- A+
所属分类：.NET技术
一：背景
1. 讲故事
最新版本 1.2402.24001.0 的WinDbg真的让人很兴奋，可以将自己伪装成 GDB 来和远程的 GDBServer 打通来实现对 Linux 上 .NET程序进行调试，这样就可以继续使用熟悉的WinDbg 命令，在这个版本中我觉得 WinDbg 不再是 WinDbg，而是 XDbg 了，画个简图如下：
简图有了，接下来就要付出实践了。
二：实操 Linux 上 .NET调试
1. 测试程序
本想在 CentOS7 上安装 .NET8，不大好装，这里就用一个现存的 .NETCore 3.1 吧，测试代码如下：
internal class Program { static void Main(string[] args) { while (true) { Console.WriteLine($"{DateTime.Now},tid={Thread.CurrentThread.ManagedThreadId}"); Thread.Sleep(1000); } } } 代码非常简单，就是1s输出一条记录，接下来编译成x64部署到 Centos7 上。
[root@localhost data]# ls ConsoleApp7 ConsoleApp7.deps.json ConsoleApp7.dll ConsoleApp7.pdb ConsoleApp7.runtimeconfig.json 2. 安装GDBServer
在 linux 上安装 gdbserver 比较简单，使用 yum 安装即可 yum install gdb-gdbserver ，输出如下：
[root@localhost data]# yum install gdb-gdbserver Loaded plugins: fastestmirror, langpacks Loading mirror speeds from cached hostfile * base: mirror-hk.koddos.net * centos-sclo-rh: ftp.sjtu.edu.cn * centos-sclo-sclo: ftp.sjtu.edu.cn * epel: mirror.hoster.kz * extras: ftp.sjtu.edu.cn * updates: mirror-hk.koddos.net Package gdb-gdbserver-7.6.1-120.el7.x86_64 already installed and latest version Nothing to do [root@localhost data]# gdbserver –version Usage: gdbserver [OPTIONS] COMM PROG [ARGS ...] gdbserver [OPTIONS] --attach COMM PID gdbserver [OPTIONS] --multi COMM COMM may either be a tty device (for serial debugging), or HOST:PORT to listen for a TCP connection. Options: --debug Enable general debugging output. --remote-debug Enable remote protocol debugging output. --version Display version information and exit. --wrapper WRAPPER -- Run WRAPPER to start new programs. --once Exit after the first connection has closed. 安装好之后，接下来用 gdbserver 来启动我们的程序，并启动调试端口为 1234，参考如下：
[root@localhost data]# gdbserver 192.168.128.130:1234 dotnet ConsoleApp7.dll Process dotnet created; pid = 3643 Listening on port 1234 3. 使用 windbg 连接
打开Windbg后，选择 Connect to remote debugger 选项, 在连接字符串中填入 gdb:server=192.168.128.130,port=1234 即可，截图如下：
连接好之后，会有一个初始中断，直接输入g就好了，输出如下：
64-bit machine not using 64-bit API ************* Path validation summary ************** Response Time (ms) Location Deferred SRV*C:mysymbols*https://msdl.microsoft.com/download/symbols Symbol search path is: SRV*C:mysymbols*https://msdl.microsoft.com/download/symbols Executable search path is: Unknown System Version 0 UP Free x64 System Uptime: not available Process Uptime: not available Reloading current modules ModLoad: 00005555`55554000 00005555`555770cd /usr/share/dotnet/dotnet ModLoad: 00007fff`f7bbf000 00007fff`f7dda488 /lib64/libpthread.so.0 ModLoad: 00007fff`f79bb000 00007fff`f7bbe130 /lib64/libdl.so.2 ModLoad: 00007fff`f76b3000 00007fff`f79ba420 /lib64/libstdc++.so.6 ModLoad: 00007fff`f73b1000 00007fff`f76b2138 /lib64/libm.so.6 ModLoad: 00007fff`f719b000 00007fff`f73b0400 /lib64/libgcc_s.so.1 ModLoad: 00007fff`f6dcd000 00007fff`f719a200 /lib64/libc.so.6 ModLoad: 00007fff`f7ddb000 00007fff`f7ffe150 /lib64/ld-linux-x86-64.so.2 ModLoad: 00007fff`f7f72000 00007fff`f7fda288 /usr/share/dotnet/host/fxr/6.0.26/libhostfxr.so ModLoad: 00007fff`f6b7c000 00007fff`f6dcc3b0 /usr/share/dotnet/shared/Microsoft.NETCore.App/3.1.32/libhostpolicy.so ModLoad: 00007fff`f63e7000 00007fff`f6b7bac8 /usr/share/dotnet/shared/Microsoft.NETCore.App/3.1.32/libcoreclr.so ModLoad: 00007fff`f61df000 00007fff`f63e6c38 /lib64/librt.so.1 ModLoad: 00007fff`f57d2000 00007fff`f59dd8c0 /lib64/libnuma.so.1 ModLoad: 00007fff`f3142000 00007fff`f3413dac /usr/share/dotnet/shared/Microsoft.NETCore.App/3.1.32/libclrjit.so ModLoad: 00007fff`f2f31000 00007fff`f3141468 /usr/share/dotnet/shared/Microsoft.NETCore.App/3.1.32/System.Native.so ModLoad: 00007fff`f2d26000 00007fff`f2f30488 /usr/share/dotnet/shared/Microsoft.NETCore.App/3.1.32/System.Globalization.Native.so ModLoad: 00007fff`f29ad000 00007fff`f2d25fe0 /lib64/libicuuc.so.50 ModLoad: 00007fff`f13da000 00007fff`f29ac030 /lib64/libicudata.so.50 ModLoad: 00007fff`f0fdb000 00007fff`f13d9340 /lib64/libicui18n.so.50 ................... ReadVirtual() failed in GetXStateConfiguration() first read attempt (error == 0.) Unable to load image /lib64/libpthread.so.0, Win32 error 0n2 *** WARNING: Unable to verify timestamp for /lib64/libpthread.so.0 Unable to load image /usr/share/dotnet/shared/Microsoft.NETCore.App/3.1.32/libcoreclr.so, Win32 error 0n2 *** WARNING: Unable to verify timestamp for /usr/share/dotnet/shared/Microsoft.NETCore.App/3.1.32/libcoreclr.so libpthread_so!_pthread_cond_timedwait+0x132: 00007fff`f7bcade2 4989c6 mov r14,rax 0:000> g 有些人可能会好奇，为什么 WinDbg 能伪装成 GDB 来和 GDBServer 来通讯，这其实得益于 WinDbg 是一个宿主，它可以被很多外来的插件无线扩容自己的功能，这和 Linux 的分而治之恰恰相反。。。
接下来可以用 .chain 命令观察插件列表，其中的 GDBServerComposition 和 ELFBinComposition 让这项功能得到实现。
0:000> .chain Extension DLL chain: GDBServerComposition: image 10.0.27553.1004, API 0.0.0, [path: C:Program FilesWindowsAppsMicrosoft.WinDbg_1.2402.24001.0_x64__8wekyb3d8bbweamd64winextGDBServerComposition.dll] ELFBinComposition: image 10.0.27553.1004, API 0.0.0, [path: C:Program FilesWindowsAppsMicrosoft.WinDbg_1.2402.24001.0_x64__8wekyb3d8bbweamd64winextELFBinComposition.dll] dbghelp: image 10.0.27553.1004, API 10.0.6, [path: C:Program FilesWindowsAppsMicrosoft.WinDbg_1.2402.24001.0_x64__8wekyb3d8bbweamd64dbghelp.dll] uext: image 10.0.27553.1004, API 1.0.0, [path: C:Program FilesWindowsAppsMicrosoft.WinDbg_1.2402.24001.0_x64__8wekyb3d8bbweamd64winextuext.dll] 接下来就可以做验证了，研究 coreclr 源码，你会发现在 Linux 上 .NET 的 Sleep 函数是借助于底层的 pthread_cond_timedwait 函数，Linux并没有提供类似Windows 的SleepEx这样的系统调用，这就比较坑了，参考如下：
PAL_ERROR CPalSynchronizationManager::ThreadNativeWait( ThreadNativeWaitData* ptnwdNativeWaitData, DWORD dwTimeout, ThreadWakeupReason* ptwrWakeupReason, DWORD* pdwSignaledObject) { //... while (FALSE == ptnwdNativeWaitData->iPred) { if (INFINITE == dwTimeout) { iWaitRet = pthread_cond_wait(&ptnwdNativeWaitData->cond, &ptnwdNativeWaitData->mutex); } else { iWaitRet = pthread_cond_timedwait(&ptnwdNativeWaitData->cond, &ptnwdNativeWaitData->mutex, &tsAbsTmo); } } //... } 
不管怎么说，我们用 WinDbg 调试 Linux 的 .NET 程序算是大功告成了。
三：总结
现在的 WinDbg 早已今非昔比，全平台(MacOs,Linux,Windows) 通吃，这也得益于 Windbg 是一个宿主模式的架构体系，给 WinDbg 点赞！
