1__COPY_FROM_USER(9)       Memory Management in Linux       __COPY_FROM_USER(9)
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NAME

6       __copy_from_user - Copy a block of data from user space, with less
7       checking.
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SYNOPSIS

10       unsigned long __copy_from_user(void * to, const void __user * from,
11                                      unsigned long n);
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ARGUMENTS

14       to
15           Destination address, in kernel space.
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17       from
18           Source address, in user space.
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20       n
21           Number of bytes to copy.
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CONTEXT

24       User context only. This function may sleep.
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DESCRIPTION

27       Copy data from user space to kernel space. Caller must check the
28       specified block with access_ok before calling this function.
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30       Returns number of bytes that could not be copied. On success, this will
31       be zero.
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33       If some data could not be copied, this function will pad the copied
34       data to the requested size using zero bytes.
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36       An alternate version - __copy_from_user_inatomic - may be called from
37       atomic context and will fail rather than sleep. In this case the
38       uncopied bytes will *NOT* be padded with zeros. See fs/filemap.h for
39       explanation of why this is needed.
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42Kernel Hackers Manual 3.10         June 2019               __COPY_FROM_USER(9)
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