LXR linux/include/linux/uaccess.h

   1#ifndef __LINUX_UACCESS_H__
   2#define __LINUX_UACCESS_H__
   3
   4#include <linux/preempt.h>
   5#include <asm/uaccess.h>
   6
   7/*
   8 * These routines enable/disable the pagefault handler in that
   9 * it will not take any locks and go straight to the fixup table.
  10 *
  11 * They have great resemblance to the preempt_disable/enable calls
  12 * and in fact they are identical; this is because currently there is
  13 * no other way to make the pagefault handlers do this. So we do
  14 * disable preemption but we don't necessarily care about that.
  15 */
  16static inline void pagefault_disable(void)
  17{
  18        preempt_count_inc();
  19        /*
  20         * make sure to have issued the store before a pagefault
  21         * can hit.
  22         */
  23        barrier();
  24}
  25
  26static inline void pagefault_enable(void)
  27{
  28#ifndef CONFIG_PREEMPT
  29        /*
  30         * make sure to issue those last loads/stores before enabling
  31         * the pagefault handler again.
  32         */
  33        barrier();
  34        preempt_count_dec();
  35#else
  36        preempt_enable();
  37#endif
  38}
  39
  40#ifndef ARCH_HAS_NOCACHE_UACCESS
  41
  42static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
  43                                const void __user *from, unsigned long n)
  44{
  45        return __copy_from_user_inatomic(to, from, n);
  46}
  47
  48static inline unsigned long __copy_from_user_nocache(void *to,
  49                                const void __user *from, unsigned long n)
  50{
  51        return __copy_from_user(to, from, n);
  52}
  53
  54#endif          /* ARCH_HAS_NOCACHE_UACCESS */
  55
  56/**
  57 * probe_kernel_address(): safely attempt to read from a location
  58 * @addr: address to read from - its type is type typeof(retval)*
  59 * @retval: read into this variable
  60 *
  61 * Safely read from address @addr into variable @revtal.  If a kernel fault
  62 * happens, handle that and return -EFAULT.
  63 * We ensure that the __get_user() is executed in atomic context so that
  64 * do_page_fault() doesn't attempt to take mmap_sem.  This makes
  65 * probe_kernel_address() suitable for use within regions where the caller
  66 * already holds mmap_sem, or other locks which nest inside mmap_sem.
  67 * This must be a macro because __get_user() needs to know the types of the
  68 * args.
  69 *
  70 * We don't include enough header files to be able to do the set_fs().  We
  71 * require that the probe_kernel_address() caller will do that.
  72 */
  73#define probe_kernel_address(addr, retval)              \
  74        ({                                              \
  75                long ret;                               \
  76                mm_segment_t old_fs = get_fs();         \
  77                                                        \
  78                set_fs(KERNEL_DS);                      \
  79                pagefault_disable();                    \
  80                ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval));            \
  81                pagefault_enable();                     \
  82                set_fs(old_fs);                         \
  83                ret;                                    \
  84        })
  85
  86/*
  87 * probe_kernel_read(): safely attempt to read from a location
  88 * @dst: pointer to the buffer that shall take the data
  89 * @src: address to read from
  90 * @size: size of the data chunk
  91 *
  92 * Safely read from address @src to the buffer at @dst.  If a kernel fault
  93 * happens, handle that and return -EFAULT.
  94 */
  95extern long probe_kernel_read(void *dst, const void *src, size_t size);
  96extern long __probe_kernel_read(void *dst, const void *src, size_t size);
  97
  98/*
  99 * probe_kernel_write(): safely attempt to write to a location
 100 * @dst: address to write to
 101 * @src: pointer to the data that shall be written
 102 * @size: size of the data chunk
 103 *
 104 * Safely write to address @dst from the buffer at @src.  If a kernel fault
 105 * happens, handle that and return -EFAULT.
 106 */
 107extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
 108extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
 109
 110#endif          /* __LINUX_UACCESS_H__ */
 111