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Add System.Diagnostics.StackFrame.GetMethodFromNativeIP API for VS4Mac #61289

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Nov 9, 2021
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,9 @@
// The .NET Foundation licenses this file to you under the MIT license.

using System.Text;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace System.Diagnostics
{
Expand Down Expand Up @@ -50,5 +53,25 @@ private void BuildStackFrame(int skipFrames, bool needFileInfo)
}

private static bool AppendStackFrameWithoutMethodBase(StringBuilder sb) => false;

[DllImport(RuntimeHelpers.QCall, EntryPoint = "StackFrame_GetMethodDescFromNativeIP")]
private static extern RuntimeMethodHandleInternal GetMethodDescFromNativeIP(IntPtr ip);

/// <summary>
/// Returns the MethodBase instance for the managed code IP address.
///
/// Warning: The implementation of this method has race for dynamic and collectible methods.
/// </summary>
/// <param name="ip">code address</param>
/// <returns>MethodBase instance for the method or null if IP not found</returns>
internal static MethodBase? GetMethodFromNativeIP(IntPtr ip)
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We should probably add a comment right here saying that the implementation of this method has known race conditions for unloadable code + MethodBase isn't a good design choice for working with NativeAOT, therefore don't make it public in the future without considering those issues. Reduces the chance we forget the history when we need a public API later.

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Or even better - create issue that tracks adding the public API and link it from here

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Is that good enough?

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I did add a comment to the method's header.

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I do think having the message that you added right here in the header is valuable. When people convert a private API to public nothing enforces that they will look at implementation code in a separate file. The comment you added calls out the race condition but doesn't mention the design issue for using MethodBase in NativeAOT. As @jkotas suggested filing an issue and linking to that is an improvement over my original suggestion.

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I'm going to use issue #61186 to detail these limitations and to propose the new 7.0 API.

{
RuntimeMethodHandleInternal method = GetMethodDescFromNativeIP(ip);

if (method.Value == IntPtr.Zero)
return null;

return RuntimeType.GetMethodBase(null, method);
}
}
}
23 changes: 22 additions & 1 deletion src/coreclr/vm/debugdebugger.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -297,7 +297,6 @@ FCIMPL0(FC_BOOL_RET, DebugDebugger::IsLogging)
}
FCIMPLEND


FCIMPL4(void, DebugStackTrace::GetStackFramesInternal,
StackFrameHelper* pStackFrameHelperUNSAFE,
INT32 iSkip,
Expand Down Expand Up @@ -778,6 +777,28 @@ FCIMPL4(void, DebugStackTrace::GetStackFramesInternal,
}
FCIMPLEND

extern MethodDesc* QCALLTYPE StackFrame_GetMethodDescFromNativeIP(LPVOID ip)
{
QCALL_CONTRACT;

MethodDesc* pResult = nullptr;

BEGIN_QCALL;

// TODO: There is a race for dynamic and collectible methods here between getting
// the MethodDesc here and when the managed wrapper converts it into a MethodBase
// where the method could be collected.
EECodeInfo codeInfo((PCODE)ip);
if (codeInfo.IsValid())
{
pResult = codeInfo.GetMethodDesc();
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}

END_QCALL;

return pResult;
}

FORCEINLINE void HolderDestroyStrongHandle(OBJECTHANDLE h) { if (h != NULL) DestroyStrongHandle(h); }
typedef Wrapper<OBJECTHANDLE, DoNothing<OBJECTHANDLE>, HolderDestroyStrongHandle, NULL> StrongHandleHolder;

Expand Down
2 changes: 2 additions & 0 deletions src/coreclr/vm/debugdebugger.h
Original file line number Diff line number Diff line change
Expand Up @@ -171,4 +171,6 @@ class DebugStackTrace

};

extern "C" MethodDesc* QCALLTYPE StackFrame_GetMethodDescFromNativeIP(LPVOID ip);

#endif // __DEBUG_DEBUGGER_h__
1 change: 1 addition & 0 deletions src/coreclr/vm/qcallentrypoints.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,7 @@ static const Entry s_QCall[] =
DllImportEntry(RuntimeModule_GetType)
DllImportEntry(RuntimeModule_GetScopeName)
DllImportEntry(RuntimeModule_GetFullyQualifiedName)
DllImportEntry(StackFrame_GetMethodDescFromNativeIP)
DllImportEntry(ModuleBuilder_GetStringConstant)
DllImportEntry(ModuleBuilder_GetTypeRef)
DllImportEntry(ModuleBuilder_GetTokenFromTypeSpec)
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -4,5 +4,9 @@
<!-- Internal API used by tests only. -->
<method name="GetICUVersion" />
</type>
<type fullname="System.Diagnostics.StackFrame">
<!-- Used by VS4Mac via reflection to symbolize stack traces -->
<method name="GetMethodFromNativeIP" />
</type>
</assembly>
</linker>