I want to compile and load module from this answer https://stackoverflow.com/a/29526520/9609843There was some errors: I included <linux/sched/clock.h> because it is needed by sched_clock and I passed parameter bool ignr after void* ignore because it is needed by (un)register_trace_sched_switch. So, now my code is compiling, but there is a warning from make:
WARNING: "__tracepoint_sched_switch" [/some_path/myclock.ko] undefined!
And when I try to insmod, there is an error:
insmod: ERROR: could not insert module myclock.ko: Unknown symbol in module
So, what I have to do to make this works?
UPD: whole code I have at this moment
#include <linux/sched/clock.h>#include <linux/sched.h>#include <linux/module.h>#include <linux/printk.h>#include <linux/types.h>#include <linux/tracepoint.h>#include <trace/events/sched.h>MODULE_LICENSE("GPL");MODULE_AUTHOR("somebody");void my_sched_switch_probe(void* ignore, bool ignr, struct task_struct* prev, struct task_struct* next) { printk("my_sched_switch_probe: %s -> %s at %lu\n", prev->comm, next->comm, (unsigned long) sched_clock());}int cswtracer_init(void) { register_trace_sched_switch(my_sched_switch_probe, 0); return 0;}void cswtracer_fini(void) { unregister_trace_sched_switch(my_sched_switch_probe, 0);}module_init(cswtracer_init);module_exit(cswtracer_fini);UPD: seems __tracepoint_sched_switch is not exported to be used by other modules:
$ sudo cat /proc/kallsyms | grep __tracepoint_sched_switchffffffff91c123a0 D __tracepoint_sched_switch$ cat /lib/modules/`uname -r`/build/Module.symvers | grep __tracepoint_sched_switch$ (nothing was shown)Maybe my Makefile is wrong and there is a way to use __tracepoint_sched_switch by using some option in Makefile? Here it is:
ifneq ($(KERNELRELEASE),) obj-m := myclock.oelse CURRENT = $(shell uname -r) KDIR = /lib/modules/$(CURRENT)/build PWD = $(shell pwd)default: $(MAKE) -C $(KDIR) M=$(PWD) modulesclean: rm *.o rm *.mod.c rm *.symvers rm *.order rm .cache.mk rm .*.*.cmd rm -r .tmp_versionsendif