booting into the kernel

src/root.zig

@@ -1 +1,39 @@
-//! By convention, root.zig is the root source file when making a package.
+//! Shared definitions that form the contract between the bootloader
+//! (src/efi.zig, built as BOOTX64.efi) and the kernel (src/main.zig).
+//!
+//! Both binaries import this as the "danos" module, so the handoff layout is
+//! defined in exactly one place.
+
+const std = @import("std");
+
+/// Calling convention for the bootloader→kernel jump. Pinned to SysV so it does
+/// not depend on each binary's target default: the UEFI bootloader's C
+/// convention is Microsoft x64 (first arg in RCX), the freestanding kernel's is
+/// SysV (first arg in RDI). Both reference this to agree on where `*BootInfo`
+/// is passed.
+pub const kernel_abi: std.builtin.CallingConvention = .{ .x86_64_sysv = .{} };
+
+/// Pixel byte order of the linear framebuffer the firmware handed us.
+pub const PixelFormat = enum(u32) {
+    /// Byte 0 = Red, 1 = Green, 2 = Blue, 3 = reserved.
+    rgbx,
+    /// Byte 0 = Blue, 1 = Green, 2 = Red, 3 = reserved.
+    bgrx,
+};
+
+/// A linear framebuffer: `width`x`height` pixels, each a 32-bit value, with
+/// `pitch` bytes between the start of one row and the next (which may be larger
+/// than `width * 4` due to hardware padding).
+pub const Framebuffer = extern struct {
+    base: usize,
+    width: u32,
+    height: u32,
+    pitch: u32,
+    format: PixelFormat,
+};
+
+/// Handoff structure the bootloader fills in and passes to the kernel's
+/// `_start` in RDI (the first argument under the SysV AMD64 C ABI).
+pub const BootInfo = extern struct {
+    framebuffer: Framebuffer,
+};