bring CONFIG_FORTIFY_SOURCE back from accidental removal...

Notice that it is not working anymore.

Rename pci.c into qemu_edu.c

Organize kernel_module readmes further

kernel_module/README.adoc

@@ -1,6 +1,4 @@
-= kernel_module
-
-Our kernel modules!
+https://github.com/cirosantilli/linux-kernel-module-cheat#directory-structure
 
 . Asynchronous
 .. link:irq.c[]
@@ -9,7 +7,3 @@ Our kernel modules!
 .. link:timer.c[]
 .. link:work_from_work.c[]
 .. link:workqueue_cheat.c[]
-. Hardening
-.. link:strlen_overflow.c[]
-. Tracing
-.. link:kprobe_example.c[]

kernel_module/fops.c

@@ -1,3 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#file-operations */
+
 #include <linux/debugfs.h>
 #include <linux/errno.h> /* EFAULT */
 #include <linux/fs.h> /* file_operations */

kernel_module/kprobe_example.c

@@ -1,3 +1,8 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#kprobes
+ *
+ * Adapted from: https://github.com/torvalds/linux/blob/v4.17/samples/kprobes/kprobe_example.c
+ */
+
 /*
  * NOTE: This example is works on x86 and powerpc.
  * Here's a sample kernel module showing the use of kprobes to dump a

kernel_module/pci_min.c

@@ -1,3 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#pci_min */
+
 #include <linux/cdev.h>
 #include <linux/fs.h>
 #include <linux/init.h>

kernel_module/pmccntr.c

@@ -1,6 +1,4 @@
-/*
-ARM only.
-*/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#pmccntr */
 
 #include <linux/debugfs.h>
 #include <linux/errno.h> /* EFAULT */

kernel_module/qemu_edu.c

@@ -1,3 +1,5 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#qemu-edu */
+
 #include <linux/cdev.h> /* cdev_ */
 #include <linux/fs.h>
 #include <linux/init.h>

kernel_module/strlen_overflow.c

@@ -1,6 +1,4 @@
-/*
-https://www.reddit.com/r/hacking/comments/8h4qxk/what_a_buffer_overflow_in_the_linux_kernel_looks/
-*/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#config_fortify_source */
 
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -8,6 +6,7 @@ https://www.reddit.com/r/hacking/comments/8h4qxk/what_a_buffer_overflow_in_the_l
 
 static int myinit(void)
 {
+	/* Missing terminaing NUL '\0'. */
 	char buf[] = {'p', 'w', 'n'};
 	pr_info("%llu\n", (long long unsigned)strlen(buf));
 	return 0;

kernel_module/user/README.adoc

@@ -1,25 +1,15 @@
-= user
+https://github.com/cirosantilli/linux-kernel-module-cheat#rootfs_overlay
 
-Userland C programs used to test our kernel modules.
-
-`sh` programs are simpler, and installed by copying directly with an overlay.
-
-C programs require cross compiling, but give us more control over system calls.
-
-These programs can also be compiled and used on host.
-
-. Standalone
-.. link:hello.c[]
-.. link:hello_cpp.cpp[]
-.. link:sched_getaffinity.c[]
-.. link:usermem.c[]
-... link:pagemap_dump.c[]
-.. inits
-.... link:sleep_forever.c[]
-.... link:poweroff.c[]
-.... link:init_dev_kmsg.c[]
-.. link:uio_read.c[]
-.. link:rand_check.c[]
-.. x86_64
-... link:rdtsc.c[]
-... link:ring0.c[]
+. link:hello.c[]
+. link:hello_cpp.cpp[]
+. link:sched_getaffinity.c[]
+. link:usermem.c[]
+.. link:pagemap_dump.c[]
+. inits
+... link:sleep_forever.c[]
+... link:poweroff.c[]
+... link:init_dev_kmsg.c[]
+. link:uio_read.c[]
+. link:rand_check.c[]
+. x86_64
+.. link:rdtsc.c[]

kernel_module/user/proc_events.c

@@ -1,8 +1,7 @@
-/*
-This file is licensed under the GPL v2 (http://www.gnu.org/licenses/gpl2.txt) (some parts was originally borrowed from proc events example)
-
-https://stackoverflow.com/questions/6075013/detect-launching-of-programs-on-linux-platform/8255487#8255487
-*/
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#config_proc_events
+ *
+ * Adapted from: https://stackoverflow.com/questions/6075013/detect-launching-of-programs-on-linux-platform/8255487#8255487
+ */
 
 #if defined(__aarch64__)