From be6319ab89eaaceca644665fce59d8c83be53c3c Mon Sep 17 00:00:00 2001
From: Ciro Santilli <ciro.santilli@gmail.com>
Date: Mon, 9 Jul 2018 16:59:13 +0100
Subject: [PATCH] move doc for inits and sanity checks to README

---
 README.adoc                        | 45 ++++++++++++++++++++++++++++--
 kernel_module/user/hello.c         |  2 ++
 kernel_module/user/hello_cpp.cpp   |  4 ++-
 kernel_module/user/poweroff.c      |  4 +--
 kernel_module/user/sleep_forever.c |  2 +-
 5 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/README.adoc b/README.adoc
index 34bf922..6b98b61 100644
--- a/README.adoc
+++ b/README.adoc
@@ -2323,7 +2323,7 @@ Remember that if your init returns, the kernel will panic, there are just two no
 * run forever in a loop or long sleep
 * `poweroff` the machine
 
-==== The kernel panics despite poweroff
+==== poweroff.out
 
 Just using BusyBox' `poweroff` at the end of the `init` does not work and the kernel panics:
 
@@ -2341,7 +2341,27 @@ But this fails when we are `init` itself!
 ./run -E 'poweroff -f'
 ....
 
-but why not just use your super simple and effective `/poweroff.out` and be done with it?
+but why not just use our minimal `/poweroff.out` and be done with it?
+
+....
+./run -E '/poweroff.out'
+....
+
+Source: link:kernel_module/user/poweroff.c[]
+
+This also illustrates how to shutdown the computer from C: https://stackoverflow.com/questions/28812514/how-to-shutdown-linux-using-c-or-qt-without-call-to-system
+
+==== sleep_forever.out
+
+I dare you to guess what this does:
+
+....
+./run -E '/sleep_forever.out'
+....
+
+Source: link:kernel_module/user/sleep_forever.c[]
+
+This executable is a convenient simple init that does not panic and sleeps instead.
 
 [[init-busybox]]
 === Run command at the end of BusyBox init
@@ -8711,6 +8731,27 @@ Then proceed to do the following tests:
 * `/count.sh` and `b __x64_sys_write`
 * `insmod /timer.ko` and `b lkmc_timer_callback`
 
+===== Sanity checks
+
+Basic C and C++ hello worlds:
+
+....
+/hello.out
+/hello_cpp.out
+....
+
+Output:
+
+....
+hello
+hello cpp
+....
+
+Sources:
+
+* link:kernel_module/user/hello.c[]
+* link:kernel_module/user/hello_cpp.c[]
+
 === About
 
 This project is for people who want to learn and modify low level system components:
diff --git a/kernel_module/user/hello.c b/kernel_module/user/hello.c
index 7a63575..81f6976 100644
--- a/kernel_module/user/hello.c
+++ b/kernel_module/user/hello.c
@@ -1,3 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sanity-checks */
+
 #include <stdio.h>
 #include <stdlib.h>
 
diff --git a/kernel_module/user/hello_cpp.cpp b/kernel_module/user/hello_cpp.cpp
index 52e3b2e..df8669e 100644
--- a/kernel_module/user/hello_cpp.cpp
+++ b/kernel_module/user/hello_cpp.cpp
@@ -1,5 +1,7 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sanity-checks */
+
 #include <iostream>
 
 int main() {
-    std::cout << "hello world" << std::endl;
+    std::cout << "hello cpp" << std::endl;
 }
diff --git a/kernel_module/user/poweroff.c b/kernel_module/user/poweroff.c
index 92f56dd..bfa9540 100644
--- a/kernel_module/user/poweroff.c
+++ b/kernel_module/user/poweroff.c
@@ -1,6 +1,4 @@
-/* Userspace is for the weak. Die.
- * https://stackoverflow.com/questions/28812514/how-to-shutdown-linux-using-c-or-qt-without-call-to-system
- **/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#poweroff-out */
 
 #define _XOPEN_SOURCE 700
 #include <stdio.h>
diff --git a/kernel_module/user/sleep_forever.c b/kernel_module/user/sleep_forever.c
index 4725548..4676458 100644
--- a/kernel_module/user/sleep_forever.c
+++ b/kernel_module/user/sleep_forever.c
@@ -1,4 +1,4 @@
-/* Sleeping beauty, your prince is called Ctrl + C. */
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#sleep_forever-out */
 
 #include <stdio.h>
 #include <unistd.h>