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 <stddef.h>
20 #include "rseq-abi.h"
21 #include "compiler.h"
22
23 /*
24 * Empty code injection macros, override when testing.
25 * It is important to consider that the ASM injection macros need to be
26 * fully reentrant (e.g. do not modify the stack).
27 */
28 #ifndef RSEQ_INJECT_ASM
29 #define RSEQ_INJECT_ASM(n)
30 #endif
31
32 #ifndef RSEQ_INJECT_C
33 #define RSEQ_INJECT_C(n)
34 #endif
35
36 #ifndef RSEQ_INJECT_INPUT
37 #define RSEQ_INJECT_INPUT
38 #endif
39
40 #ifndef RSEQ_INJECT_CLOBBER
41 #define RSEQ_INJECT_CLOBBER
42 #endif
43
44 #ifndef RSEQ_INJECT_FAILED
45 #define RSEQ_INJECT_FAILED
46 #endif
47
48 #include "rseq-thread-pointer.h"
49
50 /* Offset from the thread pointer to the rseq area. */
51 extern ptrdiff_t rseq_offset;
52 /* Size of the registered rseq area. 0 if the registration was
53 unsuccessful. */
54 extern unsigned int rseq_size;
55 /* Flags used during rseq registration. */
56 extern unsigned int rseq_flags;
57
rseq_get_abi(void)58 static inline struct rseq_abi *rseq_get_abi(void)
59 {
60 return (struct rseq_abi *) ((uintptr_t) rseq_thread_pointer() + rseq_offset);
61 }
62
63 #define rseq_likely(x) __builtin_expect(!!(x), 1)
64 #define rseq_unlikely(x) __builtin_expect(!!(x), 0)
65 #define rseq_barrier() __asm__ __volatile__("" : : : "memory")
66
67 #define RSEQ_ACCESS_ONCE(x) (*(__volatile__ __typeof__(x) *)&(x))
68 #define RSEQ_WRITE_ONCE(x, v) __extension__ ({ RSEQ_ACCESS_ONCE(x) = (v); })
69 #define RSEQ_READ_ONCE(x) RSEQ_ACCESS_ONCE(x)
70
71 #define __rseq_str_1(x) #x
72 #define __rseq_str(x) __rseq_str_1(x)
73
74 #define rseq_log(fmt, args...) \
75 fprintf(stderr, fmt "(in %s() at " __FILE__ ":" __rseq_str(__LINE__)"\n", \
76 ## args, __func__)
77
78 #define rseq_bug(fmt, args...) \
79 do { \
80 rseq_log(fmt, ##args); \
81 abort(); \
82 } while (0)
83
84 #if defined(__x86_64__) || defined(__i386__)
85 #include <rseq-x86.h>
86 #elif defined(__ARMEL__)
87 #include <rseq-arm.h>
88 #elif defined (__AARCH64EL__)
89 #include <rseq-arm64.h>
90 #elif defined(__PPC__)
91 #include <rseq-ppc.h>
92 #elif defined(__mips__)
93 #include <rseq-mips.h>
94 #elif defined(__s390__)
95 #include <rseq-s390.h>
96 #else
97 #error unsupported target
98 #endif
99
100 /*
101 * Register rseq for the current thread. This needs to be called once
102 * by any thread which uses restartable sequences, before they start
103 * using restartable sequences, to ensure restartable sequences
104 * succeed. A restartable sequence executed from a non-registered
105 * thread will always fail.
106 */
107 int rseq_register_current_thread(void);
108
109 /*
110 * Unregister rseq for current thread.
111 */
112 int rseq_unregister_current_thread(void);
113
114 /*
115 * Restartable sequence fallback for reading the current CPU number.
116 */
117 int32_t rseq_fallback_current_cpu(void);
118
119 /*
120 * Values returned can be either the current CPU number, -1 (rseq is
121 * uninitialized), or -2 (rseq initialization has failed).
122 */
rseq_current_cpu_raw(void)123 static inline int32_t rseq_current_cpu_raw(void)
124 {
125 return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id);
126 }
127
128 /*
129 * Returns a possible CPU number, which is typically the current CPU.
130 * The returned CPU number can be used to prepare for an rseq critical
131 * section, which will confirm whether the cpu number is indeed the
132 * current one, and whether rseq is initialized.
133 *
134 * The CPU number returned by rseq_cpu_start should always be validated
135 * by passing it to a rseq asm sequence, or by comparing it to the
136 * return value of rseq_current_cpu_raw() if the rseq asm sequence
137 * does not need to be invoked.
138 */
rseq_cpu_start(void)139 static inline uint32_t rseq_cpu_start(void)
140 {
141 return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id_start);
142 }
143
rseq_current_cpu(void)144 static inline uint32_t rseq_current_cpu(void)
145 {
146 int32_t cpu;
147
148 cpu = rseq_current_cpu_raw();
149 if (rseq_unlikely(cpu < 0))
150 cpu = rseq_fallback_current_cpu();
151 return cpu;
152 }
153
rseq_clear_rseq_cs(void)154 static inline void rseq_clear_rseq_cs(void)
155 {
156 RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.arch.ptr, 0);
157 }
158
159 /*
160 * rseq_prepare_unload() should be invoked by each thread executing a rseq
161 * critical section at least once between their last critical section and
162 * library unload of the library defining the rseq critical section
163 * (struct rseq_cs). This also applies to use of rseq in code generated by
164 * JIT: rseq_prepare_unload() should be invoked at least once by each
165 * thread executing a rseq critical section before reclaim of the memory
166 * holding the struct rseq_cs.
167 */
rseq_prepare_unload(void)168 static inline void rseq_prepare_unload(void)
169 {
170 rseq_clear_rseq_cs();
171 }
172
173 #endif /* RSEQ_H_ */
174