mirror of https://github.com/acidanthera/audk.git
140 lines
4.0 KiB
NASM
140 lines
4.0 KiB
NASM
;------------------------------------------------------------------------------
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; @file
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; Transition from 16 bit real mode into 32 bit flat protected mode
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;
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; Copyright (c) 2008 - 2010, Intel Corporation. All rights reserved.<BR>
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; This program and the accompanying materials
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; are licensed and made available under the terms and conditions of the BSD License
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; which accompanies this distribution. The full text of the license may be found at
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; http://opensource.org/licenses/bsd-license.php
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;
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; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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;
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;------------------------------------------------------------------------------
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%define SEC_DEFAULT_CR0 0x40000023
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%define SEC_DEFAULT_CR4 0x640
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BITS 16
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;
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; Modified: EAX, EBX
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;
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; @param[out] DS Selector allowing flat access to all addresses
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; @param[out] ES Selector allowing flat access to all addresses
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; @param[out] FS Selector allowing flat access to all addresses
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; @param[out] GS Selector allowing flat access to all addresses
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; @param[out] SS Selector allowing flat access to all addresses
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;
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TransitionFromReal16To32BitFlat:
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debugShowPostCode POSTCODE_16BIT_MODE
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cli
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mov bx, 0xf000
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mov ds, bx
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mov bx, ADDR16_OF(gdtr)
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o32 lgdt [cs:bx]
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mov eax, SEC_DEFAULT_CR0
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mov cr0, eax
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jmp LINEAR_CODE_SEL:dword ADDR_OF(jumpTo32BitAndLandHere)
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BITS 32
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jumpTo32BitAndLandHere:
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mov eax, SEC_DEFAULT_CR4
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mov cr4, eax
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debugShowPostCode POSTCODE_32BIT_MODE
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mov ax, LINEAR_SEL
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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mov ss, ax
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OneTimeCallRet TransitionFromReal16To32BitFlat
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ALIGN 2
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gdtr:
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dw GDT_END - GDT_BASE - 1 ; GDT limit
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dd ADDR_OF(GDT_BASE)
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ALIGN 16
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;
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; Macros for GDT entries
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;
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%define PRESENT_FLAG(p) (p << 7)
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%define DPL(dpl) (dpl << 5)
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%define SYSTEM_FLAG(s) (s << 4)
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%define DESC_TYPE(t) (t)
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; Type: data, expand-up, writable, accessed
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%define DATA32_TYPE 3
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; Type: execute, readable, expand-up, accessed
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%define CODE32_TYPE 0xb
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; Type: execute, readable, expand-up, accessed
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%define CODE64_TYPE 0xb
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%define GRANULARITY_FLAG(g) (g << 7)
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%define DEFAULT_SIZE32(d) (d << 6)
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%define CODE64_FLAG(l) (l << 5)
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%define UPPER_LIMIT(l) (l)
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;
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; The Global Descriptor Table (GDT)
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;
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GDT_BASE:
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; null descriptor
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NULL_SEL equ $-GDT_BASE
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DW 0 ; limit 15:0
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DW 0 ; base 15:0
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DB 0 ; base 23:16
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DB 0 ; sys flag, dpl, type
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DB 0 ; limit 19:16, flags
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DB 0 ; base 31:24
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; linear data segment descriptor
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LINEAR_SEL equ $-GDT_BASE
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DW 0xffff ; limit 15:0
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DW 0 ; base 15:0
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DB 0 ; base 23:16
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DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(DATA32_TYPE)
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DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf)
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DB 0 ; base 31:24
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; linear code segment descriptor
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LINEAR_CODE_SEL equ $-GDT_BASE
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DW 0xffff ; limit 15:0
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DW 0 ; base 15:0
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DB 0 ; base 23:16
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DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE32_TYPE)
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DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf)
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DB 0 ; base 31:24
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%ifdef ARCH_X64
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; linear code (64-bit) segment descriptor
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LINEAR_CODE64_SEL equ $-GDT_BASE
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DW 0xffff ; limit 15:0
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DW 0 ; base 15:0
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DB 0 ; base 23:16
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DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE64_TYPE)
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DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(0)|CODE64_FLAG(1)|UPPER_LIMIT(0xf)
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DB 0 ; base 31:24
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%endif
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GDT_END:
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