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 February 15, 2001 28.Dt KTR 9 29.Os 30.Sh NAME 31.Nm CTR0 , 32.Nm CTR1 , 33.Nm CTR2 , 34.Nm CTR3 , 35.Nm CTR4 , 36.Nm CTR5 37.Nd kernel tracing facility 38.Sh SYNOPSIS 39.Fd #include <sys/ktr.h> 40.Vt "extern int ktr_cpumask" ; 41.Vt "extern int ktr_entries" ; 42.Vt "extern int ktr_extend" ; 43.Vt "extern int ktr_mask" ; 44.Vt "extern int ktr_verbose" ; 45.Vt "extern struct ktr_entry ktr_buf[]" ; 46.Ft void 47.Fn CTR0 "u_int mask" "char *format" 48.Ft void 49.Fn CTR1 "u_int mask" "char *format" "arg1" 50.Ft void 51.Fn CTR2 "u_int mask" "char *format" "arg1" "arg2" 52.Ft void 53.Fn CTR3 "u_int mask" "char *format" "arg1" "arg2" "arg3" 54.Ft void 55.Fn CTR4 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" 56.Ft void 57.Fn CTR5 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" 58.Sh DESCRIPTION 59KTR provides a circular buffer of events that can be logged in a printf style 60fashion. 61These events can then be dumped either via 62.Xr ddb 4 63or 64.Xr gdb 1 . 65.Pp 66Events are created and logged in the kernel via the 67.Dv CTRx 68macros. 69The first parameter is a mask of event types 70.Pq Dv KTR_* 71defined in 72.Aq Pa sys/ktr.h . 73The event will be logged only if any of the event types specified in 74.Fa mask 75are enabled in the global event mask stored in 76.Va ktr_mask . 77The 78.Fa format 79argument is a 80.Xr printf 9 81style format string used to build the text of the event log message. 82Following the 83.Fa format 84string are zero to five arguments referenced by 85.Fa format . 86Note that the different macros differ only in the number of arguments each 87one takes, as indicated by its name. 88Each event is logged with a timestamp in addition to the log message. 89.Pp 90The 91.Va ktr_entries 92variable contains the number of entries in the 93.Va ktr_buf 94array. 95These variables are mostly useful for post-mortem crash dump tools to locate 96the base of the circular trace buffer and its length. 97.Pp 98The 99.Va ktr_mask 100variable contains the run time mask of events to log. 101.Pp 102The kernel can be configured to compile with several extensions to the base 103functionality. 104These extensions can be checked for at runtime via the 105.Va ktr_extend 106variable. 107It will be set to zero if the extensions are not compiled in and non-zero 108if they are compiled in. 109This is useful for post-mortem debugging tools such as 110.Xr gdb 1 111that are used to analyze kernel crash dumps. 112.Pp 113The CPU event mask is stored in the 114.Va ktr_cpumask 115variable. 116.Pp 117The 118.Va ktr_verbose 119variable stores the verbose flag that controls whether events are logged to 120the console in addition to the event buffer. 121.Sh EXAMPLES 122This example demonstrates the use of tracepoints at the 123.Dv KTR_PROC 124logging level. 125.Bd -literal -offset indent 126void 127mi_switch() 128{ 129 ... 130 /* 131 * Pick a new current process and record its start time. 132 */ 133 ... 134 CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d, %s)", p, p->p_pid, 135 p->p_comm); 136 ... 137 cpu_switch(); 138 ... 139 CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d, %s)", p, p->p_pid, 140 p->p_comm); 141 ... 142} 143.Ed 144.Sh SEE ALSO 145.Xr ktr 4 146.Sh HISTORY 147The KTR kernel tracing facility first appeared in 148.Bsx 3.0 149and was imported into 150.Fx 5.0 . 151.Sh BUGS 152Currently there is one global buffer shared among all CPUs. 153It might be profitable at some point in time to use per-CPU buffers instead 154so that if one CPU halts or starts spinning, then the log messages it 155emitted just prior to halting or spinning will not be drowned out by events 156from the other CPUs. 157