9f259cc59b
In accordance with the newly formalized 32-bit boot protocol, set %ebx == %ebp == %edi == 0 in order to support future extensions to the protocol. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
57 lines
1.3 KiB
ArmAsm
57 lines
1.3 KiB
ArmAsm
/* ----------------------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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/*
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* arch/i386/boot/pmjump.S
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*
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* The actual transition into protected mode
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*/
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#include <asm/boot.h>
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#include <asm/segment.h>
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.text
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.globl protected_mode_jump
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.type protected_mode_jump, @function
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.code16
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/*
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* void protected_mode_jump(u32 entrypoint, u32 bootparams);
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*/
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protected_mode_jump:
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movl %edx, %esi # Pointer to boot_params table
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movl %eax, 2f # Patch ljmpl instruction
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movw $__BOOT_DS, %cx
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xorl %ebx, %ebx # Per the 32-bit boot protocol
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xorl %ebp, %ebp # Per the 32-bit boot protocol
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xorl %edi, %edi # Per the 32-bit boot protocol
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movl %cr0, %edx
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orb $1, %dl # Protected mode (PE) bit
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movl %edx, %cr0
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jmp 1f # Short jump to serialize on 386/486
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1:
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movw %cx, %ds
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movw %cx, %es
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movw %cx, %fs
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movw %cx, %gs
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movw %cx, %ss
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# Jump to the 32-bit entrypoint
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.byte 0x66, 0xea # ljmpl opcode
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2: .long 0 # offset
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.word __BOOT_CS # segment
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.size protected_mode_jump, .-protected_mode_jump
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