get rid of lkmc package, move userland and kernel-modules to top

Rationale: we already had a non buildroot build system,
maintaining both will be hard, and having short paths is more awesome.

include/README.adoc

@@ -0,0 +1 @@
+https://github.com/cirosantilli/linux-kernel-module-cheat#include-directory

include/anonymous_inode.h

@@ -0,0 +1,9 @@
+#ifndef IOCTL_H
+#define IOCTL_H
+
+#include <linux/ioctl.h>
+
+#define LKMC_ANONYMOUS_INODE_MAGIC 0x33
+#define LKMC_ANONYMOUS_INODE_GET_FD _IOR(LKMC_ANONYMOUS_INODE_MAGIC, 0, int)
+
+#endif

include/ioctl.h

@@ -0,0 +1,42 @@
+#ifndef IOCTL_H
+#define IOCTL_H
+
+#include <linux/ioctl.h>
+
+/* Structs are the way to pass multiple arguments. */
+typedef struct {
+	int i;
+	int j;
+} lkmc_ioctl_struct;
+
+/* TODO some random number I can't understand how to choose. */
+#define LKMC_IOCTL_MAGIC 0x33
+
+/* I think those number do not *need* to be unique across, that is just to help debugging:
+ * https://stackoverflow.com/questions/22496123/what-is-the-meaning-of-this-macro-iormy-macig-0-int
+ *
+ * However, the ioctl syscall highjacks several low values at do_vfs_ioctl, e.g.
+ * This "forces" use to use the _IOx macros...
+ * https://stackoverflow.com/questions/10071296/ioctl-is-not-called-if-cmd-2
+ *
+ * Some of those magic low values are used for fnctl, which can also be used on regular files:
+ * e.g. FIOCLEX for close-on-exec:
+ * https://stackoverflow.com/questions/6125068/what-does-the-fd-cloexec-fcntl-flag-do
+ *
+ * TODO are the W or R of _IOx and type functional, or only to help with uniqueness?
+ *
+ * Documentation/ioctl/ioctl-number.txt documents:
+ *
+ * ....
+ * _IO    an ioctl with no parameters
+ * _IOW   an ioctl with write parameters (copy_from_user)
+ * _IOR   an ioctl with read parameters  (copy_to_user)
+ * _IOWR  an ioctl with both write and read parameters.
+ * ....
+ */
+/* Take an int, increment it. */
+#define LKMC_IOCTL_INC     _IOWR(LKMC_IOCTL_MAGIC, 0, int)
+/* Take a struct with two ints, increment the first, and decrement the second. */
+#define LKMC_IOCTL_INC_DEC _IOWR(LKMC_IOCTL_MAGIC, 1, lkmc_ioctl_struct)
+
+#endif

include/netlink.h

@@ -0,0 +1,10 @@
+#ifndef NETLINK_H
+#define NETLINK_H
+
+/* Socket identifier, matches userland. TODO can be anything?
+ * Is there a more scalable way to do it? E.g. ioctl device,
+ * kernel generates one on the fly, then give it back and connect?
+ * https://stackoverflow.com/questions/32898173/can-i-have-more-than-32-netlink-sockets-in-kernelspace */
+#define NETLINK_USER 31
+
+#endif

include/ring0.h

@@ -0,0 +1,58 @@
+#if defined(__x86_64__) || defined(__i386__)
+
+#ifdef THIS_MODULE
+#include <linux/kernel.h>
+#if defined(__x86_64__)
+typedef u64 T;
+#elif defined(__i386__)
+typedef u32 T;
+#endif
+#else
+#include <stdint.h>
+#if defined(__x86_64__)
+typedef uint64_t T;
+#elif defined(__i386__)
+typedef uint32_t T;
+#endif
+#endif
+
+typedef struct {
+    T cr0;
+    T cr2;
+    T cr3;
+} Ring0Regs;
+
+void ring0_get_control_regs(Ring0Regs *ring0_regs)
+{
+#if defined(__x86_64__)
+    __asm__ __volatile__ (
+        "mov %%cr0, %%rax;"
+        "mov %%eax, %0;"
+        "mov %%cr2, %%rax;"
+        "mov %%eax, %1;"
+        "mov %%cr3, %%rax;"
+        "mov %%eax, %2;"
+        : "=m" (ring0_regs->cr0),
+          "=m" (ring0_regs->cr2),
+          "=m" (ring0_regs->cr3)
+        :
+        : "%rax"
+    );
+#elif defined(__i386__)
+    __asm__ __volatile__ (
+        "mov %%cr0, %%eax;"
+        "mov %%eax, %0;"
+        "mov %%cr2, %%eax;"
+        "mov %%eax, %1;"
+        "mov %%cr3, %%eax;"
+        "mov %%eax, %2;"
+        : "=m" (ring0_regs->cr0),
+          "=m" (ring0_regs->cr2),
+          "=m" (ring0_regs->cr3)
+        :
+        : "%eax"
+    );
+#endif
+}
+
+#endif