1.\" Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org> 2.\" 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.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd November 30, 2008 28.Dt KTR 9 29.Os 30.Sh NAME 31.Nm CTR0 , CTR1 , CTR2 , CTR3 , CTR4 , CTR5 32.Nd kernel tracing facility 33.Sh SYNOPSIS 34.In sys/param.h 35.In sys/ktr.h 36.Vt "extern int ktr_cpumask" ; 37.Vt "extern int ktr_entries" ; 38.Vt "extern int ktr_extend" ; 39.Vt "extern int ktr_mask" ; 40.Vt "extern int ktr_verbose" ; 41.Vt "extern struct ktr_entry ktr_buf[]" ; 42.Ft void 43.Fn CTR0 "u_int mask" "char *format" 44.Ft void 45.Fn CTR1 "u_int mask" "char *format" "arg1" 46.Ft void 47.Fn CTR2 "u_int mask" "char *format" "arg1" "arg2" 48.Ft void 49.Fn CTR3 "u_int mask" "char *format" "arg1" "arg2" "arg3" 50.Ft void 51.Fn CTR4 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" 52.Ft void 53.Fn CTR5 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" 54.Ft void 55.Fn CTR6 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" "arg6" 56.Sh DESCRIPTION 57KTR provides a circular buffer of events that can be logged in a 58.Xr printf 9 59style 60fashion. 61These events can then be dumped with 62.Xr ddb 4 , 63.Xr gdb 1 64or 65.Xr ktrdump 8 . 66.Pp 67Events are created and logged in the kernel via the 68.Dv CTR Ns Ar x 69macros. 70The first parameter is a mask of event types 71.Pq Dv KTR_* 72defined in 73.In sys/ktr.h . 74The event will be logged only if any of the event types specified in 75.Fa mask 76are enabled in the global event mask stored in 77.Va ktr_mask . 78The 79.Fa format 80argument is a 81.Xr printf 9 82style format string used to build the text of the event log message. 83Following the 84.Fa format 85string are zero to five arguments referenced by 86.Fa format . 87Each event is logged with a file name and source line number of the 88originating CTR call, and a timestamp in addition to the log message. 89.Pp 90The event is stored in the circular buffer with supplied arguments as is, 91and formatting is done at the dump time. 92Do not use pointers to the objects with limited lifetime, for instance, 93strings, because the pointer may become invalid when buffer is printed. 94.Pp 95Note that the different macros differ only in the number of arguments each 96one takes, as indicated by its name. 97.Pp 98The 99.Va ktr_entries 100variable contains the number of entries in the 101.Va ktr_buf 102array. 103These variables are mostly useful for post-mortem crash dump tools to locate 104the base of the circular trace buffer and its length. 105.Pp 106The 107.Va ktr_mask 108variable contains the run time mask of events to log. 109.Pp 110The CPU event mask is stored in the 111.Va ktr_cpumask 112variable. 113.Pp 114The 115.Va ktr_verbose 116variable stores the verbose flag that controls whether events are logged to 117the console in addition to the event buffer. 118.Sh EXAMPLES 119This example demonstrates the use of tracepoints at the 120.Dv KTR_PROC 121logging level. 122.Bd -literal 123void 124mi_switch() 125{ 126 ... 127 /* 128 * Pick a new current process and record its start time. 129 */ 130 ... 131 CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d)", p, p->p_pid); 132 ... 133 cpu_switch(); 134 ... 135 CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d)", p, p->p_pid); 136 ... 137} 138.Ed 139.Sh SEE ALSO 140.Xr ktr 4 , 141.Xr ktrdump 8 142.Sh HISTORY 143The KTR kernel tracing facility first appeared in 144.Bsx 3.0 145and was imported into 146.Fx 5.0 . 147.Sh BUGS 148Currently there is one global buffer shared among all CPUs. 149It might be profitable at some point in time to use per-CPU buffers instead 150so that if one CPU halts or starts spinning, then the log messages it 151emitted just prior to halting or spinning will not be drowned out by events 152from the other CPUs. 153.Pp 154The arguments given in 155.Fn CTRx 156macros are stored as 157.Vt u_long , 158so do not pass arguments larger than size of an 159.Vt u_long 160type. 161For example passing 64bit arguments on 32bit architectures will give incorrect 162results. 163