2-安卓底层-java实现调用linux系统调用

java实现调用linux系统调用流程：

java –》 jni —》 driver

java 实现的是native方法

jni 实现的是调用linux 系统调用

java_open = method结构体 ==> Jopen == jni里调用 => open(系统调用) ==> driver_open

驱动：ibo.c

#include <linux/kernel.h>#include <linux/module.h>#include <linux/cdev.h>#include <linux/fs.h>#include <linux/device.h>#include <asm/uaccess.h>#include <asm/io.h>#define     IBO_MAJOR   505#define     IBO_MINOR   0#define     IBO_NUM     1#define     IBO_NAME    "ibo"#define     CLS_NAME    "ibo_cls"#define     DEV_NAME    "ibo"dev_t devno;struct cdev ibo_cdev;struct class * cls;static int ibo_open(struct inode *inode,struct file *filp){    printk("ibo_open success\n");    return 0;}static int ibo_release(struct inode *inode,struct file *filp){    printk("ibo_release success\n");    return 0;}static long ibo_ioctl(struct file *filp,unsigned int cmd,unsigned long arg){    printk("ibo_ioctl success %d\n",cmd);    return 0;}struct file_operations ibo_fops={     .owner          = THIS_MODULE,     .open           = ibo_open,     .release        = ibo_release,     .unlocked_ioctl = ibo_ioctl,};static int ibo_init(void){    int ret;    devno = MKDEV(IBO_MAJOR,IBO_MINOR);    ret = register_chrdev_region(devno,IBO_NUM,IBO_NAME);    if (ret < 0){        return -EFAULT;    }    cdev_init(&ibo_cdev,&ibo_fops);    ibo_cdev.owner = THIS_MODULE;    cdev_add(&ibo_cdev,devno,IBO_NUM);    cls = class_create(THIS_MODULE,CLS_NAME);    if (IS_ERR(cls)){        printk("class_create fail!!!\n");        return -EFAULT;    }    device_create(cls,NULL,devno,NULL,DEV_NAME);    printk("ibo_init success\n");    return 0;}static void ibo_exit(void){    device_destroy(cls,devno);    class_destroy(cls);    cdev_del(&ibo_cdev);    unregister_chrdev_region(devno,IBO_NUM);    printk("ibo_exit success\n");    return;}module_init(ibo_init);module_exit(ibo_exit);MODULE_LICENSE("GPL");

驱动:Makefile

ifeq ($(KERNELRELEASE),)KERNELDIR ?= /lib/modules/$(shell uname -r)/buildPWD := $(shell pwd)modules:    $(MAKE) -C $(KERNELDIR) M=$(PWD)clean:    rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions Module* modules*.PHONY: modules cleanelse    obj-m := ibo.oendif

1.输入make编译生成 .ko 文件

2.sudo insmod ibo.ko 把模块插入到内核中

• 输出 ibo_init success 表示成功插入到内核中

---

JAVA : Ibo.java

class Ibo{    static{        System.loadLibrary("native");    }    private native void open();    private native void ioctl(int cmd);    private native void release();    public static void main(String[] args) {        Ibo m=new Ibo();        m.open();        m.ioctl(525);        m.release();    }}

3.javac Ibo.java生成 class文件

4.javah Ibo生成 h文件

---

JNI : native.c

#include <jni.h>#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdlib.h>#include <sys/ioctl.h>int fd;void Jopen(JNIEnv *env,jobject obj){    fd = open("/dev/ibo",O_RDWR);    return;}void Jioctl(JNIEnv *env,jobject obj,jint cmd){    ioctl(fd,cmd);    return;}void Jrelease(JNIEnv *env,jobject obj){    close(fd);    return;}JNINativeMethod methods[]={    "open","()V",(void *)Jopen,    "ioctl","(I)V",(void *)Jioctl,    "release","()V",(void *)Jrelease,};JNIEXPORT jint JNICALLJNI_OnLoad(JavaVM *vm, void *reserved){    JNIEnv *env;    jclass cls;    system("sudo chmod 777 /dev/ibo");    (*vm)->GetEnv(vm, (void **)&env, JNI_VERSION_1_2);    if(env == NULL) return JNI_ERR;    cls = (*env)->FindClass(env, "Ibo");    if(cls == NULL) return JNI_ERR;    (*env)->RegisterNatives(env, cls,methods, sizeof(methods)/sizeof(JNINativeMethod));    return JNI_VERSION_1_2;}

5.gcc -shared -fPIC native.c -o libnative.so -I /usr/lib/jvm/java-7-openjdk-amd64/include/ 编译生成 libnative.so 文件

6.export LD_LIBRARY_PATH=:

7.java Ibo 运行