Commit | Line | Data |
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9f36eaed MJ |
1 | /* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1) |
2 | * | |
7b8ea3a5 MD |
3 | * lttng-probe-user.c |
4 | * | |
5 | * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7b8ea3a5 MD |
6 | */ |
7 | ||
8 | #include <linux/uaccess.h> | |
8d90c035 | 9 | #include <linux/module.h> |
156a3977 | 10 | #include <probes/lttng-probe-user.h> |
7b8ea3a5 MD |
11 | |
12 | /* | |
13 | * Calculate string length. Include final null terminating character if there is | |
14 | * one, or ends at first fault. Disabling page faults ensures that we can safely | |
15 | * call this from pretty much any context, including those where the caller | |
16 | * holds mmap_sem, or any lock which nests in mmap_sem. | |
17 | */ | |
18 | long lttng_strlen_user_inatomic(const char *addr) | |
19 | { | |
20 | long count = 0; | |
a824008c | 21 | mm_segment_t old_fs; |
7b8ea3a5 | 22 | |
a824008c MD |
23 | if (!addr) |
24 | return 0; | |
25 | ||
26 | old_fs = get_fs(); | |
7b8ea3a5 MD |
27 | set_fs(KERNEL_DS); |
28 | pagefault_disable(); | |
29 | for (;;) { | |
30 | char v; | |
2a8b83a1 | 31 | unsigned long ret; |
7b8ea3a5 | 32 | |
f127e61e MD |
33 | if (unlikely(!access_ok(VERIFY_READ, |
34 | (__force const char __user *) addr, | |
35 | sizeof(v)))) | |
36 | break; | |
7b8ea3a5 MD |
37 | ret = __copy_from_user_inatomic(&v, |
38 | (__force const char __user *)(addr), | |
39 | sizeof(v)); | |
2a8b83a1 | 40 | if (unlikely(ret > 0)) |
7b8ea3a5 MD |
41 | break; |
42 | count++; | |
43 | if (unlikely(!v)) | |
44 | break; | |
45 | addr++; | |
46 | } | |
47 | pagefault_enable(); | |
48 | set_fs(old_fs); | |
49 | return count; | |
50 | } | |
f127e61e | 51 | EXPORT_SYMBOL_GPL(lttng_strlen_user_inatomic); |