--- /dev/null
+#------------------------------------------------------------------------------\r
+#\r
+# Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>\r
+# This program and the accompanying materials\r
+# are licensed and made available under the terms and conditions of the BSD License\r
+# which accompanies this distribution. The full text of the license may be found at\r
+# http://opensource.org/licenses/bsd-license.php.\r
+#\r
+# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
+# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
+#\r
+# Abstract:\r
+#\r
+# This is the code that goes from real-mode to protected mode.\r
+# It consumes the reset vector, configures the stack.\r
+#\r
+#------------------------------------------------------------------------------\r
+\r
+\r
+#\r
+# Contrary to the name, this file contains 16 bit code as well.\r
+#\r
+.text\r
+#----------------------------------------------------------------------------\r
+#\r
+# Procedure: _ModuleEntryPoint\r
+#\r
+# Input: None\r
+#\r
+# Output: None\r
+#\r
+# Destroys: Assume all registers\r
+#\r
+# Description:\r
+#\r
+# Transition to non-paged flat-model protected mode from a\r
+# hard-coded GDT that provides exactly two descriptors.\r
+# This is a bare bones transition to protected mode only\r
+# used for a while in PEI and possibly DXE.\r
+#\r
+# After enabling protected mode, a far jump is executed to\r
+# transfer to PEI using the newly loaded GDT.\r
+#\r
+# Return: None\r
+#\r
+#----------------------------------------------------------------------------\r
+ASM_GLOBAL ASM_PFX(_ModuleEntryPoint)\r
+ASM_PFX(_ModuleEntryPoint):\r
+\r
+ #\r
+ # Load the GDT table in GdtDesc\r
+ #\r
+ .byte 0x66,0xbe #movl $GdtDesc, %esi\r
+ .long GdtDesc\r
+ \r
+ .byte 0x66,0x2e,0x0f,0x01,0x14 #lgdt %cs:(%si)\r
+\r
+ #\r
+ # Transition to 16 bit protected mode\r
+ #\r
+ .byte 0x0f,0x20,0xc0 #movl %cr0, %eax # Get control register 0\r
+ .byte 0x66,0x83,0xc8,0x03 #orl $0x0000003, %eax # Set PE bit (bit #0) & MP bit (bit #1)\r
+ .byte 0x0f,0x22,0xc0 #movl %eax, %cr0 # Activate protected mode\r
+\r
+ #\r
+ # Now we're in 16 bit protected mode\r
+ # Set up the selectors for 32 bit protected mode entry\r
+ # \r
+ .byte 0xb8 #movw SYS_DATA_SEL, %ax\r
+ .word SYS_DATA_SEL\r
+ \r
+ .byte 0x8e,0xd8 #movw %ax, %ds\r
+ .byte 0x8e,0xc0 #movw %ax, %es\r
+ .byte 0x8e,0xe0 #movw %ax, %fs\r
+ .byte 0x8e,0xe8 #movw %ax, %gs\r
+ .byte 0x8e,0xd0 #movw %ax, %ss\r
+\r
+ #\r
+ # Transition to Flat 32 bit protected mode\r
+ # The jump to a far pointer causes the transition to 32 bit mode\r
+ #\r
+ .byte 0x66,0xbe #movl ProtectedModeEntryLinearAddress, %esi\r
+ .long ProtectedModeEntryLinearAddress \r
+ .byte 0x66,0x2e,0xff,0x2c #jmp %cs:(%esi)\r
+\r
+#\r
+# Protected mode portion initializes stack, configures cache, and calls C entry point\r
+#\r
+\r
+#----------------------------------------------------------------------------\r
+#\r
+# Procedure: ProtectedModeEntryPoint\r
+#\r
+# Input: Executing in 32 Bit Protected (flat) mode\r
+# cs: 0-4GB\r
+# ds: 0-4GB\r
+# es: 0-4GB\r
+# fs: 0-4GB\r
+# gs: 0-4GB\r
+# ss: 0-4GB\r
+#\r
+# Output: This function never returns\r
+#\r
+# Destroys:\r
+# ecx\r
+# edi\r
+# esi\r
+# esp\r
+#\r
+# Description:\r
+# Perform any essential early platform initilaisation\r
+# Setup a stack\r
+#\r
+#----------------------------------------------------------------------------\r
+ProtectedModeEntryPoint:\r
+ #\r
+ # Dummy function. Consume 2 API to make sure they can be linked.\r
+ #\r
+ movl ASM_PFX(TempRamInitApi), %eax\r
+ movl ASM_PFX(FspInitApi), %eax\r
+ #\r
+ # Should never return\r
+ #\r
+ jmp . #'$'\r
+\r
+#\r
+# ROM-based Global-Descriptor Table for the PEI Phase\r
+#\r
+.align 16\r
+#\r
+# GDT[0]: 000h: Null entry, never used.\r
+#\r
+.equ NULL_SEL, . - GDT_BASE # Selector [0]\r
+GDT_BASE: \r
+BootGdtTable: \r
+ .long 0\r
+ .long 0\r
+#\r
+# Linear code segment descriptor\r
+#\r
+.equ LINEAR_CODE_SEL, . - GDT_BASE # Selector [08h]\r
+ .word 0xFFFF # limit 0FFFFh\r
+ .word 0 # base 0\r
+ .byte 0\r
+ .byte 0x9B # present, ring 0, data, expand-up, not-writable\r
+ .byte 0xCF # page-granular, 32-bit\r
+ .byte 0\r
+#\r
+# System data segment descriptor\r
+#\r
+.equ SYS_DATA_SEL, . - GDT_BASE # Selector [010h]\r
+ .word 0xFFFF # limit 0FFFFh\r
+ .word 0 # base 0\r
+ .byte 0\r
+ .byte 0x93 # present, ring 0, data, expand-up, not-writable\r
+ .byte 0xCF # page-granular, 32-bit\r
+ .byte 0\r
+\r
+.equ GDT_SIZE, . - BootGdtTable # Size, in bytes\r
+\r
+#\r
+# GDT Descriptor\r
+#\r
+GdtDesc: # GDT descriptor\r
+ .word GDT_SIZE - 1 \r
+ .long BootGdtTable \r
+\r
+ProtectedModeEntryLinearAddress:\r
+ProtectedModeEntryLinearOffset:\r
+ .long ProtectedModeEntryPoint\r
+ .word LINEAR_CODE_SEL\r
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