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

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 * Copyright (c) 2013 The FreeBSD Foundation

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 * Copyright (c) 2023 Ahmad Khalifa <[email protected]>

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 *

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 * This software was developed by Benno Rice under sponsorship from

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 * the FreeBSD Foundation.

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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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#include <machine/asmacros.h>

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	.text

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	.globl	amd64_tramp

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/*

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 * void amd64_tramp(uint32_t stack, void *copy_finish, uint32_t kernend,

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 * 		    uint32_t modulep, uint32_t pagetable, uint32_t gdtr, uint64_t entry)

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 */

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amd64_tramp:

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	cli	/* Make sure we don't get interrupted. */

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	calll *8(%esp)	/* Call copy_finish so we're all ready to go. */

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	movl %cr0, %eax	/* Paging may be enabled, disable it. */

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	andl $0x7FFFFFFF, %eax

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	movl %eax, %cr0

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	movl %cr4, %eax	/* PAE may be disabled, enable it. */

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	orl $0x20, %eax

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	movl %eax, %cr4

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	movl 20(%esp), %eax	/* Swap page tables. */

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	movl %eax, %cr3

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	movl $0xC0000080, %ecx	/* Enable long mode. */

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	rdmsr

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	orl $0x100, %eax

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	wrmsr

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	movl 12(%esp), %edi	/* Stash the kernel and GDT values for later. */

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	movl 16(%esp), %esi

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	movl 24(%esp), %ebx

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	movl 28(%esp), %edx

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	movl 32(%esp), %ebp

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	movl 4(%esp), %esp	/* Switch to our temporary stack. */

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	movl %cr0, %eax	/* Enable paging and enter compatibility mode. */

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	orl $0x80000000, %eax

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	movl %eax, %cr0

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	lgdtl (%ebx)	/* Load GDT. */

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	pushl %edi	/* Push kernend. */

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	pushl %esi	/* Push modulep. */

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	pushl $0x0

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	pushl %ebp	/* Push 64-bit entry address. */

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	pushl %edx

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	calll 0f	/* Find the address of ".longmode". */

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0:	popl %eax

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	addl $(.longmode-0b), %eax

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	pushl $0x8	/* Push CS. */

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	pushl %eax	/* Push the address. */

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	lretl	/* "Return" to 64-bit code. */

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	.code64

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.longmode:

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	retq	/* "Return" to kernel entry. */

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	.code32

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	ALIGN_TEXT

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amd64_tramp_end:

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	.data

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	.globl	amd64_tramp_size

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amd64_tramp_size:

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	.long	amd64_tramp_end-amd64_tramp

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