Make sure all new GCDacVars are reported only for v2

[cshung]

In my earlier PR #88457, I missed a few extra fields in the GcDacVars population which should be v2 as well. This is causing a crash on Linux when a .NET 8 clrgc with regions turned on is loaded in a .NET 6 process.

In particular, this line:

gcDacVars->global_free_huge_regions = reinterpret_cast<dac_region_free_list**>(&gc_heap::global_free_huge_regions);

, which should not be run on .NET 6, is accidentally overwriting the variable g_sw_ww_table defined below:

GcDacVars g_gc_dac_vars;
GPTR_IMPL(GcDacVars, g_gcDacGlobals);

#ifdef FEATURE_USE_SOFTWARE_WRITE_WATCH_FOR_GC_HEAP

uint8_t* g_sw_ww_table = nullptr;
bool g_sw_ww_enabled_for_gc_heap = false;

That leads the write-barrier to write to a bad location and got AV with this output (The user program is a the simple HelloWorld template):

Fatal error. System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
   at System.Collections.Generic.Dictionary`2[[System.ReadOnlyMemory`1[[System.Char, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.ConsoleKeyInfo, System.Console, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]].TryInsert(System.ReadOnlyMemory`1<Char>, System.ConsoleKeyInfo, System.Collections.Generic.InsertionBehavior)
   at System.Collections.Generic.Dictionary`2[[System.ReadOnlyMemory`1[[System.Char, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.ConsoleKeyInfo, System.Console, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a]].set_Item(System.ReadOnlyMemory`1<Char>, System.ConsoleKeyInfo)
   at System.ConsolePal+TerminalFormatStrings..ctor(Database)
   at System.ConsolePal+TerminalFormatStrings+<>c.<.cctor>b__28_0()
   at System.Lazy`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].ViaFactory(System.Threading.LazyThreadSafetyMode)
   at System.Lazy`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].ExecutionAndPublication(System.LazyHelper, Boolean)
   at System.Lazy`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].CreateValue()
   at System.Lazy`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].get_Value()
   at System.ConsolePal+TerminalFormatStrings.get_Instance()
   at System.ConsolePal.EnsureInitializedCore()
   at System.ConsolePal.Write(Microsoft.Win32.SafeHandles.SafeFileHandle, System.ReadOnlySpan`1<Byte>, Boolean)
   at System.ConsolePal+UnixConsoleStream.Write(System.ReadOnlySpan`1<Byte>)
   at System.IO.StreamWriter.Flush(Boolean, Boolean)
   at System.IO.StreamWriter.WriteLine(System.String)
   at System.IO.TextWriter+SyncTextWriter.WriteLine(System.String)
   at System.Console.WriteLine(System.String)
   at Program.<Main>$(System.String[])
Aborted

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Issue Details

---

In my earlier PR #88457, I missed a few extra fields in the GcDacVars population which should be v2 as well. This is causing a crash on Linux when a .NET 8 clrgc with regions turned on is loaded in a .NET 6 process.

Author:	cshung
Assignees:	cshung
Labels:	area-GC-coreclr
Milestone:	-

[Maoni0]

LGTM!

[mrsharm]

Adding setting the GCName as libclrgcexp built from .NET8 Release in .NET6 and .NET7 works successfully on a simple GCPerfSim scenario.

[mangod9]

@mrsharm, can you ascertain whether clrgc with regions was actually working with 6? From looking at the change seems like it should be failing too.

[mrsharm]

@mangod9, yes, this seems to be working with libclrgc.so (which, is regions for 6.0).

Steps

1. Checkout 3b204ac.
2. Build GCPerfSim for .NET 6.
3. Create a Corerun using 3b204ac.
4. export DOTNET_GCName=libclrgc.so
5. Invoke: ~/runtime/artifacts/tests/coreclr/Linux.x64.Debug/Tests/Core_Root/corerun /home/mrsharm/performance/artifacts/bin/GCPerfSim/Release/net6.0/GCPerfSim.dll -tc 18 -tagb 100 -tlgb 2 -lohar 0 -pohar 0 -sohsr 100-4000 -lohsr 102400-204800 -pohsr 100-204800 -sohsi 50 -lohsi 0 -pohsi 0 -sohpi 0 -lohpi 0 -sohfi 0 -lohfi 0 -pohfi 0 -allocType reference -testKind time
6. The repro doesn't fail on initialize as before.