59 lines
1.2 KiB
ArmAsm
59 lines
1.2 KiB
ArmAsm
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/*
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* linux/boot/head.S
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*
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* Copyright (C) 1991, 1992, 1993 Linus Torvalds
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*/
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/*
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* head.S contains the 32-bit startup code.
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*
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* NOTE!!! Startup happens at absolute address 0x00001000, which is also where
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* the page directory will exist. The startup code will be overwritten by
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* the page directory.
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*
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* Page 0 is deliberately kept safe, since System Management Mode code in
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* laptops may need to access the BIOS data stored there. This is also
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* useful for future device drivers that either access the BIOS via VM86
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* mode.
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*/
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.text
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#include <linux/segment.h>
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startup_32:
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cld
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cli
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movl $(KERNEL_DS),%eax
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mov %ax,%ds
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mov %ax,%es
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mov %ax,%fs
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mov %ax,%gs
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lss _stack_start,%esp
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xorl %eax,%eax
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1: incl %eax # check that A20 really IS enabled
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movl %eax,0x000000 # loop forever if it isn't
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cmpl %eax,0x100000
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je 1b
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/*
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* Initialize eflags. Some BIOS's leave bits like NT set. This would
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* confuse the debugger if this code is traced.
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* XXX - best to initialize before switching to protected mode.
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*/
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pushl $0
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popfl
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/*
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* Clear BSS
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*/
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xorl %eax,%eax
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movl $__edata,%edi
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movl $__end,%ecx
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subl %edi,%ecx
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cld
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rep
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stosb
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/*
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* Do the decompression, and jump to the new kernel..
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*/
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call _decompress_kernel
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ljmp $(KERNEL_CS), $0x100000
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