Fix x64 macOS and Linux managed debugging (#84655)

* Limit context size in DAC stackwalker

* Constrain debugger x64 context size check to Linux and macOS

* Exclude DAC and DBI cross-os compilation with context adjustment

* Fix non-x64 builds

---------

Co-authored-by: Mike McLaughlin <mikem@microsoft.com>

src/coreclr/debug/createdump/datatarget.cpp

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 #include "createdump.h"
+#include <dbgtargetcontext.h>
 
 #if defined(HOST_ARM64)
 // Flag to check if atomics feature is available on
@@ -181,7 +182,7 @@ DumpDataTarget::GetThreadContext(
     /* [in] */ ULONG32 contextSize,
     /* [out, size_is(contextSize)] */ PBYTE context)
 {
-    if (contextSize < sizeof(CONTEXT))
+    if (contextSize < sizeof(DT_CONTEXT))
     {
         assert(false);
         return E_INVALIDARG;

src/coreclr/debug/daccess/daccess.cpp

@@ -7896,7 +7896,7 @@ void DacStackReferenceWalker::WalkStack()
     // Get the current thread's context and set that as the filter context
     if (mThread->GetFilterContext() == NULL && mThread->GetProfilerFilterContext() == NULL)
     {
-        mDac->m_pTarget->GetThreadContext(mThread->GetOSThreadId(), CONTEXT_FULL, sizeof(ctx), (BYTE*)&ctx);
+        mDac->m_pTarget->GetThreadContext(mThread->GetOSThreadId(), CONTEXT_FULL, sizeof(DT_CONTEXT), (BYTE*)&ctx);
         mThread->SetProfilerFilterContext(&ctx);
         contextHolder.Activate(mThread);
     }

src/coreclr/debug/daccess/dacdbiimpl.cpp

@@ -5199,7 +5199,7 @@ void DacDbiInterfaceImpl::Hijack(
     HRESULT hr = m_pTarget->GetThreadContext(
         dwThreadId,
         CONTEXT_FULL,
-        sizeof(ctx),
+        sizeof(DT_CONTEXT),
         (BYTE*) &ctx);
     IfFailThrow(hr);
 
@@ -5346,7 +5346,7 @@ void DacDbiInterfaceImpl::Hijack(
     //
     // Commit the context.
     //
-    hr = m_pMutableTarget->SetThreadContext(dwThreadId, sizeof(ctx), reinterpret_cast<BYTE*> (&ctx));
+    hr = m_pMutableTarget->SetThreadContext(dwThreadId, sizeof(DT_CONTEXT), reinterpret_cast<BYTE*> (&ctx));
     IfFailThrow(hr);
 }
 
@@ -5717,7 +5717,7 @@ void DacDbiInterfaceImpl::GetContext(VMPTR_Thread vmThread, DT_CONTEXT * pContex
         pContextBuffer->ContextFlags = DT_CONTEXT_ALL;
         HRESULT hr = m_pTarget->GetThreadContext(pThread->GetOSThreadId(),
                                                 pContextBuffer->ContextFlags,
-                                                sizeof(*pContextBuffer),
+                                                sizeof(DT_CONTEXT),
                                                 reinterpret_cast<BYTE *>(pContextBuffer));
         if (hr == E_NOTIMPL)
         {

src/coreclr/debug/daccess/dacdbiimplstackwalk.cpp

@@ -153,9 +153,14 @@ void DacDbiInterfaceImpl::GetStackWalkCurrentContext(StackWalkHandle pSFIHandle,
 void DacDbiInterfaceImpl::GetStackWalkCurrentContext(StackFrameIterator * pIter,
                                                      DT_CONTEXT *         pContext)
 {
-    // convert the current REGDISPLAY to a CONTEXT
+    // convert the current REGDISPLAY to a DT_CONTEXT
     CrawlFrame * pCF = &(pIter->m_crawl);
-    UpdateContextFromRegDisp(pCF->GetRegisterSet(), reinterpret_cast<T_CONTEXT *>(pContext));
+    T_CONTEXT tmpContext = { };
+    UpdateContextFromRegDisp(pCF->GetRegisterSet(), &tmpContext);
+    CopyMemory(pContext, &tmpContext, sizeof(*pContext));
+#if defined(TARGET_X86) || defined(TARGET_AMD64)
+    pContext->ContextFlags &= ~(CONTEXT_XSTATE & CONTEXT_AREA_MASK);
+#endif
 }
 
 
@@ -180,7 +185,7 @@ void DacDbiInterfaceImpl::SetStackWalkCurrentContext(VMPTR_Thread           vmTh
     // Allocate a context in DDImpl's memory space. DDImpl can't contain raw pointers back into
     // the client space since that may not marshal.
     T_CONTEXT * pContext2 = GetContextBufferFromHandle(pSFIHandle);
-    *pContext2  = *reinterpret_cast<T_CONTEXT *>(pContext); // memcpy
+    CopyMemory(pContext2, pContext, sizeof(*pContext));
 
     // update the REGDISPLAY with the given CONTEXT.
     // Be sure that the context is in DDImpl's memory space and not the Right-sides.
@@ -657,8 +662,12 @@ void DacDbiInterfaceImpl::ConvertContextToDebuggerRegDisplay(const DT_CONTEXT *
 
     // This is a bit cumbersome.  First we need to convert the CONTEXT into a REGDISPLAY.  Then we need
     // to convert the REGDISPLAY to a DebuggerREGDISPLAY.
+    T_CONTEXT tmpContext = { };
+    CopyMemory(&tmpContext, pInContext, sizeof(*pInContext));
+
     REGDISPLAY rd;
-    FillRegDisplay(&rd, reinterpret_cast<T_CONTEXT *>(const_cast<DT_CONTEXT *>(pInContext)));
+    FillRegDisplay(&rd, &tmpContext);
+
     SetDebuggerREGDISPLAYFromREGDISPLAY(pOutDRD, &rd);
 }
 

src/coreclr/debug/daccess/reimpl.cpp

@@ -107,7 +107,7 @@ DacGetThreadContext(Thread* thread, T_CONTEXT* context)
     HRESULT status =
         g_dacImpl->m_pTarget->
         GetThreadContext(thread->GetOSThreadId(), contextFlags,
-                         sizeof(*context), (PBYTE)context);
+                         sizeof(DT_CONTEXT), (PBYTE)context);
     if (status != S_OK)
     {
         DacError(status);

src/coreclr/debug/daccess/stack.cpp

@@ -104,8 +104,9 @@ ClrDataStackWalk::GetContext(
         }
         else
         {
-            *(PT_CONTEXT)contextBuf = m_context;
-            UpdateContextFromRegDisp(&m_regDisp, (PT_CONTEXT)contextBuf);
+            T_CONTEXT tmpContext = m_context;
+            UpdateContextFromRegDisp(&m_regDisp, &tmpContext);
+            CopyMemory(contextBuf, &tmpContext, contextBufSize);
             status = S_OK;
         }
     }
@@ -154,7 +155,7 @@ ClrDataStackWalk::SetContext2(
     {
         // Copy the context to local state so
         // that its lifetime extends beyond this call.
-        m_context = *(PT_CONTEXT)context;
+        CopyMemory(&m_context, context, contextSize);
         m_thread->FillRegDisplay(&m_regDisp, &m_context);
         m_frameIter.ResetRegDisp(&m_regDisp, (flags & CLRDATA_STACK_SET_CURRENT_CONTEXT) != 0);
         m_stackPrev = (TADDR)GetRegdisplaySP(&m_regDisp);
@@ -660,7 +661,7 @@ ClrDataFrame::GetContext(
 
     EX_TRY
     {
-        *(PT_CONTEXT)contextBuf = m_context;
+        CopyMemory(contextBuf, &m_context, contextBufSize);
         status = S_OK;
     }
     EX_CATCH

src/coreclr/debug/di/process.cpp

@@ -6438,7 +6438,7 @@ HRESULT CordbProcess::GetThreadContext(DWORD threadID, ULONG32 contextSize, BYTE
 
     DT_CONTEXT * pContext;
 
-    if (contextSize != sizeof(DT_CONTEXT))
+    if (contextSize < sizeof(DT_CONTEXT))
     {
         LOG((LF_CORDB, LL_INFO10000, "CP::GTC: thread=0x%x, context size is invalid.\n", threadID));
         return E_INVALIDARG;
@@ -11179,10 +11179,10 @@ void CordbProcess::HandleSetThreadContextNeeded(DWORD dwThreadId)
         ThrowHR(HRESULT_FROM_GetLastError());
     }
 
-    CONTEXT context = { 0 };
+    DT_CONTEXT context = { 0 };
     context.ContextFlags = CONTEXT_FULL;
 
-    HRESULT hr = GetDataTarget()->GetThreadContext(dwThreadId, CONTEXT_FULL, sizeof(CONTEXT), reinterpret_cast<BYTE*> (&context));
+    HRESULT hr = GetDataTarget()->GetThreadContext(dwThreadId, CONTEXT_FULL, sizeof(DT_CONTEXT), reinterpret_cast<BYTE*> (&context));
     IfFailThrow(hr);
 
     TADDR lsContextAddr = (TADDR)context.Rcx;

src/coreclr/debug/inc/common.h

@@ -96,7 +96,15 @@ ULONG32 ContextSizeForFlags(ULONG32 flags)
     else
 #endif // TARGET_X86
     {
+#if !defined(CROSS_COMPILE) && !defined(TARGET_WINDOWS) && defined(TARGET_AMD64)
+        if ((flags & CONTEXT_XSTATE) == CONTEXT_XSTATE)
+        {
+            return sizeof(T_CONTEXT);
+        }
+        return offsetof(T_CONTEXT, XStateFeaturesMask);
+#else
         return sizeof(T_CONTEXT);
+#endif
     }
 }
 

src/coreclr/debug/inc/dbgtargetcontext.h

@@ -25,9 +25,15 @@
 // ByteSwapContext.
 //
 
-//
-// **** NOTE: Keep these in sync with pal/inc/pal.h ****
-//
+// ****
+// **** NOTE: T_CONTEXT (in pal/inc/pal.h) can now be larger than DT_CONTEXT (currently T_CONTEXT on Linux/MacOS
+// ****       x64 includes the XSTATE registers). This means the following:
+// ****
+// ****       1) The DBI/DAC APIs cannot assume that incoming context buffers are T_CONTEXT sized.
+// ****       2) When the DAC calls the supplied data target's context APIs, the size of the context buffer must
+// ****          be the size of the DT_CONTEXT for compatiblity.
+// ****       3) DBI/DAC code can not cast and copy from a T_CONTEXT into a DT_CONTEXT buffer.
+// ****       
 
 // This odd define pattern is needed because in DBI we set _TARGET_ to match the host and
 // DBG_TARGET to control our targeting. In x-plat DBI DBG_TARGET won't match _TARGET_ and
@@ -54,6 +60,8 @@
 #define DTCONTEXT_IS_RISCV64
 #endif
 
+#define CONTEXT_AREA_MASK 0xffff
+
 #if defined(DTCONTEXT_IS_X86)
 
 #define DT_SIZE_OF_80387_REGISTERS      80
@@ -118,6 +126,8 @@ typedef struct {
 
 } DT_CONTEXT;
 
+static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size on X86");
+
 // Since the target is little endian in this case we only have to provide a real implementation of
 // ByteSwapContext if the platform we're building on is big-endian.
 #ifdef BIGENDIAN
@@ -280,6 +290,12 @@ typedef struct DECLSPEC_ALIGN(16) {
     DWORD64 LastExceptionFromRip;
 } DT_CONTEXT;
 
+#if !defined(CROSS_COMPILE) && !defined(TARGET_WINDOWS)
+static_assert(sizeof(DT_CONTEXT) == offsetof(T_CONTEXT, XStateFeaturesMask), "DT_CONTEXT must not include the XSTATE registers on AMD64");
+#else
+static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size on AMD64");
+#endif
+
 #elif defined(DTCONTEXT_IS_ARM)
 
 #define DT_CONTEXT_ARM 0x00200000L
@@ -361,6 +377,8 @@ typedef DECLSPEC_ALIGN(8) struct {
 
 } DT_CONTEXT;
 
+static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size on ARM32");
+
 #elif defined(DTCONTEXT_IS_ARM64)
 
 #define DT_CONTEXT_ARM64 0x00400000L
@@ -452,7 +470,10 @@ typedef DECLSPEC_ALIGN(16) struct {
 
 } DT_CONTEXT;
 
+static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size on ARM64");
+
 #elif defined(DTCONTEXT_IS_LOONGARCH64)
+
 #define DT_CONTEXT_LOONGARCH64 0x00800000L
 
 #define DT_CONTEXT_CONTROL         (DT_CONTEXT_LOONGARCH64 | 0x1L)
@@ -516,7 +537,10 @@ typedef DECLSPEC_ALIGN(16) struct {
     ULONGLONG F[32];
 } DT_CONTEXT;
 
+static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size");
+
 #elif defined(DTCONTEXT_IS_RISCV64)
+
 #define DT_CONTEXT_RISCV64 0x01000000L
 
 #define DT_CONTEXT_CONTROL         (DT_CONTEXT_RISCV64 | 0x1L)
@@ -580,10 +604,10 @@ typedef DECLSPEC_ALIGN(16) struct {
     ULONGLONG F[32];
 } DT_CONTEXT;
 
+static_assert(sizeof(DT_CONTEXT) == sizeof(T_CONTEXT), "DT_CONTEXT size must equal the T_CONTEXT size");
 
 #else
 #error Unsupported platform
 #endif
 
-
 #endif // __DBG_TARGET_CONTEXT_INCLUDED