Question

我正在尝试为linux编写一个简单的嗅探器驱动程序，它会将所有请求重定向到真正的串行端口（并且还会将所有消息打印到系统日志中）。我在互联网上找到了一些例子并实现了一些功能。例如，打开假设备时调用的函数：

static int dev_open(struct inode *inodep, struct file *filep) {
   numberOpens++;
   printk(KERN_INFO "sniffer: Device has been opened %d time(s)\n", numberOpens);

   /// Connecting to real device   
   fd = open (real_device, O_RDWR | O_NOCTTY | O_SYNC);
   if (fd < 0) {
      printk(KERN_INFO "sniffer: cannot open device %s\n", real_device);
     return 1;
   }

   set_interface_attribs (fd, B115200, 0);  // set speed to 115,200 bps, 8n1 (no parity)
   set_blocking (fd, 0);                     // set no blocking
   return 0;
}

如您所见，此函数只使用标准linux open系统调用打开真实设备。或设置实际设备设置（速度和奇偶校验）的功能：

int set_interface_attribs (int fd, int speed, int parity) {
    struct termios tty;
    memset (&tty, 0, sizeof tty);
    if (tcgetattr (fd, &tty) != 0) {
        // error_message ("error %d from tcgetattr", errno);
        printk(KERN_INFO "sniffer: cannot get device attributes\n");
        return -1;
    }

    cfsetospeed (&tty, speed);
    cfsetispeed (&tty, speed);

    tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;     // 8-bit chars
    // disable IGNBRK for mismatched speed tests; otherwise receive break
    // as \000 chars
    tty.c_iflag &= ~IGNBRK;         // disable break processing
    tty.c_lflag = 0;                // no signaling chars, no echo,
                                // no canonical processing
    tty.c_oflag = 0;                // no remapping, no delays
    tty.c_cc[VMIN]  = 0;            // read doesn't block
    tty.c_cc[VTIME] = 5;            // 0.5 seconds read timeout

    tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl

    tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls,
                                    // enable reading
    tty.c_cflag &= ~(PARENB | PARODD);      // shut off parity
    tty.c_cflag |= parity;
    tty.c_cflag &= ~CSTOPB;
    tty.c_cflag &= ~CRTSCTS;

    if (tcsetattr (fd, TCSANOW, &tty) != 0) {
        printk(KERN_INFO "sniffer: cannot set device attributes\n");
        return -1;
    }
    return -1;
}

它使用tcgetattr和tcsetattr系统调用。

我包含了所有必需的头文件：

#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/fcntl.h> 
#include <linux/unistd.h>
#include <linux/string.h>
#include <linux/termios.h>
#include <linux/fs.h>
#include <asm/uaccess.h>

但是当我尝试编译这个模块时，我得到了这个系统调用的“隐式声明函数”错误。

我的Makefile：

obj-m += sniffer.o

all:
    $(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

编译错误：

sniffer.c: In function ‘set_interface_attribs’:
sniffer.c:51:9: error: implicit declaration of function ‘tcgetattr’ [-Werror=implicit-function-declaration]
     if (tcgetattr (fd, &tty) != 0) {
         ^
sniffer.c:57:5: error: implicit declaration of function ‘cfsetospeed’ [-Werror=implicit-function-declaration]
     cfsetospeed (&tty, speed);
     ^
sniffer.c:58:5: error: implicit declaration of function ‘cfsetispeed’ [-Werror=implicit-function-declaration]
     cfsetispeed (&tty, speed);
     ^
sniffer.c:79:9: error: implicit declaration of function ‘tcsetattr’ [-Werror=implicit-function-declaration]
     if (tcsetattr (fd, TCSANOW, &tty) != 0) {
         ^
sniffer.c: In function ‘dev_open’:
sniffer.c:151:9: error: implicit declaration of function ‘open’ [-Werror=implicit-function-declaration]
    fd = open (real_device, O_RDWR | O_NOCTTY | O_SYNC);
         ^
sniffer.c: In function ‘dev_read’:
sniffer.c:164:18: error: implicit declaration of function ‘read’ [-Werror=implicit-function-declaration]
    error_count = read(fd, buffer, len);
                  ^
sniffer.c: In function ‘dev_write’:
sniffer.c:177:4: error: implicit declaration of function ‘write’ [-Werror=implicit-function-declaration]
    write (fd, buffer, len);
    ^
sniffer.c: In function ‘dev_release’:
sniffer.c:184:4: error: implicit declaration of function ‘close’ [-Werror=implicit-function-declaration]
    close(fd);
    ^

它能是什么？我发现的所有示例都说我应该包含<linux/unistd.h>和<linux/termios.h>。

Answer 1

我有类似的问题，我发现是添加

#include <linux/uaccess.h>

包括列表中的问题解决了我在Ubuntu 18.04（Linux内核版本：4.15.0）上的问题。

注意：也离开#include <asm/uaccess.h>

在某些情况下，对include语句进行重新排序会有所帮助。查看此问题的答案：

warning: implicit declaration of function

Linux内核模块编译错误：隐式声明函数'open'

1 个答案: