Fix createdump SIGSEGV on Heap dumps with interpreter active

[max-charlamb]

Note

This PR was authored with assistance from GitHub Copilot.

Fixes#128044.

Problem

createdump SIGSEGVs on Linux when generating a Heap-type minidump for a
process running interpreted code. The crash reproduces locally with the
InterpreterStack DumpTests debuggee and matches the CI failure that
prompted <DumpTypes>Full</DumpTypes> to be added as a temporary workaround.

The faulting backtrace is:

#0 Thread::IsAddressInStack threads.cpp:6741
#1 Thread::EnumMemoryRegionsWorker threads.cpp:6909 (calls IsAddressInStack(currentSP))
#2 Thread::EnumMemoryRegions threads.cpp
#3 ThreadStore::EnumMemoryRegions
#4 ClrDataAccess::EnumMemDumpAllThreadsStack
#5 ClrDataAccess::EnumMemoryRegionsWorkerHeap (HEAP2-only path)

Root cause

Thread::m_pInterpThreadContext was declared as a raw
InterpThreadContext *. In non-DAC code that's a normal host pointer, but in
DAC mode the field's value is a target-process address. When
IsAddressInStack (a DAC-callable helper) dereferenced
m_pInterpThreadContext->pStackStart it read from a target-process address
as if it were a host address, which faults inside createdump.

Fix

Change the field type to PTR_InterpThreadContext (DPTR), matching the
treatment of other Thread fields like m_pFrame. In non-DAC builds
DPTR(T) is just T*, so there is no overhead or behavior change. In DAC
builds the read goes through __DPtr<T> and marshals correctly from the
target.

Also remove the <DumpTypes>Full</DumpTypes> workaround on the
InterpreterStack DumpTests debuggee so the Heap path that originally
failed is exercised again.

Validation

Locally reproduced the original SIGSEGV on Linux x64 with the auto-dump
mechanism (DOTNET_DbgMiniDumpType=2 + DOTNET_Interpreter=MethodA)
running the InterpreterStack debuggee. With this fix applied, createdump
produces a complete Heap dump (~74 MB) instead of crashing.

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Tagging subscribers to this area: @JulieLeeMSFT, @BrzVlad, @janvorli, @kg
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[Copilot]

Pull request overview

This PR aims to fix a Linux createdump crash during heap-type minidump generation when the CoreCLR interpreter is active, by making the interpreter thread-context pointer DAC-safe. It also adjusts the cDAC DumpTests “InterpreterStack” debuggee configuration so the previously-problematic heap-dump path is exercised again.

Changes:

• Update Thread::m_pInterpThreadContext to use a DAC-aware pointer type (PTR_InterpThreadContext) so DAC consumers (e.g., createdump) don’t treat target addresses as host pointers.
• Add the PTR_InterpThreadContext typedef in common.h under FEATURE_INTERPRETER.
• Remove the InterpreterStack debuggee’s DumpTypes=Full workaround (intended to re-enable heap dumps for this debuggee).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/native/managed/cdac/tests/DumpTests/Debuggees/InterpreterStack/InterpreterStack.csproj	Removes the Full-dump-only workaround so heap dump generation is used again for this debuggee.
src/coreclr/vm/threads.h	Changes m_pInterpThreadContext to a DAC-safe pointer typedef.
src/coreclr/vm/common.h	Introduces PTR_InterpThreadContext typedef under FEATURE_INTERPRETER.

[janvorli]

LGTM, thank you!