The Compiler Did What?

I was recently investigating a crash in an application.  As I researched the issue I found a very old defect in the code that was only recently being exposed by the compiler.   The crash occurred at the below instruction because the ebx register does not hold a valid pointer.   0:001> r eax=d9050cf7 ebx=003078c0…


Understanding Pool Corruption Part 2 – Special Pool for Buffer Overruns

In our previous article we discussed pool corruption that occurs when a driver writes too much data in a buffer.  In this article we will discuss how special pool can help identify the driver that writes too much data.   Pool is typically organized to allow multiple drivers to store data in the same page…


Understanding Pool Corruption Part 1 – Buffer Overflows

Before we can discuss pool corruption we must understand what pool is.  Pool is kernel mode memory used as a storage space for drivers.  Pool is organized in a similar way to how you might use a notepad when taking notes from a lecture or a book.  Some notes may be 1 line, others may…


Debugging a Debugger to Debug a Dump

Recently I came across an instance where my debugger did not do what I wanted.  Rarely do computers disobey me, but this one was unusually stubborn.  There was no other option; I had to bend the debugger to my will.   There are many ways to make a computer program do what you want.  If…


Use Caution When Implementing IPC for Performance Counters

  Recently I was working with a developer who had created performance counters that work in Performance Monitor but are never collected in a user defined data collector set.  The customer explained that their counters update named shared memory inside the application which should be read by perfmon or the data collector set.   Putting…


Troubleshooting Pool Leaks Part 7 – Windows Performance Toolkit

In Part 1 of this series we identified a pool leak in non paged pool.  In Part 2 and Part 3 of this series we identified what pool tag was leaking.  In Part 5 and Part 6 we got call stacks showing the memory being allocated.  In this article we are going to discuss a…


Troubleshooting Pool Leaks Part 5 – PoolHitTag

In Part 4 we narrowed the source of the leaked pool memory to the specific driver which is allocating it, and we identified where in the driver this allocation was taking place.  However, we did not capture contextual information such as the call stack leading up to this code.  Also, we didn’t capture information about…


Troubleshooting Pool Leaks Part 4 – Debugging Multiple Users for a Tag

In our previous articles we discussed various techniques for identifying a pool memory leak and narrowing the scope of the leak to an individual pool tag.  Knowing the leaking pool tag is often sufficient to identify the cause of the problem and find a solution.  However, there may be a scenario where multiple drivers use…


Troubleshooting Pool Leaks Part 3 – Debugging

In our previous articles we discussed identifying a pool leak with perfmon, and narrowing the source of the leak with poolmon.  These tools are often preferred because they are easy to use, provide verbose information, and can be run on a system without forcing downtime.  However, it is not always possible to get perfmon and…