2018年10月14日 | Tiny4412的MMU映射代码示例

%.o:%.c

    $(Q)$(CC) $(C_FLAGS) $@ $<

.PHONY:clean

clean:

    $(Q)$(RM) $(PREFIX)/$(TARGET:=.bin) $(PREFIX)/$(VECTOR:=.bin) $(TARGET:=.o) $(VECTOR:=.o) $(TARGET) $(VECTOR) *~

=====================================================================

小页映射源码示例：

// 李柏章　Li Baizhang,  makelinux@gmail.com, 2013-08, 

#include "regs.h"

void (*printf)(char *, ...) = 0x43e11434;

void init_ttb(unsigned long *ttb_base, unsigned long *ttb_l2);

void mmap(unsigned long *ttb_base, unsigned long va, unsigned long pa);

void memset(char *buf, char ch, int size);

void main(void)

{    

    unsigned long c1_flags, ttb = 0x53000000,     //第一级页表

                                            ttb_l2 = 0x54000000; //第二级页表

    volatile int *p = 0x52345678;

    *p = 0x52300000;    

    init_ttb(ttb, ttb_l2);

    //在ttb表中把0x12345678映射到0x52345678中去

    //因为二级页面可以映射的很细腻，也可以把0x12345678映射到0x52355678中去

    mmap(ttb, 0x12345678, 0x52345678);

    c1_flags = 1  | (1 << 3) | ( 1 << 11) | (1 << 28);

    __asm__ __volatile__ (

        "mvn r0, #0 \n"            

        "mcr p15, 0, r0, c3, c0, 0\n"

        "mov r0, #0\n"

        "mcr p15, 0, r0, c7, c7, 0\n" //invalidate I & D cache ，使 I & D cache无效

        "mcr p15, 0, r0, c8, c7, 0\n" //invalidate I & D TLB，使I & D TLB无效

        "mcr p15, 0, %1, c2, c0, 0\n" //configure ttb

        "mcr p15, 0, %0, c1, c0, 0\n" //enable mmu

        :

        : "r" (c1_flags), "r" (ttb)

        : "r0"

    );

    p = 0x12345678;

    printf("*p = 0xx\n",  *p);

}

void init_ttb(unsigned long *ttb_base, unsigned long *ttb_l2)

{

    unsigned long va, pa;

    memset(ttb_base, 0x00, 16 * 1024 );        

    for (va = 0x00000000; va < 0x14000000; ttb_l2+= 0x400) {

        unsigned long to;

        ttb_base[ va >> 20] = ((unsigned long)ttb_l2 & 0xfffffc00) | 1;    

        to = va + 0x100000;

        for (  ; va < to; va += 0x1000) {

            pa = va;

            ttb_l2[(va >> 12) & 0xff] = (pa & 0xfffff000) | 2; 

        }

    }

    for (va = 0x40000000; va < 0x80000000; ttb_l2+= 0x400) {

        unsigned long to;

        ttb_base[ va >> 20] = ((unsigned long)ttb_l2 & 0xfffffc00) | 1;    

        to = va + 0x100000;

        for (  ; va < to; va += 0x1000) {

            pa = va;

            ttb_l2[(va >> 12) & 0xff] = (pa & 0xfffff000) | 2; 

        }

    }

}

void mmap(unsigned long *ttb_base, unsigned long va, unsigned long pa)

{

    ttb_base[ va >> 20] = (pa & 0xfff00000) |  2;    

}

void memset(char *buf, char ch, int size)

{

    int i;

    for (i = 0; i < size; i ++)

        buf[i] = ch;

}

====================================================================

makefile文件：

PREFIX     =  .

#EXEC_PREFIX = /usr/local/arm/arm-none-linux-gnueabi/bin/arm-none-linux-gnueabi-

EXEC_PREFIX = arm-linux-

TARGET = test

VECTOR = vector

Q    = 

AS    = $(EXEC_PREFIX)as

LD    = $(EXEC_PREFIX)ld

CC    = $(EXEC_PREFIX)gcc

OBJCOPY = $(EXEC_PREFIX)objcopy

RM    = rm -f

AS_FLAGS    = -o

C_FLAGS     = -c -o

all: $(TARGET) 

    $(Q)$(OBJCOPY) -I elf32-littlearm -O binary $(TARGET) $(PREFIX)/$(TARGET:=.bin)    

$(TARGET):$(TARGET:=.o)

    $(Q)$(LD) -Ttext=0x70003000 $< -o $@

%.o:%.S

    $(Q)$(AS) $(AS_FLAGS) $@ $<

%.o:%.c

    $(Q)$(CC) $(C_FLAGS) $@ $<

.PHONY:clean

clean:

    $(Q)$(RM) $(PREFIX)/$(TARGET:=.bin) $(PREFIX)/$(VECTOR:=.bin) $(TARGET:=.o) $(VECTOR:=.o) $(TARGET) $(VECTOR) *~

==============================================================