xref: /illumos-gate/usr/src/man/man9f/uio_copyin.9f (revision e67da9d6e15809e01554ff9bb20d0ddf210dbc6c)

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.Dd July 11, 2026
.Dt UIO_COPYIN 9F
.Os
.Sh NAME
.Nm uio_copyin ,
.Nm uio_copyout
.Nd copy data to or from an address space named by a uio_seg_t
.Sh SYNOPSIS
.In sys/uio.h
.Ft int
.Fo uio_copyin
.Fa "const void *src"
.Fa "void *dst"
.Fa "size_t n"
.Fa "uio_seg_t seg"
.Fc
.Ft int
.Fo uio_copyout
.Fa "const void *src"
.Fa "void *dst"
.Fa "size_t n"
.Fa "uio_seg_t seg"
.Fc
.Sh INTERFACE LEVEL
illumos DDI specific
.Sh PARAMETERS
.Bl -tag -width Fa
.It Fa src
Source address of the copy.
.It Fa dst
Destination address of the copy.
.It Fa n
Number of bytes to copy.
.It Fa seg
The address space in which the caller's buffer lies, one of
.Dv UIO_USERSPACE ,
.Dv UIO_USERISPACE
or
.Dv UIO_SYSSPACE .
.El
.Sh DESCRIPTION
The
.Fn uio_copyin
function copies
.Fa n
bytes of data from
.Fa src ,
which lies in the address space named by
.Fa seg ,
to the kernel address
.Fa dst .
The
.Fn uio_copyout
function copies in the other direction, from the kernel address
.Fa src
to
.Fa dst
in the address space named by
.Fa seg .
.Pp
These functions are for code which can be handed data in either user or
kernel memory, with its location described by a
.Vt uio_seg_t ,
and which would otherwise have to select between
.Xr copyin 9F
and
.Xr kcopy 9F
itself.
They are the
.Vt uio_seg_t
counterparts of
.Xr ddi_copyin 9F
and
.Xr ddi_copyout 9F ,
which provide the same service for the mode flags passed to an
.Xr ioctl 9E
entry point.
.Pp
When
.Fa seg
is
.Dv UIO_USERSPACE
or
.Dv UIO_USERISPACE ,
the caller's buffer lies in the user address space of the calling
process and the copy behaves as
.Xr copyin 9F
or
.Xr copyout 9F .
When
.Fa seg
is
.Dv UIO_SYSSPACE ,
both addresses are kernel addresses and the copy is performed with
.Xr 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
.Fa seg
causes the system to panic.
.Sh CONTEXT
When
.Fa seg
is
.Dv UIO_USERSPACE
or
.Dv UIO_USERISPACE ,
these functions can be called from user context only.
When
.Fa seg
is
.Dv UIO_SYSSPACE ,
they can be called from user or kernel context.
.Sh RETURN VALUES
Upon successful completion, the
.Fn uio_copyin
and
.Fn uio_copyout
functions return 0.
Otherwise, -1 is returned to indicate that a fault occurred and the copy
did not complete.
.Sh SEE ALSO
.Xr ioctl 9E ,
.Xr bcopy 9F ,
.Xr copyin 9F ,
.Xr copyout 9F ,
.Xr ddi_copyin 9F ,
.Xr ddi_copyout 9F ,
.Xr kcopy 9F ,
.Xr uiomove 9F