Fix i686 thread context setup

xtoskrnl/ke/i686/kthread.cc

@@ -41,6 +41,7 @@ KE::KThread::InitializeThreadContext(IN PKTHREAD Thread,
 {
     PKTHREAD_INIT_FRAME ThreadFrame;
     PFX_SAVE_FORMAT FxSaveFormat;
+    CONTEXT ContextFrame;
 
     /* Set initial thread frame */
     ThreadFrame = ((PKTHREAD_INIT_FRAME)Thread->InitialStack) - 1;
@@ -51,18 +52,24 @@ KE::KThread::InitializeThreadContext(IN PKTHREAD Thread,
     /* Check if context provided for this thread */
     if(ContextRecord)
     {
-        /* User mode thread needs further initialization, this is not completed */
-        UNIMPLEMENTED;
+        /* Make a local copy of the context to avoid mutating caller's memory */
+        RTL::Memory::CopyMemory(&ContextFrame, ContextRecord, sizeof(CONTEXT));
+
+        /* Disable debug registers and enable control and extended registers */
+        ContextFrame.ContextFlags |= (CONTEXT_CONTROL | CONTEXT_EXTENDED_REGISTERS);
+        ContextFrame.ContextFlags &= ~CONTEXT_DEBUG_REGISTERS;
 
         /* Fill trap frame with zeroes */
         RTL::Memory::ZeroMemory(&ThreadFrame->TrapFrame, sizeof(KTRAP_FRAME));
 
-        /* Disable debug registers and enable context registers */
-        ContextRecord->ContextFlags &= ~CONTEXT_DEBUG_REGISTERS | CONTEXT_CONTROL;
+        /* Translate Context frame to Trap frame */
+        KE::Processor::RestoreProcessorContext(&ThreadFrame->TrapFrame, NULLPTR,
+                                               &ContextFrame, ContextFrame.ContextFlags);
 
         /* This is user mode thread */
-        ThreadFrame->StartFrame.UserMode = TRUE;
         Thread->PreviousMode = UserMode;
+        ThreadFrame->StartFrame.UserMode = TRUE;
+        ThreadFrame->TrapFrame.PreviousMode = UserMode;
 
         /* Disable coprocessor floating point state */
         Thread->NpxState = NPX_STATE_UNLOADED;
@@ -71,11 +78,19 @@ KE::KThread::InitializeThreadContext(IN PKTHREAD Thread,
         /* Set initial floating point state */
         FxSaveFormat = (PFX_SAVE_FORMAT)ContextRecord->ExtendedRegisters;
         FxSaveFormat->ControlWord = 0x27F;
-        FxSaveFormat->MxCsr = 0x1F80;
-        ContextRecord->FloatSave.Cr0NpxState = 0;
+        FxSaveFormat->DataOffset = 0;
+        FxSaveFormat->DataSelector = 0;
+        FxSaveFormat->ErrorOffset = 0;
+        FxSaveFormat->ErrorSelector = 0;
+        FxSaveFormat->StatusWord = 0;
+        FxSaveFormat->TagWord = 0;
+        ContextFrame.FloatSave.Cr0NpxState = 0;
         ThreadFrame->NpxFrame.Cr0NpxState = 0;
         ThreadFrame->NpxFrame.NpxSavedCpu = 0;
 
+        /* Set initial MXCSR register value */
+        FxSaveFormat->MxCsr = 0x1F80;
+
         /* Clear DR6 and DR7 registers */
         ThreadFrame->TrapFrame.Dr6 = 0;
         ThreadFrame->TrapFrame.Dr7 = 0;
@@ -84,15 +99,12 @@ KE::KThread::InitializeThreadContext(IN PKTHREAD Thread,
         ThreadFrame->TrapFrame.SegDs |= RPL_MASK;
         ThreadFrame->TrapFrame.SegEs |= RPL_MASK;
         ThreadFrame->TrapFrame.SegSs |= RPL_MASK;
-
-        /* Set user mode thread in the trap frame */
-        ThreadFrame->TrapFrame.PreviousMode = UserMode;
     }
     else
     {
         /* This is kernel mode thread */
-        ThreadFrame->StartFrame.UserMode = FALSE;
         Thread->PreviousMode = KernelMode;
+        ThreadFrame->StartFrame.UserMode = FALSE;
 
         /* Disable coprocessor floating point state */
         Thread->NpxState = NPX_STATE_UNLOADED;
@@ -110,7 +122,9 @@ KE::KThread::InitializeThreadContext(IN PKTHREAD Thread,
     /* Initialize switch frame */
     ThreadFrame->SwitchFrame.ApcBypassDisabled = TRUE;
     ThreadFrame->SwitchFrame.ExceptionList = (PEXCEPTION_REGISTRATION_RECORD) - 1;
+    ThreadFrame->SwitchFrame.Return = (PVOID)(ULONG)RunThread;
 
-    /* Set thread stack */
+    /* Set thread stack boundaries */
+    Thread->InitialStack = (PVOID)&ThreadFrame->NpxFrame;
     Thread->KernelStack = &ThreadFrame->SwitchFrame;
 }