Mac kernel programming generic kernel extension prinf() not working - c

Question

I've followed the Creating a Generic Kernel Extension with Xcode tutorial.
MyKext.c:
#include <sys/systm.h>
#include <mach/mach_types.h>
kern_return_t MyKext_start (kmod_info_t * ki, void * d)
{
printf("MyKext has started.\n");
return KERN_SUCCESS;
}
kern_return_t MyKext_stop (kmod_info_t * ki, void * d)
{
printf("MyKext has stopped.\n");
return KERN_SUCCESS;
}
I've also disabled the csrutil, which allow me to load my own kext.
# csrutil disable
When I load my own kext into kernel
$ sudo kextload -v /tmp/MyKext.kext
The result of printf() not write into /var/log/system.log.
I've also set boot-args
$ sudo nvram boot-args="original_contents debug=0x4"
Can anyone help me out?

Answer 1

Apparently, since Sierra (10.12) at least, they reorganized the way the logs are written (iOS support?), so you cannot see it in system.log anymore. Still, in your Console application, you have in the sidebar a Devices section, where you can select your device (usually your Mac system) and see real-time log limited to "kernel" in the search box. So I can see these when using kext load/kextunload:
default 11:58:27.608228 +0200 kernel MyKext has started.
default 11:58:34.446824 +0200 kernel MyKext has stopped.
default 11:58:44.803350 +0200 kernel MyKext has started.
There is no need for the csrutil and nvram changes.
Important For some freaky reason, I needed to restart the Console to reflect my messages changes, otherwise it has showing the ones (start & stop) from the previous build. Very strange indeed!
Later To recover old logs, try sudo log collect --last 1d and open the result with Console(more here).

Answer 2

Sorry to necro-post, but I found it useful to use log(1) with one of its many commands (as suggested by #pmdj in the comments above) rather than use Console. From the manual:
log -- Access system wide log messages created by os_log, os_trace and other log-
ging systems.
For example, one can run:
log stream
to see real-time output of the system, including printf() from the MacOS kernel extension.