head.s

讲述linux的初始化过程

	lea	%a2@(PTR_TABLE_SIZE*PAGE_TABLE_SIZE*PAGESIZE),%a2
	jra	L(mmu_mapnext_030)
1:
	/* Calculate the offset into the pointer table
	 */
	movel	%a3,%d0
	moveq	#PTR_INDEX_SHIFT,%d1
	lsrl	%d1,%d0
	andl	#PTR_TABLE_SIZE-1,%d0
	mmu_get_ptr_table_entry		%a0,%d0

	/* The pointer table entry must not no be busy
	 */
	tstl	%a0@
	jne	L(mmu_map_error)

	/* Do the mapping and advance the pointers
	 */
	dputs	"early term2"
	dputn	%a2
	dputn	%a3
	dputc	'\n'
	movel	%a2,%a0@

	addl	#PAGE_TABLE_SIZE*PAGESIZE,%a2
	addl	#PAGE_TABLE_SIZE*PAGESIZE,%a3

L(mmu_mapnext_030):
	/* Ready with mapping?
	 */
	lea	%a3@(-1),%a0
	cmpl	%a0,%a4
	jhi	L(mmu_map_030)
	jra	L(mmu_map_done)

L(mmu_map_error):

	dputs	"mmu_map error:"
	dputn	%a2
	dputn	%a3
	dputc	'\n'

L(mmu_map_done):

func_return	mmu_map

/*
 *	mmu_fixup
 *
 *	On the 040 class machines, all pages that are used for the
 *	mmu have to be fixed up.
 */

func_start	mmu_fixup_page_mmu_cache,%d0/%a0

	dputs	"mmu_fixup_page_mmu_cache"
	dputn	ARG1

	/* Calculate the offset into the root table
	 */
	movel	ARG1,%d0
	moveq	#ROOT_INDEX_SHIFT,%d1
	lsrl	%d1,%d0
	mmu_get_root_table_entry	%d0

	/* Calculate the offset into the pointer table
	 */
	movel	ARG1,%d0
	moveq	#PTR_INDEX_SHIFT,%d1
	lsrl	%d1,%d0
	andl	#PTR_TABLE_SIZE-1,%d0
	mmu_get_ptr_table_entry		%a0,%d0

	/* Calculate the offset into the page table
	 */
	movel	ARG1,%d0
	moveq	#PAGE_INDEX_SHIFT,%d1
	lsrl	%d1,%d0
	andl	#PAGE_TABLE_SIZE-1,%d0
	mmu_get_page_table_entry	%a0,%d0

	movel	%a0@,%d0
	andil	#_CACHEMASK040,%d0
	orl	%pc@(SYMBOL_NAME(m68k_pgtable_cachemode)),%d0
	movel	%d0,%a0@

	dputc	'\n'

func_return	mmu_fixup_page_mmu_cache

/*
 *	mmu_temp_map
 *
 *	create a temporary mapping to enable the mmu,
 *	this we don't need any transparation translation tricks.
 */

func_start	mmu_temp_map,%d0/%d1/%a0/%a1

	dputs	"mmu_temp_map"
	dputn	ARG1
	dputn	ARG2
	dputc	'\n'

	lea	%pc@(L(temp_mmap_mem)),%a1

	/* Calculate the offset in the root table
	 */
	movel	ARG2,%d0
	moveq	#ROOT_INDEX_SHIFT,%d1
	lsrl	%d1,%d0
	mmu_get_root_table_entry	%d0

	/* Check if the table is temporary allocated, so we have to reuse it
	 */
	movel	%a0@,%d0
	cmpl	%pc@(L(memory_start)),%d0
	jcc	1f

	/* Temporary allocate a ptr table and insert it into the root table
	 */
	movel	%a1@,%d0
	addl	#PTR_TABLE_SIZE*4,%a1@
	orw	#_PAGE_TABLE+_PAGE_ACCESSED,%d0
	movel	%d0,%a0@
	dputs	" (new)"
1:
	dputn	%d0
	/* Mask the root table entry for the ptr table
	 */
	andw	#-ROOT_TABLE_SIZE,%d0
	movel	%d0,%a0

	/* Calculate the offset into the pointer table
	 */
	movel	ARG2,%d0
	moveq	#PTR_INDEX_SHIFT,%d1
	lsrl	%d1,%d0
	andl	#PTR_TABLE_SIZE-1,%d0
	lea	%a0@(%d0*4),%a0
	dputn	%a0

	/* Check if a temporary page table is already allocated
	 */
	movel	%a0@,%d0
	jne	1f

	/* Temporary allocate a page table and insert it into the ptr table
	 */
	movel	%a1@,%d0
	/* The 512 should be PAGE_TABLE_SIZE*4, but that violates the
	   alignment restriction for pointer tables on the '0[46]0.  */
	addl	#512,%a1@
	orw	#_PAGE_TABLE+_PAGE_ACCESSED,%d0
	movel	%d0,%a0@
	dputs	" (new)"
1:
	dputn	%d0
	/* Mask the ptr table entry for the page table
	 */
	andw	#-PTR_TABLE_SIZE,%d0
	movel	%d0,%a0

	/* Calculate the offset into the page table
	 */
	movel	ARG2,%d0
	moveq	#PAGE_INDEX_SHIFT,%d1
	lsrl	%d1,%d0
	andl	#PAGE_TABLE_SIZE-1,%d0
	lea	%a0@(%d0*4),%a0
	dputn	%a0

	/* Insert the address into the page table
	 */
	movel	ARG1,%d0
	andw	#-PAGESIZE,%d0
	orw	#_PAGE_PRESENT+_PAGE_ACCESSED+_PAGE_DIRTY,%d0
	movel	%d0,%a0@
	dputn	%d0

	dputc	'\n'

func_return	mmu_temp_map

func_start	mmu_engage,%d0-%d2/%a0-%a3

	moveq	#ROOT_TABLE_SIZE-1,%d0
	/* Temporarily use a different root table.  */
	lea	%pc@(L(kernel_pgdir_ptr)),%a0
	movel	%a0@,%a2
	movel	%pc@(L(memory_start)),%a1
	movel	%a1,%a0@
	movel	%a2,%a0
1:
	movel	%a0@+,%a1@+
	dbra	%d0,1b

	lea	%pc@(L(temp_mmap_mem)),%a0
	movel	%a1,%a0@

	movew	#PAGESIZE-1,%d0
1:
	clrl	%a1@+
	dbra	%d0,1b

	lea	%pc@(1b),%a0
	movel	#1b,%a1
	/* Skip temp mappings if phys == virt */
	cmpl	%a0,%a1
	jeq	1f

	mmu_temp_map	%a0,%a0
	mmu_temp_map	%a0,%a1

	addw	#PAGESIZE,%a0
	addw	#PAGESIZE,%a1
	mmu_temp_map	%a0,%a0
	mmu_temp_map	%a0,%a1
1:
	movel	%pc@(L(memory_start)),%a3
	movel	%pc@(L(phys_kernel_start)),%d2

	is_not_040_or_060(L(mmu_engage_030))

L(mmu_engage_040):
	.chip	68040
	nop
	cinva	%bc
	nop
	pflusha
	nop
	movec	%a3,%srp
	movel	#TC_ENABLE+TC_PAGE4K,%d0
	movec	%d0,%tc		/* enable the MMU */
	jmp	1f:l
1:	nop
	movec	%a2,%srp
	nop
	cinva	%bc
	nop
	pflusha
	.chip	68k
	jra	L(mmu_engage_cleanup)

L(mmu_engage_030_temp):
	.space	12
L(mmu_engage_030):
	.chip	68030
	lea	%pc@(L(mmu_engage_030_temp)),%a0
	movel	#0x80000002,%a0@
	movel	%a3,%a0@(4)
	movel	#0x0808,%d0
	movec	%d0,%cacr
	pmove	%a0@,%srp
	pflusha
	/*
	 * enable,super root enable,4096 byte pages,7 bit root index,
	 * 7 bit pointer index, 6 bit page table index.
	 */
	movel	#0x82c07760,%a0@(8)
	pmove	%a0@(8),%tc	/* enable the MMU */
	jmp	1f:l
1:	movel	%a2,%a0@(4)
	movel	#0x0808,%d0
	movec	%d0,%cacr
	pmove	%a0@,%srp
	pflusha
	.chip	68k

L(mmu_engage_cleanup):
	subl	#PAGE_OFFSET,%d2
	subl	%d2,%a2
	movel	%a2,L(kernel_pgdir_ptr)
	subl	%d2,%fp
	subl	%d2,%sp
	subl	%d2,ARG0

func_return	mmu_engage

func_start	mmu_get_root_table_entry,%d0/%a1

#if 0
	dputs	"mmu_get_root_table_entry:"
	dputn	ARG1
	dputs	" ="
#endif

	movel	%pc@(L(kernel_pgdir_ptr)),%a0
	tstl	%a0
	jne	2f

	dputs	"\nmmu_init:"

	/* Find the start of free memory, get_bi_record does this for us,
	 * as the bootinfo structure is located directly behind the kernel
	 * and and we simply search for the last entry.
	 */
	get_bi_record	BI_LAST
	addw	#PAGESIZE-1,%a0
	movel	%a0,%d0
	andw	#-PAGESIZE,%d0

	dputn	%d0

	lea	%pc@(L(memory_start)),%a0
	movel	%d0,%a0@
	lea	%pc@(L(kernel_end)),%a0
	movel	%d0,%a0@

	/* we have to return the first page at _stext since the init code
	 * in mm/init.c simply expects kernel_pg_dir there, the rest of
	 * page is used for further ptr tables in get_ptr_table.
	 */
	lea	%pc@(SYMBOL_NAME(_stext)),%a0
	lea	%pc@(L(mmu_cached_pointer_tables)),%a1
	movel	%a0,%a1@
	addl	#ROOT_TABLE_SIZE*4,%a1@

	lea	%pc@(L(mmu_num_pointer_tables)),%a1
	addql	#1,%a1@

	/* clear the page
	 */
	movel	%a0,%a1
	movew	#PAGESIZE/4-1,%d0
1:
	clrl	%a1@+
	dbra	%d0,1b

	lea	%pc@(L(kernel_pgdir_ptr)),%a1
	movel	%a0,%a1@

	dputn	%a0
	dputc	'\n'
2:
	movel	ARG1,%d0
	lea	%a0@(%d0*4),%a0

#if 0
	dputn	%a0
	dputc	'\n'
#endif

func_return	mmu_get_root_table_entry



func_start	mmu_get_ptr_table_entry,%d0/%a1

#if 0
	dputs	"mmu_get_ptr_table_entry:"
	dputn	ARG1
	dputn	ARG2
	dputs	" ="
#endif

	movel	ARG1,%a0
	movel	%a0@,%d0
	jne	2f

	/* Keep track of the number of pointer tables we use
	 */
	dputs	"\nmmu_get_new_ptr_table:"
	lea	%pc@(L(mmu_num_pointer_tables)),%a0
	movel	%a0@,%d0
	addql	#1,%a0@

	/* See if there is a free pointer table in our cache of pointer tables
	 */
	lea	%pc@(L(mmu_cached_pointer_tables)),%a1
	andw	#7,%d0
	jne	1f

	/* Get a new pointer table page from above the kernel memory
	 */
	get_new_page
	movel	%a0,%a1@
1:
	/* There is an unused pointer table in our cache... use it
	 */
	movel	%a1@,%d0
	addl	#PTR_TABLE_SIZE*4,%a1@

	dputn	%d0
	dputc	'\n'

	/* Insert the new pointer table into the root table
	 */
	movel	ARG1,%a0
	orw	#_PAGE_TABLE+_PAGE_ACCESSED,%d0
	movel	%d0,%a0@
2:
	/* Extract the pointer table entry
	 */
	andw	#-PTR_TABLE_SIZE,%d0
	movel	%d0,%a0
	movel	ARG2,%d0
	lea	%a0@(%d0*4),%a0

#if 0
	dputn	%a0
	dputc	'\n'
#endif

func_return	mmu_get_ptr_table_entry


func_start	mmu_get_page_table_entry,%d0/%a1

#if 0
	dputs	"mmu_get_page_table_entry:"
	dputn	ARG1
	dputn	ARG2
	dputs	" ="
#endif

	movel	ARG1,%a0
	movel	%a0@,%d0
	jne	2f

	/* If the page table entry doesn't exist, we allocate a complete new
	 * page and use it as one continues big page table which can cover
	 * 4MB of memory, nearly almost all mappings have that alignment.
	 */
	get_new_page
	addw	#_PAGE_TABLE+_PAGE_ACCESSED,%a0

	/* align pointer table entry for a page of page tables
	 */
	movel	ARG1,%d0
	andw	#-(PAGESIZE/PAGE_TABLE_SIZE),%d0
	movel	%d0,%a1

	/* Insert the page tables into the pointer entries
	 */
	moveq	#PAGESIZE/PAGE_TABLE_SIZE/4-1,%d0
1:
	movel	%a0,%a1@+
	lea	%a0@(PAGE_TABLE_SIZE*4),%a0
	dbra	%d0,1b

	/* Now we can get the initialized pointer table entry
	 */
	movel	ARG1,%a0
	movel	%a0@,%d0
2:
	/* Extract the page table entry
	 */
	andw	#-PAGE_TABLE_SIZE,%d0
	movel	%d0,%a0
	movel	ARG2,%d0
	lea	%a0@(%d0*4),%a0

#if 0
	dputn	%a0
	dputc	'\n'
#endif

func_return	mmu_get_page_table_entry

/*
 *	get_new_page
 *
 *	Return a new page from the memory start and clear it.
 */
func_start	get_new_page,%d0/%a1

	dputs	"\nget_new_page:"

	/* allocate the page and adjust memory_start
	 */
	lea	%pc@(L(memory_start)),%a0
	movel	%a0@,%a1
	addl	#PAGESIZE,%a0@

	/* clear the new page
	 */
	movel	%a1,%a0
	movew	#PAGESIZE/4-1,%d0
1:
	clrl	%a1@+
	dbra	%d0,1b

	dputn	%a0
	dputc	'\n'

func_return	get_new_page



/*
 * Debug output support
 * Atarians have a choice between the parallel port, the serial port
 * from the MFP or a serial port of the SCC
 */

#ifdef CONFIG_MAC

L(scc_initable_mac):
	.byte	9,12		/* Reset */
	.byte	4,0x44		/* x16, 1 stopbit, no parity */
	.byte	3,0xc0		/* receiver: 8 bpc */
	.byte	5,0xe2		/* transmitter: 8 bpc, assert dtr/rts */
	.byte	9,0		/* no interrupts */
	.byte	10,0		/* NRZ */
	.byte	11,0x50		/* use baud rate generator */
	.byte	12,10,13,0	/* 9600 baud */
	.byte	14,1		/* Baud rate generator enable */
	.byte	3,0xc1		/* enable receiver */
	.byte	5,0xea		/* enable transmitter */
	.byte	-1
	.even
#endif

#ifdef CONFIG_ATARI
/* #define USE_PRINTER */
/* #define USE_SCC_B */
/* #define USE_SCC_A */
#define USE_MFP

#if defined(USE_SCC_A) || defined(USE_SCC_B)
#define USE_SCC
/* Initialisation table for SCC */
L(scc_initable):
	.byte	9,12		/* Reset */
	.byte	4,0x44		/* x16, 1 stopbit, no parity */
	.byte	3,0xc0		/* receiver: 8 bpc */
	.byte	5,0xe2		/* transmitter: 8 bpc, assert dtr/rts */
	.byte	9,0		/* no interrupts */
	.byte	10,0		/* NRZ */
	.byte	11,0x50		/* use baud rate generator */
	.byte	12,24,13,0	/* 9600 baud */
	.byte	14,2,14,3	/* use master clock for BRG, enable */
	.byte	3,0xc1		/* enable receiver */
	.byte	5,0xea		/* enable transmitter */
	.byte	-1
	.even
#endif

#i