rsnix: memory management — free-list heap, bitmap pages, paging adoption

- uefi.rs: full EfiMemoryType constants (0-14) + memory_type_name(); fix
  MEMORY_TYPE_LOADER_DATA from 6 to 2 per the UEFI spec
- memory.rs: replace the bump allocator with a first-fit free-list heap
  (splitting, coalescing, 8-byte back-pointer for alignment-safe free);
  add a bitmap physical page allocator (heap region reserved, page-0
  guard, aligned runs); grow the heap from the page allocator on demand
- paging.rs: identity page-table helpers — adopt_tables() rebuilds the
  firmware map into our own tables (OVMF maps its tables read-only, so
  the firmware tree can't be modified in place) and switches CR3;
  map_page/unmap_page/is_mapped with 2 MB/1 GB large-page splitting
- main.rs: boot self-tests for heap, pages, and paging

1 files changed, 35 insertions, 5 deletions

diff --git a/rsnix/src/uefi.rs b/rsnix/src/uefi.rs
index 2e3ed6b..619739e 100644
--- a/rsnix/src/uefi.rs
+++ b/rsnix/src/uefi.rs
@@ -116,13 +116,43 @@ pub struct MemoryDescriptor {
     pub attribute: u64,
 }
 
-pub const MEMORY_TYPE_CONVENTIONAL: u32 = 7;
-#[allow(dead_code)]
-pub const MEMORY_TYPE_LOADER_DATA: u32 = 6;
-#[allow(dead_code)]
+pub const MEMORY_TYPE_RESERVED: u32 = 0;
+pub const MEMORY_TYPE_LOADER_CODE: u32 = 1;
+pub const MEMORY_TYPE_LOADER_DATA: u32 = 2;
 pub const MEMORY_TYPE_BOOT_SERVICES_CODE: u32 = 3;
-#[allow(dead_code)]
 pub const MEMORY_TYPE_BOOT_SERVICES_DATA: u32 = 4;
+pub const MEMORY_TYPE_RUNTIME_CODE: u32 = 5;
+pub const MEMORY_TYPE_RUNTIME_DATA: u32 = 6;
+pub const MEMORY_TYPE_CONVENTIONAL: u32 = 7;
+pub const MEMORY_TYPE_UNUSABLE: u32 = 8;
+pub const MEMORY_TYPE_ACPI_RECLAIM: u32 = 9;
+pub const MEMORY_TYPE_ACPI_NVS: u32 = 10;
+pub const MEMORY_TYPE_MMIO: u32 = 11;
+pub const MEMORY_TYPE_MMIO_PORT: u32 = 12;
+pub const MEMORY_TYPE_PAL_CODE: u32 = 13;
+pub const MEMORY_TYPE_PERSISTENT: u32 = 14;
+
+/// Human-readable name for a UEFI memory type.
+pub fn memory_type_name(kind: u32) -> &'static str {
+    match kind {
+        0 => "Reserved",
+        1 => "LoaderCode",
+        2 => "LoaderData",
+        3 => "BootServicesCode",
+        4 => "BootServicesData",
+        5 => "RuntimeCode",
+        6 => "RuntimeData",
+        7 => "Conventional",
+        8 => "Unusable",
+        9 => "ACPIReclaim",
+        10 => "ACPINVS",
+        11 => "MMIO",
+        12 => "MMIOPort",
+        13 => "PalCode",
+        14 => "Persistent",
+        _ => "Unknown",
+    }
+}
 
 // ---------------------------------------------------------------------------
 // Boot services table