mirror of https://github.com/acidanthera/audk.git
122 lines
3.2 KiB
NASM
122 lines
3.2 KiB
NASM
;; @file
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; This is the code that goes from real-mode to protected mode.
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; It consumes the reset vector, configures the stack.
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;
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; Copyright (c) 2015 - 2022, Intel Corporation. All rights reserved.<BR>
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; SPDX-License-Identifier: BSD-2-Clause-Patent
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;;
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;
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; Define assembler characteristics
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;
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extern ASM_PFX(TempRamInitApi)
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SECTION .text
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%macro RET_ESI 0
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movd esi, mm7 ; restore EIP from MM7
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jmp esi
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%endmacro
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;
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; Perform early platform initialization
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;
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global ASM_PFX(SecPlatformInit)
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ASM_PFX(SecPlatformInit):
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RET_ESI
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;
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; Protected mode portion initializes stack, configures cache, and calls C entry point
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;
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;----------------------------------------------------------------------------
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;
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; Procedure: ProtectedModeEntryPoint
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;
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; Input: Executing in 32 Bit Protected (flat) mode
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; cs: 0-4GB
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; ds: 0-4GB
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; es: 0-4GB
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; fs: 0-4GB
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; gs: 0-4GB
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; ss: 0-4GB
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;
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; Output: This function never returns
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;
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; Destroys:
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; ecx
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; edi
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; esi
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; esp
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;
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; Description:
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; Perform any essential early platform initialisation
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; Setup a stack
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;
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;----------------------------------------------------------------------------
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global ASM_PFX(ProtectedModeEntryPoint)
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ASM_PFX(ProtectedModeEntryPoint):
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;
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; Dummy function. Consume 2 API to make sure they can be linked.
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;
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mov eax, ASM_PFX(TempRamInitApi)
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; Should never return
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jmp $
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;
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; ROM-based Global-Descriptor Table for the PEI Phase
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;
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align 16
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global ASM_PFX(BootGdtTable)
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;
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; GDT[0]: 0x00: Null entry, never used.
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;
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NULL_SEL equ $ - GDT_BASE ; Selector [0]
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GDT_BASE:
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ASM_PFX(BootGdtTable): DD 0
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DD 0
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;
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; Linear code segment descriptor
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;
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LINEAR_CODE_SEL equ $ - GDT_BASE ; Selector [0x8]
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DW 0FFFFh ; limit 0xFFFF
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DW 0 ; base 0
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DB 0
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DB 09Bh ; present, ring 0, data, expand-up, not-writable
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DB 0CFh ; page-granular, 32-bit
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DB 0
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;
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; System data segment descriptor
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;
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SYS_DATA_SEL equ $ - GDT_BASE ; Selector [0x10]
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DW 0FFFFh ; limit 0xFFFF
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DW 0 ; base 0
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DB 0
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DB 093h ; present, ring 0, data, expand-up, not-writable
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DB 0CFh ; page-granular, 32-bit
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DB 0
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GDT_SIZE EQU $ - GDT_BASE ; Size, in bytes
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;
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; GDT Descriptor
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;
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GdtDesc: ; GDT descriptor
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DW GDT_SIZE - 1 ; GDT limit
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DD GDT_BASE ; GDT base address
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global ASM_PFX(ProtectedModeEntryLinearAddress)
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global ASM_PFX(ProtectedModeEntryLinearOffset)
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ASM_PFX(ProtectedModeEntryLinearAddress):
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ASM_PFX(ProtectedModeEntryLinearOffset):
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DD ASM_PFX(ProtectedModeEntryPoint) ; Offset of our 32 bit code
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DW LINEAR_CODE_SEL
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