7842 - new directory organization

Baremetal is now the default build target and therefore has its sources
at the top-level. Baremetal programs build using the phase-2 Mu toolchain
that requires a Linux kernel. This phase-2 codebase which used to be at
the top-level is now under the linux/ directory. Finally, the phase-2 toolchain,
while self-hosting, has a way to bootstrap from a C implementation, which
is now stored in linux/bootstrap. The bootstrap C implementation uses some
literate programming tools that are now in linux/bootstrap/tools.

So the whole thing has gotten inverted. Each directory should build one
artifact and include the main sources (along with standard library). Tools
used for building it are relegated to sub-directories, even though those
tools are often useful in their own right, and have had lots of interesting
programs written using them.

A couple of things have gotten dropped in this process:
  - I had old ways to run on just a Linux kernel, or with a Soso kernel.
    No more.
  - I had some old tooling for running a single test at the cursor. I haven't
    used that lately. Maybe I'll bring it back one day.

The reorg isn't done yet. Still to do:
  - redo documentation everywhere. All the README files, all other markdown,
    particularly vocabulary.md.
  - clean up how-to-run comments at the start of programs everywhere
  - rethink what to do with the html/ directory. Do we even want to keep
    supporting it?

In spite of these shortcomings, all the scripts at the top-level, linux/
and linux/bootstrap are working. The names of the scripts also feel reasonable.
This is a good milestone to take stock at.

1 files changed, 31 insertions, 0 deletions

diff --git a/ex2.mu b/ex2.mu
new file mode 100644
index 00000000..adc905e9
--- /dev/null
+++ b/ex2.mu
@@ -0,0 +1,31 @@
+# Test out the video mode by filling in the screen with pixels.
+#
+# To build a disk image:
+#   ./translate_mu_baremetal baremetal/ex2.mu     # emits disk.img
+# To run:
+#   qemu-system-i386 disk.img
+# Or:
+#   bochs -f baremetal/boot.bochsrc               # boot.bochsrc loads disk.img
+#
+# Expected output:
+#   html/baremetal.png
+
+fn main {
+  var y/eax: int <- copy 0
+  {
+    compare y, 0x300/screen-height=768
+    break-if->=
+    var x/edx: int <- copy 0
+    {
+      compare x, 0x400/screen-width=1024
+      break-if->=
+      var color/ecx: int <- copy x
+      color <- and 0xff
+      pixel-on-real-screen x, y, color
+      x <- increment
+      loop
+    }
+    y <- increment
+    loop
+  }
+}