1*4882a593Smuzhiyun/* 2*4882a593Smuzhiyun * (C) Copyright 2015 Google, Inc 3*4882a593Smuzhiyun * Written by Simon Glass <sjg@chromium.org> 4*4882a593Smuzhiyun * 5*4882a593Smuzhiyun * SPDX-License-Identifier: GPL-2.0+ 6*4882a593Smuzhiyun */ 7*4882a593Smuzhiyun 8*4882a593Smuzhiyun#include <asm/global_data.h> 9*4882a593Smuzhiyun#include <asm/msr-index.h> 10*4882a593Smuzhiyun#include <asm/processor-flags.h> 11*4882a593Smuzhiyun 12*4882a593Smuzhiyun /* 13*4882a593Smuzhiyun * rdi - 32-bit code segment selector 14*4882a593Smuzhiyun * rsi - target address 15*4882a593Smuzhiyun * rdx - table address (0 if none) 16*4882a593Smuzhiyun */ 17*4882a593Smuzhiyun.code64 18*4882a593Smuzhiyun.globl cpu_call32 19*4882a593Smuzhiyuncpu_call32: 20*4882a593Smuzhiyun cli 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun /* Save table pointer */ 23*4882a593Smuzhiyun mov %edx, %ebx 24*4882a593Smuzhiyun 25*4882a593Smuzhiyun /* 26*4882a593Smuzhiyun * Debugging option, this outputs characters to the console UART 27*4882a593Smuzhiyun * mov $0x3f8,%edx 28*4882a593Smuzhiyun * mov $'a',%al 29*4882a593Smuzhiyun * out %al,(%dx) 30*4882a593Smuzhiyun */ 31*4882a593Smuzhiyun 32*4882a593Smuzhiyun pushf 33*4882a593Smuzhiyun push %rdi /* 32-bit code segment */ 34*4882a593Smuzhiyun lea compat(%rip), %rax 35*4882a593Smuzhiyun push %rax 36*4882a593Smuzhiyun .byte 0x48 /* REX prefix to force 64-bit far return */ 37*4882a593Smuzhiyun retf 38*4882a593Smuzhiyun.code32 39*4882a593Smuzhiyuncompat: 40*4882a593Smuzhiyun /* 41*4882a593Smuzhiyun * We are now in compatibility mode with a default operand size of 42*4882a593Smuzhiyun * 32 bits. First disable paging. 43*4882a593Smuzhiyun */ 44*4882a593Smuzhiyun movl %cr0, %eax 45*4882a593Smuzhiyun andl $~X86_CR0_PG, %eax 46*4882a593Smuzhiyun movl %eax, %cr0 47*4882a593Smuzhiyun 48*4882a593Smuzhiyun /* Invalidate TLB */ 49*4882a593Smuzhiyun xorl %eax, %eax 50*4882a593Smuzhiyun movl %eax, %cr3 51*4882a593Smuzhiyun 52*4882a593Smuzhiyun /* Disable Long mode in EFER (Extended Feature Enable Register) */ 53*4882a593Smuzhiyun movl $MSR_EFER, %ecx 54*4882a593Smuzhiyun rdmsr 55*4882a593Smuzhiyun btr $_EFER_LME, %eax 56*4882a593Smuzhiyun wrmsr 57*4882a593Smuzhiyun 58*4882a593Smuzhiyun /* Set up table pointer for _x86boot_start */ 59*4882a593Smuzhiyun mov %ebx, %ecx 60*4882a593Smuzhiyun 61*4882a593Smuzhiyun /* Jump to the required target */ 62*4882a593Smuzhiyun pushl %edi /* 32-bit code segment */ 63*4882a593Smuzhiyun pushl %esi /* 32-bit target address */ 64*4882a593Smuzhiyun retf 65