pagetab.s

本程序执行了MMU初始化,使能,设置domain,目的是使0x10000000开始的地址映射到0x0处. 以便可以修改异常向量表.

;本程序执行了MMU初始化,使能,设置domain,目的是使0x10000000开始的地址映射到0x0处.
;以便可以修改异常向量表.
;如果全速执行，暂停之后，r0的内容是0x56781234，则证明发生了swi，并且正确处理了它。
; pagetab.s - pagetable definition
; Copyright (C) 1997 Advanced RISC Machines Limited.
; All Rights Reserved

; BlankPageTable defines whether 'pagetab.s' exports an empty table,
; or a completed page table. There is an identical define in
; 'encache.c', and the two should be kept in step.
		        GBLL     BlankPageTable
BlankPageTable     	SETL     {FALSE}

; Generate either a blank page table for the C code to fill in, or
; generate a full page table at assemble-time
	IF BlankPageTable
	; Generate a blank page table with the % directive

	AREA		pagetab, ALIGN=14, DATA, NOINIT
	EXPORT		pagetable

pagetable
	% 16*1024

	ELSE
	; Generate a full page table, using repetitive assembly

; Access Permissions - not shifted into position.
NO_ACCESS  * 0 ; Depending on the 'R' and 'S' bit, 0
SVC_R      * 0 ;  represents one of these access
ALL_R      * 0 ;  permissions (see A.R.M. section 7.8)
SVC_RW     * 1
NO_USR_W   * 2
ALL_ACCESS * 3

; U, C and B bits in their correct positions (see A.R.M. section 7.6.5)
U_BIT      * 16
C_BIT      * 8
B_BIT      * 4

; Entry type (see A.R.M. section 7.6.5)
SECTION    * 2
PAGE       * 1
INVALID    * 0

	MACRO
	L1Entry $type, $addr, $dom, $ucb, $acc
	[ $type = SECTION
	  DCD ( (($addr) :AND: &FFF00000) :OR: \
		(($acc) :SHL: 10) :OR: \
		(($dom) :SHL: 5) :OR: $ucb :OR: $type )
	  MEXIT
	]
	[ $type = PAGE
	  DCD ( (($addr) :AND: &FFFFFC00) :OR: \
		(($dom) :SHL: 5) :OR: \
		(($ucb) :AND: U_BIT) :OR: $type )
	|
	  DCD 0 ; Invalid Level 1 Page Table Entry
	]
	MEND

    AREA        init,CODE,READONLY
    entry
    b myrst
    b .
    b myswi
myrst 
    

    ldr  r0,= mycopystart
    ldr  r1,=pagetab
    mov  r3,#0
0
   
    
    ldrcc  r2,[r0],#4;cc/lo无符号数小于
    strcc  r2,[r1],#4
    add    r3,r3,#1
    cmp    r3,#0x100
    bcc    %b0    
    
       
    ldr   r1,=pagetab
    MCR p15,0,r1,c2,c0
    
    MRC p15,0,r1,c3,c0,0
    ldr   r1,=0xffffffff
    MCR p15,0,r1,c3,c0,0
    
    
    
    
    mrc p15,0,r0,c1,c0,0
    orr r0,r0,#01
    mcr p15,0,r0,c1,c0,0
    swi 0x12345
       
        nop
        nop
    b .
myswi
    ldr   r0,=0x56781234;如果全速执行，暂停之后，r0的内容是0x56781234，则证明发生了swi，并且正确处理了它。
    b .    
    
    ltorg
mycopystart    
	AREA        pagetab, ALIGN=14, DATA

; Create the pagetable using repetitive assembly. Creates just a table
; of "section" entries. True "page tables" would need to be created in a
; similar fashion.

	EXPORT      pagetable
pagetable
	GBLA    counter

counter SETA 0
	; area 1 - 0->16MB, cacheable
	WHILE counter < 0x100+1
	L1Entry SECTION, (0x100:SHL:20), 0, \
		U_BIT+C_BIT+B_BIT, ALL_ACCESS
counter SETA counter + 1
	WEND

	
	ENDIF
mycopyend
	END

; end of file pagetab.s