centos man page for __copy_from_user

Query: __copy_from_user

OS: centos

Section: 9

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

NAME
__copy_from_user - Copy a block of data from user space, with less checking.
SYNOPSIS
unsigned long __copy_from_user(void * to, const void __user * from, unsigned long n);
ARGUMENTS
to Destination address, in kernel space. from Source address, in user space. n Number of bytes to copy.
CONTEXT
User context only. This function may sleep.
DESCRIPTION
Copy data from user space to kernel space. Caller must check the specified block with access_ok before calling this function. Returns number of bytes that could not be copied. On success, this will be zero. If some data could not be copied, this function will pad the copied data to the requested size using zero bytes. An alternate version - __copy_from_user_inatomic - may be called from atomic context and will fail rather than sleep. In this case the uncopied bytes will *NOT* be padded with zeros. See fs/filemap.h for explanation of why this is needed.
COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 __COPY_FROM_USER(9)