1.\" $NetBSD: ktrace.2,v 1.22 2017/10/25 17:30:03 abhinav Exp $ 2.\" 3.\" Copyright (c) 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)ktrace.2 8.1 (Berkeley) 6/4/93 31.\" 32.Dd March 19, 2016 33.Dt KTRACE 2 34.Os 35.Sh NAME 36.Nm ktrace , 37.Nm fktrace 38.Nd process tracing 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/param.h 43.In sys/ktrace.h 44.Ft int 45.Fn ktrace "const char *tracefile" "int ops" "int trpoints" "pid_t pid" 46.Ft int 47.Fn fktrace "int fd" "int ops" "int trpoints" "pid_t pid" 48.Sh DESCRIPTION 49The 50.Fn ktrace 51function enables or disables tracing of one or more processes. 52Users may only trace their own processes. 53Only the super-user can trace setuid or setgid programs. 54.Pp 55The 56.Ar tracefile 57gives the pathname of the file to be used for tracing. 58The file must exist and be writable by the calling process. 59All trace records are always appended to the file, 60so the file must be truncated to zero length to discard 61previous trace data. 62If tracing points are being disabled (see KTROP_CLEAR below), 63.Ar tracefile 64may be NULL. 65If using 66.Fn fktrace 67then instead of passing a filename as 68.Ar tracefile , 69a file descriptor is passed as 70.Ar fd 71and behaviour is otherwise the same. 72.Pp 73The 74.Nm ops 75parameter specifies the requested ktrace operation. 76The defined operations are: 77.Bl -column KTRFLAG_DESCENDXXX -offset indent 78.It KTROP_SET Enable trace points specified in Ar trpoints . 79.It KTROP_CLEAR Disable trace points specified in Ar trpoints . 80.It KTROP_CLEARFILE Stop all tracing. 81.It KTRFLAG_DESCEND The tracing change should apply to the 82specified process and all its current children. 83.El 84.Pp 85The 86.Nm trpoints 87parameter specifies the trace points of interest. 88The defined trace points are: 89.Bl -column KTRFAC_SYSCALLXXX -offset indent 90.It KTRFAC_SYSCALL Trace system calls. 91.It KTRFAC_SYSRET Trace return values from system calls. 92.It KTRFAC_NAMEI Trace name lookup operations. 93.It KTRFAC_GENIO Trace all I/O (note that this option can 94generate much output). 95.It KTRFAC_PSIG Trace posted signals. 96.It KTRFAC_CSW Trace context switch points. 97.It KTRFAC_EMUL Trace emulation changes. 98.It KTRFAC_INHERIT Inherit tracing to future children. 99.El 100.Pp 101Each tracing event outputs a record composed of a generic header 102followed by a trace point specific structure. 103The generic header is: 104.Bd -literal 105struct ktr_header { 106 int ktr_len; /* length of buf */ 107 short ktr_type; /* trace record type */ 108 short ktr_version; /* trace record version */ 109 pid_t ktr_pid; /* process id */ 110 char ktr_comm[MAXCOMLEN+1]; /* command name */ 111 struct timespec ktr_time; /* timestamp */ 112 lwpid_t ktr_lid; 113}; 114.Ed 115.Pp 116The 117.Nm ktr_len 118field specifies the length of the data that follows this header. 119The 120.Nm ktr_type 121and 122.Nm ktr_version 123fields (whose ordering in the structure depends on byte order) 124specify the format of this data. 125The 126.Nm ktr_pid , 127.Nm ktr_lid , 128and 129.Nm ktr_comm 130fields specify the process and command generating the record. 131The 132.Nm ktr_time 133field gives the time (with nanosecond resolution) 134that the record was generated. 135.Pp 136The generic header is followed by 137.Nm ktr_len 138bytes of a 139.Nm ktr_type 140record of version 141.Nm ktr_version . 142The type specific records are defined in the 143.Aq Pa sys/ktrace.h 144include file. 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 EACCES 155Search permission is denied for a component of the path prefix. 156.It Bq Er EINVAL 157The pathname contains a character with the high-order bit set. 158.It Bq Er EIO 159An I/O error occurred while reading from or writing to the file system. 160.It Bq Er ELOOP 161Too many symbolic links were encountered in translating the pathname. 162.It Bq Er ENAMETOOLONG 163A component of a pathname exceeded 164.Brq Dv NAME_MAX 165characters, 166or an entire path name exceeded 167.Brq Dv PATH_MAX 168characters. 169.It Bq Er ENOENT 170The named tracefile does not exist. 171.It Bq Er ENOTDIR 172A component of the path prefix is not a directory. 173.El 174.Sh SEE ALSO 175.Xr kdump 1 , 176.Xr ktrace 1 177.Sh HISTORY 178A 179.Nm ktrace 180function call first appeared in 181.Bx 4.4 . 182