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Project/Src/rt-thread/libcpu/ia32/start_gcc.S

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+/*
+ * File      : start.S
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2006 - 2012, RT-Thread Development Team
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rt-thread.org/license/LICENSE
+ *
+ * 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
+
+/* the flags for the multiboot header.  */
+#define MULTIBOOT_HEADER_FLAGS		0x00000003
+
+#define CONFIG_STACKSIZE            8192
+
+/**
+ * @addtogroup I386
+ */
+/*@{*/
+
+.section .init, "ax"
+
+/* the system entry */
+.globl _start
+_start:
+	jmp	multiboot_entry
+
+	/* Align 32 bits boundary.  */
+	.align	4
+
+	/* multiboot header.  */
+multiboot_header:
+	/* magic */
+	.long	MULTIBOOT_HEADER_MAGIC
+	/* flags */
+	.long	MULTIBOOT_HEADER_FLAGS
+	/* checksum */
+	.long	-(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
+
+multiboot_entry:
+	movl	$(_end + 0x1000),%esp
+
+	/* reset eflags.  */
+	pushl	$0
+	popf
+
+	/*rebuild globe describe table*/
+	lgdt	mygdtdesc
+
+	movl	$0x10,%eax
+	movw	%ax,%ds
+	movw	%ax,%es
+	movw	%ax,%ss
+	ljmp	$0x08, $relocated
+
+relocated:
+	/* push the pointer to the multiboot information structure.  */
+	pushl	%ebx
+
+	/* push the magic value.  */
+	pushl	%eax
+
+	call	rtthread_startup
+
+	/* never get here */
+spin:
+	hlt
+	jmp	spin
+
+.data
+.p2align	2
+mygdt:
+	.word	0,0,0,0
+
+	.word	0x07FF		/* 8Mb - limit=2047 */
+	.word	0x0000
+	.word	0x9A00		/* code read/exec */
+	.word	0x00C0
+
+	.word	0x07FF		/* 8Mb - limit=2047 */
+	.word	0x0000
+	.word	0x9200		/* data read/write */
+	.word	0x00C0
+
+mygdtdesc:
+	.word	0x17
+	.long	mygdt
+
+/*@}*/