[edk2-devel] [PATCH 4/6] UefiCpuPkg/ResetVector: Add ReloadFlat32 in UefiCpuPkg
Min Xu
min.m.xu at intel.com
Mon Jul 12 01:19:40 UTC 2021
RFC: https://bugzilla.tianocore.org/show_bug.cgi?id=3429
Load the GDT and set the default CR0, then jump to Flat 32 protected mode.
Cc: Eric Dong <eric.dong at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Ray Ni <ray.ni at intel.com>
Cc: Laszlo Ersek <lersek at redhat.com>
Signed-off-by: Min Xu <min.m.xu at intel.com>
---
.../ResetVector/Vtf0/Ia32/ReloadFlat32.asm | 43 +++++++++++++++++++
1 file changed, 43 insertions(+)
create mode 100644 UefiCpuPkg/ResetVector/Vtf0/Ia32/ReloadFlat32.asm
diff --git a/UefiCpuPkg/ResetVector/Vtf0/Ia32/ReloadFlat32.asm b/UefiCpuPkg/ResetVector/Vtf0/Ia32/ReloadFlat32.asm
new file mode 100644
index 000000000000..e8a4c47762df
--- /dev/null
+++ b/UefiCpuPkg/ResetVector/Vtf0/Ia32/ReloadFlat32.asm
@@ -0,0 +1,43 @@
+;------------------------------------------------------------------------------
+; @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
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