How to migrate an arbitrary process in a kernel module?

Question

I'm writing a kernel module that iterates over all processes (using the for_each_process macro), now, I would like to migrate ones that meet certain criteria to a new NUMA node or processor. I found a few functions defined as extern in the sched.h:

extern void sched_setnuma(struct task_struct *p, int node);
extern int migrate_task_to(struct task_struct *p, int cpu);
extern int migrate_swap(struct task_struct *, struct task_struct *);

But can't use them cause the kernel is already compiled.

Is there any way to use these functions or similar ones to achieve a task migration?

EDIT

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched/signal.h>
#include <linux/sched.h>
#include <linux/kprobes.h>
#include <linux/kallsyms.h>


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mohammad Siavashi");
MODULE_DESCRIPTION("This is a test module");

int (*migrate_task_to_func)(struct task_struct *p, int cpu);

void start(void)
{
    struct task_struct *t;
    for_each_process(t)
    {
        if (strcmp(t->comm, "stream_task") == 0)
        {
            migrate_task_to_func(t, 2);
        }
    }
}

static int __init hello_init(void)
{
    migrate_task_to_func = (void *)kallsyms_lookup_name("migrate_task_to");
    start();
    return 0;
}

static void __exit hello_cleanup(void)
{
    printk(KERN_INFO "Cleaning up module.\n");
}

module_init(hello_init);
module_exit(hello_cleanup);

score 3 · Accepted Answer · answered May 03 '22 at 01:35

You can use kallsyms_lookup_name to find it out and then use it again. If kallsyms_lookup_name is not exported (kernel>=5.7), you can use kprobe to find it first

e.g:

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kprobes.h>

void (*sched_setnuma_func)(struct task_struct *p, int node);
int (*migrate_task_to_func)(struct task_struct *p, int cpu);
int (*migrate_swap_func)(struct task_struct *, struct task_struct *);

static int __init test_init(void)
{
    unsigned long (*kallsyms_lookup_name_func)(const char *name);
    struct kprobe kp = { .symbol_name    = "kallsyms_lookup_name", };

    register_kprobe(&kp);
    kallsyms_lookup_name_func = (void *)kp.addr;
    unregister_kprobe(&kp);

    if (kallsyms_lookup_name_func) {
        sched_setnuma_func = (void *)kallsyms_lookup_name_func("sched_setnuma");
        migrate_task_to_func = (void *)kallsyms_lookup_name_func("migrate_task_to");
        migrate_swap_func = (void *)kallsyms_lookup_name_func("migrate_swap");
    }
    printk("sched_setnuma_func: %p\n", sched_setnuma_func);
    printk("migrate_task_to_func: %p\n", migrate_task_to_func);
    printk("migrate_swap_func: %p\n", migrate_swap_func);
    return 0;
}

static void __exit test_exit(void)
{
}

module_init(test_init);
module_exit(test_exit);
MODULE_LICENSE("GPL");

How to migrate an arbitrary process in a kernel module?

1 Answers1