Daniel Samson
56110b0019
Retire the kernel's spawn-every-initial-ramdisk-binary loop, resolving the
service/driver split into a real three-level supervision hierarchy:
kernel -> spawns init (PID 1) only, and publishes the initial-ramdisk
init -> the service supervisor: spawns the system services (vfs, device-manager)
device-manager -> spawns the drivers it matches (hpet)
The kernel now only hands the initial-ramdisk image to the process layer
(publishInitialRamdisk) so user space can system_spawn from it; it launches nothing
bundled itself. init gains a boot-services list ("vfs", "device-manager") and spawns
them best-effort before settling into its heartbeat — policy lives in user space,
where a microkernel keeps it. Drivers are absent from that list on purpose: the
device manager owns them. Test-only binaries (vfs-test, bus) no longer run at boot;
their kernel self-tests still spawn them directly.
This removes increment 2's transitional double-spawn: a real boot now brings hpet up
exactly once (verified — kernel -> init -> vfs/device-manager -> hpet, zero "claim
failed"). The automated suite is unaffected: test builds run their case and halt
before the normal boot path, so each already spawns its own binaries. Suite 36/36
plus host tests; normal boot verified by hand under QEMU.
54 lines
2.6 KiB
Zig
54 lines
2.6 KiB
Zig
//! /system/services/init — the first user-space program, PID 1. Built as its own
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//! freestanding binary (see build.zig), shipped on the boot volume at /system/services/init,
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//! loaded by the bootloader, and started in ring 3 as a scheduled process by the
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//! kernel (system/kernel/process.zig). It links against the shared user runtime
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//! library `runtime` and talks to the kernel only through `runtime`'s system_call wrappers.
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//!
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//! It proves the C-convention heap works, then — as PID 1 — acts as the system's
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//! **service supervisor**: it spawns the user-space services danos brings up at boot
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//! (the VFS server, the device manager), and settles into a heartbeat so it stays
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//! alive as the root of user space. Drivers are *not* its job: the device manager
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//! discovers the hardware and spawns those. This is the service half of the
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//! service/driver spawn split (docs/driver-model.md).
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const runtime = @import("runtime");
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/// The system services init brings up at boot, in order. This is init's policy — the
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/// microkernel keeps such choices in user space, not the kernel. Drivers are absent
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/// on purpose: the device manager owns those. (A future init reads this from a
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/// manifest under /system/services instead of a hardcoded list.)
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const boot_services = [_][]const u8{ "vfs", "device-manager" };
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pub fn main() void {
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// Prove the heap end to end: allocate through the runtime allocator (which
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// mmaps pages from the kernel and carves them with the free list), write into
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// that heap buffer (exercising the widened debug_write bounds check), and
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// free it. A fault here would kill init before it heartbeats — so the init
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// test doubles as the heap regression test. (C code links the same heap via
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// the extern malloc/free symbols; Zig code uses this allocator.)
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const gpa = runtime.allocator();
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if (gpa.alloc(u8, 64)) |buffer| {
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const message = "init: heap ok\n";
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@memcpy(buffer[0..message.len], message);
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_ = runtime.system.write(buffer[0..message.len]);
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gpa.free(buffer);
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} else |_| {}
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// Bring up the boot services. Best-effort and silent: each service announces its
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// own readiness (`vfs: ready`, ...), and in an isolation test that runs init with
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// no initial-ramdisk the spawns simply no-op rather than deranging the heartbeat.
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for (boot_services) |service| {
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_ = runtime.system.spawn(service);
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}
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while (true) {
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_ = runtime.system.write("init: heartbeat\n");
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runtime.system.sleep(1000);
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}
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}
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pub const panic = runtime.panic;
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comptime {
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_ = &runtime.start._start; // pull the runtime entry shim into the image
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}
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