first commit

src/main.zig

@@ -0,0 +1,47 @@
+const std = @import("std");
+const isa = @import("riscv/isa.zig");
+const Fdt = @import("Fdt.zig");
+
+const UART_BASE: usize = 0x10000000;
+
+fn uart_put(c: u8) void {
+    const uart: *volatile u8 = @ptrFromInt(UART_BASE);
+    uart.* = c;
+}
+
+fn print(s: []const u8) void {
+    for (s) |c| {
+        uart_put(c);
+    }
+}
+
+export fn _start() linksection(".text.init") callconv(.naked) noreturn {
+    asm volatile (
+        \\li sp, 0x88000000
+        \\tail kmain
+    );
+}
+
+export fn kmain(hartid: u64, fdt_ptr: *const anyopaque) callconv(.c) noreturn {
+    _ = hartid;
+    print("Booting hydra...\n");
+
+    const fdt = Fdt.parse(fdt_ptr) catch {
+        print("Failed to parse FDT\n");
+        while (true) asm volatile ("wfi");
+    };
+
+    if (fdt.findFirstCompatible("ns16550a")) |console| {
+        var iter = console.getProperty("reg").?.asU32Array();
+        const start = iter.next();
+        const end = iter.next();
+        _ = end;
+        if (start == 0x100) {
+            print("Found console\n");
+        }
+    }
+
+    while (true) {
+        asm volatile ("wfi");
+    }
+}