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#ifndef CONFIG_PREEMPT
29	/*
30	 * make sure to issue those last loads/stores before enabling
31	 * the pagefault handler again.
32	 */
33	barrier();
34	preempt_count_dec();
35#else
36	preempt_enable();
37#endif
38}
39
40#ifndef ARCH_HAS_NOCACHE_UACCESS
41
42static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
43				const void __user *from, unsigned long n)
44{
45	return __copy_from_user_inatomic(to, from, n);
46}
47
48static inline unsigned long __copy_from_user_nocache(void *to,
49				const void __user *from, unsigned long n)
50{
51	return __copy_from_user(to, from, n);
52}
53
54#endif		/* ARCH_HAS_NOCACHE_UACCESS */
55
56/**
57 * probe_kernel_address(): safely attempt to read from a location
58 * @addr: address to read from - its type is type typeof(retval)*
59 * @retval: read into this variable
60 *
61 * Safely read from address @addr into variable @revtal.  If a kernel fault
62 * happens, handle that and return -EFAULT.
63 * We ensure that the __get_user() is executed in atomic context so that
64 * do_page_fault() doesn't attempt to take mmap_sem.  This makes
65 * probe_kernel_address() suitable for use within regions where the caller
66 * already holds mmap_sem, or other locks which nest inside mmap_sem.
67 * This must be a macro because __get_user() needs to know the types of the
68 * args.
69 *
70 * We don't include enough header files to be able to do the set_fs().  We
71 * require that the probe_kernel_address() caller will do that.
72 */
73#define probe_kernel_address(addr, retval)		\
74	({						\
75		long ret;				\
76		mm_segment_t old_fs = get_fs();		\
77							\
78		set_fs(KERNEL_DS);			\
79		pagefault_disable();			\
80		ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval));		\
81		pagefault_enable();			\
82		set_fs(old_fs);				\
83		ret;					\
84	})
85
86/*
87 * probe_kernel_read(): safely attempt to read from a location
88 * @dst: pointer to the buffer that shall take the data
89 * @src: address to read from
90 * @size: size of the data chunk
91 *
92 * Safely read from address @src to the buffer at @dst.  If a kernel fault
93 * happens, handle that and return -EFAULT.
94 */
95extern long probe_kernel_read(void *dst, const void *src, size_t size);
96extern long __probe_kernel_read(void *dst, const void *src, size_t size);
97
98/*
99 * probe_kernel_write(): safely attempt to write to a location
100 * @dst: address to write to
101 * @src: pointer to the data that shall be written
102 * @size: size of the data chunk
103 *
104 * Safely write to address @dst from the buffer at @src.  If a kernel fault
105 * happens, handle that and return -EFAULT.
106 */
107extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
108extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
109
110#endif		/* __LINUX_UACCESS_H__ */
111