154 lines
4.6 KiB
Groff
154 lines
4.6 KiB
Groff
.\" Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 15, 2001
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.Dt KTR 9
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.Os
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.Sh NAME
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.Nm CTR0 , CTR1 , CTR2 , CTR3 , CTR4 , CTR5
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.Nd kernel tracing facility
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.Sh SYNOPSIS
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.In sys/ktr.h
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.Vt "extern int ktr_cpumask" ;
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.Vt "extern int ktr_entries" ;
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.Vt "extern int ktr_extend" ;
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.Vt "extern int ktr_mask" ;
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.Vt "extern int ktr_verbose" ;
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.Vt "extern struct ktr_entry ktr_buf[]" ;
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.Ft void
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.Fn CTR0 "u_int mask" "char *format"
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.Ft void
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.Fn CTR1 "u_int mask" "char *format" "arg1"
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.Ft void
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.Fn CTR2 "u_int mask" "char *format" "arg1" "arg2"
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.Ft void
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.Fn CTR3 "u_int mask" "char *format" "arg1" "arg2" "arg3"
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.Ft void
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.Fn CTR4 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4"
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.Ft void
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.Fn CTR5 "u_int mask" "char *format" "arg1" "arg2" "arg3" "arg4" "arg5"
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.Sh DESCRIPTION
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KTR provides a circular buffer of events that can be logged in a
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.Xr printf 9
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style
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fashion.
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These events can then be dumped either via
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.Xr ddb 4
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or
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.Xr gdb 1 .
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.Pp
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Events are created and logged in the kernel via the
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.Dv CTR Ns Ar x
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macros.
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The first parameter is a mask of event types
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.Pq Dv KTR_*
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defined in
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.Aq Pa sys/ktr.h .
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The event will be logged only if any of the event types specified in
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.Fa mask
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are enabled in the global event mask stored in
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.Va ktr_mask .
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The
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.Fa format
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argument is a
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.Xr printf 9
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style format string used to build the text of the event log message.
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Following the
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.Fa format
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string are zero to five arguments referenced by
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.Fa format .
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Note that the different macros differ only in the number of arguments each
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one takes, as indicated by its name.
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Each event is logged with a timestamp in addition to the log message.
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.Pp
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The
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.Va ktr_entries
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variable contains the number of entries in the
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.Va ktr_buf
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array.
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These variables are mostly useful for post-mortem crash dump tools to locate
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the base of the circular trace buffer and its length.
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.Pp
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The
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.Va ktr_mask
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variable contains the run time mask of events to log.
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.Pp
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The kernel can be configured to compile with several extensions to the base
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functionality.
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These extensions can be checked for at runtime via the
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.Va ktr_extend
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variable.
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It will be set to zero if the extensions are not compiled in and non-zero
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if they are compiled in.
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This is useful for post-mortem debugging tools such as
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.Xr gdb 1
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that are used to analyze kernel crash dumps.
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.Pp
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The CPU event mask is stored in the
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.Va ktr_cpumask
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variable.
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.Pp
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The
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.Va ktr_verbose
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variable stores the verbose flag that controls whether events are logged to
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the console in addition to the event buffer.
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.Sh EXAMPLES
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This example demonstrates the use of tracepoints at the
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.Dv KTR_PROC
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logging level.
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.Bd -literal -offset indent
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void
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mi_switch()
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{
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...
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/*
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* Pick a new current process and record its start time.
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*/
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...
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CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d, %s)", p, p->p_pid,
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p->p_comm);
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...
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cpu_switch();
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...
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CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d, %s)", p, p->p_pid,
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p->p_comm);
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...
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}
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.Ed
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.Sh SEE ALSO
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.Xr ktr 4
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.Sh HISTORY
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The KTR kernel tracing facility first appeared in
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.Bsx 3.0
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and was imported into
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.Fx 5.0 .
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.Sh BUGS
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Currently there is one global buffer shared among all CPUs.
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It might be profitable at some point in time to use per-CPU buffers instead
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so that if one CPU halts or starts spinning, then the log messages it
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emitted just prior to halting or spinning will not be drowned out by events
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from the other CPUs.
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