diff --git a/core/src/sys/ipc.zig b/core/src/sys/ipc.zig
new file mode 100644
index 0000000..b64855c
--- /dev/null
+++ b/core/src/sys/ipc.zig
@@ -0,0 +1,34 @@
+const std = @import("std");
+const system = @import("system");
+const platform = @import("../arch/platform.zig");
+const sys = @import("syscall.zig");
+const thread = @import("../thread.zig");
+const cpu = @import("../arch/cpu.zig");
+const pmm = @import("../pmm.zig");
+const vmm = @import("../arch/vmm.zig");
+
+pub fn send(regs: *platform.Registers, args: *sys.Arguments, retval: *isize) anyerror!void {
+    try asyncSend(regs, args, retval);
+
+    _ = thread.block(regs);
+}
+
+pub fn asyncSend(_: *platform.Registers, args: *sys.Arguments, _: *isize) anyerror!void {
+    const core = cpu.thisCore();
+    const target = thread.lookupThreadById(args.arg0) orelse return error.NoSuchThread;
+
+    var queue = target.event_queue orelse return error.ThreadMessagingNotAvailable;
+
+    var data: [2]u64 = std.mem.zeroes([2]u64);
+    data[0] = @intFromEnum(system.kernel.KernelMessage.MessageReceived);
+    data[1] = core.current_thread.id;
+    _ = queue.writeType([2]u64, &data);
+
+    if (target.state == .Blocked) {
+        thread.reviveThread(core, target);
+    }
+}
+
+pub fn wait(regs: *platform.Registers, _: *sys.Arguments, _: *isize) anyerror!void {
+    _ = thread.block(regs);
+}
diff --git a/core/src/sys/syscall.zig b/core/src/sys/syscall.zig
index b380c6a..9e7c7a2 100644
--- a/core/src/sys/syscall.zig
+++ b/core/src/sys/syscall.zig
@@ -5,6 +5,7 @@ const print = @import("print.zig");
 const mem = @import("mem.zig");
 const sched = @import("sched.zig");
 const tokens = @import("token.zig");
+const ipc = @import("ipc.zig");
 const cpu = @import("../arch/cpu.zig");
 
 pub const Arguments = struct {
@@ -37,6 +38,9 @@ const syscalls = [_]SystemCall{
     sched.startThread,
     sched.getThreadId,
     mem.getAddressSpace,
+    ipc.send,
+    ipc.asyncSend,
+    ipc.wait,
 };
 
 pub fn invokeSyscall(number: usize, frame: *platform.Registers, args: *Arguments, retval: *isize) void {
diff --git a/system/init/boot.zig b/system/init/boot.zig
new file mode 100644
index 0000000..7cc74d6
--- /dev/null
+++ b/system/init/boot.zig
@@ -0,0 +1,25 @@
+const system = @import("system");
+
+const vm = system.vm;
+const syscalls = system.syscalls;
+const buffer = system.ring_buffer;
+
+pub fn setupKernelRingBuffer(base: u64) !void {
+    const phys = vm.PhysFrame{ .address = try syscalls.allocFrame() };
+
+    const data: [*]u8 = @ptrCast(phys.virtualPointer(u8, base));
+
+    try syscalls.setEventQueue(syscalls.getThreadId(), phys.address);
+
+    const event_queue = buffer.RingBuffer.init(data, vm.PAGE_SIZE, true);
+
+    system.ipc.setKernelBuffer(event_queue);
+}
+
+pub fn discoverThreadLimit() u64 {
+    var pid: u64 = 1;
+    while (true) {
+        _ = syscalls.getPriority(pid) catch return (pid - 1);
+        pid += 1;
+    }
+}
diff --git a/system/init/main.zig b/system/init/main.zig
index a59c8fe..9c7f393 100644
--- a/system/init/main.zig
+++ b/system/init/main.zig
@@ -1,4 +1,7 @@
+const std = @import("std");
 const system = @import("system");
+const thread = @import("thread.zig");
+const boot = @import("boot.zig");
 
 const vm = system.vm;
 const syscalls = system.syscalls;
@@ -7,16 +10,6 @@ const heap = system.heap;
 
 const PAGE_SIZE = vm.PAGE_SIZE;
 
-fn setupKernelRingBuffer(base: u64) !buffer.RingBuffer {
-    const phys = vm.PhysFrame{ .address = try syscalls.allocFrame() };
-
-    const data: [*]u8 = @ptrCast(phys.virtualPointer(u8, base));
-
-    try syscalls.setEventQueue(syscalls.getThreadId(), phys.address);
-
-    return buffer.RingBuffer.init(data, PAGE_SIZE, true);
-}
-
 fn setTokens() void {
     var tokens: u64 = 0;
     tokens |= @intFromEnum(system.kernel.Token.Root);
@@ -25,81 +18,56 @@ fn setTokens() void {
     syscalls.setTokens(syscalls.getThreadId(), tokens) catch {};
 }
 
-fn discoverThreadLimit() u64 {
-    var pid: u64 = 1;
-    while (true) {
-        _ = syscalls.getPriority(pid) catch return (pid - 1);
-        pid += 1;
-    }
-}
-
-fn setupKernelRingBufferForThread(mapper: *const vm.MemoryMapper, pid: u64, virt: u64) !void {
-    const phys = vm.PhysFrame{ .address = try syscalls.allocFrame() };
-
-    try vm.map(mapper, virt, phys, @intFromEnum(vm.Flags.User) | @intFromEnum(vm.Flags.ReadWrite) | @intFromEnum(vm.Flags.NoExecute));
-
-    try syscalls.setEventQueue(pid, phys.address);
-}
-
-fn setupRingBufferForThread(mapper: *const vm.MemoryMapper, base: u64, virt: u64) !buffer.RingBuffer {
-    const phys = vm.PhysFrame{ .address = try syscalls.allocFrame() };
-
-    try vm.map(mapper, virt, phys, @intFromEnum(vm.Flags.User) | @intFromEnum(vm.Flags.ReadWrite) | @intFromEnum(vm.Flags.NoExecute));
-
-    const data: [*]u8 = @ptrCast(phys.virtualPointer(u8, base));
-
-    return buffer.RingBuffer.init(data, PAGE_SIZE, true);
-}
-
-fn setupThread(pid: u64, base: u64) !system.ipc.Connection {
-    const space = try syscalls.getAddressSpace(pid);
-    const mapper = vm.MemoryMapper.create(.{ .address = space }, base);
-
-    const ipc_base = 0x1000; // FIXME: Find a good place in the address space and guarantee this is free.
-
-    try setupKernelRingBufferForThread(&mapper, pid, ipc_base + system.ipc.KERNEL_BUFFER_ADDRESS_OFFSET);
-    // INIT_WRITE and INIT_READ are inverted here because when the process writes, init reads.
-    const read_buffer = try setupRingBufferForThread(&mapper, base, ipc_base + system.ipc.INIT_WRITE_BUFFER_ADDRESS_OFFSET);
-    const write_buffer = try setupRingBufferForThread(&mapper, base, ipc_base + system.ipc.INIT_READ_BUFFER_ADDRESS_OFFSET);
-
-    const connection: system.ipc.Connection = .{ .pid = pid, .read_buffer = read_buffer, .write_buffer = write_buffer };
-
-    try syscalls.setThreadArguments(pid, base, ipc_base);
-
-    try syscalls.startThread(pid);
-
-    return connection;
-}
-
 export fn _start(base: u64, address: u64) callconv(.C) noreturn {
+    main(base, address) catch {
+        while (true) {}
+    };
+}
+
+inline fn main(base: u64, address: u64) !void {
     setTokens();
 
     const mapper = vm.MemoryMapper.create(.{ .address = address }, base);
-    _ = mapper;
+    var sys_alloc = heap.SystemAllocator.init(mapper, 0x200000, base - 0x200000); // FIXME: Let's not hardcode these.
+    const allocator = sys_alloc.allocator();
 
-    const threads = discoverThreadLimit();
-    syscalls.print(threads);
+    const threads = boot.discoverThreadLimit();
 
-    const pid: u64 = 2;
-    var connection = setupThread(pid, base) catch {
-        while (true) {}
-    };
+    var thread_list = std.AutoHashMap(u64, thread.Thread).init(allocator);
+    try thread_list.ensureTotalCapacity(@intCast(threads));
+    errdefer thread_list.deinit();
 
-    const event_queue = setupKernelRingBuffer(base) catch {
-        while (true) {}
-    };
+    var pid: u64 = 1;
+    while (pid <= threads) : (pid += 1) {
+        if (pid == syscalls.getThreadId()) continue;
+        const t = try thread.setupThread(pid, base);
+        try thread_list.put(pid, t);
+    }
 
-    system.ipc.setKernelBuffer(event_queue);
+    try boot.setupKernelRingBuffer(base);
 
-    var counter: u64 = 0;
+    var kernel_queue = system.ipc.getKernelBuffer().?;
 
-    while (true) : (counter += 4) {
-        var data: u8 = undefined;
-        if (connection.read_buffer.read(@ptrCast(&data), 1)) {
-            syscalls.print(data);
+    outer: while (true) {
+        var msg_type: u64 = undefined;
+        while (kernel_queue.readType(u64, &msg_type)) {
+            switch (msg_type) {
+                @intFromEnum(system.kernel.KernelMessage.MessageReceived) => {
+                    var id: u64 = undefined;
+                    if (!kernel_queue.readType(u64, &id)) continue :outer;
+
+                    var sender = thread_list.getPtr(id).?;
+
+                    var data: u8 = undefined;
+                    if (sender.connection.read(u8, &data)) {
+                        syscalls.print(id);
+                        syscalls.print(data);
+                    }
+                },
+                else => {},
+            }
         }
 
-        syscalls.sleep(1000);
-        syscalls.print(counter);
+        syscalls.wait();
     }
 }
diff --git a/system/init/thread.zig b/system/init/thread.zig
new file mode 100644
index 0000000..55320d4
--- /dev/null
+++ b/system/init/thread.zig
@@ -0,0 +1,49 @@
+const std = @import("std");
+const system = @import("system");
+
+const vm = system.vm;
+const syscalls = system.syscalls;
+const buffer = system.ring_buffer;
+
+pub const Thread = struct {
+    address: ?[]u8,
+    connection: system.ipc.Connection,
+};
+
+pub fn setupKernelRingBufferForThread(mapper: *const vm.MemoryMapper, pid: u64, virt: u64) !void {
+    const phys = vm.PhysFrame{ .address = try syscalls.allocFrame() };
+
+    try vm.map(mapper, virt, phys, @intFromEnum(vm.Flags.User) | @intFromEnum(vm.Flags.ReadWrite) | @intFromEnum(vm.Flags.NoExecute));
+
+    try syscalls.setEventQueue(pid, phys.address);
+}
+
+pub fn setupRingBufferForThread(mapper: *const vm.MemoryMapper, base: u64, virt: u64) !buffer.RingBuffer {
+    const phys = vm.PhysFrame{ .address = try syscalls.allocFrame() };
+
+    try vm.map(mapper, virt, phys, @intFromEnum(vm.Flags.User) | @intFromEnum(vm.Flags.ReadWrite) | @intFromEnum(vm.Flags.NoExecute));
+
+    const data: [*]u8 = @ptrCast(phys.virtualPointer(u8, base));
+
+    return buffer.RingBuffer.init(data, vm.PAGE_SIZE, true);
+}
+
+pub fn setupThread(pid: u64, base: u64) !Thread {
+    const space = try syscalls.getAddressSpace(pid);
+    const mapper = vm.MemoryMapper.create(.{ .address = space }, base);
+
+    const ipc_base = 0x1000; // FIXME: Find a good place in the address space and guarantee this is free.
+
+    try setupKernelRingBufferForThread(&mapper, pid, ipc_base + system.ipc.KERNEL_BUFFER_ADDRESS_OFFSET);
+    // INIT_WRITE and INIT_READ are inverted here because when the process writes, init reads.
+    const read_buffer = try setupRingBufferForThread(&mapper, base, ipc_base + system.ipc.INIT_WRITE_BUFFER_ADDRESS_OFFSET);
+    const write_buffer = try setupRingBufferForThread(&mapper, base, ipc_base + system.ipc.INIT_READ_BUFFER_ADDRESS_OFFSET);
+
+    const connection: system.ipc.Connection = .{ .pid = pid, .read_buffer = read_buffer, .write_buffer = write_buffer };
+
+    try syscalls.setThreadArguments(pid, base, ipc_base);
+
+    try syscalls.startThread(pid);
+
+    return .{ .address = null, .connection = connection };
+}
diff --git a/system/lib/ipc.zig b/system/lib/ipc.zig
index eca8a85..7518efc 100644
--- a/system/lib/ipc.zig
+++ b/system/lib/ipc.zig
@@ -5,6 +5,22 @@ pub const Connection = struct {
     pid: u64,
     read_buffer: buffer.RingBuffer,
     write_buffer: buffer.RingBuffer,
+
+    pub fn read(self: *Connection, comptime T: type, out: *T) bool {
+        return self.read_buffer.readType(T, out);
+    }
+
+    pub fn write(self: *Connection, comptime T: type, in: *const T) bool {
+        return self.write_buffer.writeType(T, in);
+    }
+
+    pub fn readBytes(self: *Connection, bytes: [*]u8, length: usize) bool {
+        return self.read_buffer.read(bytes, length);
+    }
+
+    pub fn writeBytes(self: *Connection, bytes: []u8) bool {
+        return self.write_buffer.writeSlice(bytes);
+    }
 };
 
 pub const KERNEL_BUFFER_ADDRESS_OFFSET = 0x0000;
diff --git a/system/lib/kernel.zig b/system/lib/kernel.zig
index d6b326e..bac0a13 100644
--- a/system/lib/kernel.zig
+++ b/system/lib/kernel.zig
@@ -17,6 +17,9 @@ pub const SystemCall = enum(u64) {
     StartThread, // requires Token.CreateProcess
     GetThreadId,
     GetAddressSpace, // requires Token.CreateProcess
+    Send,
+    AsyncSend,
+    Wait,
 };
 
 pub const Token = enum(u64) {
@@ -31,3 +34,7 @@ pub const SystemError = error{
     NoSuchThread,
     NotAuthorized,
 };
+
+pub const KernelMessage = enum(u8) {
+    MessageReceived = 0,
+};
diff --git a/system/lib/ring_buffer.zig b/system/lib/ring_buffer.zig
index b630566..45ae797 100644
--- a/system/lib/ring_buffer.zig
+++ b/system/lib/ring_buffer.zig
@@ -102,6 +102,22 @@ pub const RingBuffer = struct {
         return true;
     }
 
+    pub fn readType(self: *RingBuffer, comptime T: type, out: *T) bool {
+        return self.read(@ptrCast(out), @sizeOf(@TypeOf(out.*)));
+    }
+
+    pub fn peekType(self: *RingBuffer, comptime T: type, out: *T) bool {
+        return self.peek(@ptrCast(out), @sizeOf(@TypeOf(out.*)));
+    }
+
+    pub fn writeType(self: *RingBuffer, comptime T: type, in: *const T) bool {
+        return self.write(@ptrCast(in), @sizeOf(@TypeOf(in.*)));
+    }
+
+    pub fn writeSlice(self: *RingBuffer, bytes: []const u8) bool {
+        return self.write(bytes.ptr, bytes.len);
+    }
+
     fn dataPointer(self: *RingBuffer) [*]u8 {
         return @ptrCast(&self.data.data_start);
     }
diff --git a/system/lib/syscalls.zig b/system/lib/syscalls.zig
index 25dd9c7..959ebb6 100644
--- a/system/lib/syscalls.zig
+++ b/system/lib/syscalls.zig
@@ -101,3 +101,15 @@ pub fn getAddressSpace(pid: u64) !u64 {
     if (retval < 0) return error.NoSuchThread;
     return @bitCast(retval);
 }
+
+pub fn send(pid: u64) void {
+    _ = syscall(.Send, pid, 0, 0);
+}
+
+pub fn asyncSend(pid: u64) void {
+    _ = syscall(.AsyncSend, pid, 0, 0);
+}
+
+pub fn wait() void {
+    _ = syscall(.Wait, 0, 0, 0);
+}
diff --git a/system/memory/main.zig b/system/memory/main.zig
index 7b16ba4..bfb3a0d 100644
--- a/system/memory/main.zig
+++ b/system/memory/main.zig
@@ -14,10 +14,12 @@ export fn _start(_: u64, ipc_base: u64) callconv(.C) noreturn {
 
     var connection = system.ipc.readInitBuffers(ipc_base);
 
-    const byte: u8 = 127;
+    var byte: u8 = 127;
 
-    _ = connection.write_buffer.write(@ptrCast(&byte), 1);
-    syscalls.yield();
+    while (byte > 0) : (byte -= 1) {
+        _ = connection.write(u8, &byte);
+        syscalls.asyncSend(1);
+    }
 
     while (true) {}
 }