1.\" $NetBSD: ktrace.2,v 1.21 2016/03/20 20:09:49 wiz 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.Nd process tracing 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/param.h 42.In sys/ktrace.h 43.Ft int 44.Fn ktrace "const char *tracefile" "int ops" "int trpoints" "pid_t pid" 45.Ft int 46.Fn fktrace "int fd" "int ops" "int trpoints" "pid_t 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. 52Only the super-user can trace setuid or setgid programs. 53.Pp 54The 55.Ar tracefile 56gives the pathname of the file to be used for tracing. 57The file must exist and be writable by the calling process. 58All trace records are always appended to the file, 59so the file must be truncated to zero length to discard 60previous trace data. 61If tracing points are being disabled (see KTROP_CLEAR below), 62.Ar tracefile 63may be NULL. 64If using 65.Fn fktrace 66then instead of passing a filename as 67.Ar tracefile , 68a file descriptor is passed as 69.Ar fd 70and behaviour is otherwise the same. 71.Pp 72The 73.Nm ops 74parameter specifies the requested ktrace operation. 75The defined operations are: 76.Bl -column KTRFLAG_DESCENDXXX -offset indent 77.It KTROP_SET Enable trace points specified in Ar trpoints . 78.It KTROP_CLEAR Disable trace points specified in Ar trpoints . 79.It KTROP_CLEARFILE Stop all tracing. 80.It KTRFLAG_DESCEND The tracing change should apply to the 81specified process and all its current children. 82.El 83.Pp 84The 85.Nm trpoints 86parameter specifies the trace points of interest. 87The defined trace points are: 88.Bl -column KTRFAC_SYSCALLXXX -offset indent 89.It KTRFAC_SYSCALL Trace system calls. 90.It KTRFAC_SYSRET Trace return values from system calls. 91.It KTRFAC_NAMEI Trace name lookup operations. 92.It KTRFAC_GENIO Trace all I/O (note that this option can 93generate much output). 94.It KTRFAC_PSIG Trace posted signals. 95.It KTRFAC_CSW Trace context switch points. 96.It KTRFAC_EMUL Trace emulation changes. 97.It KTRFAC_INHERIT Inherit tracing to future children. 98.El 99.Pp 100Each tracing event outputs a record composed of a generic header 101followed by a trace point specific structure. 102The generic header is: 103.Bd -literal 104struct ktr_header { 105 int ktr_len; /* length of buf */ 106 short ktr_type; /* trace record type */ 107 short ktr_version; /* trace record version */ 108 pid_t ktr_pid; /* process id */ 109 char ktr_comm[MAXCOMLEN+1]; /* command name */ 110 struct timespec ktr_time; /* timestamp */ 111 lwpid_t ktr_lid; 112}; 113.Ed 114.Pp 115The 116.Nm ktr_len 117field specifies the length of the data that follows this header. 118The 119.Nm ktr_type 120and 121.Nm ktr_version 122fields (whose ordering in the structure depends on byte order) 123specify the format of this data. 124The 125.Nm ktr_pid , 126.Nm ktr_lid , 127and 128.Nm ktr_comm 129fields specify the process and command generating the record. 130The 131.Nm ktr_time 132field gives the time (with nanosecond resolution) 133that the record was generated. 134.Pp 135The generic header is followed by 136.Nm ktr_len 137bytes of a 138.Nm ktr_type 139record of version 140.Nm ktr_version . 141The type specific records are defined in the 142.Aq Pa sys/ktrace.h 143include file. 144.Sh RETURN VALUES 145On successful completion a value of 0 is returned. 146Otherwise, a value of \-1 is returned and 147.Va errno 148is set to show the error. 149.Sh ERRORS 150.Fn ktrace 151will fail if: 152.Bl -tag -width ENAMETOOLONGAA 153.It Bq Er EACCES 154Search permission is denied for a component of the path prefix. 155.It Bq Er EINVAL 156The pathname contains a character with the high-order bit set. 157.It Bq Er EIO 158An I/O error occurred while reading from or writing to the file system. 159.It Bq Er ELOOP 160Too many symbolic links were encountered in translating the pathname. 161.It Bq Er ENAMETOOLONG 162A component of a pathname exceeded 163.Brq Dv NAME_MAX 164characters, 165or an entire path name exceeded 166.Brq Dv PATH_MAX 167characters. 168.It Bq Er ENOENT 169The named tracefile does not exist. 170.It Bq Er ENOTDIR 171A component of the path prefix is not a directory. 172.El 173.Sh SEE ALSO 174.Xr kdump 1 , 175.Xr ktrace 1 176.Sh HISTORY 177A 178.Nm ktrace 179function call first appeared in 180.Bx 4.4 . 181