diff options
Diffstat (limited to 'IntelFspPkg/Library/SecFspSecPlatformLibNull/Ia32/Flat32.s')
| -rw-r--r-- | IntelFspPkg/Library/SecFspSecPlatformLibNull/Ia32/Flat32.s | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/IntelFspPkg/Library/SecFspSecPlatformLibNull/Ia32/Flat32.s b/IntelFspPkg/Library/SecFspSecPlatformLibNull/Ia32/Flat32.s new file mode 100644 index 0000000000..4136e7646e --- /dev/null +++ b/IntelFspPkg/Library/SecFspSecPlatformLibNull/Ia32/Flat32.s @@ -0,0 +1,171 @@ +#------------------------------------------------------------------------------
+#
+# Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
+# This program and the accompanying materials
+# are licensed and made available under the terms and conditions of the BSD License
+# which accompanies this distribution. The full text of the license may be found at
+# http://opensource.org/licenses/bsd-license.php.
+#
+# THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+# WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+#
+# Abstract:
+#
+# This is the code that goes from real-mode to protected mode.
+# It consumes the reset vector, configures the stack.
+#
+#------------------------------------------------------------------------------
+
+
+#
+# Contrary to the name, this file contains 16 bit code as well.
+#
+.text
+#----------------------------------------------------------------------------
+#
+# Procedure: _ModuleEntryPoint
+#
+# Input: None
+#
+# Output: None
+#
+# Destroys: Assume all registers
+#
+# Description:
+#
+# Transition to non-paged flat-model protected mode from a
+# hard-coded GDT that provides exactly two descriptors.
+# This is a bare bones transition to protected mode only
+# used for a while in PEI and possibly DXE.
+#
+# After enabling protected mode, a far jump is executed to
+# transfer to PEI using the newly loaded GDT.
+#
+# Return: None
+#
+#----------------------------------------------------------------------------
+ASM_GLOBAL ASM_PFX(_ModuleEntryPoint)
+ASM_PFX(_ModuleEntryPoint):
+
+ #
+ # Load the GDT table in GdtDesc
+ #
+ .byte 0x66,0xbe #movl $GdtDesc, %esi
+ .long GdtDesc
+
+ .byte 0x66,0x2e,0x0f,0x01,0x14 #lgdt %cs:(%si)
+
+ #
+ # Transition to 16 bit protected mode
+ #
+ .byte 0x0f,0x20,0xc0 #movl %cr0, %eax # Get control register 0
+ .byte 0x66,0x83,0xc8,0x03 #orl $0x0000003, %eax # Set PE bit (bit #0) & MP bit (bit #1)
+ .byte 0x0f,0x22,0xc0 #movl %eax, %cr0 # Activate protected mode
+
+ #
+ # Now we're in 16 bit protected mode
+ # Set up the selectors for 32 bit protected mode entry
+ #
+ .byte 0xb8 #movw SYS_DATA_SEL, %ax
+ .word SYS_DATA_SEL
+
+ .byte 0x8e,0xd8 #movw %ax, %ds
+ .byte 0x8e,0xc0 #movw %ax, %es
+ .byte 0x8e,0xe0 #movw %ax, %fs
+ .byte 0x8e,0xe8 #movw %ax, %gs
+ .byte 0x8e,0xd0 #movw %ax, %ss
+
+ #
+ # Transition to Flat 32 bit protected mode
+ # The jump to a far pointer causes the transition to 32 bit mode
+ #
+ .byte 0x66,0xbe #movl ProtectedModeEntryLinearAddress, %esi
+ .long ProtectedModeEntryLinearAddress
+ .byte 0x66,0x2e,0xff,0x2c #jmp %cs:(%esi)
+
+#
+# Protected mode portion initializes stack, configures cache, and calls C entry point
+#
+
+#----------------------------------------------------------------------------
+#
+# Procedure: ProtectedModeEntryPoint
+#
+# Input: Executing in 32 Bit Protected (flat) mode
+# cs: 0-4GB
+# ds: 0-4GB
+# es: 0-4GB
+# fs: 0-4GB
+# gs: 0-4GB
+# ss: 0-4GB
+#
+# Output: This function never returns
+#
+# Destroys:
+# ecx
+# edi
+# esi
+# esp
+#
+# Description:
+# Perform any essential early platform initilaisation
+# Setup a stack
+#
+#----------------------------------------------------------------------------
+ProtectedModeEntryPoint:
+ #
+ # Dummy function. Consume 2 API to make sure they can be linked.
+ #
+ movl ASM_PFX(TempRamInitApi), %eax
+ movl ASM_PFX(FspInitApi), %eax
+ #
+ # Should never return
+ #
+ jmp . #'$'
+
+#
+# ROM-based Global-Descriptor Table for the PEI Phase
+#
+.align 16
+#
+# GDT[0]: 000h: Null entry, never used.
+#
+.equ NULL_SEL, . - GDT_BASE # Selector [0]
+GDT_BASE:
+BootGdtTable:
+ .long 0
+ .long 0
+#
+# Linear code segment descriptor
+#
+.equ LINEAR_CODE_SEL, . - GDT_BASE # Selector [08h]
+ .word 0xFFFF # limit 0FFFFh
+ .word 0 # base 0
+ .byte 0
+ .byte 0x9B # present, ring 0, data, expand-up, not-writable
+ .byte 0xCF # page-granular, 32-bit
+ .byte 0
+#
+# System data segment descriptor
+#
+.equ SYS_DATA_SEL, . - GDT_BASE # Selector [010h]
+ .word 0xFFFF # limit 0FFFFh
+ .word 0 # base 0
+ .byte 0
+ .byte 0x93 # present, ring 0, data, expand-up, not-writable
+ .byte 0xCF # page-granular, 32-bit
+ .byte 0
+
+.equ GDT_SIZE, . - BootGdtTable # Size, in bytes
+
+#
+# GDT Descriptor
+#
+GdtDesc: # GDT descriptor
+ .word GDT_SIZE - 1
+ .long BootGdtTable
+
+ProtectedModeEntryLinearAddress:
+ProtectedModeEntryLinearOffset:
+ .long ProtectedModeEntryPoint
+ .word LINEAR_CODE_SEL
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