在内核模块中命名变量“ current”会导致“函数声明不是原型”。错误 [英] Naming a variable `current` in a kernel module leads to "function declaration isn’t a prototype" error

问题描述

作为一个初学者，我正在学习为Linux编写内核模块。我要做的是使用DFS算法将每个任务及其子进程写入内核日志。但是，当我使用 Makefile 编译代码时，它显示了以上错误：

I'm learning to write kernel modules for linux as a beginner. What I'm trying to do is to write every task and its child process into the kernel log using DFS algorithm. But when I compile the code using Makefile, it shows the above error:

function declaration isn’t a prototype [-Werror=strict-prototypes]
struct task_struct *current;

它指出了 task_struct 关键字功能DFS。
这是我的代码：

It points out the task_struct keyword at the function DFS. Here's my code:

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

void DFS (struct task_struct *task)
{
    struct task_struct *current;
    struct list_head *list;

    list_for_each (list, &task->children)
    {
        current = list_entry(list, struct task_struct, sibling);
        printk(KERN_INFO "%d\t%d\t%s \n", (int)current->state, current->pid, current->comm);

        if (current != NULL)
        {
            DFS(current);
        }
    }
}

int DFS_init(void)
{
    printk(KERN_INFO "Loading the Second Module...\n");

    printk(KERN_INFO "State\tPID\tName\n");

    DFS(&init_task);   

    return 0;
}

void DFS_exit(void)
{
    printk(KERN_INFO "Removing the Second Module...\n");
}

任何人都知道如何解决此问题??

Anyone knows how to fix this ??

推荐答案

内核有一个名为 current 的宏，该宏指向当前正在执行进程的用户。正如这本书所述，

The kernel has a macro called current which is pointing to users currently executing process. As this book states,

当前指针指向当前正在执行的用户进程。在执行系统调用（例如打开或读取）的过程中，当前进程是调用该调用的进程。

The current pointer refers to the user process currently executing. During the execution of a system call, such as open or read, the current process is the one that invoked the call.

换句话说，如@ GilHamilton在评论中提到， current 是 #define d对函数 get_current（）在内核中。使用 current 作为变量名将产生编译时错误！

In other words, as @GilHamilton mentioned in the comments, current is #defined to the function get_current() in the kernel. Using current as a variable name will give a compile-time error!

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