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, 35 insertions, 0 deletions

diff --git a/ex2.subx b/ex2.subx
new file mode 100644
index 00000000..074d641e
--- /dev/null
+++ b/ex2.subx
@@ -0,0 +1,35 @@
+# Test out the video mode by filling in the screen with pixels.
+#
+# To build a disk image:
+#   ./translate_subx_baremetal baremetal/ex2.subx    # 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
+
+== code
+
+main:
+  # ecx <- start of video memory
+  8b/-> *0x8128 1/r32/ecx
+
+  # eax <- final pixel of video memory
+  8d/copy-address *(ecx + 0x0bffff) 0/r32/eax  # 0xbffff = 1024*768 - 1
+
+  # for each pixel in video memory
+  {
+    39/compare %eax 1/r32/ecx
+    7c/jump-if-< break/disp8
+    # write its column number to it
+    88/byte<- *eax 0/r32/AL
+    48/decrement-eax
+    eb/jump loop/disp8
+  }
+
+  # hang indefinitely
+  {
+    eb/jump loop/disp8
+  }