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/*
* (C) Copyright 2015 Google, Inc
* Written by Simon Glass <sjg@chromium.org>
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <asm/global_data.h>
#include <asm/msr-index.h>
#include <asm/processor-flags.h>
/*
* rdi - 32-bit code segment selector
* rsi - target address
* rdx - table address (0 if none)
*/
.code64
.globl cpu_call32
cpu_call32:
cli
/* Save table pointer */
mov %edx, %ebx
/*
* Debugging option, this outputs characters to the console UART
* mov $0x3f8,%edx
* mov $'a',%al
* out %al,(%dx)
*/
pushf
push %rdi /* 32-bit code segment */
lea compat(%rip), %rax
push %rax
.byte 0x48 /* REX prefix to force 64-bit far return */
retf
.code32
compat:
/*
* We are now in compatibility mode with a default operand size of
* 32 bits. First disable paging.
*/
movl %cr0, %eax
andl $~X86_CR0_PG, %eax
movl %eax, %cr0
/* Invalidate TLB */
xorl %eax, %eax
movl %eax, %cr3
/* Disable Long mode in EFER (Extended Feature Enable Register) */
movl $MSR_EFER, %ecx
rdmsr
btr $_EFER_LME, %eax
wrmsr
/* Set up table pointer for _x86boot_start */
mov %ebx, %ecx
/* Jump to the required target */
pushl %edi /* 32-bit code segment */
pushl %esi /* 32-bit target address */
retf
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