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Linux/mm/maccess.c

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  1 /*
  2  * Access kernel memory without faulting.
  3  */
  4 #include <linux/export.h>
  5 #include <linux/mm.h>
  6 #include <linux/uaccess.h>
  7 
  8 /**
  9  * probe_kernel_read(): safely attempt to read from a location
 10  * @dst: pointer to the buffer that shall take the data
 11  * @src: address to read from
 12  * @size: size of the data chunk
 13  *
 14  * Safely read from address @src to the buffer at @dst.  If a kernel fault
 15  * happens, handle that and return -EFAULT.
 16  */
 17 
 18 long __weak probe_kernel_read(void *dst, const void *src, size_t size)
 19     __attribute__((alias("__probe_kernel_read")));
 20 
 21 long __probe_kernel_read(void *dst, const void *src, size_t size)
 22 {
 23         long ret;
 24         mm_segment_t old_fs = get_fs();
 25 
 26         set_fs(KERNEL_DS);
 27         pagefault_disable();
 28         ret = __copy_from_user_inatomic(dst,
 29                         (__force const void __user *)src, size);
 30         pagefault_enable();
 31         set_fs(old_fs);
 32 
 33         return ret ? -EFAULT : 0;
 34 }
 35 EXPORT_SYMBOL_GPL(probe_kernel_read);
 36 
 37 /**
 38  * probe_kernel_write(): safely attempt to write to a location
 39  * @dst: address to write to
 40  * @src: pointer to the data that shall be written
 41  * @size: size of the data chunk
 42  *
 43  * Safely write to address @dst from the buffer at @src.  If a kernel fault
 44  * happens, handle that and return -EFAULT.
 45  */
 46 long __weak probe_kernel_write(void *dst, const void *src, size_t size)
 47     __attribute__((alias("__probe_kernel_write")));
 48 
 49 long __probe_kernel_write(void *dst, const void *src, size_t size)
 50 {
 51         long ret;
 52         mm_segment_t old_fs = get_fs();
 53 
 54         set_fs(KERNEL_DS);
 55         pagefault_disable();
 56         ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
 57         pagefault_enable();
 58         set_fs(old_fs);
 59 
 60         return ret ? -EFAULT : 0;
 61 }
 62 EXPORT_SYMBOL_GPL(probe_kernel_write);
 63 

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