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freebsd
GitHub Repository: freebsd/freebsd-src
 Path: blob/main/stand/i386/libi386/amd64_tramp.S
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/*-

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 * Copyright (c) 2003  Peter Wemm <[email protected]>

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 * All rights reserved.

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 *

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 * Redistribution and use in source and binary forms, with or without

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 * modification, are permitted provided that the following conditions

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 * are met:

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 * 1. Redistributions of source code must retain the above copyright

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 *    notice, this list of conditions and the following disclaimer.

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 * 2. Redistributions in binary form must reproduce the above copyright

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 *    notice, this list of conditions and the following disclaimer in the

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 *    documentation and/or other materials provided with the distribution.

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 *

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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND

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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

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 * SUCH DAMAGE.

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 */

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/*

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 * Quick and dirty trampoline to get into 64 bit (long) mode and running

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 * with paging enabled so that we enter the kernel at its linked address.

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 */

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#define MSR_EFER	0xc0000080

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#define EFER_LME	0x00000100

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#define CR4_PAE		0x00000020

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#define CR4_PSE		0x00000010

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#define CR0_PG		0x80000000

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/* GRRR. Deal with BTX that links us for a non-zero location */

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#define VPBASE	0xa000

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#define VTOP(x)	((x) + VPBASE)

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	.data

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	.p2align 12,0x40

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	.globl	PT4

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PT4:

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	.space	0x1000

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	.globl	PT3

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PT3:

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	.space	0x1000

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	.globl	PT2

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PT2:

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	.space	0x1000

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gdtdesc:

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	.word	gdtend - gdt

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	.long	VTOP(gdt)		# low

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	.long	0			# high

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gdt:

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	.long	0			# null descriptor

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	.long	0

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	.long	0x00000000		# %cs

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	.long	0x00209800

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	.long	0x00000000		# %ds

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	.long	0x00008000

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gdtend:

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	.text

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	.code32

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	.globl	amd64_tramp

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amd64_tramp:

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	/* Be sure that interrupts are disabled */

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	cli

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	/* Turn on EFER.LME */

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	movl	$MSR_EFER, %ecx

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	rdmsr

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	orl	$EFER_LME, %eax

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	wrmsr

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	/* Turn on PAE */

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	movl	%cr4, %eax

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	orl	$CR4_PAE, %eax

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	movl	%eax, %cr4

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	/* Set %cr3 for PT4 */

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	movl	$VTOP(PT4), %eax

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	movl	%eax, %cr3

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	/* Turn on paging (implicitly sets EFER.LMA) */

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	movl	%cr0, %eax

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	orl	$CR0_PG, %eax

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	movl	%eax, %cr0

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	/* Now we're in compatibility mode. set %cs for long mode */

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	movl	$VTOP(gdtdesc), %eax

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	movl	VTOP(entry_hi), %esi

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	movl	VTOP(entry_lo), %edi

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	lgdt	(%eax)

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	ljmp	$0x8, $VTOP(longmode)

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	.code64

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longmode:

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	/* We're still running V=P, jump to entry point */

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	movl	%esi, %eax

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	salq	$32, %rax

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	orq	%rdi, %rax

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	pushq	%rax

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	ret

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