Line data Source code
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 : */
16 : static inline void pagefault_disable(void)
17 : {
18 0 : inc_preempt_count();
19 : /*
20 : * make sure to have issued the store before a pagefault
21 : * can hit.
22 : */
23 0 : barrier();
24 0 : }
25 :
26 : static inline void pagefault_enable(void)
27 : {
28 0 : /*
29 : * make sure to issue those last loads/stores before enabling
30 : * the pagefault handler again.
31 : */
32 0 : barrier();
33 0 : dec_preempt_count();
34 : /*
35 : * make sure we do..
36 : */
37 0 : barrier();
38 0 : preempt_check_resched();
39 : }
40 :
41 : #ifndef ARCH_HAS_NOCACHE_UACCESS
42 :
43 : static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
44 : const void __user *from, unsigned long n)
45 : {
46 : return __copy_from_user_inatomic(to, from, n);
47 : }
48 :
49 : static inline unsigned long __copy_from_user_nocache(void *to,
50 : const void __user *from, unsigned long n)
51 : {
52 : return __copy_from_user(to, from, n);
53 : }
54 :
55 : #endif /* ARCH_HAS_NOCACHE_UACCESS */
56 :
57 : /**
58 : * probe_kernel_address(): safely attempt to read from a location
59 : * @addr: address to read from - its type is type typeof(retval)*
60 : * @retval: read into this variable
61 : *
62 : * Safely read from address @addr into variable @revtal. If a kernel fault
63 : * happens, handle that and return -EFAULT.
64 : * We ensure that the __get_user() is executed in atomic context so that
65 : * do_page_fault() doesn't attempt to take mmap_sem. This makes
66 : * probe_kernel_address() suitable for use within regions where the caller
67 : * already holds mmap_sem, or other locks which nest inside mmap_sem.
68 : * This must be a macro because __get_user() needs to know the types of the
69 : * args.
70 : *
71 : * We don't include enough header files to be able to do the set_fs(). We
72 : * require that the probe_kernel_address() caller will do that.
73 : */
74 : #define probe_kernel_address(addr, retval) \
75 : ({ \
76 : long ret; \
77 : mm_segment_t old_fs = get_fs(); \
78 : \
79 : set_fs(KERNEL_DS); \
80 : pagefault_disable(); \
81 : ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval)); \
82 : pagefault_enable(); \
83 : set_fs(old_fs); \
84 : ret; \
85 : })
86 :
87 : /*
88 : * probe_kernel_read(): safely attempt to read from a location
89 : * @dst: pointer to the buffer that shall take the data
90 : * @src: address to read from
91 : * @size: size of the data chunk
92 : *
93 : * Safely read from address @src to the buffer at @dst. If a kernel fault
94 : * happens, handle that and return -EFAULT.
95 : */
96 : extern long probe_kernel_read(void *dst, void *src, size_t size);
97 : extern long __probe_kernel_read(void *dst, void *src, size_t size);
98 :
99 : /*
100 : * probe_kernel_write(): safely attempt to write to a location
101 : * @dst: address to write to
102 : * @src: pointer to the data that shall be written
103 : * @size: size of the data chunk
104 : *
105 : * Safely write to address @dst from the buffer at @src. If a kernel fault
106 : * happens, handle that and return -EFAULT.
107 : */
108 : extern long notrace probe_kernel_write(void *dst, void *src, size_t size);
109 : extern long notrace __probe_kernel_write(void *dst, void *src, size_t size);
110 :
111 : #endif /* __LINUX_UACCESS_H__ */
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