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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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2ee2394b68
Jeremy Fitzhardinge wrote: > > Maybe it really does require the far jump immediately after setting PE > in cr0... > > Hm, I don't remember this paragraph being in vol 3a, section 8.9.1 > before. Is it a recent addition? > > Random failures can occur if other instructions exist between steps > 3 and 4 above. Failures will be readily seen in some situations, > such as when instructions that reference memory are inserted between > steps 3 and 4 while in system management mode. > I don't remember that, either. Signed-off-by: Ingo Molnar <mingo@elte.hu>
83 lines
1.8 KiB
ArmAsm
83 lines
1.8 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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* 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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.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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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 in_pm32 # offset
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.word __BOOT_CS # segment
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.size protected_mode_jump, .-protected_mode_jump
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.code32
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.type in_pm32, @function
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in_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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.size in_pm32, .-in_pm32
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