linux_dev_学习笔记_内存映射nopage()

2012年3月25日  Sunday

 

1、内核版本号2.6.33.20

 

2、nopage()实例

 

1）与上篇中remap_pfn_range()一样在书中的实例的实现也有所不同

 

2）struct vm_operations_struct

①在2.6.23之前struct vm_operations_struct中只有

struct page * (*nopage)(struct vm_area_struct * area, unsigned long address, int *type)

从2.6.24后在struct vm_operations_struct中的出现

int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf)

并在一段时间里，内核同时支持这两个函数，但后面的内核版本取消了

struct page * (*nopage)(struct vm_area_struct * area, unsigned long address, int *type)

在内核2.6.33.20中就取消了该函数

 

②int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf)中struct vm_fault结构体

struct vm_fault {
        unsigned int flags; /* FAULT_FLAG_xxx flags */
        pgoff_t pgoff; /* Logical page offset based on vma */
        void __user *virtual_address; /* Faulting virtual address */

        struct page *page; /* ->fault handlers should return a
                                         * page here, unless VM_FAULT_NOPAGE
                                         * is set (which is also implied by
                                         * VM_FAULT_ERROR).
                                         */
};

③为了在2.6.33上编译运行,修改书中代码

 

书中实例代码

int mmapnopage_vm_nopage(struct vm_area_struct *vma,
            unsigned long addr,
            int *type)/*修改行*/
{
    struct page *page;
    unsigned long offset;
    void *page_ptr;

    printk("\n");
    printk("CALL NOPAGE %08x\n",addr);
    /*printk("%-25s %08x\n","1)vma->flags",vmf->flags);
    printk("%-25s %08x\n","2)vmf->pgoff",vmf->pgoff);
    printk("%-25s %08x\n","3)vmf->virtual_address",vmf->virtual_address);
    printk("%-25s %08x\n","4)vma->vm_start",vma->vm_start);
    printk("%-25s %08x\n","5)vma->vm_end",vma->vm_end);
    printk("%-25s %08x\n","6)vma->vm_pgoff",vma->vm_pgoff);
    printk("%-25s %d\n","7)PAGE_SHIFT",PAGE_SHIFT);*/

    page=NOPAGE_SIGBUS;/*修改行*/
    page_ptr=NULL;

    if((NULL==vma)||(NULL==share_memory)){
        printk("return NOPAGE_SIGBUS!\n");
        return NOPAGE_SIGBUS;/*修改行*/
    }

    offset=addr-vma->vm_start;/*修改行*/

    if(offset>=SHARE_MEM_SIZE){
        printk("return NOPAGE_SIGBUS!\n");
        return NOPAGE_SIGBUS;/*修改行*/
    }

    page_ptr=share_memory+offset;
    page=vmalloc_to_page(page_ptr);
    get_page(page);

    if(type) *type=VM_FAULT_MINOR;/*修改行*/

    return page;/*修改行*/
}

struct vm_operations_struct mmapnopage_vm_ops={
    .nopage=mmapnopage_vm_nopage,/*修改行*/
};

修改后实例代码

int mmapnopage_vm_fault(struct vm_area_struct *vma,
            struct vm_fault *vmf)/*修改行*/
{
    struct page *page;
    unsigned long offset;
    void *page_ptr;

    printk("\n");
    /*printk("CALL NOPAGE %08x\n",addr);*/
    printk("%-25s %08x\n","1)vma->flags",vmf->flags);
    printk("%-25s %08x\n","2)vmf->pgoff",vmf->pgoff);
    printk("%-25s %08x\n","3)vmf->virtual_address",vmf->virtual_address);
    printk("%-25s %08x\n","4)vma->vm_start",vma->vm_start);
    printk("%-25s %08x\n","5)vma->vm_end",vma->vm_end);
    printk("%-25s %08x\n","6)vma->vm_pgoff",vma->vm_pgoff);
    /*printk("%-25s %d\n","7)PAGE_SHIFT",PAGE_SHIFT);*/

    page_ptr=NULL;

    if((NULL==vma)||(NULL==share_memory)){
        printk("return VM_FAULT_SIGBUS!\n");
        return VM_FAULT_SIGBUS;/*修改行*/
    }

    offset=vmf->virtual_address-vma->vm_start;/*修改行*/

    if(offset>=SHARE_MEM_SIZE){
        printk("return VM_FAULT_SIGBUS!");
        return VM_FAULT_SIGBUS;/*修改行*/
    }

    page_ptr=share_memory+offset;
    page=vmalloc_to_page(page_ptr);
    get_page(page);

    vmf->page=page;/*修改行*/

    return 0;/*修改行*/
}

struct vm_operations_struct mmapnopage_vm_ops={
    .fault=mmapnopage_vm_fault,
};

3、驱动模块源文件mmapnopage_dev.c

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fcntl.h>

#include <linux/vmalloc.h>
#include <linux/uaccess.h>
#include <linux/io.h>

#include <asm/page.h>
#include <linux/mm.h>

#define MMAPNOPAGE_DEV_NAME "mmapnopage"
#define MMAPNOPAGE_DEV_MAJOR 240

#define SHARE_MEM_PAGE_COUNT 4
#define SHARE_MEM_SIZE (PAGE_SIZE*SHARE_MEM_PAGE_COUNT)

char *share_memory=NULL;



int mmapnopage_vm_fault(struct vm_area_struct *vma,
            struct vm_fault *vmf)
{
    struct page *page;
    unsigned long offset;
    void *page_ptr;

    printk("\n");
    printk("%-25s %08x\n","1)vma->flags",vmf->flags);
    printk("%-25s %08x\n","2)vmf->pgoff",vmf->pgoff);
    printk("%-25s %08x\n","3)vmf->virtual_address",vmf->virtual_address);
    printk("%-25s %08x\n","4)vma->vm_start",vma->vm_start);
    printk("%-25s %08x\n","5)vma->vm_end",vma->vm_end);
    printk("%-25s %08x\n","6)vma->vm_pgoff",vma->vm_pgoff);
    /*printk("%-25s %d\n","7)PAGE_SHIFT",PAGE_SHIFT);*/

    page_ptr=NULL;

    if((NULL==vma)||(NULL==share_memory)){
        printk("return VM_FAULT_SIGBUS!\n");
        return VM_FAULT_SIGBUS;
    }

    offset=vmf->virtual_address-vma->vm_start;

    if(offset>=SHARE_MEM_SIZE){
        printk("return VM_FAULT_SIGBUS!");
        return VM_FAULT_SIGBUS;
    }

    page_ptr=share_memory+offset;
    page=vmalloc_to_page(page_ptr);
    get_page(page);

    vmf->page=page;

    return 0;
}

struct vm_operations_struct mmapnopage_vm_ops={
    .fault=mmapnopage_vm_fault,
};

int mmapnopage_mmap(struct file *filp,struct vm_area_struct *vma)
{
    vma->vm_flags |= VM_RESERVED;
    vma->vm_ops=&mmapnopage_vm_ops;
    return 0;
}

struct file_operations mmapnopage_fops={
    .owner=THIS_MODULE,
    .mmap=mmapnopage_mmap,
};

int mmapnopage_init(void)
{
    int lp;
    int result;

    result=register_chrdev(MMAPNOPAGE_DEV_MAJOR,
                MMAPNOPAGE_DEV_NAME,
                &mmapnopage_fops);
    if(result<0){
        return result;
    }

    share_memory=vmalloc(SHARE_MEM_SIZE);
    for(lp=0;lp<SHARE_MEM_PAGE_COUNT;lp++){
        sprintf(share_memory+PAGE_SIZE*lp,"TEST %d",lp);
    }
    return 0;
}

void mmapnopage_exit(void)
{
    if(share_memory!=NULL){
        vfree(share_memory);
    }
    unregister_chrdev(MMAPNOPAGE_DEV_MAJOR,
            MMAPNOPAGE_DEV_NAME);
}

module_init(mmapnopage_init);
module_exit(mmapnopage_exit);

MODULE_LICENSE("Dual BSD/GPL");

4、Makefile

obj-m += mmapnopage_dev.o

CURRENT_PATH := $(shell pwd)

LINUX_KERNEL := $(shell uname -r)

LINUX_KERNEL_PATH := /usr/src/linux-$(LINUX_KERNEL)

all:
    make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules
clean:
    #make -C $(LINUX_KERNEL_PAHT) M=$(CURRENT_PATH) clean
    rm *.mod.*
    rm *.order
    rm *.o
    rm *.symvers

5、应用程序源文件mmapnopage_app.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>

#define DEVICE_FILENAME "/dev/mmapnopage"
#define SHARE_MEM_PAGE_COUNT 5
#define SHARE_MEM_SIZE (4096*SHARE_MEM_PAGE_COUNT)

int main()
{
    int dev;
    int loop;
    char *ptrdata;

    dev=open(DEVICE_FILENAME,O_RDWR|O_NDELAY);

    if(dev>=0){
        printf("open file success!\n");
        ptrdata=(char*)mmap(0,
                SHARE_MEM_SIZE,
                PROT_READ|PROT_WRITE,
                MAP_SHARED,
                dev,
                0);
        for(loop=0;loop<SHARE_MEM_PAGE_COUNT;loop++){
            printf("[%-10s%x]\n",ptrdata+4096*loop,ptrdata+4096*loop);
        }
        munmap(ptrdata,SHARE_MEM_SIZE);
        close(dev);
    }
    return 0;
}

6、实施方法及运行结果

~/nopage_mmap# mknod /dev/mmapnopage c 240 0
~/nopage_mmap# make
~/nopage_mmap# gcc mmapnopage_app.c -o mmapnopage_app
~/nopage_mmap# insmod mmapnopage_dev.ko
~/nopage_mmap# ./mmapnopage_app
open file
[TEST 0 b77c1000]
[TEST 1 b77c2000]
[TEST 2 b77c3000]
[TEST 3 b77c4000]
~/nopage_mmap# dmesg
[ 385.633677]
[ 385.633946] 1)vma->flags 00000000
[ 385.633965] 2)vmf->pgoff 00000000
[ 385.633978] 3)vmf->virtual_address b77c1000
[ 385.633989] 4)vma->vm_start b77c1000
[ 385.634001] 5)vma->vm_end b77c5000
[ 385.634013] 6)vma->vm_pgoff 00000000
[ 385.634146]
[ 385.634149] 1)vma->flags 00000000
[ 385.634152] 2)vmf->pgoff 00000001
[ 385.634154] 3)vmf->virtual_address b77c2000
[ 385.634156] 4)vma->vm_start b77c1000
[ 385.634158] 5)vma->vm_end b77c5000
[ 385.634160] 6)vma->vm_pgoff 00000000
[ 385.634174]
[ 385.634177] 1)vma->flags 00000000
[ 385.634180] 2)vmf->pgoff 00000002
[ 385.634182] 3)vmf->virtual_address b77c3000
[ 385.634184] 4)vma->vm_start b77c1000
[ 385.634186] 5)vma->vm_end b77c5000
[ 385.634188] 6)vma->vm_pgoff 00000000
[ 385.634202]
[ 385.634204] 1)vma->flags 00000000
[ 385.634207] 2)vmf->pgoff 00000003
[ 385.634209] 3)vmf->virtual_address b77c4000
[ 385.634211] 4)vma->vm_start b77c1000
[ 385.634213] 5)vma->vm_end b77c5000
[ 385.634215] 6)vma->vm_pgoff 00000000

7、移除模块及设备文件

~/nopage_mmap# rm /dev/mmapnopage
~/nopage_mmap# rmmod mmapnopage_dev