Linux - Newbie This Linux forum is for members that are new to Linux.
Just starting out and have a question?
If it is not in the man pages or the how-to's this is the place! |
Notices |
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
Are you new to LinuxQuestions.org? Visit the following links:
Site Howto |
Site FAQ |
Sitemap |
Register Now
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Get a virtual cloud desktop with the Linux distro that you want in less than five minutes with Shells! With over 10 pre-installed distros to choose from, the worry-free installation life is here! Whether you are a digital nomad or just looking for flexibility, Shells can put your Linux machine on the device that you want to use.
Exclusive for LQ members, get up to 45% off per month. Click here for more info.
|
 |
05-22-2012, 04:22 AM
|
#1
|
Member
Registered: Apr 2012
Posts: 38
Rep: 
|
copy_from/to_user how to use it simply to get pid into kernel space from userspace?
Hello everyone,
I am looking for providing userspace pid to kernel. And one of may be many ways is copy_from/to_user.
can anyone please help me to implement this? or can you give me some examples for this that i can overcome this problem:
kernel Code:
Code:
struct siginfo sinfo;
pid_t pid;
struct task_struct *task;
int init_module () {
memset(&sinfo, 0, sizeof(struct siginfo));
sinfo.si_signo = SIGIO;
sinfo.si_code = SI_USER;
pid = 5218; // Everytime a new PID
task = pid_task(find_vpid(pid), PIDTYPE_PID);
printk("%d .\n", task);
if(task == NULL) {
printk("Cannot find PID from user program\r\n");
return 0;
}
send_sig_info(SIGIO, &sinfo, task);
return 0;
}
Userspace Code:
Code:
void signal_handler (int signum){
if (signum == SIGIO) printf ("SIGIO\r\n"); return;
}
int main () {
int i=1 ;
signal(SIGIO, signal_handler);
printf("My PID is %d.\n",getpid());
while (i);
return 0;
}
How can i copy the userspace pid to kernel space by itself?
please help me out.. 
|
|
|
05-23-2012, 03:03 AM
|
#2
|
Senior Member
Registered: Apr 2007
Location: Portland, OR
Distribution: Debian, Android, LFS
Posts: 1,168
|
The most common ways to get data from user space to kernel space are:
sysfs
procfs
chardev
There's a good discussion of these (and less popular methods), here:
http://people.ee.ethz.ch/~arkeller/l...ace_howto.html
Basically, you want to getpid(), and then write it to a file descriptor. That file descriptor will either be in /proc/something, or /sys/something, or /dev/something, depending on which of the above methods you choose.
Anyway, that's only a few lines of code. More of the work will be in the kernel module, where you implement one of the above interfaces.
|
|
|
05-23-2012, 04:55 AM
|
#3
|
Member
Registered: Apr 2012
Posts: 38
Original Poster
Rep: 
|
Quote:
Originally Posted by jhwilliams
The most common ways to get data from user space to kernel space are:
sysfs
procfs
chardev
There's a good discussion of these (and less popular methods), here:
http://people.ee.ethz.ch/~arkeller/l...ace_howto.html
Basically, you want to getpid(), and then write it to a file descriptor. That file descriptor will either be in /proc/something, or /sys/something, or /dev/something, depending on which of the above methods you choose.
Anyway, that's only a few lines of code. More of the work will be in the kernel module, where you implement one of the above interfaces.
|
thank you so much jhwilliams.
I tried to work with ioctl..
but one thing strange is that, while i am making the device /dev/cdev_example using following command:
Quote:
# mknod /dev/cdev_example c 251 0
# chmod 666 /dev/cdev_example
# ls -l /dev/cdev_example
crw-rw-rw- 1 root root 251, 0 2012-05-23 02:37 /dev/cdev_example
|
It seems that device is created fine, but when i try to insert module it prints the message that:
Quote:
[540236.331549] cdev example: assigned major: 251
[540236.347809] create node with mknod /dev/cdev_example c 251 0
|
can you please tell me that why my created file/device is not working here?
i have also tried to check using:
and
echo'd to device, but i am getting this message
Quote:
-su: /dev/cdev_example: No such device or address
|
|
|
|
05-24-2012, 04:10 AM
|
#4
|
Member
Registered: Apr 2012
Posts: 38
Original Poster
Rep: 
|
Thank you so much for response jhwilliams...
I have got succeed in getting PID at kernel space:
Here I am posting code for helping the others:
Code:
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h> //For file_operations struc
#include <linux/device.h> //For class create
#include <linux/slab.h> //For Kmalloc
#include <asm/uaccess.h> //copy_from_user and copy_to_user
pid_t id;
//int u_id;
static int major_no;
static struct class *my_class_0;
static int device_open(struct inode *inode, struct file *file){
/*sucess*/
return 0;
}
static int device_write(struct file *file, const char *gdata, size_t len, loff_t *off){
get_user (id,(int *)gdata);
if(id <0)
printk("Cann't find PID from userspace its : %i", id);
else
printk("Hurrah! I got success.. here is it. %i", id);
return len;
}
static int device_read(struct file *file, char *buf, size_t len, loff_t *off){
return 0;
}
static int device_release(struct inode *inode, struct file *file){
/*sucess*/
return 0;
}
static struct file_operations fops = {
.open = device_open,
.write = device_write,
.read = device_read,
.release = device_release,
};
static int __init my_init(void){
major_no = register_chrdev(0, "my_dev", &fops);
my_class_0 = class_create(THIS_MODULE, "my_dev_0");
device_create(my_class_0, NULL, MKDEV(major_no, 0), NULL, "my_dev_0");
printk("\n Device Registered and Created \n");
return 0;
}
static void __exit my_exit(void){
printk("User PID : %d\n", id);
unregister_chrdev(major_no, "my_dev");
device_destroy(my_class_0, MKDEV(major_no,0));
class_unregister(my_class_0);
class_destroy(my_class_0);
printk("\n Device Un-Registered and Destroyed \n");
}
module_init(my_init);
module_exit(my_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR ("Raheel Ahmed Memon") ;
MODULE_DESCRIPTION ("Testing to get userspace PID into kernel space");
Makefile:
Code:
obj-m += k_module.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
Userspace Code:
Code:
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
//#include <sys/type.h>
#include <signal.h>
int main(){
int fd;
pid_t u_id;
u_id = getpid();
fd = open("/dev/my_dev_0",O_RDWR);
write(fd, &u_id, 4);
printf("\n PID sent to device successfully: %d \n", u_id);
close(fd);
while (1);
return 0;
}
Note: Remember one should run the Kernel Module before userspace application. so that when you will remove the module you can see the PID of userspace.
Thanks for response on my queries..
Raheel..
|
|
|
All times are GMT -5. The time now is 12:15 PM.
|
LinuxQuestions.org is looking for people interested in writing
Editorials, Articles, Reviews, and more. If you'd like to contribute
content, let us know.
|
Latest Threads
LQ News
|
|