diff --git a/src/kern/cpu.zig b/src/kern/cpu.zig
index bf49b74..33bc898 100644
--- a/src/kern/cpu.zig
+++ b/src/kern/cpu.zig
@@ -28,18 +28,13 @@ pub fn current() u32 {
     return id.local().*;
 }
 
-comptime {
-    if (!@hasDecl(ki.impl, "percpu_ptr")) @compileError("impl must provide percpu_ptr()");
-    if (!@hasDecl(ki.impl, "percpu_ptr_other")) @compileError("impl must provide percpu_ptr_other()");
-}
-
 /// Wraps around CPU-local data.
 pub fn CpuLocal(comptime T: type, comptime init: T) type {
     return struct {
         var storage: T linksection(".data.percpu") = init;
 
         /// Return a pointer to local CPU data.
-        pub fn local() @TypeOf(ki.impl.percpu_ptr(&storage)) {
+        pub fn local() *T {
             return ki.impl.percpu_ptr(&storage);
         }
 
diff --git a/src/kern/ipl.zig b/src/kern/ipl.zig
index 0b0f1de..f0e6767 100644
--- a/src/kern/ipl.zig
+++ b/src/kern/ipl.zig
@@ -83,10 +83,6 @@ pub fn lower(new: Ipl) void {
     }
 }
 
-comptime {
-    if (!@hasDecl(ki.impl, "set_hardware_ipl")) @compileError("impl must provide set_hardware_ipl()");
-}
-
 /// Set the hardware IPL to `new`.
 pub fn set_hardware(new: Ipl) Ipl {
     var cpu = percpu.local();
diff --git a/src/kern/private.zig b/src/kern/private.zig
index 7ca18d1..4897d2c 100644
--- a/src/kern/private.zig
+++ b/src/kern/private.zig
@@ -1,6 +1,7 @@
+const r = @import("root");
 const std = @import("std");
+const rtl = @import("rtl");
 const config = @import("config");
-
 const init_mod = @import("init.zig");
 
 pub const impl = switch (config.arch) {
@@ -9,6 +10,63 @@ pub const impl = switch (config.arch) {
     else => @compileError("unsupported architecture"),
 };
 
+const ImplSchema = struct {
+    pub const ThreadContext = struct {};
+
+    /// Set the hardware interrupt priority level.
+    pub fn set_hardware_ipl(level: ipl.Ipl) void {
+        _ = level;
+    }
+
+    /// Read a per-cpu pointer on another CPU.
+    pub fn percpu_ptr_other(variable: anytype, id: u32) @TypeOf(variable) {
+        _ = id;
+    }
+
+    /// Read a per-cpu pointer on the current CPU.
+    pub fn percpu_ptr(variable: anytype) @TypeOf(variable) {}
+
+    /// Send a rescheduling inter-processor interrupt (IPI)
+    /// on the target CPU.
+    pub fn send_resched_ipi(target: u32) void {
+        _ = target;
+    }
+
+    /// Send a TLB shootdown IPI on the target CPU.
+    pub fn send_tlb_ipi(target: u32) void {
+        _ = target;
+    }
+
+    /// Flush the entire TLB on the current CPU.
+    pub fn flush_full_tlb() void {}
+
+    /// Flush the TLB entry matching `va` on the current CPU.
+    pub fn flush_tlb(va: r.VAddr) void {
+        _ = va;
+    }
+
+    /// Enable interrupts.
+    pub fn enable_interrupts() void {}
+
+    /// Disable interrupts.
+    /// Return the previous interrupt state.
+    pub fn disable_interrupts() bool {
+        return false;
+    }
+
+    /// Restore the state of interrupts.
+    pub fn restore_interrupts(state: bool) void {
+        _ = state;
+    }
+
+    /// Implementation-defined early initialization.
+    pub fn early_init() void {}
+};
+
+comptime {
+    rtl.assert_interface(impl, ImplSchema);
+}
+
 pub const init = init_mod.init;
 
 // === Exported Modules ===
diff --git a/src/kern/sched.zig b/src/kern/sched.zig
index 02dbdfa..8e0ad46 100644
--- a/src/kern/sched.zig
+++ b/src/kern/sched.zig
@@ -88,10 +88,6 @@ const r = @import("root");
 const ke = r.ke;
 const ki = ke.private;
 
-comptime {
-    if (!@hasDecl(ki.impl, "send_resched_ipi")) @compileError("impl must provide send_resched_ipi");
-}
-
 const runqueues_n = 64;
 const interactivity_threshold = 30;
 const scaling_factor = 50;
diff --git a/src/kern/shootdown.zig b/src/kern/shootdown.zig
index 3a29da1..479620b 100644
--- a/src/kern/shootdown.zig
+++ b/src/kern/shootdown.zig
@@ -8,12 +8,6 @@ const ke = r.ke;
 const ki = ke.private;
 const mm = r.mm;
 
-comptime {
-    if (!@hasDecl(ki.impl, "send_tlb_ipi")) @compileError("impl must provide send_tlb_ipi");
-    if (!@hasDecl(ki.impl, "flush_full_tlb")) @compileError("impl must provide flush_full_tlb");
-    if (!@hasDecl(ki.impl, "flush_tlb")) @compileError("impl must provide flush_tlb");
-}
-
 /// Structure representing a single shootdown request.
 pub const ShootdownState = struct {
     /// State of the request.
diff --git a/src/kern/thread.zig b/src/kern/thread.zig
index 9f9b3b0..5eb70d5 100644
--- a/src/kern/thread.zig
+++ b/src/kern/thread.zig
@@ -167,8 +167,3 @@ pub const Thread = struct {
         return self.priority >= Priority.low_interactive and self.priority <= Priority.high_interactive;
     }
 };
-
-comptime {
-    if (!@hasDecl(ki.impl, "ThreadContext")) @compileError("impl must provide ThreadContext");
-    if (!@hasDecl(ki.impl.ThreadContext, "init")) @compileError("ThreadContext must have init()");
-}