Add kernel support for the Statically Defined Trace provider.

This is BSD licensed code written specifically for FreeBSD.

It initialises using SYSINIT so that the SDT provider, probe and
argument description linkage is done whenever a module is loaded,
regardless of whether the DTrace modules are loaded or not.

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

1 files changed, 273 insertions, 0 deletions

diff --git a/sys/kern/kern_sdt.c b/sys/kern/kern_sdt.c
new file mode 100644
index 0000000..495a6a0
--- /dev/null
+++ b/sys/kern/kern_sdt.c
@@ -0,0 +1,273 @@
+/*-
+ * Copyright 2006-2008 John Birrell <jb@FreeBSD.org>
+ *
+ * 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 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 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.
+ *
+ * $FreeBSD$
+ *
+ * Backend for the Statically Defined Tracing (SDT) kernel support. This is
+ * required to allow a module to load even though DTrace kernel support may
+ * not be present. A module may be built with SDT probes in it which are
+ * registered and deregistered via SYSINIT/SYSUNINIT.
+ *
+ */
+
+#include "opt_kdtrace.h"
+
+#include <sys/cdefs.h>
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/linker.h>
+#include <sys/lock.h>
+#include <sys/proc.h>
+#include <sys/sx.h>
+#include <sys/sdt.h>
+
+/*
+ * This is the list of statically defined tracing providers.
+ */
+static TAILQ_HEAD(sdt_provider_list_head, sdt_provider) sdt_provider_list;
+
+/*
+ * Mutex to serialise access to the SDT provider list.
+ */
+static struct sx sdt_sx;
+
+/*
+ * Hook for the DTrace probe function. The 'sdt' provider will set this
+ * to dtrace_probe when it loads.
+ */
+sdt_probe_func_t sdt_probe_func = sdt_probe_stub;
+
+/*
+ * This is a stub for probe calls in case kernel DTrace support isn't
+ * compiled in. It should never get called because there is no DTrace
+ * support to enable it.
+ */
+void
+sdt_probe_stub(u_int32_t id, uintptr_t arg0, uintptr_t arg1,
+    uintptr_t arg2, uintptr_t arg3, uintptr_t arg4)
+{
+	printf("sdt_probe_stub: Why did this get called?\n");
+}
+
+/*
+ * Called from SYSINIT to register a provider.
+ */
+void
+sdt_provider_register(void *arg)
+{
+	struct sdt_provider *prov = arg;
+
+	sx_xlock(&sdt_sx);
+
+	TAILQ_INSERT_TAIL(&sdt_provider_list, prov, prov_entry);
+
+	TAILQ_INIT(&prov->probe_list);
+
+	sx_xunlock(&sdt_sx);
+}
+
+/*
+ * Called from SYSUNINIT to de-register a provider.
+ */
+void
+sdt_provider_deregister(void *arg)
+{
+	struct sdt_provider *prov = arg;
+
+	sx_xlock(&sdt_sx);
+
+	TAILQ_REMOVE(&sdt_provider_list, prov, prov_entry);
+
+	sx_xunlock(&sdt_sx);
+}
+
+/*
+ * Called from SYSINIT to register a statically defined trace probe.
+ */
+void
+sdt_probe_register(void *arg)
+{
+	struct sdt_probe *probe = arg;
+
+	/*
+	 * Check the reference structure version. Only version 1 is
+	 * supported at the moment.
+	 */
+	if (probe->version != sizeof(struct sdt_probe)) {
+		printf("%s:%s:%s has version %d when %d required\n", probe->mod, probe->func, probe->name, probe->version, (int) sizeof(struct sdt_probe));
+		return;
+	}
+
+	sx_xlock(&sdt_sx);
+
+	TAILQ_INSERT_TAIL(&probe->prov->probe_list, probe, probe_entry);
+
+	TAILQ_INIT(&probe->argtype_list);
+
+	probe->state = SDT_INIT;
+
+	sx_xunlock(&sdt_sx);
+}
+
+/*
+ * Called from SYSUNINIT to de-register a statically defined trace probe.
+ */
+void
+sdt_probe_deregister(void *arg)
+{
+	struct sdt_probe *probe = arg;
+
+	sx_xlock(&sdt_sx);
+
+	if (probe->state == SDT_INIT) {
+		TAILQ_REMOVE(&probe->prov->probe_list, probe, probe_entry);
+		probe->state = SDT_UNINIT;
+	}
+
+	sx_xunlock(&sdt_sx);
+}
+
+/*
+ * Called from SYSINIT to register a statically defined trace probe argument.
+ */
+void
+sdt_argtype_register(void *arg)
+{
+	struct sdt_argtype *argtype = arg;
+
+	sx_xlock(&sdt_sx);
+
+	TAILQ_INSERT_TAIL(&argtype->probe->argtype_list, argtype, argtype_entry);
+
+	argtype->probe->n_args++;
+
+	sx_xunlock(&sdt_sx);
+}
+
+/*
+ * Called from SYSUNINIT to de-register a statically defined trace probe argument.
+ */
+void
+sdt_argtype_deregister(void *arg)
+{
+	struct sdt_argtype *argtype = arg;
+
+	sx_xlock(&sdt_sx);
+
+	TAILQ_REMOVE(&argtype->probe->argtype_list, argtype, argtype_entry);
+
+	sx_xunlock(&sdt_sx);
+}
+
+static void
+sdt_init(void *arg)
+{ 
+	sx_init_flags(&sdt_sx, "Statically Defined Tracing", SX_NOWITNESS);
+
+	TAILQ_INIT(&sdt_provider_list);
+}
+
+SYSINIT(sdt, SI_SUB_KDTRACE, SI_ORDER_FIRST, sdt_init, NULL);
+
+static void
+sdt_uninit(void *arg)
+{ 
+	sx_destroy(&sdt_sx);
+}
+
+SYSUNINIT(sdt, SI_SUB_KDTRACE, SI_ORDER_FIRST, sdt_uninit, NULL);
+
+/*
+ * List statically defined tracing providers.
+ */
+int
+sdt_provider_listall(sdt_provider_listall_func_t callback_func,void *arg)
+{
+	int error = 0;
+	struct sdt_provider *prov;
+
+	sx_xlock(&sdt_sx);
+
+	TAILQ_FOREACH(prov, &sdt_provider_list, prov_entry) {
+		if ((error = callback_func(prov, arg)) != 0)
+			break;
+	}
+
+	sx_xunlock(&sdt_sx);
+
+	return (error);
+}
+
+/*
+ * List statically defined tracing probes.
+ */
+int
+sdt_probe_listall(struct sdt_provider *prov, 
+    sdt_probe_listall_func_t callback_func,void *arg)
+{
+	int error = 0;
+	int locked;
+	struct sdt_probe *probe;
+
+	locked = sx_xlocked(&sdt_sx);
+	if (!locked)
+		sx_xlock(&sdt_sx);
+
+	TAILQ_FOREACH(probe, &prov->probe_list, probe_entry) {
+		if ((error = callback_func(probe, arg)) != 0)
+			break;
+	}
+
+	if (!locked)
+		sx_xunlock(&sdt_sx);
+
+	return (error);
+}
+
+/*
+ * List statically defined tracing probe arguments.
+ */
+int
+sdt_argtype_listall(struct sdt_probe *probe, 
+    sdt_argtype_listall_func_t callback_func,void *arg)
+{
+	int error = 0;
+	int locked;
+	struct sdt_argtype *argtype;
+
+	locked = sx_xlocked(&sdt_sx);
+	if (!locked)
+		sx_xlock(&sdt_sx);
+
+	TAILQ_FOREACH(argtype, &probe->argtype_list, argtype_entry) {
+		if ((error = callback_func(argtype, arg)) != 0)
+			break;
+	}
+
+	if (!locked)
+		sx_xunlock(&sdt_sx);
+
+	return (error);
+}