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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 November 15, 2009 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. 56By default only the super-user can trace setuid or setgid programs. 57This restriction can be removed by setting the sysctl 58.Va kern.ktrace_suid 59to a non-zero value. 60.Pp 61The 62.Fa tracefile 63gives the pathname of the file to be used for tracing. 64The file must exist and be a regular file writable by the calling process. 65All trace records are always appended to the file, 66so the file must be truncated to zero length to discard 67previous trace data. 68If tracing points are being disabled (see KTROP_CLEAR below), 69.Fa tracefile 70may be NULL. 71.Pp 72The 73.Fa 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" 78.Fa trpoints . 79.It "KTROP_CLEAR Disable trace points specified in" 80.Fa trpoints . 81.It "KTROP_CLEARFILE Stop all tracing." 82.It "KTRFLAG_DESCEND The tracing change should apply to the" 83specified process and all its current children. 84.El 85.Pp 86The 87.Fa trpoints 88parameter specifies the trace points of interest. 89The defined trace points are: 90.Bl -column KTRFAC_SYSCALLXXX -offset indent 91.It "KTRFAC_SYSCALL Trace system calls." 92.It "KTRFAC_SYSRET Trace return values from system calls." 93.It "KTRFAC_NAMEI Trace name lookup operations." 94.It "KTRFAC_GENIO Trace all I/O (note that this option can" 95generate much output). 96.It "KTRFAC_PSIG Trace posted signals." 97.It "KTRFAC_CSW Trace context switch points." 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 pid_t ktr_pid; /* process id */ 109 char ktr_comm[MAXCOMLEN+1]; /* command name */ 110 struct timeval ktr_time; /* timestamp */ 111 caddr_t ktr_buf; 112}; 113.Ed 114.Pp 115The 116.Va ktr_len 117field specifies the length of the 118.Va ktr_type 119data that follows this header. 120The 121.Va ktr_pid 122and 123.Va ktr_comm 124fields specify the process and command generating the record. 125The 126.Va ktr_time 127field gives the time (with microsecond resolution) 128that the record was generated. 129The 130.Va ktr_buf 131is an internal kernel pointer and is not useful. 132.Pp 133The generic header is followed by 134.Va ktr_len 135bytes of a 136.Va ktr_type 137record. 138The type specific records are defined in the 139.In sys/ktrace.h 140include file. 141.Sh RETURN VALUES 142.Rv -std ktrace 143.Sh ERRORS 144.Fn Ktrace 145will fail if: 146.Bl -tag -width Er 147.It Bq Er ENOTDIR 148A component of the path prefix is not a directory. 149.It Bq Er ENAMETOOLONG 150A component of a pathname exceeded 255 characters, 151or an entire path name exceeded 1023 characters. 152.It Bq Er ENOENT 153The named tracefile does not exist. 154.It Bq Er EACCES 155Search permission is denied for a component of the path prefix. 156.It Bq Er ELOOP 157Too many symbolic links were encountered in translating the pathname. 158.It Bq Er EIO 159An I/O error occurred while reading from or writing to the file system. 160.It Bq Er ENOSYS 161The kernel was not compiled with 162.Nm 163support. 164.El 165.Sh SEE ALSO 166.Xr kdump 1 , 167.Xr ktrace 1 , 168.Xr utrace 2 169.Sh HISTORY 170A 171.Fn ktrace 172function call first appeared in 173.Bx 4.4 . 174