#include <sys/uio.h>

sys/uio.h Kernel.framework

includes: Availability.h, sys/cdefs.h, sys/_types.h, Kernel/sys/_types/_off_t.h, sys/_types/_size_t.h, Kernel/sys/_types/_ssize_t.h, Kernel/sys/_types/_iovec_t.h, sys/kernel_types.h

20 functions · 3 macros · 2 enums

enumuio_seg

user / kernel address space type flags. WARNING - make sure to check when adding flags! Be sure new flags don't overlap the definitions in uio_internal.h NOTES - UIO_USERSPACE is equivalent to UIO_USERSPACE32, but UIO_USERSPACE32 is preferred. UIO_USERSPACE remains for backwards compatibility. UIO_SYSSPACE is equivalent to UIO_SYSSPACE32, but UIO_SYSSPACE is preferred.

underlying type unsigned int

UIO_USERSPACE	0	kernel address is virtual, to/from user virtual
UIO_SYSSPACE	2	kernel address is virtual, to/from system virtual
UIO_USERSPACE32	5	kernel address is virtual, to/from user 32-bit virtual
UIO_USERSPACE64	8	kernel address is virtual, to/from user 64-bit virtual
UIO_SYSSPACE32	11	deprecated

enum(anonymous)

underlying type unsigned int

UIOF_USERSPACE	1
UIOF_SYSSPACE	4
UIOF_USERSPACE32	32
UIOF_USERSPACE64	256
UIOF_SYSSPACE32	2048

macroUIO_SEG_IS_USER_SPACE

#define UIO_SEG_IS_USER_SPACE(a_uio_seg) ((1 << a_uio_seg) & (UIOF_USERSPACE64 | UIOF_USERSPACE32 | UIOF_USERSPACE))

functionuio_create

uio_t uio_create(
	/* max number of iovecs */
	int a_iovcount,
	/* max number of iovecs */
	/* current offset */
	off_t a_offset,
	/* current offset */
	/* type of address space */
	int a_spacetype,
	/* type of address space */
	/* read or write flag */
	int a_iodirection
)

uio_create - create an uio_t. Space is allocated to hold up to a_iovcount number of iovecs. The uio_t is not fully initialized until all iovecs are added using uio_addiov calls. a_iovcount is the maximum number of iovecs you may add.

functionuio_reset

void uio_reset(
	uio_t a_uio,
	/* current offset */
	off_t a_offset,
	/* current offset */
	/* type of address space */
	int a_spacetype,
	/* type of address space */
	/* read or write flag */
	int a_iodirection
)

uio_reset - reset an uio_t. Reset the given uio_t to initial values. The uio_t is not fully initialized until all iovecs are added using uio_add_ov calls. The a_iovcount value passed in the uio_create is the maximum number of iovecs you may add.

functionuio_duplicate

uio_t uio_duplicate(uio_t a_uio)

uio_duplicate - allocate a new uio and make a copy of the given uio_t. may return NULL.

functionuio_restore

int uio_restore(uio_t uio, uio_t snapshot_uio)

uio_restore - restore a uio to the state it was in the provided snapshot. returns 0 if it was successful else non zero.

functionuio_free

void uio_free(uio_t a_uio)

uio_free - free a uio_t allocated via uio_create.

functionuio_addiov

int uio_addiov(uio_t a_uio, user_addr_t a_baseaddr, user_size_t a_length)

uio_addiov - add an iovec to the given uio_t. You may call this up to the a_iovcount number that was passed to uio_create. returns 0 if add was successful else non zero.

functionuio_getiov

int uio_getiov(
	uio_t a_uio,
	int a_index,
	user_addr_t * a_baseaddr_p,
	user_size_t * a_length_p
)

uio_getiov - get iovec data associated with the given uio_t. Use a_index to iterate over each iovec (0 to (uio_iovcnt(uio_t) - 1)). a_baseaddr_p and a_length_p may be NULL. returns -1 when a_index is out of range or invalid uio_t. returns 0 when data is returned.

functionuio_update

void uio_update(uio_t a_uio, user_size_t a_count)

uio_update - update the given uio_t for a_count of completed IO. This call adjusts decrements the current iovec length and residual IO, and increments the current iovec base address and offset value.

functionuio_resid

user_ssize_t uio_resid(uio_t a_uio)

uio_resid - return the residual IO value for the given uio_t

functionuio_setresid

void uio_setresid(uio_t a_uio, user_ssize_t a_value)

uio_setresid - set the residual IO value for the given uio_t

functionuio_iovcnt

int uio_iovcnt(uio_t a_uio)

uio_iovcnt - return count of active iovecs for the given uio_t

functionuio_offset

off_t uio_offset(uio_t a_uio)

uio_offset - return the current offset value for the given uio_t

functionuio_setoffset

void uio_setoffset(uio_t a_uio, off_t a_offset)

uio_setoffset - set the current offset value for the given uio_t

functionuio_rw

int uio_rw(uio_t a_uio)

uio_rw - return the read / write flag for the given uio_t

functionuio_setrw

void uio_setrw(uio_t a_uio, int a_value)

uio_setrw - set the read / write flag for the given uio_t

functionuio_isuserspace

int uio_isuserspace(uio_t a_uio)

uio_isuserspace - return non zero value if the address space flag is for a user address space (could be 32 or 64 bit).

functionuio_curriovbase

user_addr_t uio_curriovbase(uio_t a_uio)

uio_curriovbase - return the base address of the current iovec associated with the given uio_t. May return 0.

functionuio_curriovlen

user_size_t uio_curriovlen(uio_t a_uio)

uio_curriovlen - return the length value of the current iovec associated with the given uio_t.

macroUIO_MAXIOV

Limits

#define UIO_MAXIOV 1024

max 1K of iov's

macroUIO_SMALLIOV

#define UIO_SMALLIOV 8

8 on stack, else malloc

functionuiomove

extern int uiomove(const char *__sized_by(n) cp, int n, struct uio *uio)

▾

claude-fable-5, 2026-08-23 · not from Apple sources · verified against xnu bsd/kern/kern_subr.c

Moves n bytes between the kernel buffer cp and the address ranges described by uio, in the direction given by the uio's uio_rw setting (UIO_READ copies from cp into the uio, UIO_WRITE from the uio into cp), advancing the uio's offset, iovec pointers, and residual count. Handles user, system, and physical address segment types. Returns 0 on success or EFAULT if a copy fails. Wrapper for uiomove64 taking a pointer rather than a 64-bit address.

functionuiomove64

extern int uiomove64(const __uint64_t cp, int n, struct uio *uio)

▾

claude-fable-5, 2026-08-23 · not from Apple sources · verified against xnu bsd/kern/kern_subr.c

As uiomove(), but the kernel-side buffer is named by a 64-bit address (addr64_t), permitting physical addresses on configurations where those exceed pointer width. Copies up to n bytes between the buffer and the uio's iovecs according to uio_rw and the uio's segment flag, updating offset and residual. Returns 0 on success or EFAULT on a failed copy.