Mercurial > hg > truffle
view agent/src/os/win32/README.txt @ 3822:ca1f1753c866
7072341: enable hotspot builds on Linux 3.0
Summary: Add "3" to list of allowable versions
Reviewed-by: kamg, chrisphi
author | andrew |
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date | Thu, 28 Jul 2011 14:10:21 -0400 |
parents | a61af66fc99e |
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This is a "Simple Windows Debug Server" written for the purpose of enabling the Serviceability Agent on Win32. It has backends both for Windows NT 4.0 (using internal Windows APIs for a few routines) as well as for 95/98/ME/2000 via the Tool Help APIs. The reason this debug server is necessary is that the Win32 debug APIs by design tear down the target process when the debugger exits (see knowledge base article Q164205 on msdn.microsoft.com). On Solaris, one can attach to and detach from a process with no effect; this is key to allowing dbx and gcore to work. The Simple Windows Debug Server effectively implements attach/detach functionality for arbitrary debug clients. This allows the SA to attach non-destructively to a process, and will enable gcore for Win32 to be written shortly. While the debugger (the "client" in all of the source code) is attached, the target process is suspended. (Note that the debug server could be extended to support resumption of the target process and transmission of debug events over to the debugger, but this has been left for the future.) The makefile (type "nmake") builds two executables: SwDbgSrv.exe, which is the server process, and SwDbgSub.exe, which is forked by the server and should not be directly invoked by the user. The intent is that these two executables can be installed into C:\WINNT\SYSTEM32 and SwDbgSrv installed to run as a service (on NT), for example using ServiceInstaller (http://www.kcmultimedia.com/smaster/). However, SwDbgSrv can also be run from the command line. It generates no text output unless the source code is changed to enable debugging printouts. As long as any processes which have been attached to by the SA are alive, the SwDbgSrv and any forked SwDbgSub processes must be left running. Terminating them will cause termination of the target processes. The debug server opens port 27000 and accepts incoming connections from localhost only. The security model assumes that if one can run a process on the given machine then one basically has access to most or all of the machine's facilities; this seems to be in line with the standard Windows security model. The protocol used is text-based, so one can debug the debug server using telnet. See README-commands.txt for documentation on the supported commands. Testing indicates that the performance impact of attaching to a process (and therefore permanently attaching a debugger) is minimal. Some serious performance problems had been seen which ultimately appeared to be a lack of physical memory on the machine running the system. Bugs: This debug server is fundamentally incompatible with the Visual C++ debugger. Once the debug server is used to attach to a process, the Visual C++ IDE will not be able to attach to the same process (even if the debug server is "detached" from that process). Note that this system is designed to work with the same primitives that C and C++ debuggers use (like "symbol lookup" and "read from process memory") and exposes these primitives to Java, so in the long term we could solve this problem by implementing platform-specific debug symbol parsing and a platform-independent C++ debugger in Java. Note: The files IOBuf.cpp and IOBuf.hpp are also used in building src/os/solaris/agent.