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From: John Birrell <jb@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
Cc: 
Subject: PERFORCE change 143159 for review
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http://perforce.freebsd.org/chv.cgi?CH=143159

Change 143159 by jb@freebsd3 on 2008/06/09 03:11:29

	Add the exception handling hooks for the DTrace Function Boundary
	Trace Provider (fbt).

Affected files ...

.. //depot/projects/dtrace6/src/sys/i386/i386/exception.s#2 edit

Differences ...

==== //depot/projects/dtrace6/src/sys/i386/i386/exception.s#2 (text+ko) ====

@@ -31,6 +31,7 @@
  */
 
 #include "opt_apic.h"
+#include "opt_kdtrace.h"
 #include "opt_npx.h"
 
 #include <machine/asmacros.h>
@@ -40,7 +41,24 @@
 #include "assym.s"
 
 #define	SEL_RPL_MASK	0x0003
+#define	GSEL_KPL	0x0020	/* GSEL(GCODE_SEL, SEL_KPL) */
 
+
+#ifdef KDTRACE_HOOKS
+	.bss
+	.globl	dtrace_invop_jump_addr
+	.align	4
+	.type	dtrace_invop_jump_addr, @object
+        .size	dtrace_invop_jump_addr, 4
+dtrace_invop_jump_addr:
+	.zero	4
+	.globl	dtrace_invop_calltrap_addr
+	.align	4
+	.type	dtrace_invop_calltrap_addr, @object
+        .size	dtrace_invop_calltrap_addr, 4
+dtrace_invop_calltrap_addr:
+	.zero	8
+#endif
 	.text
 
 /*****************************************************************************/
@@ -86,8 +104,10 @@
 	pushl $0; TRAP(T_OFLOW)
 IDTVEC(bnd)
 	pushl $0; TRAP(T_BOUND)
+#ifndef KDTRACE_HOOKS
 IDTVEC(ill)
 	pushl $0; TRAP(T_PRIVINFLT)
+#endif
 IDTVEC(dna)
 	pushl $0; TRAP(T_DNA)
 IDTVEC(fpusegm)
@@ -145,6 +165,45 @@
 	jmp	doreti
 
 /*
+ * Privileged instruction fault.
+ */
+#ifdef KDTRACE_HOOKS
+	SUPERALIGN_TEXT
+IDTVEC(ill)
+	/* Check if there is no DTrace hook registered. */
+	cmpl	$0,dtrace_invop_jump_addr
+	je	norm_ill
+
+	/* Check if this is a user fault. */
+	cmpl	$GSEL_KPL, 4(%esp)	/* Check the code segment. */
+              
+	/* If so, just handle it as a normal trap. */
+	jne	norm_ill
+              
+	/*
+	 * This is a kernel instruction fault that might have been caused
+	 * by a DTrace provider.
+	 */
+	pushal				/* Push all registers onto the stack. */
+
+	/*
+	 * Set our jump address for the jump back in the event that
+	 * the exception wasn't caused by DTrace at all.
+	 */
+	movl	$norm_ill, dtrace_invop_calltrap_addr
+
+	/* Jump to the code hooked in by DTrace. */
+	jmpl	*dtrace_invop_jump_addr
+
+	/*
+	 * Process the instruction fault in the normal way.
+	 */
+norm_ill:
+	pushl $0
+	TRAP(T_PRIVINFLT)
+#endif
+
+/*
  * SYSCALL CALL GATE (old entry point for a.out binaries)
  *
  * The intersegment call has been set up to specify one dummy parameter.