diff options
Diffstat (limited to 'arch/x86/cpu/wakeup.S')
| -rw-r--r-- | arch/x86/cpu/wakeup.S | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/arch/x86/cpu/wakeup.S b/arch/x86/cpu/wakeup.S new file mode 100644 index 0000000..066c9b1 --- /dev/null +++ b/arch/x86/cpu/wakeup.S @@ -0,0 +1,78 @@ +/* + * Copyright (C) 2017, Bin Meng <bmeng.cn@gmail.com> + * + * From coreboot src/arch/x86/wakeup.S + * + * SPDX-License-Identifier: GPL-2.0+ + */ + +#include <asm/acpi_s3.h> +#include <asm/processor.h> +#include <asm/processor-flags.h> + +#define RELOCATED(x) ((x) - __wakeup + WAKEUP_BASE) + +#define CODE_SEG (X86_GDT_ENTRY_16BIT_CS * X86_GDT_ENTRY_SIZE) +#define DATA_SEG (X86_GDT_ENTRY_16BIT_DS * X86_GDT_ENTRY_SIZE) + + .code32 + .globl __wakeup +__wakeup: + /* First prepare the jmp to the resume vector */ + mov 0x4(%esp), %eax /* vector */ + /* last 4 bits of linear addr are taken as offset */ + andw $0x0f, %ax + movw %ax, (__wakeup_offset) + mov 0x4(%esp), %eax + /* the rest is taken as segment */ + shr $4, %eax + movw %ax, (__wakeup_segment) + + /* Activate the right segment descriptor real mode */ + ljmp $CODE_SEG, $RELOCATED(1f) +1: + /* 16 bit code from here on... */ + .code16 + + /* + * Load the segment registers w/ properly configured segment + * descriptors. They will retain these configurations (limits, + * writability, etc.) once protected mode is turned off. + */ + mov $DATA_SEG, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + mov %ax, %ss + + /* Turn off protection */ + movl %cr0, %eax + andl $~X86_CR0_PE, %eax + movl %eax, %cr0 + + /* Now really going into real mode */ + ljmp $0, $RELOCATED(1f) +1: + movw $0x0, %ax + movw %ax, %ds + movw %ax, %es + movw %ax, %ss + movw %ax, %fs + movw %ax, %gs + + /* + * This is a FAR JMP to the OS waking vector. + * The C code changes the address to be correct. + */ + .byte 0xea + +__wakeup_offset = RELOCATED(.) + .word 0x0000 + +__wakeup_segment = RELOCATED(.) + .word 0x0000 + + .globl __wakeup_size +__wakeup_size: + .long . - __wakeup |