Debufs on fstab, go back to tty login to have job control, prepare target makefile for multiple progs

README.md

@@ -10,6 +10,7 @@ First build will take a while (GCC, Linux kernel).
 
 QEMU opens up, and you can run:
 
+    root
     insmod /hello.ko
     insmod /hello2.ko
     rmmod hello

kernel_module/test/Makefile

@@ -1,9 +1,16 @@
-CC = gcc
 
 .PHONY: clean
 
-ins_rm_mod: ins_rm_mod.c
+CC ?= gcc
+IN_EXT ?= .c
+OUT_EXT ?= .out
+
+OUTS := $(addsuffix $(OUT_EXT), $(basename $(wildcard *$(IN_EXT))))
+
+all: $(OUTS)
+
+%$(OUT_EXT): %$(IN_EXT)
 	$(CC) -o '$@' '$<'
 
 clean:
-	rm ins_rm_mod
+	rm -f *'$(OUT_EXT)'

rootfs_overlay/debugfs.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 set -ex
 mkdir -p /debugfs
+# We also added a fstab entry that mounts this under /sys/kernel/debug autmoatically.
+# That is the most common place to mount it.
 mount -t debugfs none /debugfs
 insmod /debugfs.ko
 cd /debugfs/kernel_module_cheat

rootfs_overlay/etc/fstab

@@ -0,0 +1,9 @@
+# <file system>	<mount pt>	<type>	<options>	<dump>	<pass>
+/dev/root	/		ext2	rw,noauto	0	1
+proc		/proc		proc	defaults	0	0
+devpts		/dev/pts	devpts	defaults,gid=5,mode=620	0	0
+tmpfs		/dev/shm	tmpfs	mode=0777	0	0
+tmpfs		/tmp		tmpfs	mode=1777	0	0
+tmpfs		/run		tmpfs	mode=0755,nosuid,nodev	0	0
+sysfs		/sys		sysfs	defaults	0	0
+debugfs		/sys/kernel/debug	debugfs	defaults	0	0

rootfs_overlay/etc/inittab

@@ -7,8 +7,8 @@
 ::sysinit:/bin/hostname -F /etc/hostname
 ::sysinit:/etc/init.d/rcS
 # https://unix.stackexchange.com/questions/299408/how-to-login-automatically-without-typing-root-in-buildroot-x86-64-qemu
-console::respawn:/bin/sh
-#console::respawn:/sbin/getty -n -L console 0 vt100
+#console::respawn:/bin/sh
+console::respawn:/sbin/getty -n -L console 0 vt100
 ::ctrlaltdel:/sbin/reboot
 ::shutdown:/etc/init.d/rcK
 ::shutdown:/sbin/swapoff -a