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host/Makefile

@@ -0,0 +1,33 @@
+OUT_EXT := .ko
+OBJ_EXT := .o
+RUN     := hello
+RUN_EXT := $(RUN)$(OUT_EXT)
+
+obj-m += hello.o
+ccflags-y := -Wno-declaration-after-statement -std=gnu99
+
+.PHONY: clean ins log rm run my-ins
+
+all: $(RUN_EXT) ins_rm_mod.out
+
+hello.ko: hello.c
+	make -C /lib/modules/$(shell uname -r)/build M="$(PWD)" modules
+
+clean:
+	make -C /lib/modules/$(shell uname -r)/build M="$(PWD)" clean
+	rm -f *.out
+
+ins: all
+	sudo insmod '$(RUN_EXT)'
+
+log:
+	dmesg
+
+rm:
+	if lsmod | grep -Eq '^$(RUN) '; then sudo rmmod '$(RUN_EXT)'; fi
+
+ins_rm_mod.out: ins_rm_mod.c
+	gcc -Wall -std=gnu99 -o '$@' '$<'
+
+ins_rm_run: ins_rm_mod.out $(RUN_EXT)
+	sudo ./ins_rm_mod.out

host/README.md

@@ -0,0 +1,34 @@
+# Host
+
+Simple things that can be demonstrated by inserting a module into the currently running host. Tested on Ubuntu 16.04.
+
+1. [hello](hello.c)
+1. [ins_rm_mod.c](ins_rm_mod.c)
+
+## Rationale
+
+This method easier to setup, but it is not recommended for development, as:
+
+- it may break your system.
+- you can't control which kernel version to use
+
+Use VMs instead.
+
+## Usage
+
+We only use it for super simple examples.
+
+Build, insert and remove a hello world module:
+
+    make ins
+    make rm
+    make log
+
+The last lines of the log should contain:
+
+    init_module
+    cleanup_module
+
+Insert and remove a module from a C program:
+
+    make ins_rm_run

host/hello.c

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

host/ins_rm_mod.c

@@ -0,0 +1,36 @@
+/*
+http://stackoverflow.com/questions/5947286/how-can-linux-kernel-modules-be-loaded-from-c-code/38606527#38606527
+*/
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+#define init_module(mod, len, opts) syscall(__NR_init_module, mod, len, opts)
+#define delete_module(name, flags) syscall(__NR_delete_module, name, flags)
+
+int main(void) {
+    int fd = open("hello.ko", O_RDONLY);
+    struct stat st;
+    fstat(fd, &st);
+    size_t image_size = st.st_size;
+    void *image = malloc(image_size);
+    read(fd, image, image_size);
+    close(fd);
+    if (init_module(image, image_size, "") != 0) {
+        perror("init_module");
+        return EXIT_FAILURE;
+    }
+    free(image);
+    if (delete_module("hello", O_NONBLOCK) != 0) {
+        perror("delete_modul");
+        return EXIT_FAILURE;
+    }
+    return EXIT_SUCCESS;
+}