removing init heartbeat in releases

build.zig

@@ -194,8 +194,9 @@ fn addKernel(
 /// Assemble the bootable FAT32 image (the in-repo Python builder) holding what
 /// the firmware and loader need off the ESP: the EFI stub, `kernel`, `init`, and
 /// the initial-ramdisk. Factored so the serial-enabled `run-x86-64` variant can
-/// bundle its own kernel while sharing the (serial-independent) loader, init, and
+/// bundle its own serial kernel while sharing the loader, init, and ramdisk — all
-/// ramdisk. Returns the image's LazyPath.
+/// built once per invocation (the loader's boot breadcrumbs and init's heartbeat
+/// both follow the top-level -Dserial). Returns the image's LazyPath.
 fn addBootImage(
     b: *std.Build,
     kernel_bin: std.Build.LazyPath,
@@ -463,6 +464,14 @@ pub fn build(b: *std.Build) void {
     // linked into the kernel's user region against the `runtime` runtime library, and
     // started in ring 3 by the kernel's user-ELF loader.
     const init_exe = addUserBinary(b, kernel_target, runtime_module, mmio_module, xkeyboard_config_module, acpi_ids_module, "init", "system/services/init/init.zig");
+    // init reads the same `serial` flag the kernel does: its liveness heartbeat is a
+    // serial/test-build diagnostic (the QEMU harness's init tests assert on it, and
+    // -Dserial images emit it), so a flashable image runs a purely event-driven PID 1
+    // that wakes only for real work. The test harness builds with -Dserial=true, so
+    // the heartbeat stays present under test.
+    const init_options = b.addOptions();
+    init_options.addOption(bool, "serial", serial);
+    programModule(init_exe).addImport("build_options", init_options.createModule());
     const init_install = b.addInstallArtifact(init_exe, .{ .dest_dir = .{ .override = .{ .custom = "system/services" } } });
     b.getInstallStep().dependOn(&init_install.step);
 

system/services/init/init.zig

@@ -20,6 +20,7 @@
 const std = @import("std");
 const runtime = @import("runtime");
 const power = runtime.power_protocol;
+const build_options = @import("build_options");
 
 /// Where the kernel boot log is persisted on the USB FAT volume — an 8.3 name at
 /// the mount root (see system/services/log-flush). init writes it at shutdown;
@@ -90,10 +91,13 @@ pub fn main() void {
     // triggers the same shutdown path.
     subscribePower();
 
-    // A re-arming timer drives the liveness heartbeat: proof PID 1 is alive
+    // A re-arming timer drives the liveness heartbeat — proof PID 1 is alive (the
-    // (the init test's marker) while the loop stays free to receive signals,
+    // init test's marker) and a -Dserial diagnostic. It is a serial/test-build-only
-    // power events, and children's exit notifications.
+    // concern: a flashable (serial-off) image runs a purely event-driven PID 1 that
-    _ = runtime.system.timerOnce(supervision_endpoint, 1000);
+    // wakes only for real work (signals, power events, children's exits), never for a
+    // periodic beat. `build_options.serial` is comptime, so the heartbeat — its timer
+    // and the handler below — folds away entirely when serial is off.
+    if (build_options.serial) _ = runtime.system.timerOnce(supervision_endpoint, 1000);
 
     var receive: [power.message_maximum]u8 = undefined;
     while (true) {
@@ -102,7 +106,7 @@ pub fn main() void {
             if (signals.has(.terminate)) shutDown();
             continue;
         }
-        if (got.isTimer()) {
+        if (build_options.serial and got.isTimer()) {
             _ = runtime.system.write("/system/services/init: heartbeat\n");
             _ = runtime.system.timerOnce(supervision_endpoint, 1000);
             continue;