include/linux/uaccess.h

   1 #ifndef __LINUX_UACCESS_H__
   2 #define __LINUX_UACCESS_H__
   3
   4 #include <linux/sched.h>
   5 #include <asm/uaccess.h>
   6
   7 static __always_inline void pagefault_disabled_inc(void)
   8 {
   9         current->pagefault_disabled++;
  10 }
  11
  12 static __always_inline void pagefault_disabled_dec(void)
  13 {
  14         current->pagefault_disabled--;
  15         WARN_ON(current->pagefault_disabled < 0);
  16 }
  17
  18 /*
  19  * These routines enable/disable the pagefault handler. If disabled, it will
  20  * not take any locks and go straight to the fixup table.
  21  *
  22  * User access methods will not sleep when called from a pagefault_disabled()
  23  * environment.
  24  */
  25 static inline void pagefault_disable(void)
  26 {
  27         pagefault_disabled_inc();
  28         /*
  29          * make sure to have issued the store before a pagefault
  30          * can hit.
  31          */
  32         barrier();
  33 }
  34
  35 static inline void pagefault_enable(void)
  36 {
  37         /*
  38          * make sure to issue those last loads/stores before enabling
  39          * the pagefault handler again.
  40          */
  41         barrier();
  42         pagefault_disabled_dec();
  43 }
  44
  45 /*
  46  * Is the pagefault handler disabled? If so, user access methods will not sleep.
  47  */
  48 #define pagefault_disabled() (current->pagefault_disabled != 0)
  49
  50 /*
  51  * The pagefault handler is in general disabled by pagefault_disable() or
  52  * when in irq context (via in_atomic()).
  53  *
  54  * This function should only be used by the fault handlers. Other users should
  55  * stick to pagefault_disabled().
  56  * Please NEVER use preempt_disable() to disable the fault handler. With
  57  * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
  58  * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
  59  */
  60 #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
  61
  62 #ifndef ARCH_HAS_NOCACHE_UACCESS
  63
  64 static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
  65                                 const void __user *from, unsigned long n)
  66 {
  67         return __copy_from_user_inatomic(to, from, n);
  68 }
  69
  70 static inline unsigned long __copy_from_user_nocache(void *to,
  71                                 const void __user *from, unsigned long n)
  72 {
  73         return __copy_from_user(to, from, n);
  74 }
  75
  76 #endif          /* ARCH_HAS_NOCACHE_UACCESS */
  77
  78 /**
  79  * probe_kernel_address(): safely attempt to read from a location
  80  * @addr: address to read from - its type is type typeof(retval)*
  81  * @retval: read into this variable
  82  *
  83  * Safely read from address @addr into variable @revtal.  If a kernel fault
  84  * happens, handle that and return -EFAULT.
  85  * We ensure that the __get_user() is executed in atomic context so that
  86  * do_page_fault() doesn't attempt to take mmap_sem.  This makes
  87  * probe_kernel_address() suitable for use within regions where the caller
  88  * already holds mmap_sem, or other locks which nest inside mmap_sem.
  89  * This must be a macro because __get_user() needs to know the types of the
  90  * args.
  91  *
  92  * We don't include enough header files to be able to do the set_fs().  We
  93  * require that the probe_kernel_address() caller will do that.
  94  */
  95 #define probe_kernel_address(addr, retval)              \
  96         ({                                              \
  97                 long ret;                               \
  98                 mm_segment_t old_fs = get_fs();         \
  99                                                         \
 100                 set_fs(KERNEL_DS);                      \
 101                 pagefault_disable();                    \
 102                 ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval));            \
 103                 pagefault_enable();                     \
 104                 set_fs(old_fs);                         \
 105                 ret;                                    \
 106         })
 107
 108 /*
 109  * probe_kernel_read(): safely attempt to read from a location
 110  * @dst: pointer to the buffer that shall take the data
 111  * @src: address to read from
 112  * @size: size of the data chunk
 113  *
 114  * Safely read from address @src to the buffer at @dst.  If a kernel fault
 115  * happens, handle that and return -EFAULT.
 116  */
 117 extern long probe_kernel_read(void *dst, const void *src, size_t size);
 118 extern long __probe_kernel_read(void *dst, const void *src, size_t size);
 119
 120 /*
 121  * probe_kernel_write(): safely attempt to write to a location
 122  * @dst: address to write to
 123  * @src: pointer to the data that shall be written
 124  * @size: size of the data chunk
 125  *
 126  * Safely write to address @dst from the buffer at @src.  If a kernel fault
 127  * happens, handle that and return -EFAULT.
 128  */
 129 extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
 130 extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
 131
 132 #endif          /* __LINUX_UACCESS_H__ */