Commit | Line | Data |
---|---|---|
b7cdc182 | 1 | /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) |
9f36eaed | 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> |
80bb2600 | 10 | #include <wrapper/uaccess.h> |
3b4aafcb | 11 | #include <lttng/probe-user.h> |
7b8ea3a5 MD |
12 | |
13 | /* | |
14 | * Calculate string length. Include final null terminating character if there is | |
15 | * one, or ends at first fault. Disabling page faults ensures that we can safely | |
16 | * call this from pretty much any context, including those where the caller | |
17 | * holds mmap_sem, or any lock which nests in mmap_sem. | |
18 | */ | |
19 | long lttng_strlen_user_inatomic(const char *addr) | |
20 | { | |
21 | long count = 0; | |
a824008c | 22 | mm_segment_t old_fs; |
7b8ea3a5 | 23 | |
a824008c MD |
24 | if (!addr) |
25 | return 0; | |
26 | ||
27 | old_fs = get_fs(); | |
7b8ea3a5 MD |
28 | set_fs(KERNEL_DS); |
29 | pagefault_disable(); | |
30 | for (;;) { | |
31 | char v; | |
2a8b83a1 | 32 | unsigned long ret; |
7b8ea3a5 | 33 | |
80bb2600 | 34 | if (unlikely(!lttng_access_ok(VERIFY_READ, |
f127e61e MD |
35 | (__force const char __user *) addr, |
36 | sizeof(v)))) | |
37 | break; | |
7b8ea3a5 MD |
38 | ret = __copy_from_user_inatomic(&v, |
39 | (__force const char __user *)(addr), | |
40 | sizeof(v)); | |
2a8b83a1 | 41 | if (unlikely(ret > 0)) |
7b8ea3a5 MD |
42 | break; |
43 | count++; | |
44 | if (unlikely(!v)) | |
45 | break; | |
46 | addr++; | |
47 | } | |
48 | pagefault_enable(); | |
49 | set_fs(old_fs); | |
50 | return count; | |
51 | } | |
f127e61e | 52 | EXPORT_SYMBOL_GPL(lttng_strlen_user_inatomic); |