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ioctl example complete!

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Ciro Santilli
2017-06-12 08:53:28 +01:00
parent 95a1840683
commit 7d2f79dec9
3 changed files with 96 additions and 17 deletions
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53
kernel_module/ioctl.c
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@@ -1,13 +1,12 @@
/*
Give integer and a pointer to the kernel, and get one positive integer out.
Input: an integer (with some annoying restrictions) and a pointer
Feels like an archaic API... so many weird restrictions for something that could be so simple!
Output:
TODO: must the ioctl numbers be globally unique? How to ensure that?
- positive integer return value, which for sanity should only be used with negative values for success
- the input pointer data may be overwritten to contain output
Ioctl is super picky about the ioctl numbers, it is very annoying: https://stackoverflow.com/questions/10071296/ioctl-is-not-called-if-cmd-2
See how do_vfs_ioctl highjacks several values. This "forces" use to use the _IOx macros...
Feels like an archaic API... so many weird restrictions and types for something that could be so simple!
Documentation/ioctl/ioctl-number.txt has some info:
@@ -17,18 +16,54 @@ Documentation/ioctl/ioctl-number.txt has some info:
_IOWR an ioctl with both write and read parameters.
*/
#include <asm/uaccess.h> /* copy_from_user, copy_to_user */
#include <linux/debugfs.h>
#include <linux/module.h>
#include <linux/printk.h> /* printk */
#include "ioctl.h"
MODULE_LICENSE("GPL");
static struct dentry *dir;
static long unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
static long unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long argp)
{
pr_info("cmd = %u\n", cmd);
return cmd + 1;
void __user *arg_user;
union {
int i;
lkmc_ioctl_struct s;
} arg_kernel;
arg_user = (void __user *)argp;
pr_info("cmd = %x\n", cmd);
switch (cmd) {
case LKMC_IOCTL_INC:
if (copy_from_user(&arg_kernel.i, arg_user, sizeof(arg_kernel.i))) {
return -EFAULT;
}
pr_info("0 arg = %d\n", arg_kernel.i);
arg_kernel.i += 1;
if (copy_to_user(arg_user, &arg_kernel.i, sizeof(arg_kernel.i))) {
return -EFAULT;
}
break;
case LKMC_IOCTL_INC_DEC:
if (copy_from_user(&arg_kernel.s, arg_user, sizeof(arg_kernel.s))) {
return -EFAULT;
}
pr_info("1 arg = %d %d\n", arg_kernel.s.i, arg_kernel.s.j);
arg_kernel.s.i += 1;
arg_kernel.s.j -= 1;
if (copy_to_user(arg_user, &arg_kernel.s, sizeof(arg_kernel.s))) {
return -EFAULT;
}
break;
default:
return -EINVAL;
break;
}
return 0;
}
static const struct file_operations fops = {