UefiCpuPkg/CpuExceptionHandlerLib: Add stack switch support

If Stack Guard is enabled and there's really a stack overflow happened during
boot, a Page Fault exception will be triggered. Because the stack is out of
usage, the exception handler, which shares the stack with normal UEFI driver,
cannot be executed and cannot dump the processor information.

Without those information, it's very difficult for the BIOS developers locate
the root cause of stack overflow. And without a workable stack, the developer
cannot event use single step to debug the UEFI driver with JTAG debugger.

In order to make sure the exception handler to execute normally after stack
overflow. We need separate stacks for exception handlers in case of unusable
stack.

IA processor allows to switch to a new stack during handling interrupt and
exception. But X64 and IA32 provides different ways to make it. X64 provides
interrupt stack table (IST) to allow maximum 7 different exceptions to have
new stack for its handler. IA32 doesn't have IST mechanism and can only use
task gate to do it since task switch allows to load a new stack through its
task-state segment (TSS).

The new API, InitializeCpuExceptionHandlersEx, is implemented to complete
extra initialization for stack switch of exception handler. Since setting
up stack switch needs allocating new memory for new stack, new GDT table
and task-state segment but the initialization method will be called in
different phases which have no consistent way to reserve those memory, this
new API is allowed to pass the reserved resources to complete the extra
works. This is cannot be done by original InitializeCpuExceptionHandlers.

Considering exception handler initialization for MP situation, this new API
is also necessary, because AP is not supposed to allocate memory. So the
memory needed for stack switch have to be reserved in BSP before waking up
AP and then pass them to InitializeCpuExceptionHandlersEx afterwards.

Since Stack Guard feature is available only for DXE phase at this time, the
new API is fully implemented for DXE only. Other phases implement a dummy
one which just calls InitializeCpuExceptionHandlers().

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Suggested-by: Ayellet Wolman <ayellet.wolman@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Jeff Fan <vanjeff_919@hotmail.com>
Reviewed-by: Jiewen.yao@intel.com

UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuException.c

@@ -177,4 +177,36 @@ RegisterCpuInterruptHandler (
   )
 {
   return EFI_UNSUPPORTED;
-}
+}
+
+/**
+  Initializes all CPU exceptions entries with optional extra initializations.
+
+  By default, this method should include all functionalities implemented by
+  InitializeCpuExceptionHandlers(), plus extra initialization works, if any.
+  This could be done by calling InitializeCpuExceptionHandlers() directly
+  in this method besides the extra works.
+
+  InitData is optional and its use and content are processor arch dependent.
+  The typical usage of it is to convey resources which have to be reserved
+  elsewhere and are necessary for the extra initializations of exception.
+
+  @param[in]  VectorInfo    Pointer to reserved vector list.
+  @param[in]  InitData      Pointer to data optional for extra initializations
+                            of exception.
+
+  @retval EFI_SUCCESS             The exceptions have been successfully
+                                  initialized.
+  @retval EFI_INVALID_PARAMETER   VectorInfo or InitData contains invalid
+                                  content.
+
+**/
+EFI_STATUS
+EFIAPI
+InitializeCpuExceptionHandlersEx (
+  IN EFI_VECTOR_HANDOFF_INFO            *VectorInfo OPTIONAL,
+  IN CPU_EXCEPTION_INIT_DATA            *InitData OPTIONAL
+  )
+{
+  return InitializeCpuExceptionHandlers (VectorInfo);
+}