projects / lttng-modules.git / blame
| 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> |
| b5304713 | 10 | #include <lttng/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 | |
| a865837a | 33 | if (unlikely(!access_ok((__force const char __user *) addr, |
| f127e61e MD |
34 | sizeof(v)))) |
| 35 | break; | |
| 7b8ea3a5 MD |
36 | ret = __copy_from_user_inatomic(&v, |
| 37 | (__force const char __user *)(addr), | |
| 38 | sizeof(v)); | |
| 2a8b83a1 | 39 | if (unlikely(ret > 0)) |
| 7b8ea3a5 MD |
40 | break; |
| 41 | count++; | |
| 42 | if (unlikely(!v)) | |
| 43 | break; | |
| 44 | addr++; | |
| 45 | } | |
| 46 | pagefault_enable(); | |
| 47 | set_fs(old_fs); | |
| 48 | return count; | |
| 49 | } | |
| f127e61e | 50 | EXPORT_SYMBOL_GPL(lttng_strlen_user_inatomic); |