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/* SPDX-License-Identifier: GPL-2.0-only */
#define WAKEUP_BASE 0x600
#define RELOCATED(x) (x - __wakeup + WAKEUP_BASE)
/* CR0 bits */
#define PE (1 << 0)
#if ENV_X86_64
.code64
#else
.code32
#endif
.globl __wakeup
__wakeup:
#if ENV_X86_64
/* When called in x86_64 mode, the resume vector is in %rdi
* instead of the stack, save it in 4(%rsp) for the 32-bit code.
* It's OK to overwrite the return address at (%rsp) because this
* function doesn't return.
*/
mov %edi, 4(%rsp)
xor %rax,%rax
mov %ss, %ax
push %rax
mov %rsp, %rax
add $8, %rax
push %rax
pushfq
push $0x10
lea 3(%rip), %rax
push %rax
iretq
.code32
/* disable paging */
mov %cr0, %eax
btc $31, %eax
mov %eax, %cr0
/* disable long mode */
mov $0xC0000080, %ecx
rdmsr
btc $8, %eax
wrmsr
#endif
/* 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 $0x28, $RELOCATED(1f)
1:
.code16
/* 16 bit code from here on... */
/* Load the segment registers w/ properly configured
* segment descriptors. They will retain these
* configurations (limits, writability, etc.) once
* protected mode is turned off.
*/
mov $0x30, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %fs
mov %ax, %gs
mov %ax, %ss
/* Turn off protection */
movl %cr0, %eax
andl $~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 changed
* the address to be correct.
*/
.byte 0xea
__wakeup_offset = RELOCATED(.)
.word 0x0000
__wakeup_segment = RELOCATED(.)
.word 0x0000
.globl __wakeup_size
__wakeup_size:
.long . - __wakeup
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