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From: John Birrell <jb@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
Cc: 
Subject: PERFORCE change 126860 for review
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http://perforce.freebsd.org/chv.cgi?CH=126860

Change 126860 by jb@jb_freebsd1 on 2007/09/27 10:14:48

	Hi-ho, hi-ho, it's obfuscate we go.
	
	In mi_startup, get the traditional size of 'struct thread',
	including the 'struct td_sched' using sched_sizeof_thread().
	That's the offset to the start of the DTrace-specific thread
	data.
	
	The overall size of that is saved in kdtrace_thread_size
	which is used in each call to uma_zcreate() when a thread
	is allocated.

Affected files ...

.. //depot/projects/dtrace/src/sys/kern/init_main.c#14 edit

Differences ...

==== //depot/projects/dtrace/src/sys/kern/init_main.c#14 (text+ko) ====

@@ -60,6 +60,7 @@
 #include <sys/syscallsubr.h>
 #include <sys/sysctl.h>
 #include <sys/proc.h>
+#include <sys/kdtrace.h>
 #include <sys/resourcevar.h>
 #include <sys/systm.h>
 #include <sys/signalvar.h>
@@ -98,6 +99,15 @@
 struct	vmspace vmspace0;
 struct	proc *initproc;
 
+/* DTrace data for the primary thread in proc0. */
+char	kdtrace_thread0[KDTRACE_THREAD_SIZE];
+
+/* Offset from 'struct thread *' to the opaque DTrace fields. */
+int	kdtrace_thread_offset;
+
+/* Overall per-thread allocation size. */
+int	kdtrace_thread_size;
+
 int	boothowto = 0;		/* initialized so that it can be patched */
 SYSCTL_INT(_debug, OID_AUTO, boothowto, CTLFLAG_RD, &boothowto, 0, "");
 int	bootverbose;
@@ -177,6 +187,18 @@
 	int verbose;
 #endif
 
+	/* Get the size of 'struct thread' plus 'struct td_sched' */
+	kdtrace_thread_offset = sched_sizeof_thread();
+
+	/*
+	 * Allow for the DTrace-specific thread data after
+	 * struct td_sched. This space is allocated opaquely to
+	 * avoid license issues. The value of KDTRACE_THREAD_SIZE
+	 * set in sys/proc.h must be larger than that required by
+	 * the DTrace kernel modules.
+	 */
+	kdtrace_thread_size = kdtrace_thread_offset + KDTRACE_THREAD_SIZE;
+
 	if (sysinit == NULL) {
 		sysinit = SET_BEGIN(sysinit_set);
 		sysinit_end = SET_LIMIT(sysinit_set);