1 // SPDX-License-Identifier: GPL-2.0-or-later
3 #include <linux/compat.h>
4 #include <linux/syscalls.h>
5 #include <linux/time_namespace.h>
10 * Support for robust futexes: the kernel cleans up held futexes at
13 * Implementation: user-space maintains a per-thread list of locks it
14 * is holding. Upon do_exit(), the kernel carefully walks this list,
15 * and marks all locks that are owned by this thread with the
16 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
17 * always manipulated with the lock held, so the list is private and
18 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
19 * field, to allow the kernel to clean up if the thread dies after
20 * acquiring the lock, but just before it could have added itself to
21 * the list. There can only be one such pending lock.
25 * sys_set_robust_list() - Set the robust-futex list head of a task
26 * @head: pointer to the list-head
27 * @len: length of the list-head, as userspace expects
29 SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
33 * The kernel knows only one size for now:
35 if (unlikely(len != sizeof(*head)))
38 current->robust_list = head;
44 * sys_get_robust_list() - Get the robust-futex list head of a task
45 * @pid: pid of the process [zero for current task]
46 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
47 * @len_ptr: pointer to a length field, the kernel fills in the header size
49 SYSCALL_DEFINE3(get_robust_list, int, pid,
50 struct robust_list_head __user * __user *, head_ptr,
51 size_t __user *, len_ptr)
53 struct robust_list_head __user *head;
55 struct task_struct *p;
63 p = find_task_by_vpid(pid);
69 if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
72 head = p->robust_list;
75 if (put_user(sizeof(*head), len_ptr))
77 return put_user(head, head_ptr);
85 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
86 u32 __user *uaddr2, u32 val2, u32 val3)
88 int cmd = op & FUTEX_CMD_MASK;
89 unsigned int flags = 0;
91 if (!(op & FUTEX_PRIVATE_FLAG))
92 flags |= FLAGS_SHARED;
94 if (op & FUTEX_CLOCK_REALTIME) {
95 flags |= FLAGS_CLOCKRT;
96 if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
97 cmd != FUTEX_LOCK_PI2)
103 val3 = FUTEX_BITSET_MATCH_ANY;
105 case FUTEX_WAIT_BITSET:
106 return futex_wait(uaddr, flags, val, timeout, val3);
108 val3 = FUTEX_BITSET_MATCH_ANY;
110 case FUTEX_WAKE_BITSET:
111 return futex_wake(uaddr, flags, val, val3);
113 return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
114 case FUTEX_CMP_REQUEUE:
115 return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
117 return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
119 flags |= FLAGS_CLOCKRT;
122 return futex_lock_pi(uaddr, flags, timeout, 0);
123 case FUTEX_UNLOCK_PI:
124 return futex_unlock_pi(uaddr, flags);
125 case FUTEX_TRYLOCK_PI:
126 return futex_lock_pi(uaddr, flags, NULL, 1);
127 case FUTEX_WAIT_REQUEUE_PI:
128 val3 = FUTEX_BITSET_MATCH_ANY;
129 return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
131 case FUTEX_CMP_REQUEUE_PI:
132 return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
137 static __always_inline bool futex_cmd_has_timeout(u32 cmd)
143 case FUTEX_WAIT_BITSET:
144 case FUTEX_WAIT_REQUEUE_PI:
150 static __always_inline int
151 futex_init_timeout(u32 cmd, u32 op, struct timespec64 *ts, ktime_t *t)
153 if (!timespec64_valid(ts))
156 *t = timespec64_to_ktime(*ts);
157 if (cmd == FUTEX_WAIT)
158 *t = ktime_add_safe(ktime_get(), *t);
159 else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
160 *t = timens_ktime_to_host(CLOCK_MONOTONIC, *t);
164 SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
165 const struct __kernel_timespec __user *, utime,
166 u32 __user *, uaddr2, u32, val3)
168 int ret, cmd = op & FUTEX_CMD_MASK;
169 ktime_t t, *tp = NULL;
170 struct timespec64 ts;
172 if (utime && futex_cmd_has_timeout(cmd)) {
173 if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
175 if (get_timespec64(&ts, utime))
177 ret = futex_init_timeout(cmd, op, &ts, &t);
183 return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
186 /* Mask of available flags for each futex in futex_waitv list */
187 #define FUTEXV_WAITER_MASK (FUTEX_32 | FUTEX_PRIVATE_FLAG)
190 * futex_parse_waitv - Parse a waitv array from userspace
191 * @futexv: Kernel side list of waiters to be filled
192 * @uwaitv: Userspace list to be parsed
193 * @nr_futexes: Length of futexv
195 * Return: Error code on failure, 0 on success
197 static int futex_parse_waitv(struct futex_vector *futexv,
198 struct futex_waitv __user *uwaitv,
199 unsigned int nr_futexes)
201 struct futex_waitv aux;
204 for (i = 0; i < nr_futexes; i++) {
205 if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
208 if ((aux.flags & ~FUTEXV_WAITER_MASK) || aux.__reserved)
211 if (!(aux.flags & FUTEX_32))
214 futexv[i].w.flags = aux.flags;
215 futexv[i].w.val = aux.val;
216 futexv[i].w.uaddr = aux.uaddr;
217 futexv[i].q = futex_q_init;
224 * sys_futex_waitv - Wait on a list of futexes
225 * @waiters: List of futexes to wait on
226 * @nr_futexes: Length of futexv
227 * @flags: Flag for timeout (monotonic/realtime)
228 * @timeout: Optional absolute timeout.
229 * @clockid: Clock to be used for the timeout, realtime or monotonic.
231 * Given an array of `struct futex_waitv`, wait on each uaddr. The thread wakes
232 * if a futex_wake() is performed at any uaddr. The syscall returns immediately
233 * if any waiter has *uaddr != val. *timeout is an optional timeout value for
234 * the operation. Each waiter has individual flags. The `flags` argument for
235 * the syscall should be used solely for specifying the timeout as realtime, if
236 * needed. Flags for private futexes, sizes, etc. should be used on the
237 * individual flags of each waiter.
239 * Returns the array index of one of the woken futexes. No further information
240 * is provided: any number of other futexes may also have been woken by the
241 * same event, and if more than one futex was woken, the retrned index may
242 * refer to any one of them. (It is not necessaryily the futex with the
243 * smallest index, nor the one most recently woken, nor...)
246 SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
247 unsigned int, nr_futexes, unsigned int, flags,
248 struct __kernel_timespec __user *, timeout, clockid_t, clockid)
250 struct hrtimer_sleeper to;
251 struct futex_vector *futexv;
252 struct timespec64 ts;
256 /* This syscall supports no flags for now */
260 if (!nr_futexes || nr_futexes > FUTEX_WAITV_MAX || !waiters)
264 int flag_clkid = 0, flag_init = 0;
266 if (clockid == CLOCK_REALTIME) {
267 flag_clkid = FLAGS_CLOCKRT;
268 flag_init = FUTEX_CLOCK_REALTIME;
271 if (clockid != CLOCK_REALTIME && clockid != CLOCK_MONOTONIC)
274 if (get_timespec64(&ts, timeout))
278 * Since there's no opcode for futex_waitv, use
279 * FUTEX_WAIT_BITSET that uses absolute timeout as well
281 ret = futex_init_timeout(FUTEX_WAIT_BITSET, flag_init, &ts, &time);
285 futex_setup_timer(&time, &to, flag_clkid, 0);
288 futexv = kcalloc(nr_futexes, sizeof(*futexv), GFP_KERNEL);
294 ret = futex_parse_waitv(futexv, waiters, nr_futexes);
296 ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);
302 hrtimer_cancel(&to.timer);
303 destroy_hrtimer_on_stack(&to.timer);
309 COMPAT_SYSCALL_DEFINE2(set_robust_list,
310 struct compat_robust_list_head __user *, head,
313 if (unlikely(len != sizeof(*head)))
316 current->compat_robust_list = head;
321 COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
322 compat_uptr_t __user *, head_ptr,
323 compat_size_t __user *, len_ptr)
325 struct compat_robust_list_head __user *head;
327 struct task_struct *p;
335 p = find_task_by_vpid(pid);
341 if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
344 head = p->compat_robust_list;
347 if (put_user(sizeof(*head), len_ptr))
349 return put_user(ptr_to_compat(head), head_ptr);
356 #endif /* CONFIG_COMPAT */
358 #ifdef CONFIG_COMPAT_32BIT_TIME
359 SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
360 const struct old_timespec32 __user *, utime, u32 __user *, uaddr2,
363 int ret, cmd = op & FUTEX_CMD_MASK;
364 ktime_t t, *tp = NULL;
365 struct timespec64 ts;
367 if (utime && futex_cmd_has_timeout(cmd)) {
368 if (get_old_timespec32(&ts, utime))
370 ret = futex_init_timeout(cmd, op, &ts, &t);
376 return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
378 #endif /* CONFIG_COMPAT_32BIT_TIME */