Re: [SCM] master: Use libunwind cursor to get at CFA.

[Mark Wielaard <mark at klomp dot org>]

Hi Andrew,

On Mon, 2007-12-03 at 11:19 -0500, Andrew Cagney wrote:
> The confusion comes from what libunwind considers to be the cursor's 
> CFA.  It returns what you're more likely to recognize as the  
> inner-to-cursor's CFA and not the cursor''s CFA.  Effectively the 
> current frame's SP, in fact:
>
>     case UNW_X86_64_CFA:
>     case UNW_X86_64_RSP:
>       if (write)
>         return -UNW_EREADONLYREG;
>       *valp = c->dwarf.cfa;
>       return 0;

Nice catch. Well that is somewhat of a bummer. Then we must fall back on
the unwind one frame trick and get the SP again.

What is somewhat worrying is that none of the tests caught this. So I
added one that does fail with my change, and passes with that commit
reverted.

frysk-core/frysk/pkglibdir/ChangeLog
2007-12-03  Mark Wielaard  <mwielaard@redhat.com>

    * funit-stepping-asm.S: Add fifth function and _stepOverPrologue_
    marker.

frysk-core/frysk/stepping/ChangeLog
2007-12-03  Mark Wielaard  <mwielaard@redhat.com>

    * TestStepping.java (testASMFunctionStepOverPrologue): New test.

Cheers,

Mark

diff --git a/frysk-core/frysk/pkglibdir/funit-stepping-asm.S b/frysk-core/frysk/pkglibdir/funit-stepping-asm.S
index 4af1506..cde2b22 100644
--- a/frysk-core/frysk/pkglibdir/funit-stepping-asm.S
+++ b/frysk-core/frysk/pkglibdir/funit-stepping-asm.S
@@ -40,10 +40,18 @@
 
 #include "frysk-asm.h"
 
+	FUNCTION_BEGIN(fifth,1)
+	FUNCTION_PROLOGUE(fifth,1) ; NO_OP	// _stepOverPrologue_
+	FUNCTION_EPILOGUE(fifth,1)
+	FUNCTION_RETURN(fifth,1)
+	FUNCTION_END(fifth,1)
+	
+	
 	FUNCTION_BEGIN(fourth,0)
 	FUNCTION_PROLOGUE(fourth,0)
 	NO_OP					// _stepAdvanceStart_
 	NO_OP
+	FUNCTION_CALL(fifth)
 	FUNCTION_EPILOGUE(fourth,0)
 	FUNCTION_RETURN(fourth,0)
 	FUNCTION_END(fourth,0)
diff --git a/frysk-core/frysk/stepping/TestStepping.java b/frysk-core/frysk/stepping/TestStepping.java
index 7f14ea1..cab4480 100644
--- a/frysk-core/frysk/stepping/TestStepping.java
+++ b/frysk-core/frysk/stepping/TestStepping.java
@@ -952,6 +952,52 @@ public class TestStepping extends TestLib {
 	cleanup();
     }
 
+  /**
+   * Tests that the line stepper steps OK even when stack pointer
+   * changes.
+   */                                                                          
+    public void testASMFunctionStepOverPrologue() {
+
+	/** Variable setup */
+	String source = Config.getRootSrcDir()
+	    + "frysk-core/frysk/pkglibdir/funit-stepping-asm.S";
+
+	this.scanner = new TestfileTokenScanner(new File(source));
+
+	/* The line number where the test begins, prologue of fifth
+	   function. */
+	int startLine = this.scanner.findTokenLine("_stepOverPrologue_");
+
+	/* The line number the test should end up at, still the same
+	   line (only prologue is stepped over, not the NO_OP) */
+	int endLine = this.scanner.findTokenLine("_stepOverPrologue_");
+
+	/* The test process */
+	dbae = new DaemonBlockedAtEntry(Config
+					.getPkgLibFile("funit-stepping-asm"));
+
+	Task theTask = dbae.getMainTask();
+
+	this.testStarted = false;
+
+	initTaskWithTask(theTask, source, startLine, endLine);
+
+	this.currentTest = new AssertLine(endLine, theTask);
+
+	DebugInfoFrame frame = DebugInfoStackFactory
+	    .createDebugInfoStackTrace(theTask);
+	assertTrue("Line information present", frame.getLines().length > 0);
+
+	/** The stepping operation */
+	this.se.stepOver(theTask, frame);
+
+	this.testStarted = true;
+	/** Run to completion */
+	assertRunUntilStop("Running test");
+	cleanup();
+    }
+
+
     boolean genericUpdate = false;
 
     public Task initTask(Offspring process, String source, int startLine,