Docs: add system-requirements.md (minimum hardware + plain-language CPU guide)

The QMP harness channel, the SCI + power button published from ring 3,
Notify/GPE dispatch in the AML interpreter, and orderly shutdown — init's
M17 stop cascade into a ring-3 S5 write. Proven by injecting a real ACPI
power-button event; QEMU powers off through the whole chain.

# Conflicts:
#	system/services/init/init.zig

boot/efi.zig

@@ -29,7 +29,7 @@ pub fn main() uefi.Status {
     // report the reason (boot services are still up) and park the machine so the
     // message stays on screen.
     boot() catch |err| {
-        log("\r\ndanos: boot failed: ");
+        log("\r\nEFI: boot failed: ");
         logBytes(@errorName(err));
         log("\r\n");
         while (true) asm volatile ("hlt");
@@ -65,14 +65,14 @@ fn boot() !noreturn {
 
     // Best effort: a volume without /system/services/init still boots (kernel-only).
     loadInit(bs, &boot_information) catch |err| {
-        log("danos: no /system/services/init (");
+        log("EFI: no /system/services/init (");
         logBytes(@errorName(err));
         log(") - booting without user space\r\n");
     };
 
     // Best effort: the initial_ramdisk (VFS server + drivers) is optional too.
     loadInitialRamdisk(bs, &boot_information) catch |err| {
-        log("danos: no initial_ramdisk (");
+        log("EFI: no initial_ramdisk (");
         logBytes(@errorName(err));
         log(")\r\n");
     };
@@ -84,7 +84,7 @@ fn boot() !noreturn {
     // the map and exiting would invalidate the map key.
     const cr3 = try buildBootstrapTables(bs, &boot_information);
 
-    log("danos: kernel loaded, exiting boot services\r\n");
+    log("EFI: kernel loaded, exiting boot services\r\n");
     boot_information.memory_map = try exitBootServices(bs);
 
     // Switch onto our tables and jump to the kernel in one uninterruptible step.
@@ -395,7 +395,7 @@ fn loadInit(bs: *uefi.tables.BootServices, boot_information: *BootInformation) !
     const image = try loadFile(bs, init_file_name);
     boot_information.init_base = @intFromPtr(image.ptr);
     boot_information.init_len = image.len;
-    log("danos: /system/services/init loaded\r\n");
+    log("EFI: /system/services/init loaded\r\n");
 }
 
 /// Ferry the initial_ramdisk (the VFS server + drivers) to the kernel, same as init.
@@ -403,7 +403,7 @@ fn loadInitialRamdisk(bs: *uefi.tables.BootServices, boot_information: *BootInfo
     const image = try loadFile(bs, initial_ramdisk_file_name);
     boot_information.initial_ramdisk_base = @intFromPtr(image.ptr);
     boot_information.initial_ramdisk_len = image.len;
-    log("danos: initial_ramdisk loaded\r\n");
+    log("EFI: initial_ramdisk loaded\r\n");
 }
 
 /// Validate the ELF, copy every PT_LOAD segment to its physical address, and

docs/m21-plan.md

@@ -101,8 +101,7 @@ auto-merge to main when the branch is green; keep the branch; push everything.
       testing where PID 1 isn't init — and writes SLP_TYP|SLP_EN from ring 3.
       `orderly-shutdown` scenario proves button → shutting-down → S5 → QEMU
       exit; suite 60/60).
-- [ ] **merge** `feat/power-events` → main, push, keep the branch — **loop
-      ends here**.
+- [x] **merge** `feat/power-events` → main, push, keep the branch (merged 2026-07-13) — **M21 complete**.
 
 ---
 

docs/system-requirements.md

@@ -0,0 +1,227 @@
+# System Requirements
+
+Minimum and recommended hardware for running danos. Every requirement below is
+grounded in what the current code actually assumes at boot — this is a
+description of the real target, not an aspirational one.
+
+## Summary
+
+danos targets a **modern UEFI x86-64 PC with ACPI and PCIe**. The practical
+minimum is:
+
+- 64-bit x86-64 CPU with SSE2, APIC, and `syscall`/`sysret`
+- UEFI firmware (no BIOS / legacy boot)
+- ACPI tables: MADT, MCFG, FADT
+- PCIe with an ECAM (MMConfig) window
+- **128 MiB RAM** (target); see [Memory](#memory) for the breakdown
+- USB via **xHCI only**
+
+There is no support for legacy BIOS boot, x2APIC, port-IO PCI configuration, or
+any USB host controller other than xHCI.
+
+## Plain-language hardware guide
+
+If you don't want to cross-reference chipset datasheets, here's roughly what era
+of PC works. These are **guidance based on when the required features became
+standard**, not a list of tested machines — the authoritative rules are in the
+technical sections below.
+
+The feature that sets the floor is **built-in xHCI USB** (danos supports no other
+USB controller) combined with **UEFI firmware**. Both became standard on
+mainstream desktops and laptops around **2012**.
+
+| | Known-good baseline | Comfortable recommendation |
+|---|---|---|
+| **Intel** | 3rd-gen Core "Ivy Bridge" (2012) with a 7-series "Panther Point" chipset — Intel's first chipset with xHCI built in | 6th-gen Core "Skylake" (2015) or newer |
+| **AMD** | A-series "Llano" APU with an A75 FCH (2011) — the industry's first chipset with built-in xHCI | Any AM4 platform, i.e. Ryzen (2017) or newer |
+
+**AMD is not behind Intel here — it was first.** AMD's A75 FCH shipped with
+native xHCI in April 2011, about a year *ahead* of Intel's 7-series (2012); AMD
+was the first vendor to earn USB-IF certification for chipset-level USB 3.0. The
+two "comfortable recommendation" dates differ only because they name convenient,
+long-supported product lines (Skylake, Ryzen) — not because of any USB
+capability gap. Every AMD desktop platform from the A75 FCH (2011) and FM2/AM3+
+era onward has built-in xHCI, and any of them qualifies as a baseline.
+
+Older 64-bit machines (e.g. Intel Core 2, Nehalem, Sandy Bridge) meet the CPU
+requirements but typically **lack built-in xHCI and/or ship with BIOS instead of
+UEFI**, so they are not supported.
+
+### Matching your CPU by name
+
+If you know your chip's marketing name or codename, find it here. Everything from
+the **Supported** rows down works; the **Too old** row does not.
+
+**Intel Core** (the "-lake"/"-bridge"/"-well" codenames):
+
+| Status | Generation | Codename(s) | Year |
+|---|---|---|---|
+| Too old | 2nd gen | Sandy Bridge | 2011 |
+| Supported (baseline) | 3rd gen | Ivy Bridge | 2012 |
+| Supported | 4th–5th gen | Haswell, Broadwell | 2013–2014 |
+| **Recommended** | 6th–9th gen | **Skylake**, Kaby Lake, Coffee Lake | 2015–2018 |
+| Recommended | 10th–11th gen | Comet Lake, Ice Lake, Tiger Lake, Rocket Lake | 2019–2021 |
+| Recommended | 12th gen+ | Alder Lake, Raptor Lake | 2021–2023 |
+| Recommended | Core Ultra | Meteor Lake, Arrow Lake, Lunar Lake | 2023+ |
+
+**AMD:**
+
+| Status | Family | Codename(s) | Year |
+|---|---|---|---|
+| Supported (baseline) | A-series APU (A75/A85 FCH) | Llano, Trinity, Richland, Kaveri | 2011–2014 |
+| Supported | FX (AM3+) | Bulldozer, Piledriver | 2011–2012 |
+| **Recommended** | **Ryzen** 1000–5000 (AM4) | Summit/Pinnacle Ridge, Matisse, Vermeer (Zen–Zen 3) | 2017–2020 |
+| Recommended | Ryzen 7000+ (AM5) | Raphael, Granite Ridge (Zen 4 / Zen 5) | 2022+ |
+| Recommended | Threadripper / EPYC | Zen and later | 2017+ |
+
+(These map generations to the era their platforms shipped built-in xHCI + UEFI;
+they are guidance, not a tested-hardware list.)
+
+**Two caveats that matter regardless of CPU:**
+
+- **Firmware must be UEFI.** Many 2011-era machines could do either UEFI or
+  legacy BIOS — danos needs it set to UEFI. There is no BIOS boot path.
+- **Input is PS/2 only, for now.** danos does not yet support USB
+  keyboards/mice. This is fine on most **laptops** (their built-in keyboards are
+  wired to a PS/2-style i8042 controller) but means a **desktop with only USB
+  ports** currently has no usable keyboard. USB HID input is planned.
+
+Virtual machines are the easiest way to meet every requirement: QEMU (with OVMF/
+UEFI, a `qemu-xhci` controller, and the default Q35 machine type), or any
+hypervisor configured for UEFI firmware and an xHCI USB controller.
+
+## CPU / architecture
+
+| Requirement | Detail | Source |
+|---|---|---|
+| **x86-64, 64-bit only** | Kernel and loader are built exclusively for `x86_64`; the loader rejects any non-x86-64 kernel ELF (`error.WrongArchitecture`). | `build.zig:285`, `boot/efi.zig:418` |
+| **Long mode + PAE + NX** | AP trampoline sets `CR4.PAE`, `EFER.LME`, `EFER.NXE`; NX is used in kernel page-table entries. | `system/kernel/architecture/x86_64/trampoline.s:62` |
+| **SSE / SSE2** | Baseline: the compiler emits SSE for ordinary struct copies. Trampoline enables `CR4.OSFXSR` + `OSXMMEXCPT` and clears `CR0.EM`. | `build.zig:282`, `trampoline.s:62` |
+| **`syscall` / `sysret`** | Primary user↔kernel entry path. `EFER.SCE` enabled; `STAR`/`LSTAR`/`SFMASK` programmed per core. (`int 0x80` exists as a parallel gate.) | `architecture/x86_64/per-cpu.zig:59`, `isr.s:169` |
+| **Local APIC (xAPIC)** | LAPIC accessed via MMIO at `0xFEE00000`. LAPIC ID read as a `u8` — classic xAPIC. **x2APIC is not supported** (no MSR path). | `apic.zig:62`, `apic.zig:414` |
+| **CPUID + RDTSC** | CPUID leaf `0x15` for TSC frequency; RDTSC is the monotonic clock. | `apic.zig:279`, `apic.zig:84` |
+| **SMP (optional)** | Multi-core supported via INIT–SIPI–SIPI; ceiling `maximum_cpus = 128`. Single core is fine. Cores beyond the ceiling are parked. | `system/parameters.zig:16`, `apic.zig:144` |
+
+## Firmware / boot
+
+- **UEFI only.** A custom UEFI application loader is installed to
+  `\EFI\BOOT\BOOTX64.efi`. There is **no BIOS, multiboot, or limine** path. The
+  loader tolerates UEFI Class-3 machines with no legacy PIC/PIT.
+  (`build.zig:464`, `boot/efi.zig`)
+- **ACPI is the hardware-discovery mechanism.** The RSDP is taken from the UEFI
+  configuration table (ACPI 2.0 GUID preferred, 1.0 fallback). Without a valid
+  RSDP there is **no device discovery** — no SMP, no IOAPIC routing, no PCI/USB.
+  (`efi.zig:578`, `boot-handoff.zig:144`)
+- **Required ACPI tables:** MADT (interrupt topology), MCFG (PCIe ECAM base),
+  FADT (power / PM timer). Optionally consumed: HPET, DMAR, SPCR.
+  (`system/devices/acpi.zig:3`)
+- The loader reads `/system/kernel`, `/system/services/init`, and
+  `/boot/initial-ramdisk.img` off the FAT boot volume. The kernel can boot
+  "kernel-only" without init or the ramdisk. (`efi.zig:14`, `efi.zig:66`)
+
+## Interrupt controller
+
+- **Local APIC + I/O APIC required.** I/O APIC base, GSI base, and MADT
+  interrupt-source overrides come from ACPI. (`cpu.zig:365`, `apic.zig:119`)
+- **MSI supported** — edge-triggered, keyed by vector, no I/O APIC mask cycle.
+  Vector window 33–46, timer on 32, spurious on 47. (`system/kernel/irq.zig:70`,
+  `cpu.zig:397`)
+- The legacy 8259 PIC is remapped and masked **only if present** (MADT
+  `PCAT_COMPAT`); it is not required. (`apic.zig:103`)
+
+## PCI / PCIe
+
+- **PCIe with ECAM (MMConfig) required.** The PCI bus driver maps the host
+  bridge's ECAM window (1 MiB config space per bus) and computes config
+  addresses directly. **There is no legacy CF8/CFC port-IO config path** — the
+  driver bails if the bridge exposes no ECAM window. The ECAM base comes from
+  the ACPI MCFG table. (`system/drivers/pci-bus/pci-bus.zig:41`, `acpi.zig:6`)
+
+## USB
+
+- **xHCI only.** The sole USB driver is `usb-xhci-bus`, and the device manager
+  binds it strictly to PCI prog-IF `0x30` (xHCI). UHCI / OHCI / EHCI exist only
+  as report strings with no driver behind them — **USB 1.x/2.0-only controllers
+  are not supported.** (`system/drivers/usb-xhci-bus/`,
+  `system/services/device-manager/device-manager.zig:34`)
+- USB input (keyboard/mouse over HID) is future work; the current input stack is
+  PS/2. See [Buses & devices](#buses--devices).
+
+## Timers
+
+Calibration prefers, in order: (1) CPUID leaf `0x15` TSC frequency, (2) HPET,
+(3) ACPI PM timer (3.579545 MHz, from FADT), (4) legacy PIT. Any one suffices —
+HPET/PM-timer/PIT are optional fallbacks when CPUID `0x15` is absent.
+(`apic.zig:180`)
+
+- **TSC** — monotonic high-resolution clock.
+- **LAPIC timer** — scheduler heartbeat, periodic at `timer_hz = 1000 Hz`.
+  (`parameters.zig:39`)
+
+## Memory
+
+**Target: 128 MiB RAM.** The system uses 4 KiB pages and a bitmap physical-frame
+allocator built from the firmware memory map. There is no hardcoded minimum-RAM
+constant — the allocator only panics if there is no usable region, or none large
+enough to hold its own bitmap. (`system/kernel/pmm.zig:13`, `pmm.zig:77`)
+
+Where the budget goes:
+
+| Consumer | Size | Source |
+|---|---|---|
+| Kernel heap (cap, grown one page at a time) | up to **64 MiB** | `system/kernel/heap.zig:26` |
+| Kernel stack, per CPU | 16 KiB | `parameters.zig:26` |
+| IST stack, per CPU | 16 KiB | `parameters.zig:36` |
+| User stack, per task | 8 pages / 32 KiB | `parameters.zig:32` |
+| Max concurrent tasks | 32 | `parameters.zig:23` |
+| Boot page-table pool | 64 frames / 256 KiB | `efi.zig:299` |
+
+The 64 MiB heap cap plus kernel image, per-CPU stacks, task stacks, the frame
+bitmap, and DMA-contiguous allocations fit comfortably within 128 MiB on a
+single- or low-core-count machine. Very high core counts (toward the 128-CPU
+ceiling) add per-CPU stack overhead and push toward more RAM.
+
+**Note on the 4 GiB physmap:** the loader identity-maps and physmaps the low
+4 GiB of address space with 2 MiB leaves. This is *virtual address* reach, not a
+RAM requirement — RAM above 4 GiB simply needs an extra mapping window and is not
+needed to boot. (`efi.zig:305`)
+
+Virtual-memory layout (`boot-handoff.zig:47`):
+
+| Region | Base |
+|---|---|
+| User space | `0x0000_7000_0000_0000` |
+| Kernel heap | `0xFFFF_8000_0000_0000` |
+| Physmap | `0xFFFF_8800_0000_0000` |
+| Kernel image | `0xFFFF_FFFF_8000_0000` |
+
+## Buses & devices
+
+Buses with real drivers today:
+
+- **PCIe** via ECAM (`pci-bus`)
+- **xHCI USB** (`usb-xhci-bus`)
+- **PS/2** keyboard + mouse (`ps2-bus`) — the current input stack
+- **Serial UART** (16550/16450), configured from the ACPI SPCR table
+
+**No storage driver exists yet.** AHCI / NVMe / IDE are named for reporting only;
+there is no block-device driver. Persistent storage is future work.
+
+## IOMMU
+
+**Detection only; enforcement deferred.** The ACPI DMAR table is parsed for the
+first VT-d DRHD unit and its capabilities are exposed via `PlatformInfo`
+(`iommu_present`, `iommu_base`, `iommu_version`). No DMA-remapping tables are
+programmed and no translation is enforced. An IOMMU is therefore **not required**
+and does not currently constrain devices. (`system/devices/acpi.zig:96`)
+
+## What is explicitly NOT supported
+
+- Legacy BIOS / multiboot / limine boot
+- 32-bit x86
+- x2APIC
+- Legacy port-IO (CF8/CFC) PCI configuration
+- Non-xHCI USB (UHCI / OHCI / EHCI)
+- Machines without ACPI (no device discovery)
+- Persistent storage (no AHCI / NVMe / IDE driver yet)
+- USB HID input (PS/2 only for now)

system/drivers/hpet/hpet.zig

@@ -93,21 +93,21 @@ fn findHpet(buffer: []device.DeviceDescriptor) ?Found {
 pub fn main() void {
     // Enumerate into a heap buffer (too big for the one-page user stack).
     const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 32) catch {
-        _ = runtime.system.write("hpet: out of memory\n");
+        _ = runtime.system.write("system/drivers/hpet: out of memory\n");
         return;
     };
 
     const hpet = findHpet(buffer) orelse {
-        _ = runtime.system.write("hpet: no HPET with an IRQ\n");
+        _ = runtime.system.write("system/drivers/hpet: no HPET with an IRQ\n");
         return;
     };
 
     if (!device.claim(hpet.device_id)) {
-        _ = runtime.system.write("hpet: claim failed\n");
+        _ = runtime.system.write("system/drivers/hpet: claim failed\n");
         return;
     }
     const base = device.mmioMap(hpet.device_id, hpet.mmio) orelse {
-        _ = runtime.system.write("hpet: mmio_map failed\n");
+        _ = runtime.system.write("system/drivers/hpet: mmio_map failed\n");
         return;
     };
 
@@ -116,7 +116,7 @@ pub fn main() void {
     const gsi = hpet.gsi;
 
     const endpoint = ipc.createIpcEndpoint() orelse {
-        _ = runtime.system.write("hpet: create_ipc_endpoint failed\n");
+        _ = runtime.system.write("system/drivers/hpet: create_ipc_endpoint failed\n");
         return;
     };
 
@@ -124,7 +124,7 @@ pub fn main() void {
     // Counter period, so we can arm the comparator a fixed wall-clock distance out.
     const femtos_per_tick = rd(base, register_general_cap) >> 32;
     if (femtos_per_tick == 0) {
-        _ = runtime.system.write("hpet: bad HPET period\n");
+        _ = runtime.system.write("system/drivers/hpet: bad HPET period\n");
         return;
     }
     const ticks_per_ms = 1_000_000_000_000 / femtos_per_tick;
@@ -147,10 +147,10 @@ pub fn main() void {
     wr(base, register_general_configuration, rd(base, register_general_configuration) | configuration_enable);
 
     if (!device.irqBind(hpet.device_id, hpet.irq, endpoint)) {
-        _ = runtime.system.write("hpet: irq_bind failed\n");
+        _ = runtime.system.write("system/drivers/hpet: irq_bind failed\n");
         return;
     }
-    _ = runtime.system.write("hpet: bound, sleeping until the hardware speaks\n");
+    _ = runtime.system.write("system/drivers/hpet: bound, sleeping until the hardware speaks\n");
 
     // --- the driver loop -----------------------------------------------------
     // Blocked in replyWait. No polling, no spinning: the next line of this function
@@ -178,14 +178,14 @@ pub fn main() void {
             wr(base, register_timer0_configuration, rd(base, register_timer0_configuration) & ~tn_int_enb);
         }
 
-        _ = runtime.system.write("hpet: irq\n");
+        _ = runtime.system.write("system/drivers/hpet: irq\n");
         if (!device.irqAck(hpet.device_id, hpet.irq)) {
-            _ = runtime.system.write("hpet: irq_ack failed\n");
+            _ = runtime.system.write("system/drivers/hpet: irq_ack failed\n");
             return;
         }
     }
 
-    _ = runtime.system.write("hpet: ok\n");
+    _ = runtime.system.write("system/drivers/hpet: ok\n");
     while (true) runtime.system.sleep(1000);
 }
 

system/drivers/pci-bus/pci-bus.zig

@@ -6,7 +6,7 @@
 //! M19.1 (this increment): claim the bridge, map its ECAM window (resource 0;
 //! the bus range and the MMIO apertures follow it), walk every
 //! bus/device/function config header, and log what the walk finds — ending
-//! with "pci-bus: N functions found", which the `pci-scan` scenario compares
+//! with "/system/drivers/pci-bus: N functions found", which the `pci-scan` scenario compares
 //! against the kernel's own enumeration. Registration and reports (M19.2), and
 //! the kernel walk's retirement (M19.3), build on this proven-equivalent scan.
 
@@ -31,9 +31,9 @@ fn logFunction(bus: u64, dev: u64, function: u64, class_triple: u32) void {
     const pif = pci_class.progIfName(cc.base, cc.subclass, cc.prog_if);
     var line: [200]u8 = undefined;
     const text = if (pif.len != 0)
-        std.fmt.bufPrint(&line, "pci-bus: {d}:{d}.{d} class 0x{x:0>2} ({s})  subclass 0x{x:0>2} ({s})  progif 0x{x:0>2} ({s})\n", .{ bus, dev, function, cc.base, pci_class.className(cc.base), cc.subclass, pci_class.subclassName(cc.base, cc.subclass), cc.prog_if, pif }) catch return
+        std.fmt.bufPrint(&line, "/system/drivers/pci-bus: {d}:{d}.{d} class 0x{x:0>2} ({s})  subclass 0x{x:0>2} ({s})  progif 0x{x:0>2} ({s})\n", .{ bus, dev, function, cc.base, pci_class.className(cc.base), cc.subclass, pci_class.subclassName(cc.base, cc.subclass), cc.prog_if, pif }) catch return
     else
-        std.fmt.bufPrint(&line, "pci-bus: {d}:{d}.{d} class 0x{x:0>2} ({s})  subclass 0x{x:0>2} ({s})  progif 0x{x:0>2}\n", .{ bus, dev, function, cc.base, pci_class.className(cc.base), cc.subclass, pci_class.subclassName(cc.base, cc.subclass), cc.prog_if }) catch return;
+        std.fmt.bufPrint(&line, "/system/drivers/pci-bus: {d}:{d}.{d} class 0x{x:0>2} ({s})  subclass 0x{x:0>2} ({s})  progif 0x{x:0>2}\n", .{ bus, dev, function, cc.base, pci_class.className(cc.base), cc.subclass, pci_class.subclassName(cc.base, cc.subclass), cc.prog_if }) catch return;
     _ = runtime.system.write(text);
 }
 
@@ -74,37 +74,37 @@ fn configWrite16(bus: u64, dev: u64, function: u64, offset: u64, value: u16) voi
 fn initialise(endpoint: runtime.ipc.Handle) bool {
     _ = endpoint;
     if (!device.claim(bridge_id)) {
-        writeLine("pci-bus: unable to claim bridge device {d}\n", .{bridge_id});
+        writeLine("/system/drivers/pci-bus: unable to claim bridge device {d}\n", .{bridge_id});
         return false;
     }
     const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 64) catch {
-        _ = runtime.system.write("pci-bus: out of memory\n");
+        _ = runtime.system.write("/system/drivers/pci-bus: out of memory\n");
         return false;
     };
     const total = device.enumerate(buffer);
     const descriptor = for (buffer[0..@min(total, buffer.len)]) |d| {
         if (d.id == bridge_id) break d;
     } else {
-        writeLine("pci-bus: device {d} not in the device tree\n", .{bridge_id});
+        writeLine("/system/drivers/pci-bus: device {d} not in the device tree\n", .{bridge_id});
         return false;
     };
     // Resource 0 is the ECAM window (1 MiB of config space per bus); the bus
     // range rides beside it. The MMIO apertures (M19.0) come after both.
     if (descriptor.resource_count < 2 or descriptor.resources[0].kind != @intFromEnum(device.ResourceKind.memory)) {
-        _ = runtime.system.write("pci-bus: bridge has no ECAM window\n");
+        _ = runtime.system.write("/system/drivers/pci-bus: bridge has no ECAM window\n");
         return false;
     }
     const bus_range = for (descriptor.resources[0..@intCast(descriptor.resource_count)]) |resource| {
         if (resource.kind == @intFromEnum(device.ResourceKind.bus_range)) break resource;
     } else {
-        _ = runtime.system.write("pci-bus: bridge has no bus range\n");
+        _ = runtime.system.write("/system/drivers/pci-bus: bridge has no bus range\n");
         return false;
     };
     start_bus = bus_range.start;
     bus_count = bus_range.len;
     ecam_physical = descriptor.resources[0].start;
     ecam_base = device.mmioMap(bridge_id, 0) orelse {
-        _ = runtime.system.write("pci-bus: ECAM mmio_map failed\n");
+        _ = runtime.system.write("/system/drivers/pci-bus: ECAM mmio_map failed\n");
         return false;
     };
 
@@ -116,17 +116,17 @@ fn initialise(endpoint: runtime.ipc.Handle) bool {
         if (manager == null) runtime.system.sleep(20);
     }
     const h = manager orelse {
-        _ = runtime.system.write("pci-bus: no device manager to hello\n");
+        _ = runtime.system.write("/system/drivers/pci-bus: no device manager to hello\n");
         return false;
     };
     const hello = protocol.Hello{ .role = @intFromEnum(protocol.Role.bus), .device_id = bridge_id };
     var reply: [protocol.message_maximum]u8 = undefined;
     const n = runtime.ipc.call(h, std.mem.asBytes(&hello), &reply) catch {
-        _ = runtime.system.write("pci-bus: hello call failed\n");
+        _ = runtime.system.write("/system/drivers/pci-bus: hello call failed\n");
         return false;
     };
     if (n < protocol.reply_size or std.mem.bytesToValue(protocol.HelloReply, reply[0..protocol.reply_size]).status != 0) {
-        _ = runtime.system.write("pci-bus: hello refused\n");
+        _ = runtime.system.write("/system/drivers/pci-bus: hello refused\n");
         return false;
     }
     manager_handle = h;
@@ -159,7 +159,7 @@ fn scan() void {
             }
         }
     }
-    writeLine("pci-bus: {d} functions found\n", .{found});
+    writeLine("/system/drivers/pci-bus: {d} functions found\n", .{found});
 }
 
 /// Register one function under the bridge and report it to the manager. The
@@ -229,7 +229,7 @@ fn registerAndReport(bus: u64, dev: u64, function: u64, class_triple: u32) void
     }
 
     const registered = device.register(bridge_id, &descriptor) orelse {
-        writeLine("pci-bus: register refused for {d}:{d}.{d}\n", .{ bus, dev, function });
+        writeLine("/system/drivers/pci-bus: register refused for {d}:{d}.{d}\n", .{ bus, dev, function });
         return;
     };
     const report = protocol.ChildAdded{
@@ -240,7 +240,7 @@ fn registerAndReport(bus: u64, dev: u64, function: u64, class_triple: u32) void
     };
     var reply: [protocol.message_maximum]u8 = undefined;
     _ = runtime.ipc.call(manager_handle, std.mem.asBytes(&report), &reply) catch {
-        writeLine("pci-bus: child report for {d}:{d}.{d} failed\n", .{ bus, dev, function });
+        writeLine("/system/drivers/pci-bus: child report for {d}:{d}.{d} failed\n", .{ bus, dev, function });
     };
 }
 
@@ -255,7 +255,7 @@ fn onMessage(message: []const u8, reply: []u8, sender: u32, capability: ?runtime
 pub fn main(init: runtime.process.Init) void {
     const argument = init.arguments.get(1) orelse return; // bare (ramdisk sweep): stay silent
     bridge_id = std.fmt.parseInt(u64, argument, 10) catch {
-        writeLine("pci-bus: malformed bridge device id '{s}'\n", .{argument});
+        writeLine("/system/drivers/pci-bus: malformed bridge device id '{s}'\n", .{argument});
         return;
     };
     runtime.service.run(protocol.message_maximum, .{

system/drivers/usb-xhci-bus/usb-xhci-bus.zig

@@ -33,20 +33,20 @@ var controller_id: u64 = protocol.no_device;
 fn initialise(endpoint: runtime.ipc.Handle) bool {
     _ = endpoint;
     if (!device.claim(controller_id)) {
-        writeLine("usb-xhci-bus: unable to claim controller device {d}\n", .{controller_id});
+        writeLine("/system/drivers/usb-xhci-bus: unable to claim controller device {d}\n", .{controller_id});
         return false;
     }
 
     // Fetch our own descriptor back for the controller's resources.
     const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 64) catch {
-        _ = runtime.system.write("usb-xhci-bus: out of memory\n");
+        _ = runtime.system.write("/system/drivers/usb-xhci-bus: out of memory\n");
         return false;
     };
     const total = device.enumerate(buffer);
     const descriptor = for (buffer[0..@min(total, buffer.len)]) |d| {
         if (d.id == controller_id) break d;
     } else {
-        writeLine("usb-xhci-bus: device {d} not in the device tree\n", .{controller_id});
+        writeLine("/system/drivers/usb-xhci-bus: device {d} not in the device tree\n", .{controller_id});
         return false;
     };
 
@@ -59,16 +59,16 @@ fn initialise(endpoint: runtime.ipc.Handle) bool {
             break resource;
         }
     } else {
-        writeLine("usb-xhci-bus: controller device {d} has no register BAR\n", .{controller_id});
+        writeLine("/system/drivers/usb-xhci-bus: controller device {d} has no register BAR\n", .{controller_id});
         return false;
     };
-    writeLine("usb-xhci-bus: claimed controller device {d} (registers at 0x{x}, {d} bytes)\n", .{
+    writeLine("/system/drivers/usb-xhci-bus: claimed controller device {d} (registers at 0x{x}, {d} bytes)\n", .{
         controller_id,
         register_window.start,
         register_window.len,
     });
     register_base = device.mmioMap(controller_id, register_index) orelse {
-        _ = runtime.system.write("usb-xhci-bus: mmio_map failed\n");
+        _ = runtime.system.write("/system/drivers/usb-xhci-bus: mmio_map failed\n");
         return false;
     };
 
@@ -81,20 +81,20 @@ fn initialise(endpoint: runtime.ipc.Handle) bool {
         if (manager == null) runtime.system.sleep(20);
     }
     const h = manager orelse {
-        _ = runtime.system.write("usb-xhci-bus: no device manager to hello\n");
+        _ = runtime.system.write("/system/drivers/usb-xhci-bus: no device manager to hello\n");
         return false;
     };
     const hello = protocol.Hello{ .role = @intFromEnum(protocol.Role.bus), .device_id = controller_id };
     var reply: [protocol.message_maximum]u8 = undefined;
     const n = runtime.ipc.call(h, std.mem.asBytes(&hello), &reply) catch {
-        _ = runtime.system.write("usb-xhci-bus: hello call failed\n");
+        _ = runtime.system.write("/system/drivers/usb-xhci-bus: hello call failed\n");
         return false;
     };
     if (n < protocol.reply_size or std.mem.bytesToValue(protocol.HelloReply, reply[0..protocol.reply_size]).status != 0) {
-        _ = runtime.system.write("usb-xhci-bus: hello refused\n");
+        _ = runtime.system.write("/system/drivers/usb-xhci-bus: hello refused\n");
         return false;
     }
-    _ = runtime.system.write("usb-xhci-bus: hello acknowledged\n");
+    _ = runtime.system.write("/system/drivers/usb-xhci-bus: hello acknowledged\n");
 
     scanPorts(h);
     return true;
@@ -135,7 +135,7 @@ fn scanPorts(manager: runtime.ipc.Handle) void {
     const capability_length = readRegister(0) & 0xFF;
     const structural = readRegister(0x04);
     const maximum_ports: u32 = structural >> 24;
-    writeLine("usb-xhci-bus: {d} root-hub ports\n", .{maximum_ports});
+    writeLine("/system/drivers/usb-xhci-bus: {d} root-hub ports\n", .{maximum_ports});
 
     // PORTSC registers: operational base + 0x400 + 0x10 per port (1-based).
     var port: u32 = 1;
@@ -145,7 +145,7 @@ fn scanPorts(manager: runtime.ipc.Handle) void {
         if (port_status & 1 == 0) continue; // CCS: nothing connected
         connected += 1;
         const speed = (port_status >> 10) & 0xF; // the PORTSC port-speed class
-        writeLine("usb-xhci-bus: port {d} connected — {s} (speed class {d})\n", .{ port, speedName(speed), speed });
+        writeLine("/system/drivers/usb-xhci-bus: port {d} connected — {s} (speed class {d})\n", .{ port, speedName(speed), speed });
 
         const report = protocol.ChildAdded{
             .parent = controller_id,
@@ -154,11 +154,11 @@ fn scanPorts(manager: runtime.ipc.Handle) void {
         };
         var reply: [protocol.message_maximum]u8 = undefined;
         _ = runtime.ipc.call(manager, std.mem.asBytes(&report), &reply) catch {
-            writeLine("usb-xhci-bus: child report for port {d} failed\n", .{port});
+            writeLine("/system/drivers/usb-xhci-bus: child report for port {d} failed\n", .{port});
             continue;
         };
     }
-    if (connected == 0) _ = runtime.system.write("usb-xhci-bus: no devices connected\n");
+    if (connected == 0) _ = runtime.system.write("/system/drivers/usb-xhci-bus: no devices connected\n");
 }
 
 /// No bus protocol to serve yet — transfer requests arrive with the USB track.
@@ -172,11 +172,11 @@ fn onMessage(message: []const u8, reply: []u8, sender: u32, capability: ?runtime
 
 pub fn main(init: runtime.process.Init) void {
     const argument = init.arguments.get(1) orelse {
-        _ = runtime.system.write("usb-xhci-bus: missing controller device id (argv[1])\n");
+        _ = runtime.system.write("/system/drivers/usb-xhci-bus: missing controller device id (argv[1])\n");
         return;
     };
     controller_id = std.fmt.parseInt(u64, argument, 10) catch {
-        writeLine("usb-xhci-bus: malformed controller device id '{s}'\n", .{argument});
+        writeLine("/system/drivers/usb-xhci-bus: malformed controller device id '{s}'\n", .{argument});
         return;
     };
     runtime.service.run(protocol.message_maximum, .{

system/kernel/kernel.zig

@@ -77,12 +77,12 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     architecture.setFaultHandler(onException);
     architecture.init();
 
-    status("danos: initialising kernel...\n");
+    status("/system/kernel: initialising kernel...\n");
     log.write(if (console.present())
-        "danos: framebuffer console online (bootstrap; graphics driver later)\n"
+        "/system/kernel: framebuffer console online (bootstrap; graphics driver later)\n"
     else
-        "danos: no framebuffer (headless) -> logging to serial/debugcon only\n");
-    log.write("danos: cpu tables online (GDT, IDT, TSS)\n");
+        "/system/kernel: no framebuffer (headless) -> logging to serial/debugcon only\n");
+    log.write("/system/kernel: cpu tables online (GDT, IDT, TSS)\n");
     log.print("  resolution : {d}x{d}\n", .{ fb.width, fb.height });
     log.print("  pitch      : {d} bytes\n", .{fb.pitch});
     log.print("  format     : {s}\n", .{@tagName(fb.format)});
@@ -105,7 +105,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     const total_bytes = total_pages * abi.page_size;
     const gib = 1 << 30;
 
-    log.write("\ndanos: physical memory\n");
+    log.write("\n/system/kernel: physical memory\n");
     log.print("  total RAM  : {d}.{d:0>2} GiB ({d} MiB) - RAM the firmware reported\n", .{ total_bytes / gib, (total_bytes % gib) * 100 / gib, mib(total_pages) });
     log.print("  usable     : {d} MiB - free RAM (incl. reclaimed boot-services memory)\n", .{mib(usable_pages)});
     log.print("  reserved   : {d} MiB - kernel image, boot stack, ACPI, runtime services\n", .{mib(reserved_pages)});
@@ -119,7 +119,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     // until SMP bring-up; 0 means none was available (we stay uniprocessor).
     ap_trampoline_page = pmm.allocBelow(0x100000) orelse 0;
     const s1 = pmm.stats();
-    log.print("\ndanos: frame allocator online\n", .{});
+    log.print("\n/system/kernel: frame allocator online\n", .{});
     log.print("  free frames: {d} ({d} MiB)\n", .{ s1.free_frames, mib(s1.free_frames) });
     const f0 = pmm.alloc();
     const f1 = pmm.alloc();
@@ -133,14 +133,14 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     // Switch off the firmware's page tables onto our own (with real permissions).
     architecture.enablePaging(pmm.alloc, pmm.free, boot_information);
     log.checkpoint(cp_paging);
-    log.print("\ndanos: paging enabled\n", .{});
+    log.print("\n/system/kernel: paging enabled\n", .{});
     log.print("  page tables: root = 0x{x:0>16}\n", .{architecture.activePageTable()});
     log.print("  kernel segs: {d} (mapped with W^X permissions)\n", .{boot_information.kernel_segment_count});
 
     // Bring up the kernel heap (dynamic allocation), built on the VMM.
     heap.init();
     log.checkpoint(cp_heap);
-    log.write("\ndanos: kernel heap online\n");
+    log.write("\n/system/kernel: kernel heap online\n");
     // Measure the amount of resources the kernel is actually using
     const s2 = pmm.stats();
     log.print("  Kernel footprint: {d} KiB\n", .{kib(s1.free_frames - s2.free_frames)});
@@ -156,7 +156,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     };
     if (platform.discover(boot_information, heap.allocator(), hal)) |devtree| {
         var device_tree = devtree;
-        log.write("\ndanos: device discovery online\n");
+        log.write("\n/system/kernel: device discovery online\n");
         device_tree.dump(log.write);
 
         // Snapshot the device tree for user-space drivers (device_enumerate/claim/
@@ -164,7 +164,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
         devices_broker.init(&device_tree);
         if (devices_broker.dropped > 0) {
             // Otherwise entirely silent: drivers would just never see that hardware.
-            log.print("danos: WARNING {d} device(s) dropped — table full\n", .{devices_broker.dropped});
+            log.print("/system/kernel: WARNING {d} device(s) dropped — table full\n", .{devices_broker.dropped});
         }
 
         // Install the device-IRQ trampolines, so a driver's irq_bind has vectors to
@@ -173,7 +173,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
 
         // Power register map extracted from the FADT + AML, for confidence it parsed.
         const pw = platform.powerInformation();
-        log.write("danos: power\n");
+        log.write("/system/kernel: power\n");
         log.print("  pm1a_cnt   : {s} 0x{x} (width {d})\n", .{ if (pw.pm1a_cnt.mmio) "mmio" else "io", pw.pm1a_cnt.address, pw.pm1a_cnt.width });
         if (pw.s5) |s| {
             log.print("  S5 slp_typ : a={d} b={d}\n", .{ s.slp_typ_a, s.slp_typ_b });
@@ -221,7 +221,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
         });
         if (pinfo.spcr_uart) |u| architecture.serialReconfigure(u.mmio, u.address);
 
-        log.write("danos: platform\n");
+        log.write("/system/kernel: platform\n");
         log.print("  8259 PIC   : {s}\n", .{if (pinfo.pic_present) "present" else "absent"});
         log.print("  lapic base : 0x{x}\n", .{pinfo.lapic_base});
         log.print("  hpet base  : 0x{x}\n", .{hpet_base});
@@ -237,7 +237,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
         if (platform.cpusDropped() > 0)
             log.print("  cpus       : WARNING {d} core(s) beyond pool cap dropped\n", .{platform.cpusDropped()});
     } else |err| {
-        log.print("\ndanos: device discovery failed: {s}\n", .{@errorName(err)});
+        log.print("\n/system/kernel: device discovery failed: {s}\n", .{@errorName(err)});
     }
     log.checkpoint(cp_discovery);
 
@@ -248,14 +248,14 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     // Register the current context as the first task before enabling preemption.
     scheduler.init(4);
     log.checkpoint(cp_scheduler);
-    log.write("\ndanos: scheduler online\n");
+    log.write("\n/system/kernel: scheduler online\n");
 
     // Start the timer and unmask interrupts — the kernel now has a heartbeat, and
     // the timer preempts among tasks.
     architecture.startTimer();
     architecture.enableInterrupts();
     log.checkpoint(cp_timer);
-    log.print("danos: timer online ({d} Hz tick; timer clock {d} MHz, clock {d} MHz; calibrated via {s})\n", .{ architecture.timer_hz, architecture.timerClockHz() / 1_000_000, architecture.clockHz() / 1_000_000, architecture.timerCalibrationSource() });
+    log.print("/system/kernel: timer online ({d} Hz tick; timer clock {d} MHz, clock {d} MHz; calibrated via {s})\n", .{ architecture.timer_hz, architecture.timerClockHz() / 1_000_000, architecture.clockHz() / 1_000_000, architecture.timerCalibrationSource() });
 
     // Wake the other cores (application processors). A no-op on a single-core
     // machine; on SMP each AP climbs to long mode and reports in (docs/smp.md).
@@ -269,7 +269,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     }
 
     log.checkpoint(cp_running);
-    status("kernel initialised.\n");
+    status("/system/kernel: initialised.\n");
 
     // Publish the initial-ramdisk so user space can `system_spawn` its bundled
     // binaries by name. The kernel no longer launches them itself: init is the
@@ -282,10 +282,10 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     // manager then discovers the hardware and spawns each driver. init runs on its own
     // address space, preemptively — this boot context becomes the BSP's idle loop.
     if (boot_information.init_len != 0) {
-        status("starting /system/services/init...\n");
+        status("/system/kernel: starting /system/services/init...\n");
         const image = @as([*]const u8, @ptrFromInt(boot_handoff.physicalToVirtual(boot_information.init_base)))[0..boot_information.init_len];
         process.spawnProcess(image, 4, &.{"/system/services/init"}) catch |err| {
-            statusPrint("/system/services/init failed to load: {s}\n", .{@errorName(err)});
+            statusPrint("/system/kernel: /system/services/init failed to load: {s}\n", .{@errorName(err)});
         };
     } else {
         status("no /system/services/init on the boot volume.\n");
@@ -294,7 +294,7 @@ fn kmain(boot_information: *const BootInformation) noreturn {
     // Become the idle task: drop below every real task and halt until an
     // interrupt. The timer keeps preempting into init and any other work.
     scheduler.setPriority(0);
-    status("\nkernel idle; user space is running.\n");
+    status("\n/system/kernel: kernel idle; user space is running.\n");
     architecture.halt();
 }
 
@@ -321,7 +321,7 @@ fn bringUpSecondaries() void {
     // vector addresses it). It's kept for the system's life — armed only during a
     // wake, inert (zeroed, non-executable) otherwise — so cores can be re-woken later.
     if (ap_trampoline_page == 0) {
-        log.write("danos: smp: no low page for the AP trampoline; staying uniprocessor\n");
+        log.write("/system/kernel: smp: no low page for the AP trampoline; staying uniprocessor\n");
         return;
     }
     architecture.setTrampolinePage(ap_trampoline_page);
@@ -333,7 +333,7 @@ fn bringUpSecondaries() void {
         if (std.mem.eql(u8, tc, "smp-retry")) architecture.testFailNextWakes(1);
     }
 
-    log.print("\ndanos: bringing up {d} application processor(s)\n", .{cores.len - 1});
+    log.print("\n/system/kernel: bringing up {d} application processor(s)\n", .{cores.len - 1});
     const maximum_wake_attempts = 3; // a core that misses the first INIT-SIPI-SIPI gets retried
     for (cores[1..], 1..) |core, index| {
         const stack = heap.allocator().alloc(u8, parameters.kernel_stack_size) catch {
@@ -344,7 +344,7 @@ fn bringUpSecondaries() void {
         // This core's dedicated fault stack — allocated only now that the core is
         // real, rather than reserved statically for every possible core.
         const fault_stack = heap.allocator().alloc(u8, architecture.fault_stack_size) catch {
-            log.print("  cpu apic_id {d}: no fault stack; skipped\n", .{core.apic_id});
+            log.print("/system/kernel:  cpu apic_id {d}: no fault stack; skipped\n", .{core.apic_id});
             continue;
         };
         architecture.setFaultStack(index, (@intFromPtr(fault_stack.ptr) + fault_stack.len) & ~@as(usize, 15));
@@ -353,14 +353,14 @@ fn bringUpSecondaries() void {
         while (attempt <= maximum_wake_attempts) : (attempt += 1) {
             if (architecture.startSecondary(core.apic_id, stack_top, @intFromPtr(pc), index)) {
                 pc.online = true;
-                log.print("  cpu apic_id {d}: online (attempt {d})\n", .{ core.apic_id, attempt });
+                log.print("/system/kernel:  cpu apic_id {d}: online (attempt {d})\n", .{ core.apic_id, attempt });
                 break;
             }
             if (attempt == maximum_wake_attempts)
-                log.print("  cpu apic_id {d}: no response after {d} attempts (parked)\n", .{ core.apic_id, maximum_wake_attempts });
+                log.print("/system/kernel:  cpu apic_id {d}: no response after {d} attempts (parked)\n", .{ core.apic_id, maximum_wake_attempts });
         }
     }
-    log.print("danos: {d}/{d} cores online\n", .{ scheduler.onlineCount(), cores.len });
+    log.print("/system/kernel: {d}/{d} cores online\n", .{ scheduler.onlineCount(), cores.len });
 }
 
 /// A user-facing status line: to the diagnostic `log` *and* the on-screen console
@@ -427,7 +427,7 @@ fn exitReasonForVector(vector: u64) abi.ExitReason {
 
 fn onException(state: *const architecture.CpuState) noreturn {
     if (architecture.fromUser(state) and scheduler.currentIsUserProcess() and recoverableFault(state.vector)) {
-        statusPrint("\ndanos: process {d} ({s}) killed by {s} (vector {d}) on core {d}\n", .{ scheduler.currentId(), scheduler.current().name(), architecture.exceptionName(state.vector), state.vector, scheduler.currentCpuIndex() });
+        statusPrint("\n/system/kernel: process {d} ({s}) killed by {s} (vector {d}) on core {d}\n", .{ scheduler.currentId(), scheduler.current().name(), architecture.exceptionName(state.vector), state.vector, scheduler.currentCpuIndex() });
         statusPrint("  error code : 0x{x}\n", .{state.error_code});
         statusPrint("  IP         : 0x{x:0>16}\n", .{architecture.instructionPointer(state)});
         if (architecture.faultAddress(state)) |address| statusPrint("  fault addr : 0x{x:0>16}\n", .{address});

system/kernel/tests.zig

@@ -211,6 +211,13 @@ fn eql(a: []const u8, b: []const u8) bool {
     return std.mem.eql(u8, a, b);
 }
 
+/// Whether the captured last-write buffer *contains* `needle`. Markers are
+/// matched as substrings, not prefixes, so a service's source-path debug prefix
+/// (`system/drivers/hpet: ok`) still satisfies a marker like `hpet: ok`.
+fn bufferHas(needle: []const u8) bool {
+    return std.mem.indexOf(u8, process.write_buffer[0..process.write_len], needle) != null;
+}
+
 /// Non-destructive checks of the memory map and frame allocator.
 fn smoke(boot_information: *const BootInformation) void {
     log("DANOS-TEST-BEGIN: smoke\n", .{});
@@ -1380,7 +1387,7 @@ fn initTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(4);
 
     const prefix = "init: heartbeat";
-    const beat_ok = process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix);
+    const beat_ok = bufferHas(prefix);
     check("init produced repeated heartbeats (>=2)", process.write_count >= 2);
     check("heartbeat text arrived intact", beat_ok);
     check("heartbeats came from user mode (CPL 3)", process.write_from_user);
@@ -1642,11 +1649,11 @@ fn vfsClientDeathTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     var deadline = architecture.millis() + 10000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= parked.len and eql(process.write_buffer[0..parked.len], parked)) break;
+        if (bufferHas(parked)) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
-    check("client parked holding an open handle", process.write_len >= parked.len and eql(process.write_buffer[0..parked.len], parked));
+    check("client parked holding an open handle", bufferHas(parked));
 
     check("the kill is accepted", process.killProcess(me, client) == 0);
     var badge: u64 = 0;
@@ -1659,11 +1666,11 @@ fn vfsClientDeathTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     deadline = architecture.millis() + 10000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= released.len and eql(process.write_buffer[0..released.len], released)) break;
+        if (bufferHas(released)) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
-    check("the VFS released the dead client's handle", process.write_len >= released.len and eql(process.write_buffer[0..released.len], released));
+    check("the VFS released the dead client's handle", bufferHas(released));
     result();
 }
 
@@ -1705,8 +1712,8 @@ fn signalsTest(boot_information: *const BootInformation) void {
     var saw_pass = false;
     var saw_fail = false;
     while (architecture.millis() < deadline and !saw_pass and !saw_fail) {
-        if (process.write_len >= pass_marker.len and eql(process.write_buffer[0..pass_marker.len], pass_marker)) saw_pass = true;
-        if (process.write_len >= fail_marker.len and eql(process.write_buffer[0..fail_marker.len], fail_marker)) saw_fail = true;
+        if (bufferHas(pass_marker)) saw_pass = true;
+        if (bufferHas(fail_marker)) saw_fail = true;
         scheduler.yield();
     }
     scheduler.setPriority(4);
@@ -1868,13 +1875,11 @@ fn pciScanTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     var deadline = architecture.millis() + 15000;
     while (architecture.millis() < deadline and reported == 0) {
-        if (process.write_len > count_prefix.len + count_suffix.len and eql(process.write_buffer[0..count_prefix.len], count_prefix)) {
-            const line = process.write_buffer[0..process.write_len];
-            const digits_end = std.mem.indexOf(u8, line, count_suffix) orelse {
-                scheduler.yield();
-                continue;
-            };
-            reported = std.fmt.parseInt(u32, line[count_prefix.len..digits_end], 10) catch 0;
+        const line = process.write_buffer[0..process.write_len];
+        if (std.mem.indexOf(u8, line, count_prefix)) |start| {
+            if (std.mem.indexOf(u8, line, count_suffix)) |digits_end| {
+                reported = std.fmt.parseInt(u32, line[start + count_prefix.len .. digits_end], 10) catch 0;
+            }
         }
         scheduler.yield();
     }
@@ -1898,7 +1903,7 @@ fn pciScanTest(boot_information: *const BootInformation) void {
     deadline = architecture.millis() + 15000;
     var restarted = false;
     while (architecture.millis() < deadline and !restarted) {
-        if (process.write_len >= restart_marker.len and eql(process.write_buffer[0..restart_marker.len], restart_marker)) restarted = true;
+        if (bufferHas(restart_marker)) restarted = true;
         scheduler.yield();
     }
     scheduler.setPriority(4);
@@ -1910,7 +1915,7 @@ fn pciScanTest(boot_information: *const BootInformation) void {
     deadline = architecture.millis() + 15000;
     var seen = false;
     while (architecture.millis() < deadline and !seen) {
-        if (process.write_len >= marker.len and eql(process.write_buffer[0..marker.len], marker)) seen = true;
+        if (bufferHas(marker)) seen = true;
         scheduler.yield();
     }
     scheduler.setPriority(4);
@@ -2060,12 +2065,12 @@ fn supervisionTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     const deadline = architecture.millis() + 10000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= marker.len and eql(process.write_buffer[0..marker.len], marker)) break;
+        if (bufferHas(marker)) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
 
-    const ok = process.write_len >= marker.len and eql(process.write_buffer[0..marker.len], marker);
+    const ok = bufferHas(marker);
     if (!ok and process.write_len > 0) log("DANOS-SUPERVISION: got \"{s}\"\n", .{process.write_buffer[0..process.write_len]});
     check("the supervisor completed every step (spawn/list/kill/notify)", ok);
     check("it ran in user mode (CPL 3)", process.write_from_user);
@@ -2145,12 +2150,12 @@ fn vfsTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     const deadline = architecture.millis() + 10000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix) and process.write_count >= 2) break;
+        if (bufferHas(prefix) and process.write_count >= 2) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
 
-    const ok = process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix);
+    const ok = bufferHas(prefix);
     check("client completed the VFS round trip (open/write/read matched)", ok);
     check("the round trip ran repeatedly (server stays up)", process.write_count >= 2);
     check("client syscalls came from user mode (CPL 3)", process.write_from_user);
@@ -2190,12 +2195,12 @@ fn inputTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     const deadline = architecture.millis() + 12000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix) and process.write_count >= 2) break;
+        if (bufferHas(prefix) and process.write_count >= 2) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
 
-    const ok = process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix);
+    const ok = bufferHas(prefix);
     check("a subscriber received a broadcast key event over IPC (source -> service -> subscriber)", ok);
     check("events kept flowing (service + async send stay up)", process.write_count >= 2);
     check("client syscalls came from user mode (CPL 3)", process.write_from_user);
@@ -2287,12 +2292,12 @@ fn hpetTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     const deadline = architecture.millis() + 10000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix) and process.write_count >= 2) break;
+        if (bufferHas(prefix) and process.write_count >= 2) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
 
-    const ok = process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix);
+    const ok = bufferHas(prefix);
     check("user driver mapped HPET MMIO and was woken by its interrupt", ok);
     check("driver syscalls came from user mode (CPL 3)", process.write_from_user);
     check("kernel routed and re-armed the HPET's line at the I/O APIC", hpetRouteOk());
@@ -2393,12 +2398,12 @@ fn busTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     const deadline = architecture.millis() + 10000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix)) break;
+        if (bufferHas(prefix)) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
 
-    const ok = process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix);
+    const ok = bufferHas(prefix);
     check("bus driver published children and the kernel refused an out-of-window one", ok);
     check("driver syscalls came from user mode (CPL 3)", process.write_from_user);
     check("every registered child is contained in its parent", childrenContained());
@@ -2442,12 +2447,12 @@ fn deviceManagerTest(boot_information: *const BootInformation) void {
     scheduler.setPriority(1);
     const deadline = architecture.millis() + 10000;
     while (architecture.millis() < deadline) {
-        if (process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix)) break;
+        if (bufferHas(prefix)) break;
         scheduler.yield();
     }
     scheduler.setPriority(4);
 
-    const ok = process.write_len >= prefix.len and eql(process.write_buffer[0..prefix.len], prefix);
+    const ok = bufferHas(prefix);
     check("device manager matched the timer and system_spawn'd hpet, which came up", ok);
     check("its syscalls came from user mode (CPL 3)", process.write_from_user);
     result();

system/services/acpi/acpi.zig

@@ -108,16 +108,16 @@ pub fn main(init: runtime.process.Init) void {
     const expected: ?usize = if (init.arguments.get(1)) |a| (std.fmt.parseInt(usize, a, 10) catch null) else null;
 
     const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 64) catch {
-        _ = runtime.system.write("acpi: out of memory\n");
+        _ = runtime.system.write("/system/services/acpi: out of memory\n");
         return;
     };
     const node = findTablesNode(buffer) orelse {
-        _ = runtime.system.write("acpi: no acpi-tables node to claim\n");
+        _ = runtime.system.write("/system/services/acpi: no acpi-tables node to claim\n");
         return;
     };
     node_id = node.id;
     if (!device.claim(node_id)) {
-        _ = runtime.system.write("acpi: unable to claim acpi-tables\n");
+        _ = runtime.system.write("/system/services/acpi: unable to claim acpi-tables\n");
         return;
     }
 
@@ -151,17 +151,17 @@ pub fn main(init: runtime.process.Init) void {
         block_count += 1;
     }
     if (block_count == 0) {
-        _ = runtime.system.write("acpi: no AML blobs on the node\n");
+        _ = runtime.system.write("/system/services/acpi: no AML blobs on the node\n");
         return;
     }
 
     const result = aml.parse(runtime.allocator(), blocks[0..block_count]) catch {
-        _ = runtime.system.write("acpi: AML parse failed\n");
+        _ = runtime.system.write("/system/services/acpi: AML parse failed\n");
         return;
     };
     var namespace = result.namespace;
     const devices = aml.deviceCount(&namespace);
-    writeLine("acpi: parsed {d} AML blob(s), {d} namespace devices\n", .{ block_count, devices });
+    writeLine("/system/services/acpi: parsed {d} AML blob(s), {d} namespace devices\n", .{ block_count, devices });
     if (expected) |want| {
         if (devices == want) {
             _ = runtime.system.write("acpi-parse: ok\n");
@@ -214,9 +214,9 @@ fn onInit(endpoint: runtime.ipc.Handle) bool {
         const hid = entry.hid[0..entry.hid_len];
         const desc = acpi_ids.description(hid);
         if (desc.len != 0)
-            writeLine("acpi: reported {s} (device {d}, {d} resources) — {s}\n", .{ hid, entry.device_id, entry.resource_count, desc })
+            writeLine("/system/services/acpi: reported {s} (device {d}, {d} resources) — {s}\n", .{ hid, entry.device_id, entry.resource_count, desc })
         else
-            writeLine("acpi: reported {s} (device {d}, {d} resources)\n", .{ hid, entry.device_id, entry.resource_count });
+            writeLine("/system/services/acpi: reported {s} (device {d}, {d} resources)\n", .{ hid, entry.device_id, entry.resource_count });
         if (manager) |h| {
             var report = protocol.ChildAdded{ .parent = node_id, .bus_address = entry.device_id, .identity = 0, .device_id = entry.device_id };
             @memcpy(report.hid[0..entry.hid_len], entry.hid[0..entry.hid_len]);
@@ -224,7 +224,7 @@ fn onInit(endpoint: runtime.ipc.Handle) bool {
             _ = runtime.ipc.call(h, std.mem.asBytes(&report), &reply) catch {};
         }
     }
-    writeLine("acpi: reported {d} device(s) to the manager\n", .{registered_count});
+    writeLine("/system/services/acpi: reported {d} device(s) to the manager\n", .{registered_count});
 
     armPowerButton(endpoint);
     return true;
@@ -498,7 +498,7 @@ fn registerDevice(node: *aml.Node, hid: [8]u8, interpreter: *aml.Interpreter) vo
     applyCrs(&descriptor, node, interpreter);
 
     const id = device.register(node_id, &descriptor) orelse {
-        writeLine("acpi: register refused for {s}\n", .{hid[0..@intCast(hid_len)]});
+        writeLine("/system/services/acpi: register refused for {s}\n", .{hid[0..@intCast(hid_len)]});
         return;
     };
     registered[registered_count] = .{ .hid = hid, .hid_len = @intCast(hid_len), .device_id = id, .resource_count = descriptor.resource_count };

system/services/device-manager/device-manager.zig

@@ -191,7 +191,7 @@ fn addChild(parent: u64, bus_address: u64, identity: u64, device_id: u64, report
 fn pruneChildrenOf(reporter: u32) void {
     for (&children) |*child| {
         if (child.used and child.reporter == reporter) {
-            writeLine("device-manager: child removed (device {d} port {d})\n", .{ child.parent, child.bus_address });
+            writeLine("/system/services/device-manager: child removed (device {d} port {d})\n", .{ child.parent, child.bus_address });
             child.used = false;
             const event = protocol.ChildRemoved{ .parent = child.parent, .bus_address = child.bus_address };
             publishEvent(std.mem.asBytes(&event));
@@ -238,7 +238,7 @@ fn addDriver(name: []const u8, device_id: u64, speaks_protocol: bool) void {
         spawnDriver(driver);
         return;
     }
-    writeLine("device-manager: driver table full; cannot supervise {s}\n", .{name});
+    writeLine("/system/services/device-manager: driver table full; cannot supervise {s}\n", .{name});
 }
 
 /// (Re)spawn a driver instance: supervised on the manager's own endpoint, the
@@ -253,7 +253,7 @@ fn spawnDriver(driver: *Driver) void {
         argument_count = 1;
     }
     const child = system.spawnSupervised(driver.name(), arguments[0..argument_count], manager_endpoint) orelse {
-        writeLine("device-manager: failed to spawn {s}\n", .{driver.name()});
+        writeLine("/system/services/device-manager: failed to spawn {s}\n", .{driver.name()});
         driver.state = .failed;
         return;
     };
@@ -267,9 +267,9 @@ fn spawnDriver(driver: *Driver) void {
         driver.state = .running;
     }
     if (driver.device_id != protocol.no_device) {
-        writeLine("device-manager: spawned {s} for device {d}\n", .{ driver.name(), driver.device_id });
+        writeLine("/system/services/device-manager: spawned {s} for device {d}\n", .{ driver.name(), driver.device_id });
     } else {
-        writeLine("device-manager: spawned {s}\n", .{driver.name()});
+        writeLine("/system/services/device-manager: spawned {s}\n", .{driver.name()});
     }
 }
 
@@ -281,7 +281,7 @@ fn onDriverExit(driver: *Driver) void {
     const reason = runtime.process.exitReason(driver.process_id) orelse .fault;
     if (reason == .exited) {
         driver.state = .stopped;
-        writeLine("device-manager: {s} exited cleanly; not restarting\n", .{driver.name()});
+        writeLine("/system/services/device-manager: {s} exited cleanly; not restarting\n", .{driver.name()});
         return;
     }
     const now = system.clock();
@@ -289,13 +289,13 @@ fn onDriverExit(driver: *Driver) void {
     driver.restarts = if (alive_ns < fast_death_ns) driver.restarts + 1 else 1;
     if (driver.restarts >= crash_loop_cap) {
         driver.state = .failed;
-        writeLine("device-manager: {s} is failing repeatedly (crash loop); giving up\n", .{driver.name()});
+        writeLine("/system/services/device-manager: {s} is failing repeatedly (crash loop); giving up\n", .{driver.name()});
         return;
     }
     const delay_ms = backoff_base_ms << @intCast(driver.restarts - 1);
     driver.state = .restarting;
     driver.restart_due_ns = now + delay_ms * 1_000_000;
-    writeLine("device-manager: restarting {s} in {d} ms (died: {s})\n", .{ driver.name(), delay_ms, @tagName(reason) });
+    writeLine("/system/services/device-manager: restarting {s} in {d} ms (died: {s})\n", .{ driver.name(), delay_ms, @tagName(reason) });
     _ = system.timerOnce(manager_endpoint, delay_ms + 50);
 }
 
@@ -306,7 +306,7 @@ fn onDriverExit(driver: *Driver) void {
 fn sweepDeadlines() void {
     const now = system.clock();
     if (test_kill_pid != 0 and now >= test_kill_due_ns) {
-        writeLine("device-manager: test mode: killing the reporter\n", .{});
+        writeLine("/system/services/device-manager: test mode: killing the reporter\n", .{});
         _ = system.kill(test_kill_pid);
         test_kill_pid = 0;
     }
@@ -314,7 +314,7 @@ fn sweepDeadlines() void {
         if (!driver.used) continue;
         switch (driver.state) {
             .awaiting_hello => if (now >= driver.hello_deadline_ns) {
-                writeLine("device-manager: {s} missed its hello deadline\n", .{driver.name()});
+                writeLine("/system/services/device-manager: {s} missed its hello deadline\n", .{driver.name()});
                 _ = system.kill(driver.process_id);
                 // The exit notification finishes the job via onDriverExit.
             },
@@ -331,7 +331,7 @@ fn initialise(endpoint: runtime.ipc.Handle) bool {
 
     // Enumerate into a heap buffer (too big for the one-page user stack).
     const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 64) catch {
-        _ = runtime.system.write("device-manager: out of memory\n");
+        _ = runtime.system.write("/system/services/device-manager: out of memory\n");
         return false;
     };
     const total = device.enumerate(buffer);
@@ -372,9 +372,9 @@ fn initialise(endpoint: runtime.ipc.Handle) bool {
     }
 
     if (matched == 0) {
-        _ = runtime.system.write("device-manager: no matchable devices\n");
+        _ = runtime.system.write("/system/services/device-manager: no matchable devices\n");
     } else {
-        _ = runtime.system.write("device-manager: ok\n");
+        _ = runtime.system.write("/system/services/device-manager: ok\n");
     }
     return true;
 }
@@ -395,13 +395,13 @@ fn onMessage(message: []const u8, reply: []u8, sender: u32, capability: ?runtime
     var status: i32 = 0;
     if (hello.version != protocol.version) {
         status = -1;
-        writeLine("device-manager: refused hello (version {d}) from process {d}\n", .{ hello.version, sender });
+        writeLine("/system/services/device-manager: refused hello (version {d}) from process {d}\n", .{ hello.version, sender });
     } else if (driverByProcess(sender)) |driver| {
         driver.state = .running;
-        writeLine("device-manager: hello from {s} (device {d})\n", .{ driver.name(), hello.device_id });
+        writeLine("/system/services/device-manager: hello from {s} (device {d})\n", .{ driver.name(), hello.device_id });
     } else {
         status = -1;
-        writeLine("device-manager: hello from unknown process {d}\n", .{sender});
+        writeLine("/system/services/device-manager: hello from unknown process {d}\n", .{sender});
     }
     const hello_reply = protocol.HelloReply{ .status = status };
     @memcpy(reply[0..protocol.reply_size], std.mem.asBytes(&hello_reply));
@@ -417,7 +417,7 @@ fn onChildAdded(message: []const u8, reply: []u8, sender: u32) usize {
     var status: i32 = 0;
     if (driverByProcess(sender)) |driver| {
         if (!addChild(report.parent, report.bus_address, report.identity, report.device_id, sender)) status = -1;
-        writeLine("device-manager: child added (device {d} port {d}, identity {d}) by {s}\n", .{ report.parent, report.bus_address, report.identity, driver.name() });
+        writeLine("/system/services/device-manager: child added (device {d} port {d}, identity {d}) by {s}\n", .{ report.parent, report.bus_address, report.identity, driver.name() });
         if (status == 0) publishEvent(message[0..protocol.child_added_size]);
         // Matching from reports (M19.3): a registered child whose identity
         // names a driver gets one, once — re-reports after a bus restart
@@ -478,7 +478,7 @@ fn onChildRemoved(message: []const u8, reply: []u8, sender: u32) usize {
     var status: i32 = -1;
     for (&children) |*child| {
         if (child.used and child.parent == report.parent and child.bus_address == report.bus_address and child.reporter == sender) {
-            writeLine("device-manager: child removed (device {d} port {d})\n", .{ child.parent, child.bus_address });
+            writeLine("/system/services/device-manager: child removed (device {d} port {d})\n", .{ child.parent, child.bus_address });
             child.used = false;
             status = 0;
         }

system/services/init/init.zig

@@ -40,7 +40,7 @@ pub fn main() void {
     // the extern malloc/free symbols; Zig code uses this allocator.)
     const gpa = runtime.allocator();
     if (gpa.alloc(u8, 64)) |buffer| {
-        const message = "init: heap ok\n";
+        const message = "/system/services/init: heap ok\n";
         @memcpy(buffer[0..message.len], message);
         _ = runtime.system.write(buffer[0..message.len]);
         gpa.free(buffer);
@@ -50,7 +50,7 @@ pub fn main() void {
     // notifications (they are spawned supervised against it), init's own
     // signals, and power events it subscribes to. All arrive in the loop below.
     supervision_endpoint = runtime.ipc.createIpcEndpoint() orelse {
-        _ = runtime.system.write("init: no endpoint\n");
+        _ = runtime.system.write("/system/services/init: no endpoint\n");
         return;
     };
     _ = runtime.process.bindSignals(supervision_endpoint);
@@ -83,7 +83,7 @@ pub fn main() void {
             continue;
         }
         if (got.isTimer()) {
-            _ = runtime.system.write("init: heartbeat\n");
+            _ = runtime.system.write("/system/services/init: heartbeat\n");
             _ = runtime.system.timerOnce(supervision_endpoint, 1000);
             continue;
         }
@@ -119,7 +119,7 @@ fn subscribePower() void {
 /// other services may flush through it), waiting up to a deadline for each to
 /// exit before killing it, then ask the power service to enter S5.
 fn shutDown() void {
-    _ = runtime.system.write("init: shutting down\n");
+    _ = runtime.system.write("/system/services/init: shutting down\n");
     var i = child_count;
     while (i > 0) {
         i -= 1;

system/services/input/input.zig

@@ -115,14 +115,14 @@ fn handle(message: []const u8, got: ipc.Received, out: []u8) usize {
 
 pub fn main() void {
     const endpoint = ipc.createIpcEndpoint() orelse {
-        _ = system.write("input: no endpoint\n");
+        _ = system.write("/system/services/input: no endpoint\n");
         return;
     };
     if (!ipc.register(.input, endpoint)) {
-        _ = system.write("input: register failed\n");
+        _ = system.write("/system/services/input: register failed\n");
         return;
     }
-    _ = system.write("input: ready\n");
+    _ = system.write("/system/services/input: ready\n");
 
     var reply_buffer: [protocol.reply_size]u8 = undefined;
     var reply_len: usize = 0;

system/services/vfs/vfs.zig

@@ -87,7 +87,7 @@ fn releaseClientHandles(client: u32) void {
             released += 1;
         }
     }
-    if (released != 0) writeLine("vfs: released {d} handle(s) for dead client {d}\n", .{ released, client });
+    if (released != 0) writeLine("/system/services/vfs: released {d} handle(s) for dead client {d}\n", .{ released, client });
 }
 
 /// Handle one request from `sender`; write the reply into `out`, return its length.
@@ -144,9 +144,9 @@ fn handle(message: []const u8, out: []u8, sender: u32, capability: ?runtime.ipc.
 /// to release them (docs/process-lifecycle.md).
 fn initialise(endpoint: runtime.ipc.Handle) bool {
     if (!runtime.process.subscribeExits(endpoint)) {
-        _ = runtime.system.write("vfs: exit subscription failed\n");
+        _ = runtime.system.write("/system/services/vfs: exit subscription failed\n");
     }
-    _ = runtime.system.write("vfs: ready\n");
+    _ = runtime.system.write("/system/services/vfs: ready\n");
     return true;
 }