1 /* SPDX-License-Identifier: GPL-2.0+ */ 2 /* 3 * Copyright (C) 2017, Bin Meng <bmeng.cn (at) gmail.com> 4 * 5 * From coreboot src/arch/x86/wakeup.S 6 */ 7 8 #include <asm/acpi_s3.h> 9 #include <asm/processor.h> 10 #include <asm/processor-flags.h> 11 12 #define RELOCATED(x) ((x) - __wakeup + WAKEUP_BASE) 13 14 #define CODE_SEG (X86_GDT_ENTRY_16BIT_CS * X86_GDT_ENTRY_SIZE) 15 #define DATA_SEG (X86_GDT_ENTRY_16BIT_DS * X86_GDT_ENTRY_SIZE) 16 17 .code32 18 .globl __wakeup 19 __wakeup: 20 /* First prepare the jmp to the resume vector */ 21 mov 0x4(%esp), %eax /* vector */ 22 /* last 4 bits of linear addr are taken as offset */ 23 andw $0x0f, %ax 24 movw %ax, (__wakeup_offset) 25 mov 0x4(%esp), %eax 26 /* the rest is taken as segment */ 27 shr $4, %eax 28 movw %ax, (__wakeup_segment) 29 30 /* Activate the right segment descriptor real mode */ 31 ljmp $CODE_SEG, $RELOCATED(1f) 32 1: 33 /* 16 bit code from here on... */ 34 .code16 35 36 /* 37 * Load the segment registers w/ properly configured segment 38 * descriptors. They will retain these configurations (limits, 39 * writability, etc.) once protected mode is turned off. 40 */ 41 mov $DATA_SEG, %ax 42 mov %ax, %ds 43 mov %ax, %es 44 mov %ax, %fs 45 mov %ax, %gs 46 mov %ax, %ss 47 48 /* Turn off protection */ 49 movl %cr0, %eax 50 andl $~X86_CR0_PE, %eax 51 movl %eax, %cr0 52 53 /* Now really going into real mode */ 54 ljmp $0, $RELOCATED(1f) 55 1: 56 movw $0x0, %ax 57 movw %ax, %ds 58 movw %ax, %es 59 movw %ax, %ss 60 movw %ax, %fs 61 movw %ax, %gs 62 63 /* 64 * This is a FAR JMP to the OS waking vector. 65 * The C code changes the address to be correct. 66 */ 67 .byte 0xea 68 69 __wakeup_offset = RELOCATED(.) 70 .word 0x0000 71 72 __wakeup_segment = RELOCATED(.) 73 .word 0x0000 74 75 .globl __wakeup_size 76 __wakeup_size: 77 .long . - __wakeup 78
