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1 | /* | |
2 | * linux/kernel/futex_compat.c | |
3 | * | |
4 | * Futex compatibililty routines. | |
5 | * | |
6 | * Copyright 2006, Red Hat, Inc., Ingo Molnar | |
7 | */ | |
8 | ||
9 | #include <linux/linkage.h> | |
10 | #include <linux/compat.h> | |
11 | #include <linux/nsproxy.h> | |
12 | #include <linux/futex.h> | |
13 | #include <linux/ptrace.h> | |
14 | #include <linux/syscalls.h> | |
15 | ||
16 | #include <asm/uaccess.h> | |
17 | ||
18 | ||
19 | /* | |
20 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: | |
21 | */ | |
22 | static inline int | |
23 | fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry, | |
24 | compat_uptr_t __user *head, unsigned int *pi) | |
25 | { | |
26 | if (get_user(*uentry, head)) | |
27 | return -EFAULT; | |
28 | ||
29 | *entry = compat_ptr((*uentry) & ~1); | |
30 | *pi = (unsigned int)(*uentry) & 1; | |
31 | ||
32 | return 0; | |
33 | } | |
34 | ||
35 | static void __user *futex_uaddr(struct robust_list __user *entry, | |
36 | compat_long_t futex_offset) | |
37 | { | |
38 | compat_uptr_t base = ptr_to_compat(entry); | |
39 | void __user *uaddr = compat_ptr(base + futex_offset); | |
40 | ||
41 | return uaddr; | |
42 | } | |
43 | ||
44 | /* | |
45 | * Walk curr->robust_list (very carefully, it's a userspace list!) | |
46 | * and mark any locks found there dead, and notify any waiters. | |
47 | * | |
48 | * We silently return on any sign of list-walking problem. | |
49 | */ | |
50 | void compat_exit_robust_list(struct task_struct *curr) | |
51 | { | |
52 | struct compat_robust_list_head __user *head = curr->compat_robust_list; | |
53 | struct robust_list __user *entry, *next_entry, *pending; | |
54 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; | |
55 | unsigned int uninitialized_var(next_pi); | |
56 | compat_uptr_t uentry, next_uentry, upending; | |
57 | compat_long_t futex_offset; | |
58 | int rc; | |
59 | ||
60 | if (!futex_cmpxchg_enabled) | |
61 | return; | |
62 | ||
63 | /* | |
64 | * Fetch the list head (which was registered earlier, via | |
65 | * sys_set_robust_list()): | |
66 | */ | |
67 | if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi)) | |
68 | return; | |
69 | /* | |
70 | * Fetch the relative futex offset: | |
71 | */ | |
72 | if (get_user(futex_offset, &head->futex_offset)) | |
73 | return; | |
74 | /* | |
75 | * Fetch any possibly pending lock-add first, and handle it | |
76 | * if it exists: | |
77 | */ | |
78 | if (fetch_robust_entry(&upending, &pending, | |
79 | &head->list_op_pending, &pip)) | |
80 | return; | |
81 | ||
82 | next_entry = NULL; /* avoid warning with gcc */ | |
83 | while (entry != (struct robust_list __user *) &head->list) { | |
84 | /* | |
85 | * Fetch the next entry in the list before calling | |
86 | * handle_futex_death: | |
87 | */ | |
88 | rc = fetch_robust_entry(&next_uentry, &next_entry, | |
89 | (compat_uptr_t __user *)&entry->next, &next_pi); | |
90 | /* | |
91 | * A pending lock might already be on the list, so | |
92 | * dont process it twice: | |
93 | */ | |
94 | if (entry != pending) { | |
95 | void __user *uaddr = futex_uaddr(entry, futex_offset); | |
96 | ||
97 | if (handle_futex_death(uaddr, curr, pi)) | |
98 | return; | |
99 | } | |
100 | if (rc) | |
101 | return; | |
102 | uentry = next_uentry; | |
103 | entry = next_entry; | |
104 | pi = next_pi; | |
105 | /* | |
106 | * Avoid excessively long or circular lists: | |
107 | */ | |
108 | if (!--limit) | |
109 | break; | |
110 | ||
111 | cond_resched(); | |
112 | } | |
113 | if (pending) { | |
114 | void __user *uaddr = futex_uaddr(pending, futex_offset); | |
115 | ||
116 | handle_futex_death(uaddr, curr, pip); | |
117 | } | |
118 | } | |
119 | ||
120 | COMPAT_SYSCALL_DEFINE2(set_robust_list, | |
121 | struct compat_robust_list_head __user *, head, | |
122 | compat_size_t, len) | |
123 | { | |
124 | if (!futex_cmpxchg_enabled) | |
125 | return -ENOSYS; | |
126 | ||
127 | if (unlikely(len != sizeof(*head))) | |
128 | return -EINVAL; | |
129 | ||
130 | current->compat_robust_list = head; | |
131 | ||
132 | return 0; | |
133 | } | |
134 | ||
135 | COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid, | |
136 | compat_uptr_t __user *, head_ptr, | |
137 | compat_size_t __user *, len_ptr) | |
138 | { | |
139 | struct compat_robust_list_head __user *head; | |
140 | unsigned long ret; | |
141 | struct task_struct *p; | |
142 | ||
143 | if (!futex_cmpxchg_enabled) | |
144 | return -ENOSYS; | |
145 | ||
146 | rcu_read_lock(); | |
147 | ||
148 | ret = -ESRCH; | |
149 | if (!pid) | |
150 | p = current; | |
151 | else { | |
152 | p = find_task_by_vpid(pid); | |
153 | if (!p) | |
154 | goto err_unlock; | |
155 | } | |
156 | ||
157 | ret = -EPERM; | |
158 | if (!ptrace_may_access(p, PTRACE_MODE_READ)) | |
159 | goto err_unlock; | |
160 | ||
161 | head = p->compat_robust_list; | |
162 | rcu_read_unlock(); | |
163 | ||
164 | if (put_user(sizeof(*head), len_ptr)) | |
165 | return -EFAULT; | |
166 | return put_user(ptr_to_compat(head), head_ptr); | |
167 | ||
168 | err_unlock: | |
169 | rcu_read_unlock(); | |
170 | ||
171 | return ret; | |
172 | } | |
173 | ||
174 | COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, | |
175 | struct compat_timespec __user *, utime, u32 __user *, uaddr2, | |
176 | u32, val3) | |
177 | { | |
178 | struct timespec ts; | |
179 | ktime_t t, *tp = NULL; | |
180 | int val2 = 0; | |
181 | int cmd = op & FUTEX_CMD_MASK; | |
182 | ||
183 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || | |
184 | cmd == FUTEX_WAIT_BITSET || | |
185 | cmd == FUTEX_WAIT_REQUEUE_PI)) { | |
186 | if (compat_get_timespec(&ts, utime)) | |
187 | return -EFAULT; | |
188 | if (!timespec_valid(&ts)) | |
189 | return -EINVAL; | |
190 | ||
191 | t = timespec_to_ktime(ts); | |
192 | if (cmd == FUTEX_WAIT) | |
193 | t = ktime_add_safe(ktime_get(), t); | |
194 | tp = &t; | |
195 | } | |
196 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || | |
197 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) | |
198 | val2 = (int) (unsigned long) utime; | |
199 | ||
200 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); | |
201 | } |