1/* 2 * Copyright (C) 2017, Bin Meng <bmeng.cn@gmail.com> 3 * 4 * From coreboot src/arch/x86/wakeup.S 5 * 6 * SPDX-License-Identifier: GPL-2.0+ 7 */ 8 9#include <asm/acpi_s3.h> 10#include <asm/processor.h> 11#include <asm/processor-flags.h> 12 13#define RELOCATED(x) ((x) - __wakeup + WAKEUP_BASE) 14 15#define CODE_SEG (X86_GDT_ENTRY_16BIT_CS * X86_GDT_ENTRY_SIZE) 16#define DATA_SEG (X86_GDT_ENTRY_16BIT_DS * X86_GDT_ENTRY_SIZE) 17 18 .code32 19 .globl __wakeup 20__wakeup: 21 /* First prepare the jmp to the resume vector */ 22 mov 0x4(%esp), %eax /* vector */ 23 /* last 4 bits of linear addr are taken as offset */ 24 andw $0x0f, %ax 25 movw %ax, (__wakeup_offset) 26 mov 0x4(%esp), %eax 27 /* the rest is taken as segment */ 28 shr $4, %eax 29 movw %ax, (__wakeup_segment) 30 31 /* Activate the right segment descriptor real mode */ 32 ljmp $CODE_SEG, $RELOCATED(1f) 331: 34 /* 16 bit code from here on... */ 35 .code16 36 37 /* 38 * Load the segment registers w/ properly configured segment 39 * descriptors. They will retain these configurations (limits, 40 * writability, etc.) once protected mode is turned off. 41 */ 42 mov $DATA_SEG, %ax 43 mov %ax, %ds 44 mov %ax, %es 45 mov %ax, %fs 46 mov %ax, %gs 47 mov %ax, %ss 48 49 /* Turn off protection */ 50 movl %cr0, %eax 51 andl $~X86_CR0_PE, %eax 52 movl %eax, %cr0 53 54 /* Now really going into real mode */ 55 ljmp $0, $RELOCATED(1f) 561: 57 movw $0x0, %ax 58 movw %ax, %ds 59 movw %ax, %es 60 movw %ax, %ss 61 movw %ax, %fs 62 movw %ax, %gs 63 64 /* 65 * This is a FAR JMP to the OS waking vector. 66 * The C code changes the address to be correct. 67 */ 68 .byte 0xea 69 70__wakeup_offset = RELOCATED(.) 71 .word 0x0000 72 73__wakeup_segment = RELOCATED(.) 74 .word 0x0000 75 76 .globl __wakeup_size 77__wakeup_size: 78 .long . - __wakeup 79