How to pass data to kthread_run

I'm try to make simple kernel module with multithreading. So I'm using linux/kthread.h, kernel v. 5.2.11

Problem: I can't passing the char array into thread: Segmentation fault.

That's what I'm doing:

typedef struct { int num; char origin[MAXSTR]; //part of input for current thread struct completion wait_for_thread; //completion struct
} kthread_arg;

Then:

struct task_struct *task;
static kthread_arg kta_first_thread;
kta_first_thread.num = 1;
strncpy(kta_first_thread.origin, dat1, MAXSTR );
//Here I have normal char array 'origin'
init_completion(&kta_first_thread.wait_for_thread);
task = kthread_run(&thread_function, (void*)&kta_first_thread, "one");

And after that I have the error. Moreover, if you remove the array from struct, then everything works. I'm sure doing something wrong?

1 Answer

The args passed to kernel_run must be kmalloced, your args is in stack. I have met the same problem, your code should like this:

struct your_struct* test=NULL;
struct task_struct* t=NULL;
test=(struct your_struct*)kmalloc(sizeof(struct your_struct),GFP_KERNEL);
t=kthread_run(your_function,(void*)test,name);