boot: longmode to realmode stub

This is the initial commit to the repo. It adds all the code.
The last proper thing that I got working before committing is
calling real mode functions from long mode using a stub.
Next up, I would like to implement a disk reader abstraction over
the BIOS in order to read form partitions (most notably FAT32).

1 files changed, 24 insertions, 0 deletions

diff --git a/rt/start.ha b/rt/start.ha
new file mode 100644
index 0000000..edbc5a5
--- /dev/null
+++ b/rt/start.ha
@@ -0,0 +1,24 @@
+@symbol("main") fn main() void;
+
+const @symbol("__init_array_start") init_start: [*]*fn() void;
+const @symbol("__init_array_end") init_end: [*]*fn() void;
+const @symbol("__fini_array_start") fini_start: [*]*fn() void;
+const @symbol("__fini_array_end") fini_end: [*]*fn() void;
+
+export @noreturn @symbol("_hare") fn _hare() void = {
+	const ninit = (&init_end: uintptr - &init_start: uintptr): size
+		/ size(*fn() void);
+	for (let i = 0z; i < ninit; i += 1) {
+		init_start[i]();
+	};
+
+	main();
+
+	const nfini = (&fini_end: uintptr - &fini_start: uintptr): size
+		/ size(*fn() void);
+	for (let i = 0z; i < nfini; i += 1) {
+		fini_start[i]();
+	};
+
+	halt();
+};