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  */
  16 static 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
  26 static 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
  42 static 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
  48 static 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  */
  95 extern long probe_kernel_read(void *dst, const void *src, size_t size);
  96 extern 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  */
 107 extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
 108 extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
 109
 110 #endif          /* __LINUX_UACCESS_H__ */