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75 lines
1.7 KiB
75 lines
1.7 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
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/* ----------------------------------------------------------------------- * |
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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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* ----------------------------------------------------------------------- */ |
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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/processor-flags.h> |
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#include <asm/segment.h> |
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#include <linux/linkage.h> |
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.text |
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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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SYM_FUNC_START_NOALIGN(protected_mode_jump) |
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movl %edx, %esi # Pointer to boot_params table |
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xorl %ebx, %ebx |
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movw %cs, %bx |
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shll $4, %ebx |
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addl %ebx, 2f |
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jmp 1f # Short jump to serialize on 386/486 |
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1: |
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movw $__BOOT_DS, %cx |
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movw $__BOOT_TSS, %di |
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movl %cr0, %edx |
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orb $X86_CR0_PE, %dl # Protected mode |
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movl %edx, %cr0 |
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# Transition to 32-bit mode |
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.byte 0x66, 0xea # ljmpl opcode |
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2: .long .Lin_pm32 # offset |
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.word __BOOT_CS # segment |
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SYM_FUNC_END(protected_mode_jump) |
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.code32 |
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.section ".text32","ax" |
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SYM_FUNC_START_LOCAL_NOALIGN(.Lin_pm32) |
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# Set up data segments for flat 32-bit mode |
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movl %ecx, %ds |
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movl %ecx, %es |
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movl %ecx, %fs |
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movl %ecx, %gs |
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movl %ecx, %ss |
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# The 32-bit code sets up its own stack, but this way we do have |
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# a valid stack if some debugging hack wants to use it. |
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addl %ebx, %esp |
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# Set up TR to make Intel VT happy |
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ltr %di |
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# Clear registers to allow for future extensions to the |
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# 32-bit boot protocol |
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xorl %ecx, %ecx |
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xorl %edx, %edx |
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xorl %ebx, %ebx |
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xorl %ebp, %ebp |
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xorl %edi, %edi |
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# Set up LDTR to make Intel VT happy |
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lldt %cx |
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jmpl *%eax # Jump to the 32-bit entrypoint |
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SYM_FUNC_END(.Lin_pm32)
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