From 313d86c956d4599054a9dcd524668f67797d317a Mon Sep 17 00:00:00 2001 From: Ray Ni Date: Tue, 16 Mar 2021 11:32:33 +0800 Subject: [PATCH] UefiCpuPkg/CpuDxe: Guarantee GDT is below 4GB REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3233 GDT needs to be allocated below 4GB in 64bit environment because AP needs it for entering to protected mode. CPU running in big real mode cannot access above 4GB GDT. But CpuDxe driver contains below code: gdt = AllocateRuntimePool (sizeof (GdtTemplate) + 8); ..... gdtPtr.Base = (UINT32)(UINTN)(VOID*) gdt; The AllocateRuntimePool() may allocate memory above 4GB. Thus, we cannot use AllocateRuntimePool (), instead, we should use AllocatePages() to make sure GDT is below 4GB space. Signed-off-by: Ray Ni Reviewed-by: Eric Dong Reviewed-by: Laszlo Ersek Cc: Rahul Kumar --- UefiCpuPkg/CpuDxe/CpuGdt.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/UefiCpuPkg/CpuDxe/CpuGdt.c b/UefiCpuPkg/CpuDxe/CpuGdt.c index 8847bc4819..692402c55d 100644 --- a/UefiCpuPkg/CpuDxe/CpuGdt.c +++ b/UefiCpuPkg/CpuDxe/CpuGdt.c @@ -124,15 +124,26 @@ InitGlobalDescriptorTable ( VOID ) { + EFI_STATUS Status; GDT_ENTRIES *Gdt; IA32_DESCRIPTOR Gdtr; + EFI_PHYSICAL_ADDRESS Memory; // - // Allocate Runtime Data for the GDT + // Allocate Runtime Data below 4GB for the GDT + // AP uses the same GDT when it's waken up from real mode so + // the GDT needs to be below 4GB. // - Gdt = AllocateRuntimePool (sizeof (mGdtTemplate) + 8); - ASSERT (Gdt != NULL); - Gdt = ALIGN_POINTER (Gdt, 8); + Memory = SIZE_4GB - 1; + Status = gBS->AllocatePages ( + AllocateMaxAddress, + EfiRuntimeServicesData, + EFI_SIZE_TO_PAGES (sizeof (mGdtTemplate)), + &Memory + ); + ASSERT_EFI_ERROR (Status); + ASSERT ((Memory != 0) && (Memory < SIZE_4GB)); + Gdt = (GDT_ENTRIES *) (UINTN) Memory; // // Initialize all GDT entries