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---
layout: default
---
<?xml version="1.0" encoding="utf8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"
>
<head><title>5 Debugging Jikes RVM</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf8" />
<meta name="generator" content="TeX4ht (https://tug.org/tex4ht/)" />
<meta name="originator" content="TeX4ht (https://tug.org/tex4ht/)" />
<!-- xhtml,charset=utf8,2,html -->
<meta name="src" content="index.tex" />
<link rel="stylesheet" type="text/css" href="index.css" />
</head><body
>
<!--l. 2--><div class="crosslinks"><p class="noindent"></p></div>
<h2 class="chapterHead"><span class="titlemark">Chapter 5</span><br /><a
id="x7-470005"></a>Debugging Jikes RVM</h2>
<!--l. 5--><p class="noindent" >This page contains some debugging hints for Jikes RVM. It is assumed that you are
familiar with debugging techniques. If you aren’t, it is advisable to read a book about
the subject.
</p>
<h3 class="sectionHead"><span class="titlemark">5.1 </span> <a
id="x7-480005.1"></a>General debugging tips</h3>
<!--l. 9--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.1.1 </span> <a
id="x7-490005.1.1"></a>Strange NullPointerExceptions</h4>
<!--l. 11--><p class="noindent" >Jikes RVM converts every segmentation fault to a <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">NullPointerException</span></span></span>. If a NPE
occurs at a point where it really shouldn’t be able to, it’s likely that the real cause is
a segmentation fault.
</p><!--l. 15--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.1.2 </span> <a
id="x7-500005.1.2"></a>Assertions</h4>
<!--l. 17--><p class="noindent" >All debugging should be done with assertion-enabled builds if possible. You can also
try using ExtremeAssertion builds.
</p><!--l. 21--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.1.3 </span> <a
id="x7-510005.1.3"></a>Options</h4>
<!--l. 23--><p class="noindent" >The Jikes RVM and MMTk provide several options to print out debugging
information.
</p><!--l. 25--><p class="noindent" >If you’re debugging a problem in the optimizing compiler, you can also print out the
IR.
</p><!--l. 27--><p class="noindent" >You can also use the options to change the behaviour in various ways (e.g. switch
off certain optimizations) if you have a suspicion about the causes of the
problem.
</p><!--l. 31--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.1.4 </span> <a
id="x7-520005.1.4"></a>Debugger Thread</h4>
<!--l. 33--><p class="noindent" >Jikes has an interactive debugger that you can invoke by sending SIGQUIT to Jikes
while it’s running:
</p>
<!--l. 35-->
<div class="lstlisting" id="listing-28"><span class="label"><a
id="x7-52001r1"></a></span><span
class="cmtt-10">pkill</span><span
class="cmtt-10"> </span><span
class="cmtt-10">-</span><span
class="cmtt-10">SIGQUIT</span><span
class="cmtt-10"> </span><span
class="cmtt-10">JikesRVM</span>
</div>
<!--l. 39--><p class="noindent" >In previous versions of Jikes, that stopped all threads and provided an interactive
prompt, but currently it just dumps the state of the VM and continues immediately
(that’s a known issue: <a
href="https://xtenlang.atlassian.net/browse/RVM-570" >RVM-570</a>). Debug fields in classes
</p><!--l. 42--><p class="noindent" >Several classes in the code base provide static boolean fields like DEBUG or
VERBOSE which can be set to get more debugging information.
</p><!--l. 46--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.1.5 </span> <a
id="x7-530005.1.5"></a>Shutdown hooks</h4>
<!--l. 48--><p class="noindent" >You can write custom shutdown hooks to dump gathered information when the VM
terminates. Note that shutdown hooks won’t be run if the VM is terminated via a
signal (see <a
href="https://xtenlang.atlassian.net/browse/RVM-555" >RVM-555</a>)
</p><!--l. 50--><p class="noindent" >Do not use the ExitMonitor from the Callbacks class because it’s less reliable.
</p><!--l. 54--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.1.6 </span> <a
id="x7-540005.1.6"></a>Tests</h4>
<!--l. 56--><p class="noindent" >The test coverage is poor at the moment. Nevertheless, if you’re very lucky, one of
the smaller test cases will fail. See <a
href="/UserGuide/TestingJikesRVM/index.html#x12-11000010">Testing Jikes RVM</a> for details on how to run the
tests and define your own.
</p><!--l. 62--><p class="noindent" >
</p>
<h3 class="sectionHead"><span class="titlemark">5.2 </span> <a
id="x7-550005.2"></a>Tools</h3>
<!--l. 64--><p class="noindent" >There are different tools for debugging Jikes RVM:
</p><!--l. 66--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.2.1 </span> <a
id="x7-560005.2.1"></a>GDB</h4>
<!--l. 68--><p class="noindent" >There is a limited amount of C code used to start Jikes RVM. The rvm script will
start Jikes RVM using GDB (the GNU debugger) if the first argument is -gdb. Break
points can be set in the C code, variables, registers can be expected in the C
code.
</p>
<!--l. 70-->
<div class="lstlisting" id="listing-29"><span class="label"><a
id="x7-56001r1"></a></span><span
class="cmtt-10">rvm</span><span
class="cmtt-10"> </span><span
class="cmtt-10">-</span><span
class="cmtt-10">gdb</span><span
class="cmtt-10"> </span><span
class="cmtt-10"><</span><span
class="cmtt-10">RVM</span><span
class="cmtt-10"> </span><span
class="cmtt-10">args</span><span
class="cmtt-10">></span><span
class="cmtt-10"> </span><span
class="cmtt-10"><</span><span
class="cmtt-10">name</span><span
class="cmtt-10"> </span><span
class="cmtt-10">of</span><span
class="cmtt-10"> </span><span
class="cmtt-10">Java</span><span
class="cmtt-10"> </span><span
class="cmtt-10">application</span><span
class="cmtt-10">></span><span
class="cmtt-10"> </span><span
class="cmtt-10"><</span><span
class="cmtt-10">application</span><span
class="cmtt-10"> </span><span
class="cmtt-10">args</span><span
class="cmtt-10">></span>
</div>
<!--l. 74--><p class="noindent" >The dynamically created Java code doesn’t provide GDB with the necessary symbol
information for debugging. As some of the Java code is created in the boot image, it
is possible to find the location of some Java methods and to break upon them. To
build with debug symbols, you’ll need to set the appropriate property as described in
<a
href="/UserGuide/BuildingJikesRVM/index.html#x5-60003">Building Jikes RVM</a>.
</p><!--l. 76--><p class="noindent" >Details of how to manually walk the stack in GDB can be found <a
href="#x7-630005.5">here</a>.
</p><!--l. 79--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.2.2 </span> <a
id="x7-570005.2.2"></a>rdb</h4>
<!--l. 81--><p class="noindent" ><a
href="http://sape.inf.usi.ch/rdb" >rdb</a> is a debugger that was developed specifically for Jikes RVM. It allows you to
inspect the bootimage. If you’re running Mac OS, you can also use it to debug a
running Jikes RVM.
</p><!--l. 84--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.2.3 </span> <a
id="x7-580005.2.3"></a>Other Tools</h4>
<!--l. 86--><p class="noindent" >Other tools, such as valgrind, are occasionally useful in debugging or understanding
the behaviour of JikesRVM. The rvm script facilitates using these tools with the
’-wrap’ argument.
</p>
<!--l. 88-->
<div class="lstlisting" id="listing-30"><span class="label"><a
id="x7-58001r1"></a></span><span
class="cmtt-10">rvm</span><span
class="cmtt-10"> </span><span
class="cmtt-10">-</span><span
class="cmtt-10">wrap</span><span
class="cmtt-10"> </span><span
class="cmtt-10">"<</span><span
class="cmtt-10">wrapper</span><span
class="cmtt-10">-</span><span
class="cmtt-10">script</span><span
class="cmtt-10">-</span><span
class="cmtt-10">and</span><span
class="cmtt-10">-</span><span
class="cmtt-10">args</span><span
class="cmtt-10">>"</span><span
class="cmtt-10"> </span><span
class="cmtt-10"><</span><span
class="cmtt-10">rest</span><span
class="cmtt-10"> </span><span
class="cmtt-10">of</span><span
class="cmtt-10"> </span><span
class="cmtt-10">command</span><span
class="cmtt-10"> </span><span
class="cmtt-10">line</span><span
class="cmtt-10">></span>
</div>
<!--l. 92--><p class="noindent" >For example, cachegrind can be invoked by
</p>
<!--l. 94-->
<div class="lstlisting" id="listing-31"><span class="label"><a
id="x7-58002r1"></a></span><span
class="cmtt-10">rvm</span><span
class="cmtt-10"> </span><span
class="cmtt-10">-</span><span
class="cmtt-10">wrap</span><span
class="cmtt-10"> </span><span
class="cmtt-10">"/</span><span
class="cmtt-10">path</span><span
class="cmtt-10">/</span><span
class="cmtt-10">to</span><span
class="cmtt-10">/</span><span
class="cmtt-10">valgrind</span><span
class="cmtt-10"> </span><span
class="cmtt-10">--</span><span
class="cmtt-10">tool</span><span
class="cmtt-10">=</span><span
class="cmtt-10">cachegrind</span><span
class="cmtt-10">"</span><span
class="cmtt-10"> </span><span
class="cmtt-10"><</span><span
class="cmtt-10">java</span><span
class="cmtt-10">-</span><span
class="cmtt-10">command</span><span
class="cmtt-10">-</span><span
class="cmtt-10">line</span><span
class="cmtt-10">></span>
</div>
<!--l. 98--><p class="noindent" >The command and arguments immediately after the -wrap argument will be inserted
into the script on the command line that invokes the boot image runner. One useful
variant is
</p>
<!--l. 100-->
<div class="lstlisting" id="listing-32"><span class="label"><a
id="x7-58003r1"></a></span><span
class="cmtt-10">rvm</span><span
class="cmtt-10"> </span><span
class="cmtt-10">-</span><span
class="cmtt-10">wrap</span><span
class="cmtt-10"> </span><span
class="cmtt-10">echo</span><span
class="cmtt-10"> </span><span
class="cmtt-10"><</span><span
class="cmtt-10">rest</span><span
class="cmtt-10"> </span><span
class="cmtt-10">of</span><span
class="cmtt-10"> </span><span
class="cmtt-10">command</span><span
class="cmtt-10"> </span><span
class="cmtt-10">line</span><span
class="cmtt-10">></span>
</div>
<!--l. 108--><p class="noindent" >
</p>
<h3 class="sectionHead"><span class="titlemark">5.3 </span> <a
id="x7-590005.3"></a>Debugging Optimizing Compiler Problems</h3>
<!--l. 110--><p class="noindent" >To debug problems in the optimizing compiler, use a configuration whose bootimage
is compiled with the baseline compiler and which contains the AOS (prototype-opt,
BaseAdaptive*). Faster configurations (such as development) have the drawback of a
longer bootimage compilation time which won’t be amortized unless the problem
occurs late.
</p><!--l. 112--><p class="noindent" >It is advisable to use <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">-X:vm:errorsFatal=true</span></span></span> when debugging optimizing compiler
problems. This will prevent the optimizing compiler from reverting to the baseline
compiler for certain kinds of errors.
</p><!--l. 114--><p class="noindent" >It is strongly recommended to run with advice file generation (see <a
href="/UserGuide/ExperimentalGuidelines/index.html#x8-640006">Experimental
Guidelines</a>). The produced advice files can then be used to try to reproduce the bug.
If this step is successful, the advice files should be minimized to determine the set of
methods that cause the failures. This can be done automatically (e.g. via delta
debugging) or by hand.
</p><!--l. 116--><p class="noindent" >You can also switch on paranoid IR verification in IR.java. Note that this is
not well tested at the moment because we don’t run any regression tests
with it. Use a BaseAdaptive* configuration if you switch this on (bootimage
builds with the optimizing compiler and paranoid IR fail at the time of this
writing).
</p><!--l. 118--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.3.1 </span> <a
id="x7-600005.3.1"></a>Deadlocks</h4>
<!--l. 120--><p class="noindent" >To debug a deadlock, run the VM under a time limit and send SIGQUIT (to force a
thread dump) a few seconds before killing the VM. On Linux, you can use the
timelimit program (should be available in the repositories for Debian-based
distributions).
</p><!--l. 123--><p class="noindent" >
</p>
<h4 class="subsectionHead"><span class="titlemark">5.3.2 </span> <a
id="x7-610005.3.2"></a>Excluding Garbage Collection problems</h4>
<!--l. 125--><p class="noindent" >The garbage collectors that are included with the Jikes RVM are generally stable.
Therefore, if you see a problem that does not occur during the collection
itself, it is likely not a garbage collection problem. You can exclude problems
related to garbage collection by building with other collectors. For example,
you can choose a collector that doesn’t move objects (e.g. MarkSweep) or a
collector that doesn’t require write barriers (e.g. Immix instead of GenImmix).
</p><!--l. 130--><p class="noindent" >
</p>
<h3 class="sectionHead"><span class="titlemark">5.4 </span> <a
id="x7-620005.4"></a>Debugging problems related to the class library</h3>
<!--l. 132--><p class="noindent" >The classes in the <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">libraryInterface</span></span></span> directory overwrite those in the class library. This
allows replacement of classes for debugging purposes. For example, if you wanted to
debug a problem with the class <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">java.example.Foo</span></span></span> from the class library, you could
simply copy its source file to the appropriate path of the <span class="obeylines-h"><span class="verb"><span
class="cmtt-10">libraryInterface</span></span></span> (e.g.
<span class="obeylines-h"><span class="verb"><span
class="cmtt-10">libraryInterface/GNUClasspath/LGPL/src/java/example/Foo.java</span></span></span>). You can
then adapt the source in the library interface to your needs.
</p><!--l. 2--><p class="noindent" >
</p>
<h3 class="sectionHead"><span class="titlemark">5.5 </span> <a
id="x7-630005.5"></a>GDB Stack Walking</h3>
<!--l. 7--><p class="noindent" >Sometimes it is desirable to examine the state of the Java stack whilst using GDB to
step instructions, break on addresses or watch particular variables. These instructions
are based on an email sent by Martin Hirzel to the rvm-devel list around 15th
September 2003. The instructions have been updated by Laurence Hellyer to deal
with native threading and renamed RVM classes.
</p><!--l. 9--><p class="noindent" >1) To learn about the stack frame layout on IA32, look at
rvm/src/org/jikesrvm/ia32/StackframeLayoutConstants.java
</p><!--l. 11--><p class="noindent" >Currently (2009/10/23) the layout is: </p><!--l. 12-->
<div class="lstlisting" id="listing-33"><span class="label"><a
id="x7-63001r1"></a></span><span
class="cmtt-10">+4:</span><span
class="cmtt-10"> </span><span
class="cmtt-10">return</span><span
class="cmtt-10"> </span><span
class="cmtt-10">address</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63002r2"></a></span><span
class="cmtt-10">fp</span><span
class="cmtt-10"> </span><span
class="cmtt-10">-></span><span
class="cmtt-10"> </span><span
class="cmtt-10">0:</span><span
class="cmtt-10"> </span><span
class="cmtt-10">caller</span><span
class="cmtt-10">’</span><span
class="cmtt-10">s</span><span
class="cmtt-10"> </span><span
class="cmtt-10">fp</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63003r3"></a></span><span
class="cmtt-10">-4:</span><span
class="cmtt-10"> </span><span
class="cmtt-10">method</span><span
class="cmtt-10"> </span><span
class="cmtt-10">id</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63004r4"></a></span><span
class="cmtt-10">(</span><span
class="cmtt-10">remember</span><span
class="cmtt-10"> </span><span
class="cmtt-10">stack</span><span
class="cmtt-10"> </span><span
class="cmtt-10">grows</span><span
class="cmtt-10"> </span><span
class="cmtt-10">from</span><span
class="cmtt-10"> </span><span
class="cmtt-10">high</span><span
class="cmtt-10"> </span><span
class="cmtt-10">to</span><span
class="cmtt-10"> </span><span
class="cmtt-10">low</span><span
class="cmtt-10">)</span>
</div>
<!--l. 19--><p class="noindent" >2) To learn how to get the current frame pointer and other
context information, look at the genPrologue() method in
rvm/src/org/jikesrvm/compilers/baseline/ia32/BaselineCompilerImpl.java. It first
retrieves the thread register (esi on IA32), which points to an instance of
RVMThread, and then retrieve fields from that instance.
</p><!--l. 21--><p class="noindent" >3) To find the offset of field RVMThread.framePointer, add the following lines to the
end of BootImageWriter.main(String[]):
</p>
<!--l. 23-->
<div class="lstlisting" id="listing-34"><span class="label"><a
id="x7-63005r1"></a></span><span
class="cmitt-10"> </span><span
class="cmitt-10"> </span><span
class="cmitt-10"> </span><span
class="cmitt-10">//</span><span
class="cmitt-10"> </span><span
class="cmitt-10">added</span><span
class="cmitt-10"> </span><span
class="cmitt-10">to</span><span
class="cmitt-10"> </span><span
class="cmitt-10">get</span><span
class="cmitt-10"> </span><span
class="cmitt-10">framePointer</span><span
class="cmitt-10"> </span><span
class="cmitt-10">offset</span><span
class="cmitt-10"> </span><span
class="cmitt-10">from</span><span
class="cmitt-10"> </span><span
class="cmitt-10">RVMThread</span><span
class="cmitt-10"> </span><span
class="cmitt-10">to</span><span
class="cmitt-10"> </span><span
class="cmitt-10">manually</span><span
class="cmitt-10"> </span><span
class="cmitt-10">walk</span><span
class="cmitt-10"> </span><span
class="cmitt-10">stacks</span><span
class="cmitt-10"> </span><span
class="cmitt-10">in</span><span
class="cmitt-10"> </span><span
class="cmitt-10">GDB</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63006r2"></a></span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">say</span><span
class="cmtt-10">(</span><span
class="cmtt-10">"</span><span
class="cmtt-10">offset</span><span
class="cmtt-10">␣</span><span
class="cmtt-10">of</span><span
class="cmtt-10">␣</span><span
class="cmtt-10">RVMThread</span><span
class="cmtt-10">.</span><span
class="cmtt-10">framePointer</span><span
class="cmtt-10">==</span><span
class="cmtt-10">␣</span><span
class="cmtt-10">"</span><span
class="cmtt-10"> </span><span
class="cmtt-10">+</span><span
class="cmtt-10"> </span><span
class="cmtt-10">ArchEntrypoints</span><span
class="cmtt-10">.</span><span
class="cmtt-10">framePointerField</span><span
class="cmtt-10">.</span><span
class="cmtt-10">getOffset</span><span
class="cmtt-10">()</span><span
class="cmtt-10">)</span><span
class="cmtt-10">;</span>
</div>
<!--l. 28--><p class="noindent" >Do a build to print this info. On my config I got +148, but this can change between
versions
</p><!--l. 30--><p class="noindent" >4) To get started, let’s examine an example stack that contains methods whose
code is in the boot image. We pick one that is likely to be invoked even in a
simple hello-world program. In my RVM.map, 0x351eae9c is the address of
org.jikesrvm.mm.mmtk.ReferenceProcessor.growReferenceTable();
</p><!--l. 32--><p class="noindent" >5) Setting a break point on this address
</p>
<!--l. 34-->
<div class="lstlisting" id="listing-35"><span class="label"><a
id="x7-63007r1"></a></span><span
class="cmtt-10">(</span><span
class="cmtt-10">gdb</span><span
class="cmtt-10">)</span><span
class="cmtt-10"> </span><span
class="cmtt-10">break</span><span
class="cmtt-10"> </span><span
class="cmtt-10">*0</span><span
class="cmtt-10">x351eae9c</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63008r2"></a></span><span
class="cmtt-10">Breakpoint</span><span
class="cmtt-10"> </span><span
class="cmtt-10">2</span><span
class="cmtt-10"> </span><span
class="cmtt-10">at</span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x351eae9c</span>
</div>
<!--l. 39--><p class="noindent" >And run the program to the break point
</p>
<!--l. 41-->
<div class="lstlisting" id="listing-36"><span class="label"><a
id="x7-63009r1"></a></span><span
class="cmtt-10">Breakpoint</span><span
class="cmtt-10"> </span><span
class="cmtt-10">2,</span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x351eae9c</span><span
class="cmtt-10"> </span><span
class="cmtt-10">in</span><span
class="cmtt-10"> </span><span
class="cmtt-10">??</span><span
class="cmtt-10"> </span><span
class="cmtt-10">()</span>
</div>
<!--l. 45--><p class="noindent" >Step some instructions into the method and then dump the registers
</p>
<!--l. 47-->
<div class="lstlisting" id="listing-37"><span class="label"><a
id="x7-63010r1"></a></span><span
class="cmtt-10">(</span><span
class="cmtt-10">gdb</span><span
class="cmtt-10">)</span><span
class="cmtt-10"> </span><span
class="cmtt-10">stepi</span><span
class="cmtt-10"> </span><span
class="cmtt-10">30</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63011r2"></a></span><span
class="cmtt-10">0</span><span
class="cmtt-10">x351eaf03</span><span
class="cmtt-10"> </span><span
class="cmtt-10">in</span><span
class="cmtt-10"> </span><span
class="cmtt-10">??</span><span
class="cmtt-10"> </span><span
class="cmtt-10">()</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63012r3"></a></span><span
class="cmtt-10">(</span><span
class="cmtt-10">gdb</span><span
class="cmtt-10">)</span><span
class="cmtt-10"> </span><span
class="cmtt-10">info</span><span
class="cmtt-10"> </span><span
class="cmtt-10">registers</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63013r4"></a></span><span
class="cmtt-10">eax</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x200</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">512</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63014r5"></a></span><span
class="cmtt-10">ecx</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x0</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63015r6"></a></span><span
class="cmtt-10">edx</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x0</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63016r7"></a></span><span
class="cmtt-10">ebx</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x7431</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">29745</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63017r8"></a></span><span
class="cmtt-10">esp</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x420e1934</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x420e1934</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63018r9"></a></span><span
class="cmtt-10">ebp</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">xb0206ed0</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">xb0206ed0</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63019r10"></a></span><span
class="cmtt-10">esi</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x4100758c</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">1090549132</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63020r11"></a></span><span
class="cmtt-10">edi</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x19c54</span><span
class="cmtt-10">105556</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63021r12"></a></span><span
class="cmtt-10">eip</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x351eaf03</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x351eaf03</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63022r13"></a></span><span
class="cmtt-10">eflags</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x202</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">514</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63023r14"></a></span><span
class="cmtt-10">cs</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x17</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">23</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63024r15"></a></span><span
class="cmtt-10">ss</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x1f</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">31</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63025r16"></a></span><span
class="cmtt-10">ds</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x1f</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">31</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63026r17"></a></span><span
class="cmtt-10">es</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x1f</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">31</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63027r18"></a></span><span
class="cmtt-10">fs</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x1f</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">31</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63028r19"></a></span><span
class="cmtt-10">gs</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x37</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">55</span>
</div>
<!--l. 69--><p class="noindent" >The current FP is stored in RVMThread.framePointer which we found out in 3) is at
offset +148. ESI points to the current RVMThread object so we can access the FP
value like so:
</p>
<!--l. 71-->
<div class="lstlisting" id="listing-38"><span class="label"><a
id="x7-63029r1"></a></span><span
class="cmtt-10">(</span><span
class="cmtt-10">gdb</span><span
class="cmtt-10">)</span><span
class="cmtt-10"> </span><span
class="cmtt-10">x</span><span
class="cmtt-10"> </span><span
class="cmtt-10">(</span><span
class="tctt-1000">$</span><span
class="cmtt-10">esi</span><span
class="cmtt-10">+148)</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63030r2"></a></span><span
class="cmtt-10">0</span><span
class="cmtt-10">x41007620</span><span
class="cmtt-10">:</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x420e1954</span>
</div>
<!--l. 76--><p class="noindent" >Note that the FP is at a higher address than ESP which is what we would
expect
</p><!--l. 78--><p class="noindent" >The return address is at FP+4 so to get the return address we can do:
</p>
<!--l. 80-->
<div class="lstlisting" id="listing-39"><span class="label"><a
id="x7-63031r1"></a></span><span
class="cmtt-10">(</span><span
class="cmtt-10">gdb</span><span
class="cmtt-10">)</span><span
class="cmtt-10"> </span><span
class="cmtt-10">x</span><span
class="cmtt-10"> </span><span
class="cmtt-10">(*(</span><span
class="tctt-1000">$</span><span
class="cmtt-10">esi</span><span
class="cmtt-10">+148)</span><span
class="cmtt-10">)</span><span
class="cmtt-10">+4</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63032r2"></a></span><span
class="cmtt-10">0</span><span
class="cmtt-10">x420e1958</span><span
class="cmtt-10">:</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x351eadde</span>
</div>
<!--l. 85--><p class="noindent" >We can look in RVM.map for the largest method address smaller than 0x351eadde which
is org.jikesrvm.mm.mmtk.ReferenceProcessor.addCandidate(java.lang.ref.Reference,
org.vmmagic.unboxed.ObjectReference). Examining ReferenceProcessor.java we
find that this is the only method that calls growReferenceTable so this is
correct
</p><!--l. 87--><p class="noindent" >Get the return address from the next frame
</p>
<!--l. 89-->
<div class="lstlisting" id="listing-40"><span class="label"><a
id="x7-63033r1"></a></span><span
class="cmtt-10">(</span><span
class="cmtt-10">gdb</span><span
class="cmtt-10">)</span><span
class="cmtt-10"> </span><span
class="cmtt-10">x</span><span
class="cmtt-10"> </span><span
class="cmtt-10">*(*(</span><span
class="tctt-1000">$</span><span
class="cmtt-10">esi</span><span
class="cmtt-10">+148)</span><span
class="cmtt-10">)</span><span
class="cmtt-10">+4</span><span
class="cmtt-10"> </span><br /><span class="label"><a
id="x7-63034r2"></a></span><span
class="cmtt-10">0</span><span
class="cmtt-10">x420e1980</span><span
class="cmtt-10">:</span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10"> </span><span
class="cmtt-10">0</span><span
class="cmtt-10">x352ebd1e</span>
</div>
<!--l. 94--><p class="noindent" >Which corresponds to org.jikesrvm.mm.mmtk.ReferenceProcessor.addSoftCandidate(java.lang.ref.SoftReference,
org.vmmagic.unboxed.ObjectReference) which is a caller of addCandidate.
</p><!--l. 96--><p class="noindent" >We can follow the stack back up to the top where we will read a FP of 0
(look in rvm/src/org/jikesrvm/ia32/StackframeLayoutConstants.java for
details)
</p>
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id="tailDebuggingJikesRVM.html"></a></p>
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