There is a good discussion on managed debugging in the documentation. You can set a breakpoint at a managed code function only after it has been invoked at least once; because that is when it is JIT-compiled to ASM code. Keep in mind:. If the debugger does not handle a second-chance exception, the application quits. You can also use the. Note also that you can change the first-chance handling option for an exception using the sxe , sxd , sxn and sxi commands.
Debugger extensions are DLLs that you can hook up with a debugger to execute custom commands from within the debugger. In the next article, we shall learn how to write an extension DLL yourself. The bang!
Note that extension DLLs are loaded in the process space of the debugger. You can take snapshot information of a process using the dump facility. A mini-dump is usually small, unless you take a full-memory minidump. It is useful to dump handle information also, as. A mini-dump contains information about all threads including their stacks and list of loaded modules. A full dump contains more information, like that of the process heap. It is also possible to take dumps of any live process by breaking into it.
You can also take a dump of any process. Note that figuring out bugs in the code from a crash dump could be an involved process. Step 3 : Set your symbol path and source path properly. If you cannot match symbols, you could have a hard time figuring out control flow. If you can match the symbols to source code of the appropriate version, it should be easy to figure out the bug at this point.
Note that debugging drivers or managed code is much different. Refer to [2] for debugging techniques for device drivers. You need symbols in order to be able to do effective debugging.
PDBs are program database files and contain public symbols. These debuggers allow you to mention a list of URIs where they would look for symbols for loaded binaries. Driver symbols. DBG or. PDB files are usually in the same folder as the driver. Private symbol files contain information about functions, local and global variables, and line information to correlate assembly code to source code; symbol files that are usually made available to customers are public symbol files — these files contain information about public members only.
To add reference to a symbol server on the web, add:. Note that this particular symbol server exposes public symbols only. The sympath can consist of multiple URIs. If you set source code directories, the debugger will pull up matching source code based on line number information from the PDB files during debugging. The help file that comes with the WinDbg installation documents commands well, but the following basic commands should get you started:.
Means that when your code is compiled, frame pointers EBP will not be put on the stack. This makes function calls faster and makes the EBP register available as a scratch register.
Create a key named x. The bp command accepts a list of commands as argument that you can execute every time a breakpoint is hit. This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.
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This is the first part of a multipart tutorial on debugging using WinDbg. Download source files - 3. This article is based on WinDbg 6. Overview of Debuggers A brief overview of the Windows debuggers that you can download for free from here : KD — Kernel debugger. You want to use this to remote debug OS problems like blue screens. You want it if you develop device drivers. CDB — Command-line debugger. This is a console application. This is a user-mode debugger that you can use to debug your user-mode applications.
WinDbg can function both as a kernel-mode and user-mode debugger. Visual Studio, Visual Studio. It supports three types of commands: regular commands e.
The regular commands are to debug processes. The dot commands are to control the debugger. Debugging Scenarios Remote Debugging Doing remote debugging using WinDbg is easy and can be done in one of a number of ways.
The server and client have choices of TCP and named pipes for communication protocol. Note: use q not q to quit the client without quitting the server. To start a server: Remote. Managed Debugging WinDbg 6. Points to note: You can set a breakpoint at a managed code function only after it has been invoked at least once; because that is when it is JIT-compiled to ASM code. Keep in mind: Complications with function addresses and hence breakpoints: The CLR can discard compiled code, so function addresses may change.
The same code may be multiply compiled if multiple app domains do not share the code. For example, you might be able to use a virtual PC that is running on the same PC as the code that you need to debug.
However, if your code is communicating to low-level hardware, using a virtual PC may not be the best approach. Kernel mode is the processor-access mode in which the operating system and privileged programs run.
Kernel-mode code has permission to access any part of the system, and it is not restricted like user-mode code. Kernel-mode code can gain access to any part of any other process running in either user mode or kernel mode. Much of the core OS functionality and many hardware device drivers run in kernel mode. User mode is the mode that applications and subsystems on the computer run in. Processes that run in user mode do so within their own virtual address spaces.
They are restricted from gaining direct access to many parts of the system, including system hardware, memory that was not allocated for their use, and other portions of the system that might compromise system integrity. Because processes that run in user mode are effectively isolated from the system and other user-mode processes, they cannot interfere with these resources. If your goal is to debug a driver, determine if the driver is a kernel-mode driver or a user-mode driver.
For some issues, it can be difficult to determine which mode the code executes in. In that case, you may need to pick one mode and look to see what information is available in that mode. Some issues require using the debugger in both user mode and kernel mode. Depending on what mode you decide to debug in, you will need to configure and use the debuggers in different ways. Some debugging commands operate the same in both modes, and some commands operate differently in different modes.
For information about using the debugger in user mode, see Getting started with WinDbg user-mode. WinDbg works well in most situations, but there are times when you may want to use another debugger, such as console debuggers for automation or Visual Studio. Learn algorithms for solving classic computer science problems with this concise guide covering everything from fundamental ….
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Overview Chapter 1.
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