Get process id by its name in kernel space in linux

Question

I am working on embedded linux. I need to send a signal to certain user space process from kernel space(kernel module). Since the PID is dynamic, I need to obtain the pid for this process to send a signal to it? How do it obtain PID of a process from its name in kernel space?

Answer 1

For every user process in user space there is an associated task_struct( which is a circular linked list) in kernel space.Which have all the process details ,So you can just walk through that and check for your process name.

Writing down example

for_each_process(task) {

       /* compare your process name with each of the task struct process name*/    

        if ( (strcmp( task->comm,your_process_name) == 0 ) ) {

              /* if matched that is your user process PID */      
              process_id = task->pid;
           }
}

Answer 2

Processes don't necessarily have a name. A running program can have changed its name, So your plan only works if the process you try to find is collaborative and well-behaved. Try for instance to run the program below and (from a different terminal) run ps:

#include <stdio.h>
#include <unistd.h>

int main(void)
{
int pid,rc;
char *args[] = { "", "-", NULL };

pid = fork();

if (pid) {
        sleep(60);
        }
else    {
        execve( "/bin/cat" , args, NULL);
        }

return 0;
}