PERFORCE change 132678 for review

[John Birrell]

http://perforce.freebsd.org/chv.cgi?CH=132678

Change 132678 by jb at jb_freebsd1 on 2008/01/07 07:21:49

	Add the hook to allow the dtrace module to process breakpoint
	interrupts if it is loaded.
	
	The Function Boundary Trace (fbt) and Statically Defined Trace (sdt)
	providers trigger probes on amd64 by replacing the "pushl %ebp" and
	'ret' opcodes with int3 (#BP, 0xcc) and then checking the trap
	address against the list of installed probes. If the address has
	a probe associated with it, the dtrace module calls it's probes
	and the function that was broken by the breakpoint, then repairs
	the trap frame and returns via 'doreti'.
	
	In the case that the trap address isn't from a DTrace probe, the
	return path takes execution back to the calltrap code and the
	trap is handled in the usual way.
	
	No doubt there is a simpler way to do this pointer ping pong.

Affected files ...

.. //depot/projects/dtrace/src/sys/amd64/amd64/exception.S#7 edit

Differences ...

==== //depot/projects/dtrace/src/sys/amd64/amd64/exception.S#7 (text+ko) ====

@@ -37,6 +37,7 @@
 #include "opt_atpic.h"
 #include "opt_compat.h"
 #include "opt_hwpmc_hooks.h"
+#include "opt_kdtrace.h"
 
 #include <machine/asmacros.h>
 #include <machine/psl.h>
@@ -44,6 +45,27 @@
 
 #include "assym.s"
 
+#ifdef KDTRACE_HOOKS
+	.bss
+	.globl	dtrace_invop_jump_addr
+	.align	8
+	.type	dtrace_invop_jump_addr, @object
+        .size	dtrace_invop_jump_addr, 8
+dtrace_invop_jump_addr:
+	.zero	8
+	.globl	dtrace_invop_calltrap_addr
+	.align	8
+	.type	dtrace_invop_calltrap_addr, @object
+        .size	dtrace_invop_calltrap_addr, 8
+dtrace_invop_calltrap_addr:
+	.zero	8
+	.globl	dtrace_invop_return_addr
+	.align	8
+	.type	dtrace_invop_return_addr, @object
+        .size	dtrace_invop_return_addr, 8
+dtrace_invop_return_addr:
+	.zero	8
+#endif
 	.text
 #ifdef HWPMC_HOOKS
 	ENTRY(start_exceptions)
@@ -170,6 +192,28 @@
 	movq	%r14,TF_R14(%rsp)
 	movq	%r15,TF_R15(%rsp)
 	FAKE_MCOUNT(TF_RIP(%rsp))
+#ifdef KDTRACE_HOOKS
+	/*
+	 * DTrace Function Boundary Trace (fbt) and Statically Defined
+	 * Trace (sdt) probes are triggered by int3 (0xcc) which causes
+	 * the #BP (T_BPTFLT) breakpoint interrupt. For all other trap
+	 * types, just handle them in the usual way.
+	 */
+	cmpq	$T_BPTFLT,TF_TRAPNO(%rsp)
+	jne	calltrap
+
+	/* Check if there is no DTrace hook registered. */
+	cmpq	$0,dtrace_invop_jump_addr
+	je	calltrap
+
+	/* Set our alternate jump addresses for the jump back. */
+	movq	$calltrap, dtrace_invop_calltrap_addr(%rip)
+	movq	$doreti, dtrace_invop_return_addr(%rip)
+
+	/* Jump to the code hooked in by DTrace. */
+	movq	dtrace_invop_jump_addr, %rax
+	jmpq	*dtrace_invop_jump_addr
+#endif
 	.globl	calltrap
 	.type	calltrap, at function
 calltrap: