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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)ktrace.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/ktrace.2,v 1.9.2.7 2001/12/14 18:34:01 ru Exp $ 30.\" $DragonFly: src/lib/libc/sys/ktrace.2,v 1.4 2008/10/16 08:15:18 swildner Exp $ 31.\" 32.Dd November 15, 2009 33.Dt KTRACE 2 34.Os 35.Sh NAME 36.Nm ktrace 37.Nd process tracing 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/param.h 42.In sys/time.h 43.In sys/uio.h 44.In sys/ktrace.h 45.Ft int 46.Fn ktrace "const char *tracefile" "int ops" "int trpoints" "int pid" 47.Sh DESCRIPTION 48The 49.Fn ktrace 50function enables or disables tracing of one or more processes. 51Users may only trace their own processes. 52By default only the super-user can trace setuid or setgid programs. 53This restriction can be removed by setting the sysctl 54.Va kern.ktrace_suid 55to a non-zero value. 56.Pp 57The 58.Fa tracefile 59gives the pathname of the file to be used for tracing. 60The file must exist and be a regular file writable by the calling process. 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 KTROP_CLEAR below), 65.Fa tracefile 66may be NULL. 67.Pp 68The 69.Fa ops 70parameter specifies the requested ktrace operation. 71The defined operations are: 72.Bl -column KTRFLAG_DESCENDXXX -offset indent 73.It "KTROP_SET Enable trace points specified in" 74.Fa trpoints . 75.It "KTROP_CLEAR Disable trace points specified in" 76.Fa trpoints . 77.It "KTROP_CLEARFILE Stop all tracing." 78.It "KTRFLAG_DESCEND The tracing change should apply to the" 79specified process and all its current children. 80.El 81.Pp 82The 83.Fa trpoints 84parameter specifies the trace points of interest. 85The defined trace points are: 86.Bl -column KTRFAC_SYSCALLXXX -offset indent 87.It "KTRFAC_SYSCALL Trace system calls." 88.It "KTRFAC_SYSRET Trace return values from system calls." 89.It "KTRFAC_NAMEI Trace name lookup operations." 90.It "KTRFAC_GENIO Trace all I/O (note that this option can" 91generate much output). 92.It "KTRFAC_PSIG Trace posted signals." 93.It "KTRFAC_CSW Trace context switch points." 94.It "KTRFAC_INHERIT Inherit tracing to future children." 95.El 96.Pp 97Each tracing event outputs a record composed of a generic header 98followed by a trace point specific structure. 99The generic header is: 100.Bd -literal 101struct ktr_header { 102 int ktr_len; /* length of buf */ 103 short ktr_type; /* trace record type */ 104 pid_t ktr_pid; /* process id */ 105 char ktr_comm[MAXCOMLEN+1]; /* command name */ 106 struct timeval ktr_time; /* timestamp */ 107 caddr_t ktr_buf; 108}; 109.Ed 110.Pp 111The 112.Va ktr_len 113field specifies the length of the 114.Va ktr_type 115data that follows this header. 116The 117.Va ktr_pid 118and 119.Va ktr_comm 120fields specify the process and command generating the record. 121The 122.Va ktr_time 123field gives the time (with microsecond resolution) 124that the record was generated. 125The 126.Va ktr_buf 127is an internal kernel pointer and is not useful. 128.Pp 129The generic header is followed by 130.Va ktr_len 131bytes of a 132.Va ktr_type 133record. 134The type specific records are defined in the 135.In sys/ktrace.h 136include file. 137.Sh RETURN VALUES 138.Rv -std ktrace 139.Sh ERRORS 140.Fn Ktrace 141will fail if: 142.Bl -tag -width Er 143.It Bq Er ENOTDIR 144A component of the path prefix is not a directory. 145.It Bq Er ENAMETOOLONG 146A component of a pathname exceeded 255 characters, 147or an entire path name exceeded 1023 characters. 148.It Bq Er ENOENT 149The named tracefile does not exist. 150.It Bq Er EACCES 151Search permission is denied for a component of the path prefix. 152.It Bq Er ELOOP 153Too many symbolic links were encountered in translating the pathname. 154.It Bq Er EIO 155An I/O error occurred while reading from or writing to the file system. 156.It Bq Er ENOSYS 157The kernel was not compiled with 158.Nm 159support. 160.El 161.Sh SEE ALSO 162.Xr kdump 1 , 163.Xr ktrace 1 , 164.Xr utrace 2 165.Sh HISTORY 166A 167.Fn ktrace 168function call first appeared in 169.Bx 4.4 . 170