Articles I recently published on the Google Cloud websiteA key part of my job as Solutions Architect at Google Cloud is to work with customers to identify and capture best practices and to turn these into public documentation.
Over the past six months, I have published the following guides
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Runtime Code Modification Explained, Part 4: Keeping Execution Flow IntactConcurrent Execution A typical user mode process on a Windows system can be expected to have more than one thread. In addition to user threads, the Windows kernel employs a number of system threads. Given the presence of multiple threads, it is likely that whenever a code modification is performed, more than one thread is affected, i.e. more than one thread is sooner or later going to execute the modified code sequence. Continue »
Runtime Code Modification Explained, Part 3: Cross-Modifying Code and AtomicityPerforming modifications on existing code is a technique commonly encountered among instrumentation solutions such as DTrace. Assuming a multiprocessor machine, altering code brings up the challenge of properly synchronizing such activity among processors. As stated before, IA-32/Intel64 allows code to be modified in the same manner as data. Whether modifying data is an atomic operation or not, depends on the size of the operand. If the total number of bytes to be modified is less than 8 and the target address adheres to certain alignment requirements, current IA-32 processors guarantee atomicity of the write operation. Continue »
Runtime Code Modification Explained, Part 2: Cache Coherency IssuesInstrumentation of a routine may comprise multiple steps. As an example, a trampoline may need to be generated or updated, followed by a modification on the original routine, which may include updatating or replacing a branch instruction to point to the trampoline. In such cases, it is essential for maintaining consistency that the code changes take effect in a specific order. Otherwise, if the branch was written before the trampoline code has been stored, the branch would temporarily point to uninitialized memory. Continue »
Runtime Code Modification Explained, Part 1: Dealing With MemoryRuntime code modification, of self modifying code as it is often referred to, has been used for decades – to implement JITters, writing highly optimized algorithms, or to do all kinds of interesting stuff. Using runtime code modification code has never been really easy – it requires a solid understanding of machine code and it is straightforward to screw up. What’s not so well known, however, is that writing such code has actually become harder over the last years, at least on the IA-32 platform: Comparing the 486 and current Core architectures, it becomes obvious that Intel, in order to allow more advanced CPU-interal optimizations, has actually lessened certain gauarantees made by the CPU, which in turn requires the programmer to pay more attection to certain details. Continue »
Windows Hotpatching: A WalkthroughAs discussed in the last post, Windows 2003 SP1 introduced a technology known as Hotpatching. An integral part of this technology is Hotpatching, which refers to the process of applying an updated on the fly by using runtime code modification techniques. Although Hotpatching has caught a bit of attention, suprisingly little information has been published about its inner workings. As the technology is patented, however, there is quite a bit of information that can be obtained by reading the patent description. Continue »
#ifdef _WIN32When writing processor-specific code, the _M_IX86, _M_AMD64 and _M_IA64 can be used for conditional compilation – so far, so good. But sometimes code is not exactly processor-specific but rather specific to the natural machine word length (i.e. 32 bit or 64 bit). Fur such situations, there are defines, too – however there is a little catch: For ancient 16 bit code, there is _WIN16. For 64 bit, the WDK build environment defines _WIN64 by default. Continue »
Windows HotpatchingSeveral years ago, with Windows Server 2003 SP1, Microsoft introduced a technology and infrastructure called Hotpatching. The basic intent of this infrastructure is to provide a means to apply hotfixes on the fly, i.e. without having to reboot the system – even if the hotfix contains changes on critical system components such as the kernel iteself, important drivers, or user mode libraries such as shell32.dll. Trying to applying hotfixes on the fly introduces a variety of problems – the most important being: Continue »
How to test MFC applications using Visual Assert or cfixAutomated testing of GUI applications is tricky. It is not only tricky because testing the GUI itself is hard (despite there being good tools around), it is also tricky because GUI applications often tend to be a bit hostile towards unit testing. One class of GUI applications for which this kind of hostility often applies is MFC applications. Although MFC allows the use of DLLs, components, etc, the framework still encourages the use of relatively monolithic architectures. Continue »
Visual Assert 1.1 beta and cfix 1.7 releasedSlightly delayed, Visual Assert 1.1 beta is now available for download. As announced in a previous post, the most important change in the new version is added suport for the latest version of Visual Studio, Visual Studio 2010. However, the new version also brings a couple of new features that apply to all versions of Visual Studio. Most importantly, cfix and Visual Assert now expose an API that allows developers to plug in custom event sinks. Continue »
Coming soon: Visual Assert for Visual Studio 2010Now that Visual Studio 2010 has oficially been released, I keep getting questions about a Visual Studio 2010-enabled version of Visual Assert. The fact that Visual Studio 2010 is already out, yet there is no Visual Assert version for it is unfortunate. It would have been nice to have Visual Studio 2010 support ready on Visual Studio’s release date, however, that was not possible due to lack of time. Having solved most compatibilty issues though (of which there were many, Visual Studio 2010 is a truly painful release for AddIn developers), I am now confident to be able to offer a first beta by begin of May. Continue »
What a weirdo: How the /analyze switch changes its behavior depending on its environmentIn Visual Studio 2005 Team System (VSTS), the “ultimate” SKU of Visual Studio 2005, Microsoft introduced the /analyze compiler switch. When the /analyze switch is used, the cl compiler not only does its regular checks, but performs a much more thorough static code analysis. While /analyze is very useful indeed, it was only available in the top SKU – the Standard and Professional versions of Visual Studio lacked support for this compiler switch (this has changed by now, Professional now also supports this feature). Continue »
Visual Assert hits RTM, now available for freeVisual Assert, the unit testing Add-In for Visual Studio/Visual C++ has finally left its beta status and – better yet – is now available for free, both for commercial and non-commercial use. Visual Assert, based on the cfix 1.6 unit testing framework, allows you to easily write, manage, run, and debug your C/C++ unit tests -– without ever leaving the Visual Studio® IDE. No fiddling with command line tools, no complex configuration, and no boilerplate code required. Continue »
cfix 1.6 released, simplifies authoring of multi-threaded testsA new release of cfix, the unit testing framework for C and C++, is now available for download. Besides some minor enhancements like extending the maximum permitted fixture name, cfix 1.6 introduces a major new feature, Anonymous Thread Auto-Registration. Since its very first release, cfix has supported multi-threaded test cases, i.e. test cases that spawn child threads, each of which potentially making use of the various assertion statements like CFIX_ASSERT. To make this work and ensure that failing assertions are handled properly, however, usage of CfixCreateThread (rather than the native Win32 CreateThread) was mandatory when spawning such threads. Continue »
How to customize test run execution to make your cfix test runs more effectiveOne of the features introduced back in cfix 1.2 was the ability to customize test execution with the command line parameters -fsr and -fsf. Using these switches can make your test runs more effective and can help simplify debugging – so it is worth spending a minute on this topic. Assume our test run comprises two fixtures, Fixture A and Fixture B. As fixtures are always run in alphabetic order, and tests run in the order they are defined, the first test to be executed is Test 1 of Fixture A, followed by Test 2 of Fixture A, and so on. Continue »
The hidden danger of forgetting to specify %SystemRoot% in a custom environment blockWhen spawning a process using CreateProcess and friends, the child process usually inherits the environment (i.e. all environment variables) of the spawning process. Of course, this behavior can be overridden by creating a custom environment block and passing it to the lpEnvironment parameter of CreateProcess. While the MSDN documentation on CreateProcess does contain a remark saying that current directory information (=C: and friends) should be included in such a custom environment block, it does not mention the importance of SystemRoot. Continue »
cfix finished 2nd in ATI's Automation Honors Awards, surpassed only by JUnitAlong with JUnit, JWebUnit, NUnit, and SimpleTest, cfix was one of the nominees for the Automated Testing Institute’s Automation Honors Award 2009 in the category Best Open Source Unit Automated Test Tool. A few days ago, the results were published and cfix finished second – surpassed only by JUnit, which finished 1st (No real surprise here). If you are interested, there is a video in which the results are presented. Continue »
NTrace paper published on computer.orgOur paper NTrace: Function Boundary Tracing for Windows on IA-32 from WCRE 2009 has now been published on computer.org: Abstract: For a long time, dynamic tracing has been an enabling technique for reverse engineering tools. Tracing can not only be used to record the control flow of a particular component such as a piece of malware itself, it is also a way to analyze the interactions of a component and their impact on the rest of the system. Continue »
Visual Assert Beta 3 releasedA third beta release of Visual Assert is now available for download on www.visualassert.com. Visual Assert, in case you have not tried it yet, is an Add-In for Visual Studio that adds unit testing capabilities to the Visual C++ IDE: Based on the cfix unit testing framework, Visual Assert allows unit tests to be written, run, and debugged from within the IDE. Pretty much like Junit/Eclipse, TestDriven.Net or MSTest, but for real, native code – code written in C or C++. Continue »
cfix 1.5.1 releasedA new version of cfix, the unit testing framework for C and C++ on Windows, is now available on Sourceforge. Despite fixing several minor issues, the new version resolves the following two issues that were reported by users: Definiting multiple WinUnit fixtures with setup/teardown routines in a single .cpp file leads to a compilation error A thread handle is leaked during execution of a test (#2889511) Updated binaries and source code are available for download on Sourceforge. Continue »