[docs] Add instructions for debugging native runtime code on Android (d…

…otnet#59183)

docs/workflow/debugging/mono/android-debugging.md

@@ -0,0 +1,99 @@
+# Debugging Android runtime issues
+
+## Enable verbose runtime logging
+
+If a `net6.0-android` (or later) C# project is available, adding the following:
+
+```xml
+ <ItemGroup>
+   <AndroidEnvironment Include="AndroidEnv.txt" />
+ </ItemGroup>
+```
+
+with `AndroidEnv.txt`:
+
+```
+debug.mono.log=mono_log_level=debug,mono_log_mask=all
+MONO_SDB_ENV_OPTIONS=loglevel=10    # only needed if you're debugging the managed debugger
+```
+
+Will enable additional Mono runtime logging in the adb log.  This is often
+enough to diagnose issues such as missing assemblies or other loader problems.
+
+## Managed Debugging
+
+Should work from Visual Studio (Windows)
+
+## Native debugging
+
+Install Android Studio.
+
+Download the symbols nupkg corresponding to the runtime pack that is used by
+the app.  The runtime pack for the android workload is in a folder like
+`${DOTNET_ROOT}/packs/Microsoft.NETCore.App.Runtime.Mono.android-x86/6.0.0-rc.1.21451.13`
+
+The symbols are in a package called
+`Microsoft.NETCore.App.Runtime.Mono.android-x86.6.0.0-rc.1.21451.13.symbols.nupkg`
+uploaded to (FIXME: where does the symbols nuget go?).  Extract it to some folder using `unzip` and in the
+`runtimes/android-x86/native/` folder rename the `*.so.dbg` files to `*.so.so`
+(we will need to add the symbols files to Android Studio, but its file picker
+only shows `*.so` extensions)
+
+
+1. Build the APK normally using `dotnet build`, (this will produce a `AppName-Signed.apk` in the output folder)
+2. Start an Android emultator
+3. Install the app on the emulator using `dotnet build -t:Install`
+2. Open the APK in Android Studio with "Profile or Debug APK"
+3. In the "Project" viewer, choose the "cpp" folder, then `libmonosgen-2.0.so` then double-click `libmonosgen-2.0.so` inside the `libmonosgen-2.0.so` folder.
+4. In the "Debug Symbols" view click "Add", navigate to the extracted runtime symbols nuget and select `libmonosgen-2.0.so.so`
+5. In the "Path Mappings" section, select the toplevel folder and add a Local
+   Path to a git checkout of the `release/6.0` tree corresponding to the nuget.  Click Apply Changes.
+6. Start an emulator or connect to a device
+7. On the menu bar select  "Run > Edit Configurations..." and on the "Debugger" tab make sure the "Debug Type" is something other than "Java Only"
+8. Start debugging.
+9. You should now have function names, local variables, as well as stepping through the runtime C code.
+
+Since you're debugging an optimized release build, it is likely the debugger will not be able to materialize every local variable.
+
+## Native debugging using a local debug build of Mono
+
+Build the runtime for your android architecture: `ANDROID_NDK_ROOT=<path_to_android_ndk> ./build.sh --os android --arch x86 -c Debug`. See the instructions for [Testing Android](../../testing/libraries/testing-android.md) for details.
+
+
+In the source code for the C# project, add the following to the .csproj (replacing `<RUNTIME_GIT_ROOT>` by the apropriate location):
+
+```
+  <Target Name="UpdateRuntimePack"
+            AfterTargets="ResolveFrameworkReferences">
+      <ItemGroup>
+        <ResolvedRuntimePack PackageDirectory="<RUNTIME_GIT_ROOT>/artifacts/bin/microsoft.netcore.app.runtime.android-x86/Debug"
+                             Condition="'%(ResolvedRuntimePack.FrameworkName)' == 'Microsoft.NETCore.App'" />
+      </ItemGroup>
+  </Target>
+```
+
+Then rebuild and reinstall the project, open the apk in Android Studio, and debug.  The
+runtime native libraries will be stripped, so to make use of debug symbols, you
+will need to follow the steps above (rename `*.so.dbg` in the artifacts to
+`*.so.so` and add them to the APK project in Android Studio)
+
+## Native and managed debugging or debugging the managed debugger
+
+This workflow is useful to look for issues in the debugger itself, or to debug using a mixture of C and C# debugging.
+
+Install [sdb](https://github.com/mono/sdb).
+
+Start `sdb` and set it to listen  `listen 127.0.0.1 5000` (the port number is up to you).
+
+Run the following `adb` command to set Mono apps to connect to a debugger on startup:
+
+```
+$ adb shell setprop debug.mono.extra "debug=10.0.2.2:5000,loglevel=10"
+```
+
+(`loglevel=10` will produce debugger protocol messages in the `adb` log.  If
+you're not debugging the debugger it can be omitted.  For other debugger
+options see [`print_usage()`](https://github.com/dotnet/runtime/blob/main/src/mono/mono/component/debugger-agent.c#L573) in `src/mono/mono/component/debugger-agent.c`)
+
+Now launch the app from Android Studio. It should run and connect to the debugger.
+

docs/workflow/testing/libraries/testing-android.md

@@ -106,3 +106,7 @@ The emulator can be launched with a variety of options. Run `emulator -help` to
 - `-os Android` is not supported for Windows yet (`WSL` can be used instead)
 - XHarness.CLI is not able to boot emulators yet (so you need to boot via `AVD Manager` or IDE)
 - AOT and Interpreter modes are not supported yet
+
+### Debugging the native runtime code using Android Studio
+
+See [Debugging Android](../../debugging/mono/android-debugging.md)