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1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/******************************************************************************
3 *
4 * Copyright © International Business Machines Corp., 2009
5 *
6 * DESCRIPTION
7 * Glibc independent futex library for testing kernel functionality.
8 *
9 * AUTHOR
10 * Darren Hart <dvhart@linux.intel.com>
11 *
12 * HISTORY
13 * 2009-Nov-6: Initial version by Darren Hart <dvhart@linux.intel.com>
14 *
15 *****************************************************************************/
16
17#ifndef _FUTEXTEST_H
18#define _FUTEXTEST_H
19
20#include <unistd.h>
21#include <sys/syscall.h>
22#include <sys/types.h>
23#include <linux/futex.h>
24
25typedef volatile u_int32_t futex_t;
26#define FUTEX_INITIALIZER 0
27
28/* Define the newer op codes if the system header file is not up to date. */
29#ifndef FUTEX_WAIT_BITSET
30#define FUTEX_WAIT_BITSET 9
31#endif
32#ifndef FUTEX_WAKE_BITSET
33#define FUTEX_WAKE_BITSET 10
34#endif
35#ifndef FUTEX_WAIT_REQUEUE_PI
36#define FUTEX_WAIT_REQUEUE_PI 11
37#endif
38#ifndef FUTEX_CMP_REQUEUE_PI
39#define FUTEX_CMP_REQUEUE_PI 12
40#endif
41#ifndef FUTEX_WAIT_REQUEUE_PI_PRIVATE
42#define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \
43 FUTEX_PRIVATE_FLAG)
44#endif
45#ifndef FUTEX_REQUEUE_PI_PRIVATE
46#define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \
47 FUTEX_PRIVATE_FLAG)
48#endif
49
50/*
51 * SYS_futex is expected from system C library, in glibc some 32-bit
52 * architectures (e.g. RV32) are using 64-bit time_t, therefore it doesn't have
53 * SYS_futex defined but just SYS_futex_time64. Define SYS_futex as
54 * SYS_futex_time64 in this situation to ensure the compilation and the
55 * compatibility.
56 */
57#if !defined(SYS_futex) && defined(SYS_futex_time64)
58#define SYS_futex SYS_futex_time64
59#endif
60
61/*
62 * On 32bit systems if we use "-D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64" or if
63 * we are using a newer compiler then the size of the timestamps will be 64bit,
64 * however, the SYS_futex will still point to the 32bit futex system call.
65 */
66#if __SIZEOF_POINTER__ == 4 && defined(SYS_futex_time64) && \
67 defined(_TIME_BITS) && _TIME_BITS == 64
68# undef SYS_futex
69# define SYS_futex SYS_futex_time64
70#endif
71
72/**
73 * futex() - SYS_futex syscall wrapper
74 * @uaddr: address of first futex
75 * @op: futex op code
76 * @val: typically expected value of uaddr, but varies by op
77 * @timeout: typically an absolute struct timespec (except where noted
78 * otherwise). Overloaded by some ops
79 * @uaddr2: address of second futex for some ops\
80 * @val3: varies by op
81 * @opflags: flags to be bitwise OR'd with op, such as FUTEX_PRIVATE_FLAG
82 *
83 * futex() is used by all the following futex op wrappers. It can also be
84 * used for misuse and abuse testing. Generally, the specific op wrappers
85 * should be used instead. It is a macro instead of an static inline function as
86 * some of the types over overloaded (timeout is used for nr_requeue for
87 * example).
88 *
89 * These argument descriptions are the defaults for all
90 * like-named arguments in the following wrappers except where noted below.
91 */
92#define futex(uaddr, op, val, timeout, uaddr2, val3, opflags) \
93 syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3)
94
95/**
96 * futex_wait() - block on uaddr with optional timeout
97 * @timeout: relative timeout
98 */
99static inline int
100futex_wait(futex_t *uaddr, futex_t val, struct timespec *timeout, int opflags)
101{
102 return futex(uaddr, FUTEX_WAIT, val, timeout, NULL, 0, opflags);
103}
104
105/**
106 * futex_wake() - wake one or more tasks blocked on uaddr
107 * @nr_wake: wake up to this many tasks
108 */
109static inline int
110futex_wake(futex_t *uaddr, int nr_wake, int opflags)
111{
112 return futex(uaddr, FUTEX_WAKE, nr_wake, NULL, NULL, 0, opflags);
113}
114
115/**
116 * futex_wait_bitset() - block on uaddr with bitset
117 * @bitset: bitset to be used with futex_wake_bitset
118 */
119static inline int
120futex_wait_bitset(futex_t *uaddr, futex_t val, struct timespec *timeout,
121 u_int32_t bitset, int opflags)
122{
123 return futex(uaddr, FUTEX_WAIT_BITSET, val, timeout, NULL, bitset,
124 opflags);
125}
126
127/**
128 * futex_wake_bitset() - wake one or more tasks blocked on uaddr with bitset
129 * @bitset: bitset to compare with that used in futex_wait_bitset
130 */
131static inline int
132futex_wake_bitset(futex_t *uaddr, int nr_wake, u_int32_t bitset, int opflags)
133{
134 return futex(uaddr, FUTEX_WAKE_BITSET, nr_wake, NULL, NULL, bitset,
135 opflags);
136}
137
138/**
139 * futex_lock_pi() - block on uaddr as a PI mutex
140 * @detect: whether (1) or not (0) to perform deadlock detection
141 */
142static inline int
143futex_lock_pi(futex_t *uaddr, struct timespec *timeout, int detect,
144 int opflags)
145{
146 return futex(uaddr, FUTEX_LOCK_PI, detect, timeout, NULL, 0, opflags);
147}
148
149/**
150 * futex_unlock_pi() - release uaddr as a PI mutex, waking the top waiter
151 */
152static inline int
153futex_unlock_pi(futex_t *uaddr, int opflags)
154{
155 return futex(uaddr, FUTEX_UNLOCK_PI, 0, NULL, NULL, 0, opflags);
156}
157
158/**
159 * futex_wake_op() - FIXME: COME UP WITH A GOOD ONE LINE DESCRIPTION
160 */
161static inline int
162futex_wake_op(futex_t *uaddr, futex_t *uaddr2, int nr_wake, int nr_wake2,
163 int wake_op, int opflags)
164{
165 return futex(uaddr, FUTEX_WAKE_OP, nr_wake, nr_wake2, uaddr2, wake_op,
166 opflags);
167}
168
169/**
170 * futex_requeue() - requeue without expected value comparison, deprecated
171 * @nr_wake: wake up to this many tasks
172 * @nr_requeue: requeue up to this many tasks
173 *
174 * Due to its inherently racy implementation, futex_requeue() is deprecated in
175 * favor of futex_cmp_requeue().
176 */
177static inline int
178futex_requeue(futex_t *uaddr, futex_t *uaddr2, int nr_wake, int nr_requeue,
179 int opflags)
180{
181 return futex(uaddr, FUTEX_REQUEUE, nr_wake, nr_requeue, uaddr2, 0,
182 opflags);
183}
184
185/**
186 * futex_cmp_requeue() - requeue tasks from uaddr to uaddr2
187 * @nr_wake: wake up to this many tasks
188 * @nr_requeue: requeue up to this many tasks
189 */
190static inline int
191futex_cmp_requeue(futex_t *uaddr, futex_t val, futex_t *uaddr2, int nr_wake,
192 int nr_requeue, int opflags)
193{
194 return futex(uaddr, FUTEX_CMP_REQUEUE, nr_wake, nr_requeue, uaddr2,
195 val, opflags);
196}
197
198/**
199 * futex_wait_requeue_pi() - block on uaddr and prepare to requeue to uaddr2
200 * @uaddr: non-PI futex source
201 * @uaddr2: PI futex target
202 *
203 * This is the first half of the requeue_pi mechanism. It shall always be
204 * paired with futex_cmp_requeue_pi().
205 */
206static inline int
207futex_wait_requeue_pi(futex_t *uaddr, futex_t val, futex_t *uaddr2,
208 struct timespec *timeout, int opflags)
209{
210 return futex(uaddr, FUTEX_WAIT_REQUEUE_PI, val, timeout, uaddr2, 0,
211 opflags);
212}
213
214/**
215 * futex_cmp_requeue_pi() - requeue tasks from uaddr to uaddr2 (PI aware)
216 * @uaddr: non-PI futex source
217 * @uaddr2: PI futex target
218 * @nr_wake: wake up to this many tasks
219 * @nr_requeue: requeue up to this many tasks
220 */
221static inline int
222futex_cmp_requeue_pi(futex_t *uaddr, futex_t val, futex_t *uaddr2, int nr_wake,
223 int nr_requeue, int opflags)
224{
225 return futex(uaddr, FUTEX_CMP_REQUEUE_PI, nr_wake, nr_requeue, uaddr2,
226 val, opflags);
227}
228
229/**
230 * futex_cmpxchg() - atomic compare and exchange
231 * @uaddr: The address of the futex to be modified
232 * @oldval: The expected value of the futex
233 * @newval: The new value to try and assign the futex
234 *
235 * Implement cmpxchg using gcc atomic builtins.
236 * http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html
237 *
238 * Return the old futex value.
239 */
240static inline u_int32_t
241futex_cmpxchg(futex_t *uaddr, u_int32_t oldval, u_int32_t newval)
242{
243 return __sync_val_compare_and_swap(uaddr, oldval, newval);
244}
245
246/**
247 * futex_dec() - atomic decrement of the futex value
248 * @uaddr: The address of the futex to be modified
249 *
250 * Return the new futex value.
251 */
252static inline u_int32_t
253futex_dec(futex_t *uaddr)
254{
255 return __sync_sub_and_fetch(uaddr, 1);
256}
257
258/**
259 * futex_inc() - atomic increment of the futex value
260 * @uaddr: the address of the futex to be modified
261 *
262 * Return the new futex value.
263 */
264static inline u_int32_t
265futex_inc(futex_t *uaddr)
266{
267 return __sync_add_and_fetch(uaddr, 1);
268}
269
270/**
271 * futex_set() - atomic decrement of the futex value
272 * @uaddr: the address of the futex to be modified
273 * @newval: New value for the atomic_t
274 *
275 * Return the new futex value.
276 */
277static inline u_int32_t
278futex_set(futex_t *uaddr, u_int32_t newval)
279{
280 *uaddr = newval;
281 return newval;
282}
283
284#endif