如果 cmd = 2，则不调用 ioctl [英] ioctl is not called if cmd = 2

问题描述

我正在开发一个使用 unlocked_ioctl 的内核模块.我使用内核版本 2.6.24-23-generic 对其进行了测试，它运行良好.现在我用内核版本 3.3.1-1-ARCH 进行了尝试，但发生了一些奇怪的事情:当请求值 (cmd) 为 2 时，ioctl 函数不会执行.它返回 0，但该函数没有执行.为了检查它是否未执行，我执行了以下操作:

I am developing a kernel module that uses unlocked_ioctl. I tested it with kernel version 2.6.24-23-generic and it works perfectly. Now I tried it with kernel version 3.3.1-1-ARCH and something weird happens: the ioctl function is not executed when the request value (cmd) is 2. It returns 0, but the function is not executed. In order to check that it is not executed I did the following:

static long midriver_ioctl(struct file *file,
    unsigned int cmd, unsigned long arg) {

printk("Called with cmd = %d
", cmd);

我编写了一个测试程序，该程序从 0 到 4096 为该设备调用 ioctl，并且我可以在 dmesg 中看到所有这些值的消息使用 cmd = n 调用"，除了2"，唯一一个是未显示.

I wrote a test program that calls ioctl for this device from 0 to 4096, and I can see in dmesg the message "Called with cmd = n" for all those values, except of "2", the only one that is not shown.

任何关于我做错了什么的线索?

Any clues about what I am doing wrong?

先谢谢你，

推荐答案

查看这个:

 546 int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 547             unsigned long arg)
 548 {
 549        int error = 0;
 550        int __user *argp = (int __user *)arg;
 551        struct inode *inode = filp->f_path.dentry->d_inode;
 552
 553        switch (cmd) {
 554        case FIOCLEX:
 555                set_close_on_exec(fd, 1);
 556                break;
 557
 558        case FIONCLEX:
 559                set_close_on_exec(fd, 0);
 560                break;
 561
 562        case FIONBIO:
 563                error = ioctl_fionbio(filp, argp);
 564                break;
 565
 566        case FIOASYNC:
 567                error = ioctl_fioasync(fd, filp, argp);
 568                break;
 569
 570        case FIOQSIZE:
 571                if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode) ||
 572                    S_ISLNK(inode->i_mode)) {
 573                        loff_t res = inode_get_bytes(inode);
 574                        error = copy_to_user(argp, &res, sizeof(res)) ?
 575                                        -EFAULT : 0;
 576                } else
 577                        error = -ENOTTY;
 578                break;
 579
 580        case FIFREEZE:
 581                error = ioctl_fsfreeze(filp);
 582                break;
 583
 584        case FITHAW:
 585                error = ioctl_fsthaw(filp);
 586                break;
 587
 588        case FS_IOC_FIEMAP:
 589                return ioctl_fiemap(filp, arg);
 590
 591        case FIGETBSZ:
 592                return put_user(inode->i_sb->s_blocksize, argp);
 593
 594        default:
 595                if (S_ISREG(inode->i_mode))
 596                        error = file_ioctl(filp, cmd, arg);
 597                else
 598                        error = vfs_ioctl(filp, cmd, arg);
 599                break;
 600        }
 601        return error;
 602 

如您所见，在 vfs_ioctl 或 file_ioctl 调用之前有一些切换案例.

As you can see, there is some of the switch-cases before vfs_ioctl or file_ioctl call.

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