Code for recording timestamps of events, especially function entries/exits.
This is a very primitive system, intended for use in measuring performance during the early system boot, before more sophisticated tools like DTrace or infrastructure like kernel memory allocation and mutexes are available. Because this code records pointers to strings rather than copying strings (in order to keep the memory usage more manageable), if a kernel module is unloaded after logging an event, Bad Things can happen. Users are advised to not do that. Since cycle counts from the early kernel boot are used as an initial entropy source, publishing this information to userland could result in inadequate entropy being kept private to the kernel RNG. Users are advised to not enable this on systems with untrusted users. Discussed on: freebsd-current
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cperciva
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118
sys/kern/kern_tslog.c
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118
sys/kern/kern_tslog.c
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/*-
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* Copyright (c) 2017 Colin Percival
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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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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/sbuf.h>
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#include <sys/sysctl.h>
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#include <sys/systm.h>
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#include <sys/tslog.h>
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#include <machine/atomic.h>
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#include <machine/cpu.h>
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#ifndef TSLOGSIZE
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#define TSLOGSIZE 262144
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#endif
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static volatile long nrecs = 0;
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static struct timestamp {
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void * td;
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int type;
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const char * f;
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const char * s;
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uint64_t tsc;
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} timestamps[TSLOGSIZE];
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void
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tslog(void * td, int type, const char * f, const char * s)
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{
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uint64_t tsc = get_cyclecount();
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long pos;
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/* Grab a slot. */
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pos = atomic_fetchadd_long(&nrecs, 1);
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/* Store record. */
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if (pos < nitems(timestamps)) {
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timestamps[pos].td = td;
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timestamps[pos].type = type;
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timestamps[pos].f = f;
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timestamps[pos].s = s;
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timestamps[pos].tsc = tsc;
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}
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}
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static int
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sysctl_debug_tslog(SYSCTL_HANDLER_ARGS)
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{
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int error;
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struct sbuf *sb;
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size_t i, limit;
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/*
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* This code can race against the code in tslog() which stores
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* records: Theoretically we could end up reading a record after
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* its slots have been reserved but before it has been written.
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* Since this code takes orders of magnitude longer to run than
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* tslog() takes to write a record, it is highly unlikely that
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* anyone will ever experience this race.
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*/
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sb = sbuf_new_for_sysctl(NULL, NULL, 1024, req);
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limit = MIN(nrecs, nitems(timestamps));
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for (i = 0; i < limit; i++) {
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sbuf_printf(sb, "%p", timestamps[i].td);
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sbuf_printf(sb, " %llu",
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(unsigned long long)timestamps[i].tsc);
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switch (timestamps[i].type) {
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case TS_ENTER:
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sbuf_printf(sb, " ENTER");
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break;
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case TS_EXIT:
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sbuf_printf(sb, " EXIT");
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break;
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case TS_THREAD:
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sbuf_printf(sb, " THREAD");
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break;
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case TS_EVENT:
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sbuf_printf(sb, " EVENT");
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break;
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}
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sbuf_printf(sb, " %s", timestamps[i].f ? timestamps[i].f : "(null)");
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if (timestamps[i].s)
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sbuf_printf(sb, " %s\n", timestamps[i].s);
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else
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sbuf_printf(sb, "\n");
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}
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error = sbuf_finish(sb);
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sbuf_delete(sb);
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return (error);
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}
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SYSCTL_PROC(_debug, OID_AUTO, tslog, CTLTYPE_STRING|CTLFLAG_RD|CTLFLAG_MPSAFE,
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0, 0, sysctl_debug_tslog, "", "Dump recorded event timestamps");
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60
sys/sys/tslog.h
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60
sys/sys/tslog.h
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@ -0,0 +1,60 @@
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/*-
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* Copyright (c) 2017 Colin Percival
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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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*
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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 ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _TSLOG_H_
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#define _TSLOG_H_
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#include <sys/_types.h>
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#include <sys/pcpu.h>
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#define TS_ENTER 0
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#define TS_EXIT 1
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#define TS_THREAD 2
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#define TS_EVENT 3
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#define TSENTER() TSRAW(curthread, TS_ENTER, __func__, NULL)
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#define TSENTER2(x) TSRAW(curthread, TS_ENTER, __func__, x)
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#define TSEXIT() TSRAW(curthread, TS_EXIT, __func__, NULL)
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#define TSEXIT2(x) TSRAW(curthread, TS_EXIT, __func__, x)
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#define TSTHREAD(td, x) TSRAW(td, TS_THREAD, x, NULL)
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#define TSEVENT(x) TSRAW(curthread, TS_EVENT, x, NULL)
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#define TSEVENT2(x, y) TSRAW(curthread, TS_EVENT, x, y)
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#define TSLINE() TSEVENT2(__FILE__, __XSTRING(__LINE__))
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#define TSWAIT(x) TSEVENT2("WAIT", x);
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#define TSUNWAIT(x) TSEVENT2("UNWAIT", x);
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#define TSHOLD(x) TSEVENT2("HOLD", x);
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#define TSRELEASE(x) TSEVENT2("RELEASE", x);
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#ifdef TSLOG
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#define TSRAW(a, b, c, d) tslog(a, b, c, d)
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void tslog(void *, int, const char *, const char *);
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#else
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#define TSRAW(a, b, c, d) /* Timestamp logging disabled */
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#endif
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#endif /* _TSLOG_H_ */
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