mirror of
https://github.com/AsahiLinux/u-boot
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200182a748
Add code to jump to a 64-bit Linux kernel. We need to set up a flat page table structure, a new GDT and then go through a few hoops in the right order. Signed-off-by: Simon Glass <sjg@chromium.org>
93 lines
2.1 KiB
ArmAsm
93 lines
2.1 KiB
ArmAsm
/*
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* (C) Copyright 2014 Google, Inc
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* Copyright (C) 1991, 1992, 1993 Linus Torvalds
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*
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* Parts of this copied from Linux arch/x86/boot/compressed/head_64.S
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#include <asm/global_data.h>
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#include <asm/msr-index.h>
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#include <asm/processor-flags.h>
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.code32
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.globl cpu_call64
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cpu_call64:
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/*
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* cpu_call64(ulong pgtable, ulong setup_base, ulong target)
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*
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* eax - pgtable
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* edx - setup_base
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* ecx - target
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*/
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cli
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push %ecx /* arg2 = target */
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push %edx /* arg1 = setup_base */
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mov %eax, %ebx
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/* Load new GDT with the 64bit segments using 32bit descriptor */
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leal gdt, %eax
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movl %eax, gdt+2
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lgdt gdt
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/* Enable PAE mode */
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movl $(X86_CR4_PAE), %eax
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movl %eax, %cr4
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/* Enable the boot page tables */
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leal (%ebx), %eax
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movl %eax, %cr3
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/* Enable Long mode in EFER (Extended Feature Enable Register) */
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movl $MSR_EFER, %ecx
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rdmsr
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btsl $_EFER_LME, %eax
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wrmsr
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/* After gdt is loaded */
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xorl %eax, %eax
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lldt %ax
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movl $0x20, %eax
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ltr %ax
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/*
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* Setup for the jump to 64bit mode
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*
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* When the jump is performed we will be in long mode but
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* in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1
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* (and in turn EFER.LMA = 1). To jump into 64bit mode we use
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* the new gdt/idt that has __KERNEL_CS with CS.L = 1.
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* We place all of the values on our mini stack so lret can
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* used to perform that far jump. See the gdt below.
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*/
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pop %esi /* setup_base */
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pushl $0x10
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leal lret_target, %eax
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pushl %eax
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/* Enter paged protected Mode, activating Long Mode */
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movl $(X86_CR0_PG | X86_CR0_PE), %eax
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movl %eax, %cr0
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/* Jump from 32bit compatibility mode into 64bit mode. */
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lret
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code64:
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lret_target:
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pop %eax /* target */
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mov %eax, %eax /* Clear bits 63:32 */
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jmp *%eax /* Jump to the 64-bit target */
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.data
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gdt:
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.word gdt_end - gdt
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.long gdt
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.word 0
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.quad 0x0000000000000000 /* NULL descriptor */
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.quad 0x00af9a000000ffff /* __KERNEL_CS */
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.quad 0x00cf92000000ffff /* __KERNEL_DS */
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.quad 0x0080890000000000 /* TS descriptor */
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.quad 0x0000000000000000 /* TS continued */
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gdt_end:
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