1 /* 2 * Access kernel memory without faulting. 3 */ 4 #include <linux/uaccess.h> 5 #include <linux/module.h> 6 #include <linux/mm.h> 7 8 /** 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 13 * 14 * Safely read from address @src to the buffer at @dst. If a kernel fault 15 * happens, handle that and return -EFAULT. 16 */ 17 long probe_kernel_read(void *dst, void *src, size_t size) 18 { 19 long ret; 20 mm_segment_t old_fs = get_fs(); 21 22 set_fs(KERNEL_DS); 23 pagefault_disable(); 24 ret = __copy_from_user_inatomic(dst, 25 (__force const void __user *)src, size); 26 pagefault_enable(); 27 set_fs(old_fs); 28 29 return ret ? -EFAULT : 0; 30 } 31 EXPORT_SYMBOL_GPL(probe_kernel_read); 32 33 /** 34 * probe_kernel_write(): safely attempt to write to a location 35 * @dst: address to write to 36 * @src: pointer to the data that shall be written 37 * @size: size of the data chunk 38 * 39 * Safely write to address @dst from the buffer at @src. If a kernel fault 40 * happens, handle that and return -EFAULT. 41 */ 42 long probe_kernel_write(void *dst, void *src, size_t size) 43 { 44 long ret; 45 mm_segment_t old_fs = get_fs(); 46 47 set_fs(KERNEL_DS); 48 pagefault_disable(); 49 ret = __copy_to_user_inatomic((__force void __user *)dst, src, size); 50 pagefault_enable(); 51 set_fs(old_fs); 52 53 return ret ? -EFAULT : 0; 54 } 55 EXPORT_SYMBOL_GPL(probe_kernel_write); 56