1.\" $OpenBSD: ktrace.2,v 1.19 2007/07/17 16:30:10 jmc Exp $ 2.\" $NetBSD: ktrace.2,v 1.2 1995/02/27 12:33:58 cgd Exp $ 3.\" 4.\" Copyright (c) 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)ktrace.2 8.1 (Berkeley) 6/4/93 32.\" 33.Dd $Mdocdate: July 17 2007 $ 34.Dt KTRACE 2 35.Os 36.Sh NAME 37.Nm ktrace 38.Nd process tracing 39.Sh SYNOPSIS 40.Fd #include <sys/types.h> 41.Fd #include <sys/param.h> 42.Fd #include <sys/uio.h> 43.Fd #include <sys/ktrace.h> 44.Ft int 45.Fn ktrace "const char *tracefile" "int ops" "int trpoints" "pid_t pid" 46.Sh DESCRIPTION 47The 48.Fn ktrace 49function enables or disables tracing of one or more processes. 50Users may only trace their own processes. 51Only the superuser can trace setuid or setgid programs. 52.Fn ktrace 53is only available on kernels compiled with the 54.Cm KTRACE 55option. 56.Pp 57.Fa tracefile 58gives the pathname of the file to be used for tracing. 59The file must exist, be writable by the calling process, and 60not be a symbolic link. 61All trace records are always appended to the file, 62so the file must be truncated to zero length to discard 63previous trace data. 64If tracing points are being disabled (see 65.Dv KTROP_CLEAR 66below), 67.Ar tracefile 68may be 69.Dv NULL . 70.Pp 71The 72.Fa ops 73parameter specifies the requested ktrace operation. 74The defined operations are: 75.Bl -column KTRFLAG_DESCENDXXX -offset indent 76.It Dv KTROP_SET Enable trace points specified in Ar trpoints . 77.It Dv KTROP_CLEAR Disable trace points specified in Ar trpoints . 78.It Dv KTROP_CLEARFILE Stop all tracing. 79.It Dv KTRFLAG_DESCEND The tracing change should apply to the 80specified process and all its current children. 81.El 82.Pp 83The 84.Fa trpoints 85parameter specifies the trace points of interest. 86The defined trace points are: 87.Bl -column KTRFAC_SYSCALLXXX -offset indent 88.It Dv KTRFAC_SYSCALL Trace system calls. 89.It Dv KTRFAC_SYSRET Trace return values from system calls. 90.It Dv KTRFAC_NAMEI Trace name lookup operations. 91.It Dv KTRFAC_GENIO Trace all I/O (note that this option can 92generate much output). 93.It Dv KTRFAC_PSIG Trace posted signals. 94.It Dv KTRFAC_EMUL Trace emulation changes. 95.It Dv KTRFAC_CSW Trace context switch points. 96.It Dv KTRFAC_INHERIT Inherit tracing to future children. 97.El 98.Pp 99Each tracing event outputs a record composed of a generic header 100followed by a trace point specific structure. 101The generic header is: 102.Bd -literal 103struct ktr_header { 104 size_t ktr_len; /* length of buf */ 105 pid_t ktr_pid; /* process id */ 106 char ktr_comm[MAXCOMLEN+1]; /* command name */ 107 short ktr_type; /* trace record type */ 108 struct timeval ktr_time; /* timestamp */ 109 caddr_t ktr_buf; 110}; 111.Ed 112.Pp 113The 114.Fa ktr_len 115field specifies the length of the 116.Fa ktr_type 117data that follows this header. 118The 119.Fa ktr_pid 120and 121.Fa ktr_comm 122fields specify the process and command generating the record. 123The 124.Fa ktr_time 125field gives the time (with microsecond resolution) 126that the record was generated. 127The 128.Fa ktr_buf 129is an internal kernel pointer and is not useful. 130.Pp 131The generic header is followed by 132.Fa ktr_len 133bytes of a 134.Fa ktr_type 135record. 136The type specific records are defined in the 137.Aq Pa sys/ktrace.h 138include file. 139.Pp 140The 141.Fa pid 142parameter refers to a process ID. 143If it is negative, 144it refers to a process group ID. 145.Sh RETURN VALUES 146On successful completion a value of 0 is returned. 147Otherwise, a value of \-1 is returned and 148.Va errno 149is set to show the error. 150.Sh ERRORS 151.Fn ktrace 152will fail if: 153.Bl -tag -width ENAMETOOLONGAA 154.It Bq Er ENOTDIR 155A component of the path prefix is not a directory. 156.It Bq Er EINVAL 157The pathname contains a character with the high-order bit set. 158.It Bq Er ENAMETOOLONG 159A component of a pathname exceeded 255 characters, 160or an entire path name exceeded 1023 characters. 161.It Bq Er ENOENT 162The named tracefile does not exist. 163.It Bq Er EACCES 164Search permission is denied for a component of the path prefix or the 165path refers to a symbolic link. 166.It Bq Er ELOOP 167Too many symbolic links were encountered in translating the pathname. 168.It Bq Er EIO 169An I/O error occurred while reading from or writing to the file system. 170.It Bq Er ESRCH 171No process can be found corresponding to that specified by 172.Fa pid . 173.El 174.Sh SEE ALSO 175.Xr kdump 1 , 176.Xr ktrace 1 177.Sh HISTORY 178A 179.Fn ktrace 180function call first appeared in 181.Bx 4.4 . 182