1 /* 2 * Access kernel memory without faulting. 3 */ 4 #include <linux/export.h> 5 #include <linux/mm.h> 6 #include <linux/uaccess.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 18 long __weak probe_kernel_read(void *dst, const void *src, size_t size) 19 __attribute__((alias("__probe_kernel_read"))); 20 21 long __probe_kernel_read(void *dst, const void *src, size_t size) 22 { 23 long ret; 24 mm_segment_t old_fs = get_fs(); 25 26 set_fs(KERNEL_DS); 27 pagefault_disable(); 28 ret = __copy_from_user_inatomic(dst, 29 (__force const void __user *)src, size); 30 pagefault_enable(); 31 set_fs(old_fs); 32 33 return ret ? -EFAULT : 0; 34 } 35 EXPORT_SYMBOL_GPL(probe_kernel_read); 36 37 /** 38 * probe_kernel_write(): safely attempt to write to a location 39 * @dst: address to write to 40 * @src: pointer to the data that shall be written 41 * @size: size of the data chunk 42 * 43 * Safely write to address @dst from the buffer at @src. If a kernel fault 44 * happens, handle that and return -EFAULT. 45 */ 46 long __weak probe_kernel_write(void *dst, const void *src, size_t size) 47 __attribute__((alias("__probe_kernel_write"))); 48 49 long __probe_kernel_write(void *dst, const void *src, size_t size) 50 { 51 long ret; 52 mm_segment_t old_fs = get_fs(); 53 54 set_fs(KERNEL_DS); 55 pagefault_disable(); 56 ret = __copy_to_user_inatomic((__force void __user *)dst, src, size); 57 pagefault_enable(); 58 set_fs(old_fs); 59 60 return ret ? -EFAULT : 0; 61 } 62 EXPORT_SYMBOL_GPL(probe_kernel_write); 63