bak

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "buildroot"]
+	path = buildroot
+	url = https://github.com/buildroot/buildroot

Config.in

@@ -0,0 +1,6 @@
+config BR2_PACKAGE_KERNEL_MODULE
+	bool "kernel_module"
+	help
+	  Kernel module hello world.
+
+	  http://example.com/

Makefile

@@ -0,0 +1,10 @@
+obj-m += hello.o
+ccflags-y := -Wno-declaration-after-statement -std=gnu99
+
+.PHONY: all clean
+
+all:
+	$(MAKE) -C '$(LINUX_DIR)' M='$(PWD)' modules
+
+clean:
+	$(MAKE) -C '$(LINUX_DIR)' M='$(PWD)' clean

README.md

@@ -4,6 +4,6 @@
 1.  [Build](build.md)
 1.  [kmod](kmod.md)
 1.  Examples
-    1. [Host](host/)
+    1.  [Host](host/)
-
+    1.  Buildroot
-TODO: use Buildroot as in this answer http://stackoverflow.com/a/38813400/895245 to install and test modules on QEMU.
+        1. [hello](hello.c)

external.desc

@@ -0,0 +1 @@
+name: KERNEL_MODULE

external.mk

@@ -0,0 +1,20 @@
+################################################################################
+#
+# kernel_module
+#
+################################################################################
+
+KERNEL_MODULE_VERSION = 1.0
+KERNEL_MODULE_SITE = ..
+KERNEL_MODULE_SITE_METHOD = local
+
+define KERNEL_MODULE_BUILD_CMDS
+	$(MAKE) -C '$(@D)' LINUX_DIR='$(LINUX_DIR)' PWD='$(@D)' CC='$(TARGET_CC)' LD='$(TARGET_LD)'
+endef
+
+define KERNEL_MODULE_INSTALL_TARGET_CMDS
+	$(INSTALL) -D -m 0755 '$(@D)/kernel_module.ko' '$(TARGET_DIR)/kernel_module.ko'
+endef
+
+$(eval $(kernel-module))
+$(eval $(generic-package))

hello.c

@@ -0,0 +1,13 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+int init_module(void)
+{
+	printk(KERN_INFO "hello init\n");
+	return 0;
+}
+
+void cleanup_module(void)
+{
+	printk(KERN_INFO "hello cleanup\n");
+}

run

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -e
+cd buildroot
+make BR2_EXTERNAL="$(pwd)/.." qemu_x86_64_defconfig
+echo '
+BR2_TOOLCHAIN_EXTERNAL=y
+BR2_PACKAGE_KERNEL_MODULE=y
+' >> .config
+make BR2_JLEVEL="$(($(nproc) - 2))"
+qemu-system-x86_64 -M pc -kernel output/images/bzImage -drive file=output/images/rootfs.ext2,if=virtio,format=raw -append root=/dev/vda -net nic,model=virtio -net user