191 lines
4.1 KiB
ArmAsm
191 lines
4.1 KiB
ArmAsm
/*
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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. [According to comments etc elsewhere on a compressed
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* kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
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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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/*
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* High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
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*/
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.text
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#include <linux/linkage.h>
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#include <asm/segment.h>
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#include <asm/page.h>
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#include <asm/boot.h>
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#include <asm/asm-offsets.h>
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.section ".text.head","ax",@progbits
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.globl startup_32
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startup_32:
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cld
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/* test KEEP_SEGMENTS flag to see if the bootloader is asking
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* us to not reload segments */
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testb $(1<<6), BP_loadflags(%esi)
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jnz 1f
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cli
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movl $(__BOOT_DS),%eax
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movl %eax,%ds
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movl %eax,%es
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movl %eax,%fs
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movl %eax,%gs
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movl %eax,%ss
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1:
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/* Calculate the delta between where we were compiled to run
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* at and where we were actually loaded at. This can only be done
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* with a short local call on x86. Nothing else will tell us what
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* address we are running at. The reserved chunk of the real-mode
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* data at 0x1e4 (defined as a scratch field) are used as the stack
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* for this calculation. Only 4 bytes are needed.
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*/
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leal (0x1e4+4)(%esi), %esp
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call 1f
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1: popl %ebp
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subl $1b, %ebp
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/* %ebp contains the address we are loaded at by the boot loader and %ebx
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* contains the address where we should move the kernel image temporarily
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* for safe in-place decompression.
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*/
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#ifdef CONFIG_RELOCATABLE
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movl %ebp, %ebx
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addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebx
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andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx
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#else
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movl $LOAD_PHYSICAL_ADDR, %ebx
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#endif
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/* Replace the compressed data size with the uncompressed size */
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subl input_len(%ebp), %ebx
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movl output_len(%ebp), %eax
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addl %eax, %ebx
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/* Add 8 bytes for every 32K input block */
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shrl $12, %eax
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addl %eax, %ebx
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/* Add 32K + 18 bytes of extra slack */
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addl $(32768 + 18), %ebx
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/* Align on a 4K boundary */
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addl $4095, %ebx
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andl $~4095, %ebx
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/* Copy the compressed kernel to the end of our buffer
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* where decompression in place becomes safe.
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*/
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pushl %esi
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leal _end(%ebp), %esi
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leal _end(%ebx), %edi
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movl $(_end - startup_32), %ecx
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std
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rep
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movsb
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cld
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popl %esi
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/* Compute the kernel start address.
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*/
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#ifdef CONFIG_RELOCATABLE
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addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp
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andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp
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#else
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movl $LOAD_PHYSICAL_ADDR, %ebp
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#endif
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/*
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* Jump to the relocated address.
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*/
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leal relocated(%ebx), %eax
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jmp *%eax
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.section ".text"
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relocated:
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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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leal _edata(%ebx),%edi
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leal _end(%ebx), %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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* Setup the stack for the decompressor
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*/
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leal boot_stack_end(%ebx), %esp
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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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movl output_len(%ebx), %eax
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pushl %eax
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pushl %ebp # output address
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movl input_len(%ebx), %eax
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pushl %eax # input_len
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leal input_data(%ebx), %eax
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pushl %eax # input_data
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leal boot_heap(%ebx), %eax
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pushl %eax # heap area as third argument
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pushl %esi # real mode pointer as second arg
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call decompress_kernel
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addl $20, %esp
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popl %ecx
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#if CONFIG_RELOCATABLE
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/* Find the address of the relocations.
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*/
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movl %ebp, %edi
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addl %ecx, %edi
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/* Calculate the delta between where vmlinux was compiled to run
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* and where it was actually loaded.
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*/
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movl %ebp, %ebx
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subl $LOAD_PHYSICAL_ADDR, %ebx
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jz 2f /* Nothing to be done if loaded at compiled addr. */
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/*
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* Process relocations.
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*/
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1: subl $4, %edi
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movl 0(%edi), %ecx
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testl %ecx, %ecx
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jz 2f
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addl %ebx, -__PAGE_OFFSET(%ebx, %ecx)
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jmp 1b
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2:
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#endif
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/*
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* Jump to the decompressed kernel.
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*/
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xorl %ebx,%ebx
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jmp *%ebp
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.bss
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/* Stack and heap for uncompression */
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.balign 4
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boot_heap:
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.fill BOOT_HEAP_SIZE, 1, 0
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boot_stack:
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.fill BOOT_STACK_SIZE, 1, 0
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boot_stack_end:
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