Move to multi arch support and added memory map

src/root.zig

@@ -32,8 +32,49 @@ pub const Framebuffer = extern struct {
     format: PixelFormat,
 };
 
+/// Page size the memory map is measured in. 4 KiB on every architecture danos
+/// targets so far.
+pub const page_size = 4096;
+
+/// danos's own classification of a span of physical memory — deliberately not
+/// UEFI's vocabulary. Each boot path (UEFI now, device tree later) translates its
+/// native memory description into these kinds, so the kernel never learns what
+/// booted it. [[arch]] keeps the same discipline for CPU code.
+pub const MemoryKind = enum(u32) {
+    /// Free RAM the kernel may allocate.
+    usable,
+    /// Firmware, MMIO, the kernel image, our own boot buffers — never hand out.
+    reserved,
+    /// Usable once the kernel is done with boot-time structures (e.g. UEFI boot
+    /// services memory, which is free after ExitBootServices).
+    reclaimable,
+    /// ACPI tables: parse, then reclaim.
+    acpi_tables,
+    /// ACPI non-volatile storage: preserve across sleep, do not allocate.
+    acpi_nvs,
+};
+
+/// One contiguous span of physical memory. Because danos defines this layout
+/// itself (unlike the UEFI descriptor it's built from), `@sizeOf` is
+/// authoritative — the kernel walks a plain `[]MemoryRegion`, with none of the
+/// firmware's variable descriptor-stride to worry about.
+pub const MemoryRegion = extern struct {
+    base: u64, // physical start address
+    pages: u64, // length in `page_size` units
+    kind: MemoryKind,
+    _pad: u32 = 0,
+};
+
+/// The physical memory layout handed to the kernel: a pointer to an array of
+/// `len` `MemoryRegion`s, in a buffer that outlives the loader.
+pub const MemoryMap = extern struct {
+    regions: usize, // address of a `[len]MemoryRegion`
+    len: usize,
+};
+
 /// 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,
+    memory_map: MemoryMap,
 };