mm/maccess.c

   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);