__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.