mirror of
https://github.com/cirosantilli/linux-kernel-module-cheat.git
synced 2026-01-13 20:12:26 +00:00
62 lines
1.1 KiB
C
62 lines
1.1 KiB
C
/*
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Let's block the entire kernel! Yay!
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kthreads only allow interrupting if you call schedule.
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If you don't, they just run forever, and you have to kill the VM.
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Sleep functions like usleep_range also end up calling schedule.
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Test with:
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dmesg -n 1
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insmod /schedule.ko yn=[01]
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dmesg | tail
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Then:
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- yn=0:
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- `qemu -smp 1`: everything blocks!
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- `qemu -smp 2`: you can still use the board, but is it noticeably slow
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- yn=1: all good
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*/
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#include <linux/kernel.h>
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#include <linux/kthread.h>
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#include <linux/module.h>
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#include <uapi/linux/stat.h> /* S_IRUSR | S_IWUSR */
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static int yn = 1;
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module_param(yn, int, S_IRUSR | S_IWUSR);
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MODULE_PARM_DESC(yn, "A short integer");
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static struct task_struct *kthread;
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static int work_func(void *data)
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{
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unsigned int i = 0;
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while (!kthread_should_stop()) {
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pr_info("%u\n", i);
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i++;
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if (yn)
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schedule();
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}
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return 0;
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}
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static int myinit(void)
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{
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kthread = kthread_create(work_func, NULL, "mykthread");
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wake_up_process(kthread);
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return 0;
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}
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static void myexit(void)
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{
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kthread_stop(kthread);
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}
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module_init(myinit)
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module_exit(myexit)
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MODULE_LICENSE("GPL");
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