseq_cpu_start(void)125 static inline uint32_t rseq_cpu_start(void)
126 {
127 return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id_start);
128 }
129
rseq_current_cpu(void)130 static inline uint32_t rseq_current_cpu(void)
131 {
132 int32_t cpu;
133
134 cpu = rseq_current_cpu_raw();
135 if (rseq_unlikely(cpu < 0))
136 cpu = rseq_fallback_current_cpu();
137 return cpu;
138 }
139
rseq_clear_rseq_cs(void)140 static inline void rseq_clear_rseq_cs(void)
141 {
142 #ifdef __LP64__
143 __rseq_abi.rseq_cs.ptr = 0;
144 #else
145 __rseq_abi.rseq_cs.ptr.ptr32 = 0;
146 #endif
147 }
148
149 /*
150 * rseq_prepare_unload() should be invoked by each thread executing a rseq
151 * critical section at least once between their last critical section and
152 * library unload of the library defining the rseq critical section
153 * (struct rseq_cs). This also applies to use of rseq in code generated by
154 * JIT: rseq_prepare_unload() should be invoked at least once by each
155 * thread executing a rseq critical section before reclaim of the memory
156 * holding the struct rseq_cs.
157 */
rseq_prepare_unload(void)158 static inline void rseq_prepare_unload(void)
159 {
160 rseq_clear_rseq_cs();
161 }
162
163 #endif /* RSEQ_H_ */
164
