1.\" $NetBSD: errno.9,v 1.6 2021/06/29 22:40:53 dholland Exp $ 2.\" 3.\" Copyright (c) 2004 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Andrew Brown. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. Neither the name of the University nor the names of its contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.Dd December 3, 2004 34.Dt ERRNO 9 35.Os 36.Sh NAME 37.Nm errno 38.Nd kernel internal error numbers 39.Sh SYNOPSIS 40.In sys/errno.h 41.Sh DESCRIPTION 42This section provides an overview of the error numbers used internally 43by the kernel and indicate neither success nor failure. 44These error numbers are not returned to userland code. 45.Sh DIAGNOSTICS 46Kernel functions that indicate success or failure by means of either 0 47or an 48.Xr errno 2 49value sometimes have a need to indicate that 50.Dq special 51handling is required at an upper layer or, in the case of 52.Xr ioctl 2 53processing, that 54.Dq nothing was wrong but the request was not handled . 55To handle these cases, some negative 56.Xr errno 2 57values are defined which are handled by the kernel before returning a 58different 59.Xr errno 2 60value to userland or simply zero. 61.Pp 62The following is a list of the defined names and their meanings as 63given in 64.In errno.h . 65It is important to note that the value \-1 is 66.Em not 67used, since it is commonly used to indicate generic failure and leaves 68it up to the caller to determine the action to take. 69.Bl -hang -width Ds 70.It Er \-2 EJUSTRETURN Em "Modify regs, just return" . 71No more work is required and the function should just return. 72.It Er \-3 ERESTART Em "Restart syscall" . 73The system call should be restarted. 74This typically means that the machine dependent system call trap code 75will reposition the process's instruction pointer or program counter 76to re-execute the current system call with no other work required. 77.It Er \-4 EPASSTHROUGH Em "Operation not handled by this layer" . 78The operation was not handled and should be passed through to another 79layer. 80This often occurs when processing 81.Xr ioctl 2 82requests since lower layer processing may not handle something that 83subsequent code at a higher level will. 84.It Er \-5 EDUPFD Em "Duplicate file descriptor." 85This error is returned from the device open routine indicating that 86the 87.Ar l_dupfd 88field contains the file descriptor information to be returned to the caller, 89instead of the file descriptor that has been opened already. 90This error is used by cloning device multiplexors. 91Cloning device multiplexors open a new file descriptor and associate that 92file descriptor with the appropriate cloned device. 93They set 94.Ar l_dupfd 95to that new file descriptor and return 96.Er EDUPFD . 97.Xr vn_open 9 98takes the file descriptor pointed to by 99.Ar l_dupfd 100and arranges for it to be copied to the file descriptor that the open 101call will return. 102.It Er \-6 EMOVEFD Em "Move file descriptor." 103This error is similar to 104.Er EDUPFD 105except that the file descriptor in 106.Ar l_dupfd 107is closed after it has been copied. 108.El 109.Sh SEE ALSO 110.Xr errno 2 , 111.Xr ioctl 9 112.Sh HISTORY 113An 114.Nm 115manual page appeared in 116.At v6 . 117This 118.Nm 119manual page appeared in 120.Nx 3.0 . 121