LXR linux/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 */
  17long 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}
  31EXPORT_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 */
  42long notrace __weak 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}
  55EXPORT_SYMBOL_GPL(probe_kernel_write);
  56