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#ifndef rseq_sizeof_field
24#define rseq_sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
25#endif
26
27#ifndef rseq_offsetofend
28#define rseq_offsetofend(TYPE, MEMBER) \
29	(offsetof(TYPE, MEMBER)	+ rseq_sizeof_field(TYPE, MEMBER))
30#endif
31
32/*
33 * Empty code injection macros, override when testing.
34 * It is important to consider that the ASM injection macros need to be
35 * fully reentrant (e.g. do not modify the stack).
36 */
37#ifndef RSEQ_INJECT_ASM
38#define RSEQ_INJECT_ASM(n)
39#endif
40
41#ifndef RSEQ_INJECT_C
42#define RSEQ_INJECT_C(n)
43#endif
44
45#ifndef RSEQ_INJECT_INPUT
46#define RSEQ_INJECT_INPUT
47#endif
48
49#ifndef RSEQ_INJECT_CLOBBER
50#define RSEQ_INJECT_CLOBBER
51#endif
52
53#ifndef RSEQ_INJECT_FAILED
54#define RSEQ_INJECT_FAILED
55#endif
56
57#include "rseq-thread-pointer.h"
58
59/* Offset from the thread pointer to the rseq area. */
60extern ptrdiff_t rseq_offset;
61
62/*
63 * Size of the registered rseq area. 0 if the registration was
64 * unsuccessful.
65 */
66extern unsigned int rseq_size;
67
68/* Flags used during rseq registration. */
69extern unsigned int rseq_flags;
70
71/*
72 * rseq feature size supported by the kernel. 0 if the registration was
73 * unsuccessful.
74 */
75extern unsigned int rseq_feature_size;
76
77enum rseq_mo {
78	RSEQ_MO_RELAXED = 0,
79	RSEQ_MO_CONSUME = 1,	/* Unused */
80	RSEQ_MO_ACQUIRE = 2,	/* Unused */
81	RSEQ_MO_RELEASE = 3,
82	RSEQ_MO_ACQ_REL = 4,	/* Unused */
83	RSEQ_MO_SEQ_CST = 5,	/* Unused */
84};
85
86enum rseq_percpu_mode {
87	RSEQ_PERCPU_CPU_ID = 0,
88	RSEQ_PERCPU_MM_CID = 1,
89};
90
91static inline struct rseq_abi *rseq_get_abi(void)
92{
93	return (struct rseq_abi *) ((uintptr_t) rseq_thread_pointer() + rseq_offset);
94}
95
96#define rseq_likely(x)		__builtin_expect(!!(x), 1)
97#define rseq_unlikely(x)	__builtin_expect(!!(x), 0)
98#define rseq_barrier()		__asm__ __volatile__("" : : : "memory")
99
100#define RSEQ_ACCESS_ONCE(x)	(*(__volatile__  __typeof__(x) *)&(x))
101#define RSEQ_WRITE_ONCE(x, v)	__extension__ ({ RSEQ_ACCESS_ONCE(x) = (v); })
102#define RSEQ_READ_ONCE(x)	RSEQ_ACCESS_ONCE(x)
103
104#define __rseq_str_1(x)	#x
105#define __rseq_str(x)		__rseq_str_1(x)
106
107#define rseq_log(fmt, args...)						       \
108	fprintf(stderr, fmt "(in %s() at " __FILE__ ":" __rseq_str(__LINE__)"\n", \
109		## args, __func__)
110
111#define rseq_bug(fmt, args...)		\
112	do {				\
113		rseq_log(fmt, ##args);	\
114		abort();		\
115	} while (0)
116
117#if defined(__x86_64__) || defined(__i386__)
118#include <rseq-x86.h>
119#elif defined(__ARMEL__)
120#include <rseq-arm.h>
121#elif defined (__AARCH64EL__)
122#include <rseq-arm64.h>
123#elif defined(__PPC__)
124#include <rseq-ppc.h>
125#elif defined(__mips__)
126#include <rseq-mips.h>
127#elif defined(__s390__)
128#include <rseq-s390.h>
129#elif defined(__riscv)
130#include <rseq-riscv.h>
131#else
132#error unsupported target
133#endif
134
135/*
136 * Register rseq for the current thread. This needs to be called once
137 * by any thread which uses restartable sequences, before they start
138 * using restartable sequences, to ensure restartable sequences
139 * succeed. A restartable sequence executed from a non-registered
140 * thread will always fail.
141 */
142int rseq_register_current_thread(void);
143
144/*
145 * Unregister rseq for current thread.
146 */
147int rseq_unregister_current_thread(void);
148
149/*
150 * Restartable sequence fallback for reading the current CPU number.
151 */
152int32_t rseq_fallback_current_cpu(void);
153
154/*
155 * Restartable sequence fallback for reading the current node number.
156 */
157int32_t rseq_fallback_current_node(void);
158
159/*
160 * Values returned can be either the current CPU number, -1 (rseq is
161 * uninitialized), or -2 (rseq initialization has failed).
162 */
163static inline int32_t rseq_current_cpu_raw(void)
164{
165	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id);
166}
167
168/*
169 * Returns a possible CPU number, which is typically the current CPU.
170 * The returned CPU number can be used to prepare for an rseq critical
171 * section, which will confirm whether the cpu number is indeed the
172 * current one, and whether rseq is initialized.
173 *
174 * The CPU number returned by rseq_cpu_start should always be validated
175 * by passing it to a rseq asm sequence, or by comparing it to the
176 * return value of rseq_current_cpu_raw() if the rseq asm sequence
177 * does not need to be invoked.
178 */
179static inline uint32_t rseq_cpu_start(void)
180{
181	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id_start);
182}
183
184static inline uint32_t rseq_current_cpu(void)
185{
186	int32_t cpu;
187
188	cpu = rseq_current_cpu_raw();
189	if (rseq_unlikely(cpu < 0))
190		cpu = rseq_fallback_current_cpu();
191	return cpu;
192}
193
194static inline bool rseq_node_id_available(void)
195{
196	return (int) rseq_feature_size >= rseq_offsetofend(struct rseq_abi, node_id);
197}
198
199/*
200 * Current NUMA node number.
201 */
202static inline uint32_t rseq_current_node_id(void)
203{
204	assert(rseq_node_id_available());
205	return RSEQ_ACCESS_ONCE(rseq_get_abi()->node_id);
206}
207
208static inline bool rseq_mm_cid_available(void)
209{
210	return (int) rseq_feature_size >= rseq_offsetofend(struct rseq_abi, mm_cid);
211}
212
213static inline uint32_t rseq_current_mm_cid(void)
214{
215	return RSEQ_ACCESS_ONCE(rseq_get_abi()->mm_cid);
216}
217
218static inline void rseq_clear_rseq_cs(void)
219{
220	RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.arch.ptr, 0);
221}
222
223/*
224 * rseq_prepare_unload() should be invoked by each thread executing a rseq
225 * critical section at least once between their last critical section and
226 * library unload of the library defining the rseq critical section (struct
227 * rseq_cs) or the code referred to by the struct rseq_cs start_ip and
228 * post_commit_offset fields. This also applies to use of rseq in code
229 * generated by JIT: rseq_prepare_unload() should be invoked at least once by
230 * each thread executing a rseq critical section before reclaim of the memory
231 * holding the struct rseq_cs or reclaim of the code pointed to by struct
232 * rseq_cs start_ip and post_commit_offset fields.
233 */
234static inline void rseq_prepare_unload(void)
235{
236	rseq_clear_rseq_cs();
237}
238
239static inline __attribute__((always_inline))
240int rseq_cmpeqv_storev(enum rseq_mo rseq_mo, enum rseq_percpu_mode percpu_mode,
241		       intptr_t *v, intptr_t expect,
242		       intptr_t newv, int cpu)
243{
244	if (rseq_mo != RSEQ_MO_RELAXED)
245		return -1;
246	switch (percpu_mode) {
247	case RSEQ_PERCPU_CPU_ID:
248		return rseq_cmpeqv_storev_relaxed_cpu_id(v, expect, newv, cpu);
249	case RSEQ_PERCPU_MM_CID:
250		return rseq_cmpeqv_storev_relaxed_mm_cid(v, expect, newv, cpu);
251	}
252	return -1;
253}
254
255/*
256 * Compare @v against @expectnot. When it does _not_ match, load @v
257 * into @load, and store the content of *@v + voffp into @v.
258 */
259static inline __attribute__((always_inline))
260int rseq_cmpnev_storeoffp_load(enum rseq_mo rseq_mo, enum rseq_percpu_mode percpu_mode,
261			       intptr_t *v, intptr_t expectnot, long voffp, intptr_t *load,
262			       int cpu)
263{
264	if (rseq_mo != RSEQ_MO_RELAXED)
265		return -1;
266	switch (percpu_mode) {
267	case RSEQ_PERCPU_CPU_ID:
268		return rseq_cmpnev_storeoffp_load_relaxed_cpu_id(v, expectnot, voffp, load, cpu);
269	case RSEQ_PERCPU_MM_CID:
270		return rseq_cmpnev_storeoffp_load_relaxed_mm_cid(v, expectnot, voffp, load, cpu);
271	}
272	return -1;
273}
274
275static inline __attribute__((always_inline))
276int rseq_addv(enum rseq_mo rseq_mo, enum rseq_percpu_mode percpu_mode,
277	      intptr_t *v, intptr_t count, int cpu)
278{
279	if (rseq_mo != RSEQ_MO_RELAXED)
280		return -1;
281	switch (percpu_mode) {
282	case RSEQ_PERCPU_CPU_ID:
283		return rseq_addv_relaxed_cpu_id(v, count, cpu);
284	case RSEQ_PERCPU_MM_CID:
285		return rseq_addv_relaxed_mm_cid(v, count, cpu);
286	}
287	return -1;
288}
289
290#ifdef RSEQ_ARCH_HAS_OFFSET_DEREF_ADDV
291/*
292 *   pval = *(ptr+off)
293 *  *pval += inc;
294 */
295static inline __attribute__((always_inline))
296int rseq_offset_deref_addv(enum rseq_mo rseq_mo, enum rseq_percpu_mode percpu_mode,
297			   intptr_t *ptr, long off, intptr_t inc, int cpu)
298{
299	if (rseq_mo != RSEQ_MO_RELAXED)
300		return -1;
301	switch (percpu_mode) {
302	case RSEQ_PERCPU_CPU_ID:
303		return rseq_offset_deref_addv_relaxed_cpu_id(ptr, off, inc, cpu);
304	case RSEQ_PERCPU_MM_CID:
305		return rseq_offset_deref_addv_relaxed_mm_cid(ptr, off, inc, cpu);
306	}
307	return -1;
308}
309#endif
310
311static inline __attribute__((always_inline))
312int rseq_cmpeqv_trystorev_storev(enum rseq_mo rseq_mo, enum rseq_percpu_mode percpu_mode,
313				 intptr_t *v, intptr_t expect,
314				 intptr_t *v2, intptr_t newv2,
315				 intptr_t newv, int cpu)
316{
317	switch (rseq_mo) {
318	case RSEQ_MO_RELAXED:
319		switch (percpu_mode) {
320		case RSEQ_PERCPU_CPU_ID:
321			return rseq_cmpeqv_trystorev_storev_relaxed_cpu_id(v, expect, v2, newv2, newv, cpu);
322		case RSEQ_PERCPU_MM_CID:
323			return rseq_cmpeqv_trystorev_storev_relaxed_mm_cid(v, expect, v2, newv2, newv, cpu);
324		}
325		return -1;
326	case RSEQ_MO_RELEASE:
327		switch (percpu_mode) {
328		case RSEQ_PERCPU_CPU_ID:
329			return rseq_cmpeqv_trystorev_storev_release_cpu_id(v, expect, v2, newv2, newv, cpu);
330		case RSEQ_PERCPU_MM_CID:
331			return rseq_cmpeqv_trystorev_storev_release_mm_cid(v, expect, v2, newv2, newv, cpu);
332		}
333		return -1;
334	default:
335		return -1;
336	}
337}
338
339static inline __attribute__((always_inline))
340int rseq_cmpeqv_cmpeqv_storev(enum rseq_mo rseq_mo, enum rseq_percpu_mode percpu_mode,
341			      intptr_t *v, intptr_t expect,
342			      intptr_t *v2, intptr_t expect2,
343			      intptr_t newv, int cpu)
344{
345	if (rseq_mo != RSEQ_MO_RELAXED)
346		return -1;
347	switch (percpu_mode) {
348	case RSEQ_PERCPU_CPU_ID:
349		return rseq_cmpeqv_cmpeqv_storev_relaxed_cpu_id(v, expect, v2, expect2, newv, cpu);
350	case RSEQ_PERCPU_MM_CID:
351		return rseq_cmpeqv_cmpeqv_storev_relaxed_mm_cid(v, expect, v2, expect2, newv, cpu);
352	}
353	return -1;
354}
355
356static inline __attribute__((always_inline))
357int rseq_cmpeqv_trymemcpy_storev(enum rseq_mo rseq_mo, enum rseq_percpu_mode percpu_mode,
358				 intptr_t *v, intptr_t expect,
359				 void *dst, void *src, size_t len,
360				 intptr_t newv, int cpu)
361{
362	switch (rseq_mo) {
363	case RSEQ_MO_RELAXED:
364		switch (percpu_mode) {
365		case RSEQ_PERCPU_CPU_ID:
366			return rseq_cmpeqv_trymemcpy_storev_relaxed_cpu_id(v, expect, dst, src, len, newv, cpu);
367		case RSEQ_PERCPU_MM_CID:
368			return rseq_cmpeqv_trymemcpy_storev_relaxed_mm_cid(v, expect, dst, src, len, newv, cpu);
369		}
370		return -1;
371	case RSEQ_MO_RELEASE:
372		switch (percpu_mode) {
373		case RSEQ_PERCPU_CPU_ID:
374			return rseq_cmpeqv_trymemcpy_storev_release_cpu_id(v, expect, dst, src, len, newv, cpu);
375		case RSEQ_PERCPU_MM_CID:
376			return rseq_cmpeqv_trymemcpy_storev_release_mm_cid(v, expect, dst, src, len, newv, cpu);
377		}
378		return -1;
379	default:
380		return -1;
381	}
382}
383
384#endif  /* RSEQ_H_ */
385