如何在XV6中将值传递给系统调用函数? [英] How to pass a value into a system call function in XV6?

问题描述

我正在尝试在XV6中创建一个基于优先级的简单调度程序.为此，我还必须创建一个系统调用，该调用将允许进程设置其优先级.我已经完成了创建系统调用所需的一切，如此处和其他地方所述:

I am attempting to create a simple priority based scheduler in XV6. To do this, I also have to create a system call that will allow a process to set its priority. I have done everything required to create the system call as discussed here and elsewhere:

如何添加系统调用/实用程序在xv6中

问题是，我在调用函数时不能传递任何变量，或者说，它像没有错一样运行，但是正确的值未在函数内部显示.

The problem is, I cannot pass any variables when I call the function, or rather, it runs like nothing is wrong but the correct values do not show up inside the function.

外部声明(syscall.c):

Extern declaration (syscall.c):

...
extern int sys_setpty(void);

static int (*syscalls[])(void) = {
...
[SYS_setpty]  sys_setpty,
};

系统调用向量(syscall.h):

Sys-call Vector (syscall.h):

#define SYS_setpty 22

实施(sysproc.c):

Implementation (sysproc.c):

void
sys_setpty(int pid, int pty)
{
  cprintf("function pid: %d \n", pid);
  cprintf("function pty: %d \n", pty);
}

(defs.h& user.h):

(defs.h & user.h):

void setpty(int, int);

微距(usys.S):

Macro (usys.S):

SYSCALL(setpty)

函数调用:

setpty(3, 50);

输出:

function pid: 16843009
function pty: 16843009

这些值始终是相同的精确数字:16843009.我已经通过将值分配给pid和pty来检查cprintf是否正常工作.我花了大约6个小时来尝试我能想到的所有可能组合，而且我开始认为没有内置的机制可以通过XV6中的系统调用来传递值.我想念什么吗?预先谢谢你.

The values are always the same exact number: 16843009. I have checked to see if the cprintf is working correctly by assigning values to pid and pty. I have spent about 6 hours trying every possible combination of everything I can think of and I'm starting to think that there is no built in mechanism for passing values via a system call in XV6. Am I missing something? Thank you in advance.

推荐答案

在XV6中无法将参数从用户级函数传递到内核级函数. XV6具有自己的内置函数，用于将参数传递给内核函数.例如，要传入整数，将调用argint()函数.在我用于set-priority函数的实现中，它看起来类似于:

Passing arguments from user-level functions to kernel-level functions cannot be done in XV6. XV6 has its own built-in functions for passing arguments into a kernel function. For instance, to pass in an integer, the argint() function is called. In the implementation that I used for the set-priority function, that would look something like:

argint(0, &pid);

...获取第一个参数，即进程ID，并且:

... to get the first argument which is the Process ID, and:

argint(1, &pty);

...获取第二个参数，它是所需的优先级.来自用户进程的函数调用如下所示:

... to get the second argument which is the desired priority. The function call from the user process looks like this:

setpty(getpid(), priority);

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