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.  */
51extern ptrdiff_t rseq_offset;
52/* Size of the registered rseq area.  0 if the registration was
53   unsuccessful.  */
54extern unsigned int rseq_size;
55/* Flags used during rseq registration.  */
56extern unsigned int rseq_flags;
57
58static 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 */
107int rseq_register_current_thread(void);
108
109/*
110 * Unregister rseq for current thread.
111 */
112int rseq_unregister_current_thread(void);
113
114/*
115 * Restartable sequence fallback for reading the current CPU number.
116 */
117int32_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 */
123static 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 */
139static inline uint32_t rseq_cpu_start(void)
140{
141	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id_start);
142}
143
144static 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
154static 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 (struct
163 * rseq_cs) or the code referred to by the struct rseq_cs start_ip and
164 * post_commit_offset fields. This also applies to use of rseq in code
165 * generated by JIT: rseq_prepare_unload() should be invoked at least once by
166 * each thread executing a rseq critical section before reclaim of the memory
167 * holding the struct rseq_cs or reclaim of the code pointed to by struct
168 * rseq_cs start_ip and post_commit_offset fields.
169 */
170static inline void rseq_prepare_unload(void)
171{
172	rseq_clear_rseq_cs();
173}
174
175#endif  /* RSEQ_H_ */
176