Add heap allocator

test/mock/kernel/vmm_mock.zig

@@ -1,14 +1,37 @@
 const mem = @import("mem_mock.zig");
 const multiboot = @import("../../../src/kernel/multiboot.zig");
+const bitmap = @import("../../../src/kernel/bitmap.zig");
 const arch = @import("arch_mock.zig");
 const std = @import("std");
 
+pub const VmmError = error{
+    /// A memory region expected to be allocated wasn't
+    NotAllocated,
+};
+
+pub const Attributes = struct {
+    kernel: bool,
+    writable: bool,
+    cachable: bool,
+};
+pub const BLOCK_SIZE: u32 = 1024;
+
 pub fn Mapper(comptime Payload: type) type {
     return struct {};
 }
 
 pub fn VirtualMemoryManager(comptime Payload: type) type {
-    return struct {};
+    return struct {
+        const Self = @This();
+
+        pub fn alloc(self: *Self, num: u32, attrs: Attributes) std.mem.Allocator.Error!?usize {
+            return std.mem.Allocator.Error.OutOfMemory;
+        }
+
+        pub fn free(self: *Self, vaddr: usize) (bitmap.Bitmap(u32).BitmapError || VmmError)!void {
+            return VmmError.NotAllocated;
+        }
+    };
 }
 
 pub fn init(mem_profile: *const mem.MemProfile, mb_info: *multiboot.multiboot_info_t, allocator: *std.mem.Allocator) std.mem.Allocator.Error!VirtualMemoryManager(arch.VmmPayload) {