实现方式

基础版本的进程间通信比较简单，由三个系统调用完成

linux/arch/x86/entry/syscalls/syscall_64.tbl

新增三个系统调用[作者使用的源码是最新版]

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# follow three syscall is used for process_communication
442 common  zqd_call        sys_zqd_call
443 common  zqd_server      sys_zqd_server
444 common  zqd_reply       sys_zqd_reply

linux/arch/x86/kernel/sys_x86_64.c

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char data[50];
unsigned long rpc_data_len;
long rpc_result;

// struct completion RPC_call_done;         initial need
// struct completion RPC_reply_done;

DECLARE_COMPLETION(RPC_reply_done);
DECLARE_COMPLETION(RPC_call_done);

SYSCALL_DEFINE2(zqd_call,void*,rpc_data,size_t,data_len)
{
    printk(KERN_INFO "zqd_call...\n");
    if(copy_from_user(data,rpc_data,data_len))  // (*to, *from, length) 将client发送的消息copy到data
    {
        printk(KERN_INFO "zqd_call: failed to copy data to buffer! \n");
        return 0;
    }

    rpc_data_len = data_len;
    complete(&RPC_call_done);
    wait_for_completion(&RPC_reply_done);
    printk(KERN_INFO "rpc_result = ", rpc_result);
    return rpc_result;
}

SYSCALL_DEFINE2(zqd_server,void*,buf,size_t*,data_len)
{
    printk(KERN_INFO "zqd_server...\n");
    wait_for_completion(&RPC_call_done);

    if(copy_to_user(buf,data,rpc_data_len))   // (*to, *from, length) 将data内容copy到server的buffer
    {
        printk(KERN_INFO "zqd_server: failed to copy data to buffer! \n");
        return 0;
    }
    put_user(rpc_data_len,data_len);
    return 0;
}

SYSCALL_DEFINE1(zqd_reply,long,result)
{
    printk(KERN_INFO "zqd_reply...\n");
    rpc_result = result;
    complete(&RPC_reply_done);
    return 0;
}

测试用例：

client.c

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#include <unistd.h>                                                                 
#include <stdio.h>
#include <string.h>
#define __NR_zqd_call   442
typedef unsigned long   size_t;

int main(int argc, char const *argv[])
{
    char *data = "Hi, top!";
    size_t data_len = strlen(data) + 1;
    long zqd_call_result = syscall(__NR_zqd_call,data,data_len);
    printf("zqd_call_result = %ld\n", zqd_call_result);
    printf("\n");
    return 0;
}

server.c

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#include <unistd.h>                                                               
#include <stdio.h>
#define __NR_zqd_server     443
#define __NR_zqd_reply      444

int main(int argc, char const *argv[])
{
    char buffer[20];
    long data_len;                                                                  
    long result_server = syscall(__NR_zqd_server,buffer,&data_len);
    long result_reply = syscall(__NR_zqd_reply,2048);

    printf("data_len = %ld\n", data_len);
    printf("data = %s\n", buffer);
    printf("server end...\n");
    printf("result_server: %ld\n",result_server);
    printf("result_reply: %ld\n",result_reply);
    return 0;
}

实践小结

服务端正确的打开方式：

启动qemu之后，找到编译后的server.out和client.out

先执行

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./server.out &		//启动并且后台运行

再执行

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./client.out

以上代码完成了简化版本的进程间通信，注意编译的时候加上-static参数。如有错误请联系作者更正