core: Add global FrameAllocator with locking

core/src/main.zig

@@ -99,6 +99,11 @@ export fn _start(magic: u32, info: MultibootInfo) callconv(.C) noreturn {
     };
     thread.arch.setStack(&init.regs, stack);
 
+    pmm.setGlobalAllocator(&allocator) catch |err| {
+        debug.print("Error while setting up global frame allocator: {}\n", .{err});
+        while (true) {}
+    };
+
     platform.platformEndInit();
 
     thread.enterTask(init);

core/src/pmm.zig

@@ -1,8 +1,10 @@
 const std = @import("std");
 const easyboot = @cImport(@cInclude("easyboot.h"));
 const platform = @import("arch/platform.zig").arch;
+const vmm = @import("arch/vmm.zig").arch;
 const mmap = @import("mmap.zig");
 const bmap = @import("lib/bitmap.zig");
+const locking = @import("lib/spinlock.zig");
 
 const FrameAllocatorError = error{
     InvalidMemoryMap,
@@ -104,3 +106,28 @@ pub fn initializeFrameAllocator(tag: *easyboot.multiboot_tag_mmap_t) !FrameAlloc
 
     return allocator;
 }
+
+var lock: locking.SpinLock = .{};
+var global_allocator: *FrameAllocator = undefined;
+
+pub fn setGlobalAllocator(allocator: *FrameAllocator) !void {
+    const frame = try allocFrame(allocator);
+    const virt = frame.virtualAddress(vmm.PHYSICAL_MAPPING_BASE);
+
+    global_allocator = @ptrFromInt(virt);
+    global_allocator.* = allocator.*;
+}
+
+pub fn lockGlobalAllocator() *FrameAllocator {
+    lock.lock();
+    return global_allocator;
+}
+
+pub fn tryLockGlobalAllocator() ?*FrameAllocator {
+    if (!lock.tryLock()) return null;
+    return global_allocator;
+}
+
+pub fn unlockGlobalAllocator() void {
+    lock.unlock();
+}