UIO_COPYIN(9F) Kernel Functions for Drivers UIO_COPYIN(9F)
uio_copyin, uio_copyout - copy data to or from an address space named
by a uio_seg_t
#include <sys/uio.h>
int
uio_copyin(const void *src, void *dst, size_t n, uio_seg_t seg);
int
uio_copyout(const void *src, void *dst, size_t n, uio_seg_t seg);
illumos DDI specific
src Source address of the copy.
dst Destination address of the copy.
n Number of bytes to copy.
seg The address space in which the caller's buffer lies, one
of UIO_USERSPACE, UIO_USERISPACE or UIO_SYSSPACE.
The uio_copyin() function copies n bytes of data from src, which lies
in the address space named by seg, to the kernel address dst. The
uio_copyout() function copies in the other direction, from the kernel
address src to dst in the address space named by seg.
These functions are for code which can be handed data in either user or
kernel memory, with its location described by a uio_seg_t, and which
would otherwise have to select between copyin(9F) and kcopy(9F) itself.
They are the uio_seg_t counterparts of ddi_copyin(9F) and
ddi_copyout(9F), which provide the same service for the mode flags
passed to an ioctl(9E) entry point.
When seg is UIO_USERSPACE or UIO_USERISPACE, the caller's buffer lies
in the user address space of the calling process and the copy behaves
as copyin(9F) or copyout(9F). When seg is UIO_SYSSPACE, both addresses
are kernel addresses and the copy is performed with kcopy(9F). In
every case a fault taken during the copy is returned to the caller
rather than causing the system to panic. Passing any other value as
seg causes the system to panic.
When seg is UIO_USERSPACE or UIO_USERISPACE, these functions can be
called from user context only. When seg is UIO_SYSSPACE, they can be
called from user or kernel context.
Upon successful completion, the uio_copyin() and uio_copyout()
functions return 0. Otherwise, -1 is returned to indicate that a fault
occurred and the copy did not complete.
ioctl(9E), bcopy(9F), copyin(9F), copyout(9F), ddi_copyin(9F),
ddi_copyout(9F), kcopy(9F), uiomove(9F)
illumos July 11, 2026 illumos
NAME
uio_copyin, uio_copyout - copy data to or from an address space named
by a uio_seg_t
SYNOPSIS
#include <sys/uio.h>
int
uio_copyin(const void *src, void *dst, size_t n, uio_seg_t seg);
int
uio_copyout(const void *src, void *dst, size_t n, uio_seg_t seg);
INTERFACE LEVEL
illumos DDI specific
PARAMETERS
src Source address of the copy.
dst Destination address of the copy.
n Number of bytes to copy.
seg The address space in which the caller's buffer lies, one
of UIO_USERSPACE, UIO_USERISPACE or UIO_SYSSPACE.
DESCRIPTION
The uio_copyin() function copies n bytes of data from src, which lies
in the address space named by seg, to the kernel address dst. The
uio_copyout() function copies in the other direction, from the kernel
address src to dst in the address space named by seg.
These functions are for code which can be handed data in either user or
kernel memory, with its location described by a uio_seg_t, and which
would otherwise have to select between copyin(9F) and kcopy(9F) itself.
They are the uio_seg_t counterparts of ddi_copyin(9F) and
ddi_copyout(9F), which provide the same service for the mode flags
passed to an ioctl(9E) entry point.
When seg is UIO_USERSPACE or UIO_USERISPACE, the caller's buffer lies
in the user address space of the calling process and the copy behaves
as copyin(9F) or copyout(9F). When seg is UIO_SYSSPACE, both addresses
are kernel addresses and the copy is performed with kcopy(9F). In
every case a fault taken during the copy is returned to the caller
rather than causing the system to panic. Passing any other value as
seg causes the system to panic.
CONTEXT
When seg is UIO_USERSPACE or UIO_USERISPACE, these functions can be
called from user context only. When seg is UIO_SYSSPACE, they can be
called from user or kernel context.
RETURN VALUES
Upon successful completion, the uio_copyin() and uio_copyout()
functions return 0. Otherwise, -1 is returned to indicate that a fault
occurred and the copy did not complete.
SEE ALSO
ioctl(9E), bcopy(9F), copyin(9F), copyout(9F), ddi_copyin(9F),
ddi_copyout(9F), kcopy(9F), uiomove(9F)
illumos July 11, 2026 illumos