Enable use of DTRACE_PROBE* macros in "spl" module

This change modifies some of the infrastructure for enabling the use of
the DTRACE_PROBE* macros, such that we can use tehm in the "spl" module.

Currently, when the DTRACE_PROBE* macros are used, they get expanded to
create new functions, and these dynamically generated functions become
part of the "zfs" module.

Since the "spl" module does not depend on the "zfs" module, the use of
DTRACE_PROBE* in the "spl" module would result in undefined symbols
being used in the "spl" module. Specifically, DTRACE_PROBE* would turn
into a function call, and the function being called would be a symbol
only contained in the "zfs" module; which results in a linker and/or
runtime error.

Thus, this change adds the necessary logic to the "spl" module, to
mirror the tracing functionality available to the "zfs" module. After
this change, we'll have a "trace_zfs.h" header file which defines the
probes available only to the "zfs" module, and a "trace_spl.h" header
file which defines the probes available only to the "spl" module.

Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Prakash Surya <prakash.surya@delphix.com>
Closes #9525

include/os/linux/zfs/sys/Makefile.am

@@ -4,7 +4,7 @@ KERNEL_H = \
 	$(top_srcdir)/include/os/linux/zfs/sys/trace_acl.h \
 	$(top_srcdir)/include/os/linux/zfs/sys/trace_arc.h \
 	$(top_srcdir)/include/os/linux/zfs/sys/trace_common.h \
-	$(top_srcdir)/include/os/linux/zfs/sys/trace_defs.h \
+	$(top_srcdir)/include/os/linux/zfs/sys/trace_zfs.h \
 	$(top_srcdir)/include/os/linux/zfs/sys/trace_dbgmsg.h \
 	$(top_srcdir)/include/os/linux/zfs/sys/trace_dbuf.h \
 	$(top_srcdir)/include/os/linux/zfs/sys/trace_dmu.h \

include/os/linux/zfs/sys/trace_dbgmsg.h

@@ -22,10 +22,16 @@
 #if defined(_KERNEL)
 #if defined(HAVE_DECLARE_EVENT_CLASS)
 
-/* Do not include this file directly. Please use <sys/trace.h> instead. */
-#ifndef _SYS_TRACE_DBGMSG_INDIRECT
-#error "trace_dbgmsg.h included directly"
-#endif
+#undef TRACE_SYSTEM
+#define	TRACE_SYSTEM zfs
+
+#undef TRACE_SYSTEM_VAR
+#define	TRACE_SYSTEM_VAR zfs_dbgmsg
+
+#if !defined(_TRACE_DBGMSG_H) || defined(TRACE_HEADER_MULTI_READ)
+#define	_TRACE_DBGMSG_H
+
+#include <linux/tracepoint.h>
 
 /*
  * This file defines tracepoint events for use by the dbgmsg(),
@@ -67,6 +73,14 @@ DEFINE_EVENT(zfs_dprintf_class, name, \
 /* END CSTYLED */
 DEFINE_DPRINTF_EVENT(zfs_zfs__dprintf);
 
+#endif /* _TRACE_DBGMSG_H */
+
+#undef TRACE_INCLUDE_PATH
+#undef TRACE_INCLUDE_FILE
+#define	TRACE_INCLUDE_PATH sys
+#define	TRACE_INCLUDE_FILE trace_dbgmsg
+#include <trace/define_trace.h>
+
 #else
 
 DEFINE_DTRACE_PROBE1(zfs__dprintf);

include/os/linux/zfs/sys/trace_zfs.h

@@ -38,6 +38,7 @@
 #include <sys/trace.h>
 #include <sys/trace_acl.h>
 #include <sys/trace_arc.h>
+#include <sys/trace_dbgmsg.h>
 #include <sys/trace_dbuf.h>
 #include <sys/trace_dmu.h>
 #include <sys/trace_dnode.h>