]>
git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/blob - mm/maccess.c
2 * Access kernel memory without faulting.
4 #include <linux/export.h>
6 #include <linux/uaccess.h>
9 * probe_kernel_read(): safely attempt to read from a location
10 * @dst: pointer to the buffer that shall take the data
11 * @src: address to read from
12 * @size: size of the data chunk
14 * Safely read from address @src to the buffer at @dst. If a kernel fault
15 * happens, handle that and return -EFAULT.
17 * We ensure that the copy_from_user is executed in atomic context so that
18 * do_page_fault() doesn't attempt to take mmap_sem. This makes
19 * probe_kernel_read() suitable for use within regions where the caller
20 * already holds mmap_sem, or other locks which nest inside mmap_sem.
23 long __weak
probe_kernel_read(void *dst
, const void *src
, size_t size
)
24 __attribute__((alias("__probe_kernel_read")));
26 long __probe_kernel_read(void *dst
, const void *src
, size_t size
)
29 mm_segment_t old_fs
= get_fs();
33 current
->kernel_uaccess_faults_ok
++;
34 ret
= __copy_from_user_inatomic(dst
,
35 (__force
const void __user
*)src
, size
);
36 current
->kernel_uaccess_faults_ok
--;
40 return ret
? -EFAULT
: 0;
42 EXPORT_SYMBOL_GPL(probe_kernel_read
);
45 * probe_kernel_write(): safely attempt to write to a location
46 * @dst: address to write to
47 * @src: pointer to the data that shall be written
48 * @size: size of the data chunk
50 * Safely write to address @dst from the buffer at @src. If a kernel fault
51 * happens, handle that and return -EFAULT.
53 long __weak
probe_kernel_write(void *dst
, const void *src
, size_t size
)
54 __attribute__((alias("__probe_kernel_write")));
56 long __probe_kernel_write(void *dst
, const void *src
, size_t size
)
59 mm_segment_t old_fs
= get_fs();
63 current
->kernel_uaccess_faults_ok
++;
64 ret
= __copy_to_user_inatomic((__force
void __user
*)dst
, src
, size
);
65 current
->kernel_uaccess_faults_ok
--;
69 return ret
? -EFAULT
: 0;
71 EXPORT_SYMBOL_GPL(probe_kernel_write
);
74 * strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
75 * @dst: Destination address, in kernel space. This buffer must be at
76 * least @count bytes long.
77 * @unsafe_addr: Unsafe address.
78 * @count: Maximum number of bytes to copy, including the trailing NUL.
80 * Copies a NUL-terminated string from unsafe address to kernel buffer.
82 * On success, returns the length of the string INCLUDING the trailing NUL.
84 * If access fails, returns -EFAULT (some data may have been copied
85 * and the trailing NUL added).
87 * If @count is smaller than the length of the string, copies @count-1 bytes,
88 * sets the last byte of @dst buffer to NUL and returns @count.
90 long strncpy_from_unsafe(char *dst
, const void *unsafe_addr
, long count
)
92 mm_segment_t old_fs
= get_fs();
93 const void *src
= unsafe_addr
;
96 if (unlikely(count
<= 0))
101 current
->kernel_uaccess_faults_ok
++;
104 ret
= __get_user(*dst
++, (const char __user __force
*)src
++);
105 } while (dst
[-1] && ret
== 0 && src
- unsafe_addr
< count
);
107 current
->kernel_uaccess_faults_ok
--;
112 return ret
? -EFAULT
: src
- unsafe_addr
;