Add support for the DTrace struct proc and struct thread extended

data via ctor and dtor event handlers.

The size of the extra data is allocated opaquely and this file
contains a function which the dtrace module can call to check
that the kernel supports at least the amount of data that it needs.

This file is optionally compiled into nthe kernel if the KDTRACE_HOOKS
kernel option is defined.

sys/kern/kern_dtrace.c

@@ -0,0 +1,120 @@
+/*-
+ * Copyright (c) 2007-2008 John Birrell <jb@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_kdb.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/eventhandler.h>
+#include <sys/kdb.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/proc.h>
+#include <sys/dtrace_bsd.h>
+
+#define KDTRACE_PROC_SIZE	64
+#define KDTRACE_PROC_ZERO	8
+#define	KDTRACE_THREAD_SIZE	256
+#define	KDTRACE_THREAD_ZERO	64
+
+MALLOC_DEFINE(M_KDTRACE, "kdtrace", "DTrace hooks");
+
+/* Return the DTrace process data size compiled in the kernel hooks. */
+size_t
+kdtrace_proc_size()
+{
+	return(KDTRACE_PROC_SIZE);
+}
+
+static void
+kdtrace_proc_ctor(void *arg __unused, struct proc *p)
+{
+	p->p_dtrace = malloc(KDTRACE_PROC_SIZE, M_KDTRACE, M_WAITOK);
+
+	bzero(p->p_dtrace, KDTRACE_PROC_ZERO);
+}
+
+static void
+kdtrace_proc_dtor(void *arg __unused, struct proc *p)
+{
+	if (p->p_dtrace != NULL) {
+		free(p->p_dtrace, M_KDTRACE);
+		p->p_dtrace = NULL;
+	}
+}
+
+/* Return the DTrace thread data size compiled in the kernel hooks. */
+size_t
+kdtrace_thread_size()
+{
+	return(KDTRACE_THREAD_SIZE);
+}
+
+static void
+kdtrace_thread_ctor(void *arg __unused, struct thread *td)
+{
+	td->td_dtrace = malloc(KDTRACE_THREAD_SIZE, M_KDTRACE, M_WAITOK);
+
+	bzero(td->td_dtrace, KDTRACE_THREAD_ZERO);
+}
+
+static void
+kdtrace_thread_dtor(void *arg __unused, struct thread *td)
+{
+	if (td->td_dtrace != NULL) {
+		free(td->td_dtrace, M_KDTRACE);
+		td->td_dtrace = NULL;
+	}
+}
+
+/*
+ *  Initialise the kernel DTrace hooks.
+ */
+static void
+init_dtrace(void *dummy __unused)
+{
+	EVENTHANDLER_REGISTER(process_ctor, kdtrace_proc_ctor, NULL, EVENTHANDLER_PRI_ANY);
+	EVENTHANDLER_REGISTER(process_dtor, kdtrace_proc_dtor, NULL, EVENTHANDLER_PRI_ANY);
+	EVENTHANDLER_REGISTER(thread_ctor, kdtrace_thread_ctor, NULL, EVENTHANDLER_PRI_ANY);
+	EVENTHANDLER_REGISTER(thread_dtor, kdtrace_thread_dtor, NULL, EVENTHANDLER_PRI_ANY);
+}
+
+SYSINIT(kdtrace, SI_SUB_KDTRACE, SI_ORDER_FIRST, init_dtrace, NULL);
+
+#ifndef KDB
+/*
+ * This is a stub for the kernel debugger for the DTrace actions to call
+ * when the kernel has been built without KDB.
+ */
+void
+kdb_enter(const char *why, const char *msg)
+{
+	printf("Cannot enter kernel debugger - No KDB in kernel.\n%s - %s\n", why, msg);
+}
+#endif