OSROnline：设置在Vista及以上操作系统中的KdPrint输出

开发驱动的朋友一定会碰到在Vista及以上操作系统版本中，KdPrint没有向调试器输出内容的情况，之前我还一直以为是我把free build当chk build用了。后来偶然在OSR上发觉了事实和真相:)

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Interoffice Memorandum

Date:  11-May-04, Modified: 10-Mar-06
From: Hector J. Rodriguez
To:    Driver Developers

Re: Getting DbgPrint Output To Appear In Longhorn

The problem: Your DbgPrint or KdPrint messages don't appear in WinDbg (or KD) when you run your driver on Windows Vista.

The reason?  Vista automatically maps DbgPrint and friends to DbgPrintEx.  Now, you may recall that DbgPrintEx allows you to control the conditions under which messages will be sent to the kernel debugger by filtering messages via a component name and level in the function call and an associated filter mask in either the registry or in memory.

In Vista, DbgPrint and KdPrint are mapped to component "DPFLTR_DEFAULT_ID" and level "DPFLTR_INFO_LEVEL".  Of course, in Vista, xxx_INFO_LEVEL output is disabled by default.  So, by default, your DbgPrint/KdPrint doesn't get sent to the kernel debugger.

How to fix it? Two choices:

• Enable output of DbgPrint/KdPrint messages by default --Open the key "HKLM\SYSTEM\CCS\Control\Session Manager\Debug Print Filter". Under this key, create a value with the name "DEFAULT" Set the value of this key equal to the DWORD value 8 to enable xxx_INFO_LEVEL output as well as xxx_ERROR_LEVEL output.  Or try setting the mask to 0xF so you get all output.  You must reboot for these changes to take effect.

• Specifically change the component filter mast for DPFLTR.  In early releases of Vista/LH you changed the default printout mask by specifying a mask value for the DWORD at Kd_DPFLTR_MASK ("ed Kd_DPFLTR_MASK").  In build 5308 (the February CTP of Vista), it seems that the mask variable has changed and you need to set the mask value for the DWORD at Kd_DEFAULT_MASK ("ed Kd_DEFAULT_MASK).  In either case, specify 8 to enable DPFLTR_INFO_LEVEL output in addition to DPFLTR_ERROR_LEVEL output, or 0xF to get all levels of output.

See the WDK documentation for Reading and Filtering Debugging Messages (follow the path: Driver Development Tools\Tools for Debugging Drivers\Using Debugging Code in a Driver\Debugging Code Overview) for the complete details on the use of DbgPrintEx/KdPrintEx.  Or look at the Debugging Tools For Windows documentation (Appendix A) on DbgPrintEx.

If your interested in setting the registry keys to enable output, then check out the SetDbgPrintFiltering utility at http://www.osronline.com/downloads.