1.\" Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org> 2.\" 3.\" Redistribution and use in source and binary forms, with or without 4.\" modification, are permitted provided that the following conditions 5.\" are met: 6.\" 1. Redistributions of source code must retain the above copyright 7.\" notice, this list of conditions and the following disclaimer. 8.\" 2. Redistributions in binary form must reproduce the above copyright 9.\" notice, this list of conditions and the following disclaimer in the 10.\" documentation and/or other materials provided with the distribution. 11.\" 12.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 13.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 14.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 15.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 16.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 17.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 18.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 19.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 20.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 21.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 22.\" SUCH DAMAGE. 23.\" 24.Dd April 12, 2022 25.Dt KTR 9 26.Os 27.Sh NAME 28.Nm CTR0 , CTR1 , CTR2 , CTR3 , CTR4 , CTR5 29.Nd kernel tracing facility 30.Sh SYNOPSIS 31.In sys/param.h 32.In sys/ktr.h 33.Vt "extern int ktr_cpumask" ; 34.Vt "extern int ktr_entries" ; 35.Vt "extern int ktr_extend" ; 36.Vt "extern int ktr_mask" ; 37.Vt "extern int ktr_verbose" ; 38.Vt "extern struct ktr_entry ktr_buf[]" ; 39.Ft void 40.Fn CTR "u_int mask" "char *format" "..." 41.Ft void 42.Fn CTR0 "u_int mask" "char *format" 43.Ft void 44.Fn CTR1 "u_int mask" "char *format" "arg1" 45.Ft void 46.Fn CTR2 "u_int mask" "char *format" "arg1" "arg2" 47.Ft void 48.Fn CTR3 "u_int mask" "char *format" "arg1" "arg2" "arg3" 49.Ft void 50.Fn CTR4 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" 51.Ft void 52.Fn CTR5 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" 53.Ft void 54.Fn CTR6 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5" "arg6" 55.Sh DESCRIPTION 56KTR provides a circular buffer of events that can be logged in a 57.Xr printf 9 58style 59fashion. 60These events can then be dumped with 61.Xr ddb 4 , 62.Xr gdb 1 Pq Pa ports/devel/gdb 63or 64.Xr ktrdump 8 . 65.Pp 66Events are created and logged in the kernel via the 67.Dv CTR 68and 69.Dv CTR Ns Ar x 70macros. 71The first parameter is a mask of event types 72.Pq Dv KTR_* 73defined in 74.In sys/ktr_class.h . 75The event will be logged only if any of the event types specified in 76.Fa mask 77are enabled in the global event mask stored in 78.Va ktr_mask . 79The 80.Fa format 81argument is a 82.Xr printf 9 83style format string used to build the text of the event log message. 84Following the 85.Fa format 86string are zero to six arguments referenced by 87.Fa format . 88Each event is logged with a file name and source line number of the 89originating CTR call, and a timestamp in addition to the log message. 90.Pp 91The event is stored in the circular buffer with supplied arguments as is, 92and formatting is done at the dump time. 93Do not use pointers to the objects with limited lifetime, for instance, 94strings, because the pointer may become invalid when buffer is printed. 95.Pp 96The 97.Dv CTR Ns Ar x 98macros differ only in the number of arguments each 99one takes, as indicated by its name. 100.Pp 101The 102.Va ktr_entries 103variable contains the number of entries in the 104.Va ktr_buf 105array. 106These variables are mostly useful for post-mortem crash dump tools to locate 107the base of the circular trace buffer and its length. 108.Pp 109The 110.Va ktr_mask 111variable contains the run time mask of events to log. 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 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)", p, p->p_pid); 135 ... 136 cpu_switch(); 137 ... 138 CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d)", p, p->p_pid); 139 ... 140} 141.Ed 142.Sh SEE ALSO 143.Xr ktr 4 , 144.Xr ktrdump 8 145.Sh HISTORY 146The KTR kernel tracing facility first appeared in 147.Bsx 3.0 148and was imported into 149.Fx 5.0 . 150.Pp 151The 152.Fn CTR 153macro accepting a variable number of arguments first appeared in 154.Fx 14.0 . 155.Sh BUGS 156Currently there is one global buffer shared among all CPUs. 157It might be profitable at some point in time to use per-CPU buffers instead 158so that if one CPU halts or starts spinning, then the log messages it 159emitted just prior to halting or spinning will not be drowned out by events 160from the other CPUs. 161.Pp 162The arguments given in 163.Fn CTRx 164macros are stored as 165.Vt u_long , 166so do not pass arguments larger than size of an 167.Vt u_long 168type. 169For example passing 64bit arguments on 32bit architectures will give incorrect 170results. 171