mirror of
https://github.com/cirosantilli/linux-kernel-module-cheat.git
synced 2026-01-23 10:15:57 +01:00
52 lines
1.3 KiB
C
52 lines
1.3 KiB
C
/*
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Give integer and a pointer to the kernel, and get one positive integer out.
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Feels like an archaic API... so many weird restrictions for something that could be so simple!
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TODO: must the ioctl numbers be globally unique? How to ensure that?
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Ioctl is super picky about the ioctl numbers, it is very annoying: https://stackoverflow.com/questions/10071296/ioctl-is-not-called-if-cmd-2
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See how do_vfs_ioctl highjacks several values. This "forces" use to use the _IOx macros...
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Documentation/ioctl/ioctl-number.txt has some info:
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_IO an ioctl with no parameters
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_IOW an ioctl with write parameters (copy_from_user)
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_IOR an ioctl with read parameters (copy_to_user)
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_IOWR an ioctl with both write and read parameters.
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*/
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#include <linux/debugfs.h>
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#include <linux/module.h>
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#include <linux/printk.h> /* printk */
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MODULE_LICENSE("GPL");
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static struct dentry *dir;
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static long unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
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{
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pr_info("cmd = %u\n", cmd);
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return cmd + 1;
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}
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static const struct file_operations fops = {
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.unlocked_ioctl = unlocked_ioctl
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};
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static int myinit(void)
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{
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dir = debugfs_create_dir("lkmc_ioctl", 0);
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debugfs_create_file("f", 0666, dir, NULL, &fops);
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return 0;
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}
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static void myexit(void)
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{
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debugfs_remove_recursive(dir);
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}
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module_init(myinit)
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module_exit(myexit)
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