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 #elif defined(__riscv)
97 #include <rseq-riscv.h>
98 #else
99 #error unsupported target
100 #endif
101 
102 /*
103  * Register rseq for the current thread. This needs to be called once
104  * by any thread which uses restartable sequences, before they start
105  * using restartable sequences, to ensure restartable sequences
106  * succeed. A restartable sequence executed from a non-registered
107  * thread will always fail.
108  */
109 int rseq_register_current_thread(void);
110 
111 /*
112  * Unregister rseq for current thread.
113  */
114 int rseq_unregister_current_thread(void);
115 
116 /*
117  * Restartable sequence fallback for reading the current CPU number.
118  */
119 int32_t rseq_fallback_current_cpu(void);
120 
121 /*
122  * Values returned can be either the current CPU number, -1 (rseq is
123  * uninitialized), or -2 (rseq initialization has failed).
124  */
rseq_current_cpu_raw(void)125 static inline int32_t rseq_current_cpu_raw(void)
126 {
127 	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id);
128 }
129 
130 /*
131  * Returns a possible CPU number, which is typically the current CPU.
132  * The returned CPU number can be used to prepare for an rseq critical
133  * section, which will confirm whether the cpu number is indeed the
134  * current one, and whether rseq is initialized.
135  *
136  * The CPU number returned by rseq_cpu_start should always be validated
137  * by passing it to a rseq asm sequence, or by comparing it to the
138  * return value of rseq_current_cpu_raw() if the rseq asm sequence
139  * does not need to be invoked.
140  */
rseq_cpu_start(void)141 static inline uint32_t rseq_cpu_start(void)
142 {
143 	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id_start);
144 }
145 
rseq_current_cpu(void)146 static inline uint32_t rseq_current_cpu(void)
147 {
148 	int32_t cpu;
149 
150 	cpu = rseq_current_cpu_raw();
151 	if (rseq_unlikely(cpu < 0))
152 		cpu = rseq_fallback_current_cpu();
153 	return cpu;
154 }
155 
rseq_clear_rseq_cs(void)156 static inline void rseq_clear_rseq_cs(void)
157 {
158 	RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.arch.ptr, 0);
159 }
160 
161 /*
162  * rseq_prepare_unload() should be invoked by each thread executing a rseq
163  * critical section at least once between their last critical section and
164  * library unload of the library defining the rseq critical section (struct
165  * rseq_cs) or the code referred to by the struct rseq_cs start_ip and
166  * post_commit_offset fields. This also applies to use of rseq in code
167  * generated by JIT: rseq_prepare_unload() should be invoked at least once by
168  * each thread executing a rseq critical section before reclaim of the memory
169  * holding the struct rseq_cs or reclaim of the code pointed to by struct
170  * rseq_cs start_ip and post_commit_offset fields.
171  */
rseq_prepare_unload(void)172 static inline void rseq_prepare_unload(void)
173 {
174 	rseq_clear_rseq_cs();
175 }
176 
177 #endif  /* RSEQ_H_ */
178