uaccess.h revision bdb43806589096ac4272fe1307e789846ac08d7c 
1#ifndef __LINUX_UACCESS_H__
2#define __LINUX_UACCESS_H__
3
4#include <linux/preempt.h>
5#include <asm/uaccess.h>
6
7/*
8 * These routines enable/disable the pagefault handler in that
9 * it will not take any locks and go straight to the fixup table.
10 *
11 * They have great resemblance to the preempt_disable/enable calls
12 * and in fact they are identical; this is because currently there is
13 * no other way to make the pagefault handlers do this. So we do
14 * disable preemption but we don't necessarily care about that.
15 */
16static inline void pagefault_disable(void)
17{
18	preempt_count_inc();
19	/*
20	 * make sure to have issued the store before a pagefault
21	 * can hit.
22	 */
23	barrier();
24}
25
26static inline void pagefault_enable(void)
27{
28	/*
29	 * make sure to issue those last loads/stores before enabling
30	 * the pagefault handler again.
31	 */
32	barrier();
33	preempt_count_dec();
34	preempt_check_resched();
35}
36
37#ifndef ARCH_HAS_NOCACHE_UACCESS
38
39static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
40				const void __user *from, unsigned long n)
41{
42	return __copy_from_user_inatomic(to, from, n);
43}
44
45static inline unsigned long __copy_from_user_nocache(void *to,
46				const void __user *from, unsigned long n)
47{
48	return __copy_from_user(to, from, n);
49}
50
51#endif		/* ARCH_HAS_NOCACHE_UACCESS */
52
53/**
54 * probe_kernel_address(): safely attempt to read from a location
55 * @addr: address to read from - its type is type typeof(retval)*
56 * @retval: read into this variable
57 *
58 * Safely read from address @addr into variable @revtal.  If a kernel fault
59 * happens, handle that and return -EFAULT.
60 * We ensure that the __get_user() is executed in atomic context so that
61 * do_page_fault() doesn't attempt to take mmap_sem.  This makes
62 * probe_kernel_address() suitable for use within regions where the caller
63 * already holds mmap_sem, or other locks which nest inside mmap_sem.
64 * This must be a macro because __get_user() needs to know the types of the
65 * args.
66 *
67 * We don't include enough header files to be able to do the set_fs().  We
68 * require that the probe_kernel_address() caller will do that.
69 */
70#define probe_kernel_address(addr, retval)		\
71	({						\
72		long ret;				\
73		mm_segment_t old_fs = get_fs();		\
74							\
75		set_fs(KERNEL_DS);			\
76		pagefault_disable();			\
77		ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval));		\
78		pagefault_enable();			\
79		set_fs(old_fs);				\
80		ret;					\
81	})
82
83/*
84 * probe_kernel_read(): safely attempt to read from a location
85 * @dst: pointer to the buffer that shall take the data
86 * @src: address to read from
87 * @size: size of the data chunk
88 *
89 * Safely read from address @src to the buffer at @dst.  If a kernel fault
90 * happens, handle that and return -EFAULT.
91 */
92extern long probe_kernel_read(void *dst, const void *src, size_t size);
93extern long __probe_kernel_read(void *dst, const void *src, size_t size);
94
95/*
96 * probe_kernel_write(): safely attempt to write to a location
97 * @dst: address to write to
98 * @src: pointer to the data that shall be written
99 * @size: size of the data chunk
100 *
101 * Safely write to address @dst from the buffer at @src.  If a kernel fault
102 * happens, handle that and return -EFAULT.
103 */
104extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
105extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
106
107#endif		/* __LINUX_UACCESS_H__ */
108