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compat\u ioctl对于无符号long long数据类型工作不正常

ioctl linux-device-driver linux-kernel linux

0

md.jamal · 技术社区 · 5 年前

文件操作中有一个函数指针.compat\u ioctl,它允许32位进程在64位机器中使用ioctl。

以下是我的驱动程序代码:

#ifndef __IOCTL_CMD_H
#define __IOCTL_CMD_H

#define MSG_MAGIC_NUMBER    0x21

#define MSG_IOCTL_GET_LENGTH    _IOR(MSG_MAGIC_NUMBER, 1, unsigned int)

#define MSG_IOCTL_CLEAR_BUFFER  _IO(MSG_MAGIC_NUMBER, 2)

#define MSG_IOCTL_FILL_BUFFER   _IOW(MSG_MAGIC_NUMBER, 3, unsigned char)

#define MSG_GET_ADDRESS     _IOR(MSG_MAGIC_NUMBER, 4, unsigned long)

#define MSG_IOCTL_MAX_CMDS      4

#endif


long device_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    unsigned char ch;
    int retval = 0;
    long size = _IOC_SIZE(cmd);

    pr_info("%s: Cmd:%u\t Arg:%lu Size:%lu add:%p\n", __func__, cmd, arg, size, &ch);

    if (_IOC_TYPE(cmd) != MSG_MAGIC_NUMBER) return -ENOTTY;
    if (_IOC_NR(cmd) > MSG_IOCTL_MAX_CMDS) return -ENOTTY;

    //access_ok is kernel-oriented, so the concept of read and write is reversed

    retval = access_ok((void __user *)arg, size);

    pr_info("access_ok returned:%d\n", retval);
    if (!retval)
        return -EFAULT;

    switch(cmd)
    {
        //Get Length of buffer
        case MSG_IOCTL_GET_LENGTH:
            pr_info("Get Buffer Length\n");
            put_user(MAX_SIZE, (unsigned int *)arg);
            break;
        //clear buffer
        case MSG_IOCTL_CLEAR_BUFFER:
            pr_info("Clear buffer\n");
            memset(kernel_buffer, 0, sizeof(kernel_buffer));
            break;
        //fill character
        case MSG_IOCTL_FILL_BUFFER:
            get_user(ch, (unsigned char *)arg);
            pr_info("Fill Character:%c\n", ch);
            memset(kernel_buffer, ch, sizeof(kernel_buffer));
            buffer_index = sizeof(kernel_buffer);
            break;
        //address of kernel buffer
        case MSG_GET_ADDRESS:
            put_user(0x12345678, (unsigned long*)arg);
            pr_info("MSG_GET_ADDRESS\n");
            break;
        default:
            pr_info("Unknown Command:%u\n", cmd);
            return -ENOTTY;
    }
    return 0;
}


long device_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    unsigned char ch;
    int retval = 0;
    long size = _IOC_SIZE(cmd);

    pr_info("%s: Cmd:%u\t Arg:%lu Size:%lu add:%p\n", __func__, cmd, arg, size, &ch);

    if (_IOC_TYPE(cmd) != MSG_MAGIC_NUMBER) return -ENOTTY;
    if (_IOC_NR(cmd) > MSG_IOCTL_MAX_CMDS) return -ENOTTY;

    //access_ok is kernel-oriented, so the concept of read and write is reversed

    retval = access_ok((void __user *)arg, size);

    pr_info("access_ok returned:%d\n", retval);
    if (!retval)
        return -EFAULT;

    switch(cmd)
    {
        //Get Length of buffer
        case MSG_IOCTL_GET_LENGTH:
            pr_info("Get Buffer Length\n");
            put_user(MAX_SIZE, (unsigned int *)arg);
            break;
        //clear buffer
        case MSG_IOCTL_CLEAR_BUFFER:
            pr_info("Clear buffer\n");
            memset(kernel_buffer, 0, sizeof(kernel_buffer));
            break;
        //fill character
        case MSG_IOCTL_FILL_BUFFER:
            get_user(ch, (unsigned char *)arg);
            pr_info("Fill Character:%c\n", ch);
            memset(kernel_buffer, ch, sizeof(kernel_buffer));
            buffer_index = sizeof(kernel_buffer);
            break;
        //address of kernel buffer
        case MSG_GET_ADDRESS:
            put_user(0x12345678, (unsigned long*)arg);
            pr_info("MSG_GET_ADDRESS\n");
            break;
        default:
            pr_info("Unknown Command:%u\n", cmd);
            return -ENOTTY;
    }
    return 0;
}




struct file_operations device_fops = {
    .read = device_read,
    .write = device_write,
    .open = device_open,
    .release = device_release,
    .llseek = device_lseek,
    .unlocked_ioctl = device_ioctl,
    .compat_ioctl = device_compat_ioctl
};

当我从用户空间(32位进程)调用下面的代码时,它在compat\u ioctl定义中以未知ioctl失败。

int main(int argc, char *argv[])
{
    char buffer[1024];  
    int fd;
    unsigned int length;
    int i = 0;
    unsigned long addr;

    fd = open("/dev/msg", O_RDWR);
    if (fd < 0) {
        perror("fd failed");
        exit(2);
    }

    printf("Size:%d\n", _IOC_SIZE(MSG_GET_ADDRESS));
    printf("cmd:%u\n", MSG_GET_ADDRESS);

    ioctl(fd, MSG_GET_ADDRESS, &addr);
    perror("ioctl");
    getchar();
    printf("address:%x\n", addr);

    close(fd);
}

0 回复 | 直到 5 年前

1

Ian Abbott 5 年前

你的 MSG_GET_ADDRESS ioctl请求代码定义为:

#define MSG_GET_ADDRESS _IOR(MSG_MAGIC_NUMBER, 4, unsigned long)

第三个参数的大小被编码到ioctl请求代码中。可以使用 _IOC_SIZE(req) 宏。

消息\u获取\u地址 与64位进程/内核相比,32位进程/内核将有所不同。特别是,编码的大小将不同。

在32位进程/内核上, _IOC_SIZE(MSG_GET_ADDRESS) 四岁。在64位进程/内核上, _IOC\大小(消息\获取\地址) sizeof(unsigned long) 32位和64位系统上的值。

在支持32位兼容性的64位内核上运行32位进程时,32位进程将调用 ioctl() 消息\u获取\u地址 请求代码。但是,你的司机 device_compat_ioctl() 正在寻找64位版本的 消息\u获取\u地址 请求代码。

一个解决方案是在驱动程序中定义一个32位版本的ioctl请求代码来镜像“官方” 消息\u获取\u地址

#define MSG32_GET_ADDRESS _IOR(MSG_MAGIC_NUMBER, 4, compat_ulong_t)

请注意,此请求代码不需要位于用户模式标头中,因为它仅用于内核模式。但是,如果更方便的话,可以将其包含在用户模式标头中,但要包装在 #ifdef __KERNEL__ #endif 一对:

#ifdef __KERNEL__
#define MSG32_GET_ADDRESS _IOR(MSG_MAGIC_NUMBER, 4, compat_ulong_t)
#endif

现在,你的 device_compat_ioctl 函数应更改为处理 MSG32_GET_ADDRESS 消息\u获取\u地址 请求代码:

        //address of kernel buffer
        case MSG32_GET_ADDRESS:
            put_user(0x12345678, (compat_ulong_t*)arg);
            pr_info("MSG_GET_ADDRESS\n");
            break;

注: 根据代码中的注释 消息\u获取\u地址 实际上应该获取内核缓冲区的地址。我不知道您的用户空间代码打算用它做什么,但是请注意,64位内核地址不适合32位 unsigned long (或32位 compat_ulong_t 类型)。