xref: /openbmc/linux/include/linux/uaccess.h (revision b6dcefde)
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 	inc_preempt_count();
19 	/*
20 	 * make sure to have issued the store before a pagefault
21 	 * can hit.
22 	 */
23 	barrier();
24 }
25 
26 static 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 	dec_preempt_count();
34 	/*
35 	 * make sure we do..
36 	 */
37 	barrier();
38 	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__ */
112