arch/x86/lib/usercopy.c

   1 /*
   2  * User address space access functions.
   3  *
   4  *  For licencing details see kernel-base/COPYING
   5  */
   6
   7 #include <linux/highmem.h>
   8 #include <linux/export.h>
   9
  10 #include <asm/word-at-a-time.h>
  11 #include <linux/sched.h>
  12
  13 /*
  14  * We rely on the nested NMI work to allow atomic faults from the NMI path; the
  15  * nested NMI paths are careful to preserve CR2.
  16  */
  17 unsigned long
  18 copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
  19 {
  20         unsigned long ret;
  21
  22         if (__range_not_ok(from, n, TASK_SIZE))
  23                 return n;
  24
  25         /*
  26          * Even though this function is typically called from NMI/IRQ context
  27          * disable pagefaults so that its behaviour is consistent even when
  28          * called form other contexts.
  29          */
  30         pagefault_disable();
  31         ret = __copy_from_user_inatomic(to, from, n);
  32         pagefault_enable();
  33
  34         return ret;
  35 }
  36 EXPORT_SYMBOL_GPL(copy_from_user_nmi);
  37
  38 /**
  39  * copy_to_user: - Copy a block of data into user space.
  40  * @to:   Destination address, in user space.
  41  * @from: Source address, in kernel space.
  42  * @n:    Number of bytes to copy.
  43  *
  44  * Context: User context only. This function may sleep if pagefaults are
  45  *          enabled.
  46  *
  47  * Copy data from kernel space to user space.
  48  *
  49  * Returns number of bytes that could not be copied.
  50  * On success, this will be zero.
  51  */
  52 unsigned long _copy_to_user(void __user *to, const void *from, unsigned n)
  53 {
  54         if (access_ok(VERIFY_WRITE, to, n))
  55                 n = __copy_to_user(to, from, n);
  56         return n;
  57 }
  58 EXPORT_SYMBOL(_copy_to_user);
  59
  60 /**
  61  * copy_from_user: - Copy a block of data from user space.
  62  * @to:   Destination address, in kernel space.
  63  * @from: Source address, in user space.
  64  * @n:    Number of bytes to copy.
  65  *
  66  * Context: User context only. This function may sleep if pagefaults are
  67  *          enabled.
  68  *
  69  * Copy data from user space to kernel space.
  70  *
  71  * Returns number of bytes that could not be copied.
  72  * On success, this will be zero.
  73  *
  74  * If some data could not be copied, this function will pad the copied
  75  * data to the requested size using zero bytes.
  76  */
  77 unsigned long _copy_from_user(void *to, const void __user *from, unsigned n)
  78 {
  79         if (access_ok(VERIFY_READ, from, n))
  80                 n = __copy_from_user(to, from, n);
  81         else
  82                 memset(to, 0, n);
  83         return n;
  84 }
  85 EXPORT_SYMBOL(_copy_from_user);