Correctly restore floating point context on x86 interop step-in scenarios (#117632)

* Correctly restore floating point context on x86 interop step-in scenarios

* Update DAC Hijack context assert for cross-plat

* Exclude XStateFeaturesMask in assert outside of amd64 and arm64

Author: tommcdon

src/coreclr/debug/daccess/dacdbiimpl.cpp

@@ -4963,9 +4963,21 @@ void DacDbiInterfaceImpl::Hijack(
     // Setup context for hijack
     //
     T_CONTEXT ctx;
+#if !defined(CROSS_COMPILE) && !defined(TARGET_WINDOWS) && (defined(DTCONTEXT_IS_AMD64) || defined(DTCONTEXT_IS_ARM64))
+    // If the host or target is not Windows, then we can assume that the DT_CONTEXT
+    // is the same as the T_CONTEXT, except for the XSTATE registers.
+    static_assert(sizeof(DT_CONTEXT) == offsetof(T_CONTEXT, XStateFeaturesMask), "DT_CONTEXT does not include the XSTATE registers");
+#else
+    // Since Dac + DBI are tightly coupled, context sizes should be the same.
+    static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size");
+#endif
     HRESULT hr = m_pTarget->GetThreadContext(
         dwThreadId,
-        CONTEXT_FULL,
+        CONTEXT_FULL | CONTEXT_FLOATING_POINT
+#ifdef CONTEXT_EXTENDED_REGISTERS
+        | CONTEXT_EXTENDED_REGISTERS
+#endif
+        ,
         sizeof(DT_CONTEXT),
         (BYTE*) &ctx);
     IfFailThrow(hr);

src/coreclr/debug/di/process.cpp

@@ -13281,9 +13281,9 @@ void CordbProcess::HandleDebugEventForInteropDebugging(const DEBUG_EVENT * pEven
             LOG((LF_CORDB, LL_INFO100000, "W32ET::W32EL: hijack complete will restore context...\n"));
             DT_CONTEXT tempContext = { 0 };
 #if defined(DT_CONTEXT_EXTENDED_REGISTERS)
-            tempContext.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_EXTENDED_REGISTERS;
+            tempContext.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT | DT_CONTEXT_EXTENDED_REGISTERS;
 #else
-            tempContext.ContextFlags = DT_CONTEXT_FULL;
+            tempContext.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT;
 #endif
             HRESULT hr = pUnmanagedThread->GetThreadContext(&tempContext);
             _ASSERTE(SUCCEEDED(hr));

src/coreclr/debug/di/rsthread.cpp

@@ -3706,9 +3706,9 @@ HRESULT CordbUnmanagedThread::SetupFirstChanceHijackForSync()
     // to avoid getting incomplete information and corrupt the thread context
     DT_CONTEXT context;
 #if defined(DT_CONTEXT_EXTENDED_REGISTERS)
-    context.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_EXTENDED_REGISTERS;
+    context.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT | DT_CONTEXT_EXTENDED_REGISTERS;
 #else
-    context.ContextFlags = DT_CONTEXT_FULL;
+    context.ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT;
 #endif
     BOOL succ = DbiGetThreadContext(m_handle, &context);
     _ASSERTE(succ);
@@ -3719,9 +3719,9 @@ HRESULT CordbUnmanagedThread::SetupFirstChanceHijackForSync()
         LOG((LF_CORDB, LL_ERROR, "CUT::SFCHFS: DbiGetThreadContext error=0x%x\n", error));
     }
 #if defined(DT_CONTEXT_EXTENDED_REGISTERS)
-    GetHijackCtx()->ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_EXTENDED_REGISTERS;
+    GetHijackCtx()->ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT | DT_CONTEXT_EXTENDED_REGISTERS;
 #else
-    GetHijackCtx()->ContextFlags = DT_CONTEXT_FULL;
+    GetHijackCtx()->ContextFlags = DT_CONTEXT_FULL | DT_CONTEXT_FLOATING_POINT;
 #endif
     CORDbgCopyThreadContext(GetHijackCtx(), &context);
     LOG((LF_CORDB, LL_INFO10000, "CUT::SFCHFS: thread=0x%x Hijacking for sync. Original context is:\n", this));

src/coreclr/debug/inc/dbgtargetcontext.h

@@ -474,7 +474,7 @@ typedef DECLSPEC_ALIGN(16) struct {
 
 
 #if !defined(CROSS_COMPILE) && !defined(TARGET_WINDOWS)
-static_assert(sizeof(DT_CONTEXT) == offsetof(T_CONTEXT, XStateFeaturesMask), "DT_CONTEXT must not include the SVE registers on AMD64");
+static_assert(sizeof(DT_CONTEXT) == offsetof(T_CONTEXT, XStateFeaturesMask), "DT_CONTEXT must not include the SVE registers on ARM64");
 #else
 static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size on ARM64");
 #endif