1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)ktrace.2 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/sys/ktrace.2,v 1.9.2.7 2001/12/14 18:34:01 ru Exp $ 34.\" $DragonFly: src/lib/libc/sys/ktrace.2,v 1.4 2008/10/16 08:15:18 swildner Exp $ 35.\" 36.Dd June 4, 1993 37.Dt KTRACE 2 38.Os 39.Sh NAME 40.Nm ktrace 41.Nd process tracing 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/param.h 46.In sys/time.h 47.In sys/uio.h 48.In sys/ktrace.h 49.Ft int 50.Fn ktrace "const char *tracefile" "int ops" "int trpoints" "int pid" 51.Sh DESCRIPTION 52The 53.Fn ktrace 54function enables or disables tracing of one or more processes. 55Users may only trace their own processes. 56Only the super-user can trace setuid or setgid programs. 57.Pp 58The 59.Fa tracefile 60gives the pathname of the file to be used for tracing. 61The file must exist and be a regular file writable by the calling process. 62All trace records are always appended to the file, 63so the file must be truncated to zero length to discard 64previous trace data. 65If tracing points are being disabled (see KTROP_CLEAR below), 66.Fa tracefile 67may be NULL. 68.Pp 69The 70.Fa ops 71parameter specifies the requested ktrace operation. 72The defined operations are: 73.Bl -column KTRFLAG_DESCENDXXX -offset indent 74.It "KTROP_SET Enable trace points specified in" 75.Fa trpoints . 76.It "KTROP_CLEAR Disable trace points specified in 77.Fa trpoints . 78.It "KTROP_CLEARFILE Stop all tracing." 79.It "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 "KTRFAC_SYSCALL Trace system calls." 89.It "KTRFAC_SYSRET Trace return values from system calls." 90.It "KTRFAC_NAMEI Trace name lookup operations." 91.It "KTRFAC_GENIO Trace all I/O (note that this option can" 92generate much output). 93.It "KTRFAC_PSIG Trace posted signals." 94.It "KTRFAC_CSW Trace context switch points." 95.It "KTRFAC_INHERIT Inherit tracing to future children." 96.El 97.Pp 98Each tracing event outputs a record composed of a generic header 99followed by a trace point specific structure. 100The generic header is: 101.Bd -literal 102struct ktr_header { 103 int ktr_len; /* length of buf */ 104 short ktr_type; /* trace record type */ 105 pid_t ktr_pid; /* process id */ 106 char ktr_comm[MAXCOMLEN+1]; /* command name */ 107 struct timeval ktr_time; /* timestamp */ 108 caddr_t ktr_buf; 109}; 110.Ed 111.Pp 112The 113.Va ktr_len 114field specifies the length of the 115.Va ktr_type 116data that follows this header. 117The 118.Va ktr_pid 119and 120.Va ktr_comm 121fields specify the process and command generating the record. 122The 123.Va ktr_time 124field gives the time (with microsecond resolution) 125that the record was generated. 126The 127.Va ktr_buf 128is an internal kernel pointer and is not useful. 129.Pp 130The generic header is followed by 131.Va ktr_len 132bytes of a 133.Va ktr_type 134record. 135The type specific records are defined in the 136.In sys/ktrace.h 137include file. 138.Sh RETURN VALUES 139.Rv -std ktrace 140.Sh ERRORS 141.Fn Ktrace 142will fail if: 143.Bl -tag -width Er 144.It Bq Er ENOTDIR 145A component of the path prefix is not a directory. 146.It Bq Er ENAMETOOLONG 147A component of a pathname exceeded 255 characters, 148or an entire path name exceeded 1023 characters. 149.It Bq Er ENOENT 150The named tracefile does not exist. 151.It Bq Er EACCES 152Search permission is denied for a component of the path prefix. 153.It Bq Er ELOOP 154Too many symbolic links were encountered in translating the pathname. 155.It Bq Er EIO 156An I/O error occurred while reading from or writing to the file system. 157.It Bq Er ENOSYS 158The kernel was not compiled with 159.Nm 160support. 161.El 162.Sh SEE ALSO 163.Xr kdump 1 , 164.Xr ktrace 1 , 165.Xr utrace 2 166.Sh HISTORY 167A 168.Fn ktrace 169function call first appeared in 170.Bx 4.4 . 171