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7b8ea3a5 MD |
1 | /* |
2 | * lttng-probe-user.c | |
3 | * | |
4 | * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
5 | * | |
6 | * This library is free software; you can redistribute it and/or | |
7 | * modify it under the terms of the GNU Lesser General Public | |
8 | * License as published by the Free Software Foundation; only | |
9 | * version 2.1 of the License. | |
10 | * | |
11 | * This library is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | * Lesser General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU Lesser General Public | |
17 | * License along with this library; if not, write to the Free Software | |
18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
19 | */ | |
20 | ||
21 | #include <linux/uaccess.h> | |
8d90c035 | 22 | #include <linux/module.h> |
0039dbe9 | 23 | #include <wrapper/uaccess.h> |
156a3977 | 24 | #include <probes/lttng-probe-user.h> |
7b8ea3a5 MD |
25 | |
26 | /* | |
27 | * Calculate string length. Include final null terminating character if there is | |
28 | * one, or ends at first fault. Disabling page faults ensures that we can safely | |
29 | * call this from pretty much any context, including those where the caller | |
30 | * holds mmap_sem, or any lock which nests in mmap_sem. | |
31 | */ | |
32 | long lttng_strlen_user_inatomic(const char *addr) | |
33 | { | |
34 | long count = 0; | |
a824008c | 35 | mm_segment_t old_fs; |
7b8ea3a5 | 36 | |
a824008c MD |
37 | if (!addr) |
38 | return 0; | |
39 | ||
40 | old_fs = get_fs(); | |
7b8ea3a5 MD |
41 | set_fs(KERNEL_DS); |
42 | pagefault_disable(); | |
43 | for (;;) { | |
44 | char v; | |
2a8b83a1 | 45 | unsigned long ret; |
7b8ea3a5 | 46 | |
0039dbe9 | 47 | if (unlikely(!lttng_access_ok(VERIFY_READ, |
f127e61e MD |
48 | (__force const char __user *) addr, |
49 | sizeof(v)))) | |
50 | break; | |
7b8ea3a5 MD |
51 | ret = __copy_from_user_inatomic(&v, |
52 | (__force const char __user *)(addr), | |
53 | sizeof(v)); | |
2a8b83a1 | 54 | if (unlikely(ret > 0)) |
7b8ea3a5 MD |
55 | break; |
56 | count++; | |
57 | if (unlikely(!v)) | |
58 | break; | |
59 | addr++; | |
60 | } | |
61 | pagefault_enable(); | |
62 | set_fs(old_fs); | |
63 | return count; | |
64 | } | |
f127e61e | 65 | EXPORT_SYMBOL_GPL(lttng_strlen_user_inatomic); |