DummyDisassembler for fstep

[Mark Wielaard <mark@klomp.org>]

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Hi,

In the last test reports I saw that FStep.testFirstStep was disabled
because we don't have a disassembler anymore. This made me a little
nervous since the test isn't actually testing the disassembler at all
and the test is a good indicator of subtle observer issues with stepping
and breakpoints. So I added a quick and dirty DummyDisassembler to fstep
that is used when no full blown Disassembler is available.

2007-08-28  Mark Wielaard  <mwielaard@redhat.com>

    * fstep.java (DummyDisassembler): New static helper class.
    (updateAttached): Create DummyDisassembler when needed.
    (updateHit): Add new observers first before removing Code observer.
    * TestFStep.java: Always supported.

With this the test passes again and now fstep even gives some useful
output even without the full disassembler. Maybe someone wants to make
this more generic for other consumers of the disassembler?

Cheers,

Mark



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Index: frysk-core/frysk/bindir/TestFStep.java
===================================================================
RCS file: /cvs/frysk/frysk-core/frysk/bindir/TestFStep.java,v
retrieving revision 1.5
diff -u -r1.5 TestFStep.java
--- frysk-core/frysk/bindir/TestFStep.java	16 Aug 2007 20:15:11 -0000	1.5
+++ frysk-core/frysk/bindir/TestFStep.java	28 Aug 2007 10:58:46 -0000
@@ -54,8 +54,6 @@
   // stepped program.
   public void testFirstStep() throws Exception
   {
-      if (unsupported("disassembler", !lib.opcodes.Disassembler.available()))
-	  return;
     Elf e = new Elf("/bin/true", ElfCommand.ELF_C_READ);
     try
       {
Index: frysk-core/frysk/bindir/fstep.java
===================================================================
RCS file: /cvs/frysk/frysk-core/frysk/bindir/fstep.java,v
retrieving revision 1.10
diff -u -r1.10 fstep.java
--- frysk-core/frysk/bindir/fstep.java	9 Jul 2007 16:31:29 -0000	1.10
+++ frysk-core/frysk/bindir/fstep.java	28 Aug 2007 10:58:46 -0000
@@ -42,6 +42,7 @@
 import frysk.proc.*;
 import frysk.util.CommandlineParser;
 import lib.opcodes.*;
+import inua.eio.ByteBuffer;
 import gnu.classpath.tools.getopt.*;
 import java.util.*;
 
@@ -186,12 +187,49 @@
     Manager.eventLoop.run();
   }
 
+  /**
+   * Disassembler to use when real disassembler isn't available.
+   * Only implements <code>disassembleInstructions</code> and just
+   * returns address and four bytes in raw hex form.
+   */
+  static class DummyDisassembler extends Disassembler
+  {
+    private final ByteBuffer memory;
+    DummyDisassembler(ByteBuffer memory)
+    {
+      super(memory);
+      this.memory = memory;
+    }
+
+    public List disassembleInstructions(long address, long count)
+    {
+      ArrayList list = new ArrayList();
+      memory.position(address);
+      while (count > 0)
+	{
+	  list.add("0x" + Long.toHexString(address)
+		   + "\t0x" + Integer.toHexString(memory.getByte() & 0xff)
+		   + " 0x" + Integer.toHexString(memory.getByte() & 0xff)
+		   + " 0x" + Integer.toHexString(memory.getByte() & 0xff)
+		   + " 0x" + Integer.toHexString(memory.getByte() & 0xff));
+          address++;
+	  count--;
+	}
+      return list;
+    }
+  }
+
   // TaskObserver.Attached interface
   public Action updateAttached(Task task)
   {
     // We only need one disassembler since all Tasks share their memory.
     if (disassembler == null)
-      disassembler = new Disassembler(task.getMemory());
+      {
+	if (Disassembler.available())
+	  disassembler = new Disassembler(task.getMemory());
+	else
+	  disassembler = new DummyDisassembler(task.getMemory());
+      }
 
     tasks.put(task, Long.valueOf(0));
 
@@ -226,9 +264,9 @@
   // TaskObserver.Code interface
   public Action updateHit(Task task, long address)
   {
-    task.requestDeleteCodeObserver(this, address);
     task.requestAddInstructionObserver(this);
     task.requestAddTerminatedObserver(this);
+    task.requestDeleteCodeObserver(this, address);
     return Action.BLOCK;
   }