feat(mm): add allocators

src/mm/heap.zig

@@ -0,0 +1,26 @@
+const b = @import("base");
+const ke = b.ke;
+const mm = b.mm;
+const mi = mm.private;
+
+var heap_lock: ke.SpinLock = .init();
+var heap_arena: mm.vmem.Arena = undefined;
+
+pub fn init() void {
+    heap_arena.init("kernel heap", mi.impl.kernel_heap_base, b.tib(16), mm.page_size) catch @panic("failed to initialize kernel heap arena");
+}
+
+pub fn alloc_pages(size: usize) mm.Error!*anyopaque {
+    const ipl = heap_lock.acquire();
+    defer heap_lock.release(ipl);
+
+    const addr = try heap_arena.alloc(size, .{});
+
+    mi.kernel_pmap.map_range_allocating(addr, size, .{
+        .read = true,
+        .write = true,
+        .global = true,
+    });
+
+    return @ptrFromInt(addr);
+}