kernel symbol marked with “T” in /proc/kallsyms is not exported

Question

Symbol machine_power_off is marked with \"T\" in /proc/kallsyms:

$ grep -w machine_power_off /proc/kallsyms 
ffffffff8102391b T mac         


        

Answer 1

To use kernel symbols that are global, but not exported (such as the machine_power_off symbol that you mention), you can use kallsyms_lookup in your module code:

#include 

static void (*machine_power_off_p)(void);
machine_power_off_p = (void*) kallsyms_lookup_name("machine_power_off");

Now you can call the machine_power_off function via the machine_power_off_p pointer:

(*machine_power_off_p)();