[KERNEL32] Fix register initialization in BaseInitializeContext Get rid of BaseThreadStartupThunk and BaseProcessStartThunk asm wrappers and go to the C functions directly (home space is allocated on the stack by the kernel)

dll/win32/kernel32/CMakeLists.txt

···
         client/i386/thread.S)
 elseif(ARCH STREQUAL "amd64")
     list(APPEND ASM_SOURCE
-        client/amd64/fiber.S
-        client/amd64/thread.S)
+        client/amd64/fiber.S)
 elseif(ARCH STREQUAL "arm")
     list(APPEND ASM_SOURCE
         client/arm/fiber.S

dll/win32/kernel32/client/amd64/thread.S

···
-/*
- * COPYRIGHT:  See COPYING in the top level directory
- * PROJECT:    ReactOS system libraries
- * FILE:       dll/win32/kernel32/client/amd64/thread.S
- * PURPOSE:    Thread Start Thunks
- * PROGRAMMER: Alex Ionescu ([e-mail])
- */
-
-#include <asm.inc>
-.code64
-
-EXTERN BaseThreadStartup:PROC
-EXTERN BaseProcessStartup:PROC
-
-PUBLIC BaseThreadStartupThunk
-PUBLIC BaseProcessStartThunk
-
-BaseThreadStartupThunk:
-
-    /* Start out fresh */
-    xor rbp, rbp
-
-    push rbx                  /* lpParameter */
-    push rax                  /* lpStartAddress */
-    push 0                    /* Return RIP */
-    jmp BaseThreadStartup
-
-BaseProcessStartThunk:
-
-    /* Start out fresh */
-    xor rbp, rbp
-
-    push rax                  /* lpStartAddress */
-    push 0                    /* Return RIP */
-    jmp BaseProcessStartup
-
-END
-/* EOF */

dll/win32/kernel32/client/utils.c

···
 
 #elif defined(_M_AMD64)
     DPRINT("BaseInitializeContext: %p\n", Context);
+    ASSERT(((ULONG_PTR)StackAddress & 15) == 0);
+
+    RtlZeroMemory(Context, sizeof(*Context));
 
     /* Setup the Initial Win32 Thread Context */
-    Context->Rax = (ULONG_PTR)StartAddress;
-    Context->Rbx = (ULONG_PTR)Parameter;
-    Context->Rsp = (ULONG_PTR)StackAddress;
-    /* The other registers are undefined */
+    Context->Rcx = (ULONG_PTR)StartAddress;
+    Context->Rdx = (ULONG_PTR)Parameter;
+    Context->Rsp = (ULONG_PTR)StackAddress - 5 * sizeof(PVOID);
 
     /* Setup the Segments */
     Context->SegGs = KGDT64_R3_DATA | RPL_MASK;
···
     Context->SegFs = KGDT64_R3_CMTEB | RPL_MASK;
 
     /* Set the EFLAGS */
-    Context->EFlags = 0x3000; /* IOPL 3 */
+    Context->EFlags = 0x3000 | EFLAGS_INTERRUPT_MASK; /* IOPL 3 */
 
     if (ContextType == 1)      /* For Threads */
     {
-        Context->Rip = (ULONG_PTR)BaseThreadStartupThunk;
+        Context->Rip = (ULONG_PTR)BaseThreadStartup;
     }
     else if (ContextType == 2) /* For Fibers */
     {
···
     }
     else                       /* For first thread in a Process */
     {
-        Context->Rip = (ULONG_PTR)BaseProcessStartThunk;
+        Context->Rip = (ULONG_PTR)BaseProcessStartup;
     }
 
     /* Set the Context Flags */
     Context->ContextFlags = CONTEXT_FULL;
-
-    /* Give it some room for the Parameter */
-    Context->Rsp -= sizeof(PVOID);
 #elif defined(_M_ARM)
     DPRINT("BaseInitializeContext: %p\n", Context);