rt-thread-official/libcpu/ia32/start_gcc.S

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/*
* Copyright (c) 2006-2022, RT-Thread Development Team
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*
* SPDX-License-Identifier: Apache-2.0
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*
* Change Logs:
* Date Author Notes
* 2006-09-15 QiuYi The first version.
* 2012-02-15 aozima update.
*/
/* the magic number for the multiboot header. */
#define MULTIBOOT_HEADER_MAGIC 0x1BADB002
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/* the flags for the multiboot header. */
#define MULTIBOOT_HEADER_FLAGS 0x00000003
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#define CONFIG_STACKSIZE 8192
/**
* @addtogroup I386
*/
/*@{*/
.section .init, "ax"
/* the system entry */
.globl _start
_start:
jmp multiboot_entry
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/* Align 32 bits boundary. */
.align 4
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/* multiboot header. */
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multiboot_header:
/* magic */
.long MULTIBOOT_HEADER_MAGIC
/* flags */
.long MULTIBOOT_HEADER_FLAGS
/* checksum */
.long -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
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multiboot_entry:
movl $(_end + 0x1000),%esp
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/* reset eflags. */
pushl $0
popf
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/* rebuild globe describe table */
lgdt __gdtdesc
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movl $0x10,%eax
movw %ax,%ds
movw %ax,%es
movw %ax,%ss
ljmp $0x08, $relocated
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relocated:
/* push the pointer to the multiboot information structure. */
pushl %ebx
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/* push the magic value. */
pushl %eax
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call rtthread_startup
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/* never get here */
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spin:
hlt
jmp spin
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.data
.p2align 2
__gdt:
.word 0,0,0,0
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.word 0x07FF /* 8Mb - limit=2047 */
.word 0x0000
.word 0x9A00 /* code read/exec */
.word 0x00C0
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.word 0x07FF /* 8Mb - limit=2047 */
.word 0x0000
.word 0x9200 /* data read/write */
.word 0x00C0
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__gdtdesc:
.word 0x17
.long __gdt
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/*@}*/