From: Jian J Wang Date: Thu, 7 Dec 2017 12:15:12 +0000 (+0800) Subject: UefiCpuPkg/CpuExceptionHandlerLib: Add stack switch support X-Git-Tag: edk2-stable201903~2903 X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=0ff5aa9cae1ea276668fa4398d047aa9fda3c2c7;hp=0ff5aa9cae1ea276668fa4398d047aa9fda3c2c7 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 Cc: Eric Dong Cc: Laszlo Ersek Cc: Michael Kinney Suggested-by: Ayellet Wolman Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Jian J Wang Reviewed-by: Jeff Fan Reviewed-by: Jiewen.yao@intel.com ---