RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429
Load the GDT and set the CR0, then jump to Flat 32 protected mode. After that CR4 is set. Cc: Ard Biesheuvel <[email protected]> Cc: Jordan Justen <[email protected]> Cc: Brijesh Singh <[email protected]> Cc: Erdem Aktas <[email protected]> Cc: James Bottomley <[email protected]> Cc: Jiewen Yao <[email protected]> Cc: Tom Lendacky <[email protected]> Signed-off-by: Min Xu <[email protected]> --- OvmfPkg/ResetVector/Ia32/ReloadFlat32.asm | 44 +++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 OvmfPkg/ResetVector/Ia32/ReloadFlat32.asm diff --git a/OvmfPkg/ResetVector/Ia32/ReloadFlat32.asm b/OvmfPkg/ResetVector/Ia32/ReloadFlat32.asm new file mode 100644 index 000000000000..cfcea06fbd11 --- /dev/null +++ b/OvmfPkg/ResetVector/Ia32/ReloadFlat32.asm @@ -0,0 +1,44 @@ +;------------------------------------------------------------------------------ +; @file +; Load the GDT and set the CR0, then jump to Flat 32 protected mode. +; +; Copyright (c) 2021, Intel Corporation. All rights reserved.<BR> +; SPDX-License-Identifier: BSD-2-Clause-Patent +; +;------------------------------------------------------------------------------ + +%define SEC_DEFAULT_CR0 0x00000023 +%define SEC_DEFAULT_CR4 0x640 + +BITS 32 + +; +; Modified: EAX, EBX, CR0, CR4, DS, ES, FS, GS, SS +; +ReloadFlat32: + + cli + mov ebx, ADDR_OF(gdtr) + lgdt [ebx] + + mov eax, SEC_DEFAULT_CR0 + mov cr0, eax + + jmp LINEAR_CODE_SEL:dword ADDR_OF(jumpToFlat32BitAndLandHere) +BITS 32 +jumpToFlat32BitAndLandHere: + + mov eax, SEC_DEFAULT_CR4 + mov cr4, eax + + debugShowPostCode POSTCODE_32BIT_MODE + + mov ax, LINEAR_SEL + mov ds, ax + mov es, ax + mov fs, ax + mov gs, ax + mov ss, ax + + OneTimeCallRet ReloadFlat32 + -- 2.29.2.windows.2 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#78197): https://edk2.groups.io/g/devel/message/78197 Mute This Topic: https://groups.io/mt/84476065/21656 Group Owner: [email protected] Unsubscribe: https://edk2.groups.io/g/devel/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
