linux/include/linux/uaccess.h
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   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        inc_preempt_count();
  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        /*
  29         * make sure to issue those last loads/stores before enabling
  30         * the pagefault handler again.
  31         */
  32        barrier();
  33        dec_preempt_count();
  34        /*
  35         * make sure we do..
  36         */
  37        barrier();
  38        preempt_check_resched();
  39}
  40
  41#ifndef ARCH_HAS_NOCACHE_UACCESS
  42
  43static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
  44                                const void __user *from, unsigned long n)
  45{
  46        return __copy_from_user_inatomic(to, from, n);
  47}
  48
  49static inline unsigned long __copy_from_user_nocache(void *to,
  50                                const void __user *from, unsigned long n)
  51{
  52        return __copy_from_user(to, from, n);
  53}
  54
  55#endif          /* ARCH_HAS_NOCACHE_UACCESS */
  56
  57/**
  58 * probe_kernel_address(): safely attempt to read from a location
  59 * @addr: address to read from - its type is type typeof(retval)*
  60 * @retval: read into this variable
  61 *
  62 * Safely read from address @addr into variable @revtal.  If a kernel fault
  63 * happens, handle that and return -EFAULT.
  64 * We ensure that the __get_user() is executed in atomic context so that
  65 * do_page_fault() doesn't attempt to take mmap_sem.  This makes
  66 * probe_kernel_address() suitable for use within regions where the caller
  67 * already holds mmap_sem, or other locks which nest inside mmap_sem.
  68 * This must be a macro because __get_user() needs to know the types of the
  69 * args.
  70 *
  71 * We don't include enough header files to be able to do the set_fs().  We
  72 * require that the probe_kernel_address() caller will do that.
  73 */
  74#define probe_kernel_address(addr, retval)              \
  75        ({                                              \
  76                long ret;                               \
  77                mm_segment_t old_fs = get_fs();         \
  78                                                        \
  79                set_fs(KERNEL_DS);                      \
  80                pagefault_disable();                    \
  81                ret = __copy_from_user_inatomic(&(retval), (__force typeof(retval) __user *)(addr), sizeof(retval));            \
  82                pagefault_enable();                     \
  83                set_fs(old_fs);                         \
  84                ret;                                    \
  85        })
  86
  87/*
  88 * probe_kernel_read(): safely attempt to read from a location
  89 * @dst: pointer to the buffer that shall take the data
  90 * @src: address to read from
  91 * @size: size of the data chunk
  92 *
  93 * Safely read from address @src to the buffer at @dst.  If a kernel fault
  94 * happens, handle that and return -EFAULT.
  95 */
  96extern long probe_kernel_read(void *dst, const void *src, size_t size);
  97extern long __probe_kernel_read(void *dst, const void *src, size_t size);
  98
  99/*
 100 * probe_kernel_write(): safely attempt to write to a location
 101 * @dst: address to write to
 102 * @src: pointer to the data that shall be written
 103 * @size: size of the data chunk
 104 *
 105 * Safely write to address @dst from the buffer at @src.  If a kernel fault
 106 * happens, handle that and return -EFAULT.
 107 */
 108extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
 109extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
 110
 111#endif          /* __LINUX_UACCESS_H__ */
 112
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