diff options
author | Andrew Morton <akpm@osdl.org> | 2006-09-27 04:51:14 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-27 11:26:20 -0400 |
commit | 1b79e5513d52e8533a08af35a3595dad80c74d1f (patch) | |
tree | 01d69b3e5e9fca89fc44b462bfe24cb06243ac0f | |
parent | aafe6c2a2b6bce5a3a4913ce5c07e85ea143144d (diff) |
[PATCH] add probe_kernel_address()
Add a version of __get_user() which is safe to call inside mmap_sem.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r-- | include/linux/uaccess.h | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 391e7ed1eb3f..a48d7f11c7be 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h | |||
@@ -19,4 +19,26 @@ static inline unsigned long __copy_from_user_nocache(void *to, | |||
19 | 19 | ||
20 | #endif /* ARCH_HAS_NOCACHE_UACCESS */ | 20 | #endif /* ARCH_HAS_NOCACHE_UACCESS */ |
21 | 21 | ||
22 | /** | ||
23 | * probe_kernel_address(): safely attempt to read from a location | ||
24 | * @addr: address to read from - its type is type typeof(retval)* | ||
25 | * @retval: read into this variable | ||
26 | * | ||
27 | * Safely read from address @addr into variable @revtal. If a kernel fault | ||
28 | * happens, handle that and return -EFAULT. | ||
29 | * We ensure that the __get_user() is executed in atomic context so that | ||
30 | * do_page_fault() doesn't attempt to take mmap_sem. This makes | ||
31 | * probe_kernel_address() suitable for use within regions where the caller | ||
32 | * already holds mmap_sem, or other locks which nest inside mmap_sem. | ||
33 | */ | ||
34 | #define probe_kernel_address(addr, retval) \ | ||
35 | ({ \ | ||
36 | long ret; \ | ||
37 | \ | ||
38 | inc_preempt_count(); \ | ||
39 | ret = __get_user(retval, addr); \ | ||
40 | dec_preempt_count(); \ | ||
41 | ret; \ | ||
42 | }) | ||
43 | |||
22 | #endif /* __LINUX_UACCESS_H__ */ | 44 | #endif /* __LINUX_UACCESS_H__ */ |