universalisos/kernel/GAP_ANALYSIS_PIKEOS_PARITY.md

UniversalisOS Gap Analysis: PikeOS 3-Layer Parity

Audit Date: 2026-07-14

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1. CODEBASE OVERVIEW

Metric	Value
Total codebase	126,469 LOC (C/C++/H/S)
Core kernel (src/core)	51,484 LOC
ARMv7 arch	3,637 LOC
AArch64 arch	15,883 LOC
RISC-V arch	11,570 LOC
x86_64 arch	20,916 LOC
Tests	2,295 LOC (16 test files)
ARMv7 ELF binary	1.9 MB (290KB text, 215KB data, 24MB BSS)
Total TODO/stub markers	243 across core

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2. SYSCALL TABLE (119 Syscalls)

Classification

Category	Count	Status
REAL implementations	41	Call into core subsystems with logic
Stubs (return 0)	78	No-op, no real implementation
Not implemented (-8)	0	All have at least a stub handler

Syscalls with REAL implementations (41)

SC#	Name	Subsystem	Quality
0	FAST_GET_UID	Identity	Trivial (returns 0)
1	KERNEL_CONTROL	Control	Trivial (returns 0)
2	SLEEP	Task	✅ Calls task_sleep_us()
3	FAST_GET_CPUID	Identity	✅ Reads MPIDR/TP
4	TASK_ACTIVATE	Task	✅ scheduler_add_task()
5	TASK_START	Task	✅ scheduler_start()
6	TASK_TERMINATE	Task	✅ task_destroy_complete()
7	TASK_GET_ATTR	Task	⚠️ Partial (TODO: priority accessor)
8	TASK_DONATE	Task	✅ scheduler_yield()
9	THREAD_CREATE	Thread	✅ uos_task_create()
10	THREAD_DELETE	Thread	✅ uos_task_delete()
11	THREAD_YIELD	Thread	✅ scheduler_yield()
12	THREAD_EX_REGS	Thread	✅ Get PC/SP/LR
13	THREAD_GET_ATTR	Thread	Delegates to TASK_GET_ATTR
15	THREAD_SET_REGS	Thread	✅ uos_task_set_regs()
18	THREAD_RESUME	Thread	✅ task_unblock()
20	COMM_GRANT	IPC	✅ uos_ipc_shmem_create()
21	COMM_LINK	IPC	✅ uos_ipc_channel_create()
23	IPC	IPC	✅ Send/receive dispatch
24	EV_MASK	Event	✅ uos_event_set_mask()
25	EV_WAIT	Event	✅ uos_event_wait()
26	EV_SIGNAL	Event	✅ uos_event_signal()
27	INT_ATTACH	Interrupt	✅ uos_int_attach()
30	FAST_GET_PRIO	Priority	✅ uos_task_get_priority()
31	FAST_SET_PRIO	Priority	✅ uos_task_set_priority()
32	MEM_MAP	Memory	✅ mm_map_page()
33	MEM_UNMAP	Memory	✅ mm_unmap_page()
36	MEM_CREATE	Memory	✅ mm_create_page_table()
47	MEMMAP_ALLOC_PHYS	Memory	✅ uos_mm_ralloc_boot()
48	MEMMAP_ALLOC_ALIGNED	Memory	✅ uos_mm_ralloc_boot()
55	GET_TIME	Time	✅ uos_time_get_ticks()
56	MEM_READ	MemIO	✅ Direct memory read
57	MEM_WRITE	MemIO	✅ Direct memory write
66	MEM_CLEAR	MemIO	✅ Zero-fill
70	THREAD_PREEMPT	Sched	✅ scheduler_preempt()
71	TLS_REGISTER	TLS	✅ uos_task_set_tls()
72	ULOCK_WAIT	Futex	⚠️ Partial (needs wake_by_addr)
73	ULOCK_WAKE	Futex	⚠️ TODO: iterate task list
74	GET_TS	Time	✅ uos_time_get_ts()
76	RESPART_ALLOC	Memory	✅ uos_mm_ralloc_boot()
78	KDEV_DISCOVER	KDEV	✅ uos_kdev_init_all()
80	KDEV_OPEN	KDEV	✅ uos_kdev_find()
106	WAITQ_WAIT	WaitQ	✅ task_block()

Stubs returning 0 — grouped by subsystem (78)

KDEV (19 stubs): dup, alert_module, alert_part, close_all, ping, negotiate, close, pstat, read, write, discard, control, map_to, psync, test, descend, spawn, lseek, unlink, rename, dir_create, dir_read, statvfs, discover_gate

Trace (7): start, stop, get_attr, set_attr, write, read, control

Monitoring (7): mon_mem_list, mon_start, mon_stop, mon_get_attr, mon_set_attr, mon_control, mon_write

Time Partitioning (5): load, switch, switch_disable, switch_enable, window_get_attr

HM (6): inject, task_hm_set, task_hm_get, get_attr, set_attr, control, write

IO Ports (3): map, unmap, create

Device (2): dev_grant, dev_call

Other (29): thread_ex_sched, thread_ex_exh, thread_stop_syscall, thread_except, ipc_mask, int_wait, int_grant, mem_set_attr, mem_build_sglist, thread_get_regs, thread_ex_affinity, sysemu_enter, respart_get_kmem, thread_alarm, tls_sync_prio, waitq_init, waitq_wake, waitq_get_attr, cache, fast_get_timepart, mon_memreg_get_attr

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3. SUBSYSTEM GAP ANALYSIS

3.1 Scheduler

Metric	Value
LOC	sched_core: 314, scheduler.cpp: 1034, sched.cpp: 452
TODOs	11 (sched), 1 (scheduler)
Status	✅ FUNCTIONAL

What works:

• Cyclic partition scheduler with cooperative yield (sched_core.cpp)
• Timer-driven preemption demo: 2 tasks, interleaved A/B output proven on QEMU
• Priority-based scheduling framework (scheduler.cpp)
• EDF/RM policy framework
• MCS-style budget accounting
• Context switch (ARM assembly: ctx_switch.S + preempt_switch.S)
• Priority inheritance/ceiling protocols (API-level)

Gaps vs PikeOS:

• No multi-core scheduling (single-CPU only)
• No proper time-partition window enforcement (budget accounting present but not enforced at boundaries)
• No scheduler activations
• Priority inheritance not tested end-to-end

Severity: MEDIUM | Effort: 2-3 weeks

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3.2 Memory Management

Metric	Value
LOC	mm.cpp: 795, mm_list.cpp: 346, mm_store.cpp: 203, mm_kmem.cpp: 80, mm_balloc.cpp: 199, physmem.c: 323
TODOs	59
Status	⚠️ FRAMEWORK + BASIC

What works:

• Boot-time physical memory allocator (mm_store.cpp)
• Flat 4GB section map MMU (ARMv7)
• Page table create/map/unmap
• Bitmap allocator (mm_balloc.cpp)
• Physical memory manager (physmem.c)

Gaps vs PikeOS:

• brk/mmap/sbrk all TODO (no user-space memory management)
• No page fault handling
• No COW (Copy-on-Write)
• No memory protection enforcement
• No per-partition memory isolation enforcement (framework present but not enforced)
• No demand paging
• No memory region API completion

Severity: HIGH | Effort: 4-6 weeks

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3.3 IPC

Metric	Value
LOC	2,662 total across 11 files
TODOs	0
Status	✅ FUNCTIONAL (multiple mechanisms)

What works:

• Shared memory mailbox (uos_shmem.cpp: 152 LOC)
• Event flags (uos_event.cpp: 115 LOC)
• Blackboard/buffer/logbook ARINC 653 ports (uos_blackboard.cpp: 374 LOC)
• Sampling + queuing channels (uos_ipc_core.cpp, uos_queuing.cpp)
• IPC fastpath framework (uos_fastpath.cpp: 193 LOC)
• IVSHMEM inter-VM comm (uos_ivshmem.cpp: 152 LOC)
• PCI passthrough framework (uos_pci_passthru.cpp: 212 LOC)
• Secure vault (uos_secure_vault.cpp: 179 LOC)

Gaps vs PikeOS:

• No real multi-partition message passing (demos exist, not boot-tested end-to-end)
• IVSHMEM and PCI passthrough are framework-only
• No capability-checked IPC (seL4 caps compiled but not wired to IPC path)
• No priority inheritance on IPC blocking

Severity: LOW-MEDIUM | Effort: 2-3 weeks

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3.4 Health Monitoring (HM)

Metric	Value
LOC	uos_hm.cpp: 191, uos_hm.h: 106, uos_hm_demo.cpp: 75
TODOs	3
Status	⚠️ FRAMEWORK

What works:

• 3-tier HM dispatch (uos_hm.cpp)
• Module/partition/task error levels
• Demo exercises error path

Gaps vs PikeOS:

• All 6 HM syscalls are stubs (return 0)
• No actual error recovery actions
• No HM table configuration from system model
• No partition restart/degradation modes

Severity: HIGH | Effort: 3-4 weeks

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3.5 KDEV Framework

Metric	Value
LOC	uos_kdev.cpp: 96, uos_kdev_prov.cpp: 297, uos_kdev_framework.h: 203
TODOs	0
Status	⚠️ SKELETON

What works:

• Self-registering driver framework
• discover_prov + find + open (3 of 22 syscalls have real logic)
• Test driver demo passes

Gaps vs PikeOS:

• 19 of 22 KDEV syscalls are stubs
• No actual device read/write/control
• No filesystem operations (lseek, unlink, rename, dir_create, dir_read, statvfs)
• No provider negotiation
• No device sharing between partitions
• No KDEV alert system

Severity: HIGH | Effort: 6-8 weeks

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3.6 VFS (Virtual File System)

Metric	Value
LOC	vfs.cpp: 500, vfs.c: 353, vfs.h: 255
TODOs	17
Status	⚠️ FRAMEWORK ONLY

What works:

• ISO 9660 read-only filesystem (iso9660.c)
• Block device abstraction (block_dev.c)
• VFS API surface (mount, open, read, write, close, stat, etc.)

Gaps vs PikeOS:

• ALL VFS operations have TODO bodies (mount, unmount, open, close, read, write, stat, unlink, rename, etc.)
• No actual filesystem implementation beyond ISO9660
• No RAM filesystem
• No proper fd table

Severity: HIGH | Effort: 4-6 weeks

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3.7 Signals / Threading / TLS / Futex

Metric	Value
Status	⚠️ MINIMAL

Signals:

• No POSIX signal framework
• task_kill() has TODO: "Implement signal handling"
• seL4 Notifications present (cap layer) but not wired to POSIX signals

Threading:

• Thread create/delete/yield/resume: ✅ functional via task.cpp
• Thread ex_regs/set_regs: ✅ basic register exchange
• Thread ex_sched, ex_exh, stop_syscall, except: stubs

TLS:

• sys_tls_register (SC 71): ✅ stores TLS pointer per task
• sys_tls_sync_prio (SC 97): stub
• No proper __thread support

Futex:

• sys_ulock_wait (SC 72): ⚠️ Partial — checks lock value, blocks with timeout
• sys_ulock_wake (SC 73): ⚠️ Stub — needs wake_by_addr scheduler API
• No proper futex hash table

Severity: MEDIUM | Effort: 3-4 weeks

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3.8 Capability System (seL4-style)

Metric	Value
LOC	1,385 total (cap + sel4)
TODOs	0
Status	✅ FUNCTIONAL (framework)

What works:

• seL4 CNode/MDB implementation
• Capability derivation/revocation graph
• Untyped registration, Retype
• Notification capabilities
• Capability compiler from P4 config
• Demo passes

Gaps vs PikeOS:

• Caps not wired to syscall path (no cap check on IPC/memory)
• No CSpace management syscalls
• No cap transfer between partitions

Severity: LOW | Effort: 1-2 weeks

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3.9 Device Emulation

Metric	Value
LOC	devemu: 692, device.cpp: included
TODOs	21
Status	⚠️ FRAMEWORK

What works:

• MMIO dispatch framework
• IRQ routing structure
• Emulator registration API

Gaps vs PikeOS:

• No actual device emulators registered
• No virtio emulation
• No PCI/PCIe ECAM emulation

Severity: MEDIUM | Effort: 4-6 weeks

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3.10 Partition Management

Metric	Value
LOC	partition.cpp: ~500, respart.cpp: ~364
TODOs	13
Status	⚠️ FRAMEWORK

What works:

• Partition config parsing from P4 manifest
• 2 partitions parsed in boot demo
• Resource partition API surface

Gaps vs PikeOS:

• No partition lifecycle enforcement (start/stop/suspend are framework)
• No partition restart on HM error
• No partition memory isolation enforcement

Severity: MEDIUM | Effort: 3-4 weeks

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4. ARMv7 BUILD & BOOT STATUS

Build

• ✅ Compiles clean with arm-none-eabi-g++ (Cortex-A15 target)
• ✅ Links successfully — 1.9MB ELF
• ⚠️ Warnings: unused parameters in spinlock.h (cosmetic)
• ⚠️ Linker warning: RWX segment (no separate data/text pages)
• ⚠️ Cannot find entry _start (defaults to 0x40000000)

Boot (QEMU virt)

• ✅ Boots to completion
• ✅ MMU enabled (flat 4GB map)
• ✅ GIC initialized (1024 IRQs)
• ✅ Timer subsystem: 62 MHz, 1ms tick, ticker fires correctly
• ✅ IRQ dispatch: 1024-slot table, SGI attach works
• ✅ KDEV: 1 test driver registered and found
• ✅ VFP/NEON: lazy enable works
• ✅ SMP framework: per-CPU + IPI (single CPU)
• ✅ PREEMPT DEMO: INTERLEAVED A/B OUTPUT PROVEN — genuine timer-driven preemption
• ✅ P4 config: 2 partitions parsed, 2 schedule windows, HM module, kdev pool, 2 connections, 1 shared memory

What runs at boot

1. Exception handlers init
2. P4 manifest parsing (2 partitions)
3. Memory management (512MB total, 510MB free)
4. MMU flat map
5. GIC interrupt controller
6. IRQ dispatch demo ✅
7. Time subsystem demo ✅ (timer ticks)
8. KDEV framework demo ✅
9. VFP/NEON demo ✅
10. SMP demo ✅ (IPI weak on QEMU)
11. Preemptive scheduler demo ✅ (never returns — A/B interleaving)

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5. GAP SEVERITY MATRIX

PikeOS Feature	UOS Status	Gap Severity	Est. Effort
Cyclic partition scheduler	✅ Functional	LOW	1w (enforce window boundaries)
Preemptive scheduling	✅ Proven	LOW	1w (multi-task, priority)
Context switch (ARM)	✅ Assembly	NONE	Done
Priority scheduling	✅ Framework	LOW	1w (EDF/RM enforcement)
Multi-core scheduling	❌ Single CPU	HIGH	3-4w
Physical memory allocator	✅ Boot allocator	LOW	1w (runtime allocator)
MMU/page tables	✅ Section map	MEDIUM	2-3w (fine-grained pages)
Memory protection	❌ Not enforced	HIGH	3-4w
Demand paging / COW	❌ TODO	HIGH	4-6w
Per-partition memory isolation	⚠️ Framework	HIGH	2-3w
IPC: shared memory	✅ Functional	LOW	1w
IPC: sampling/queuing ports	✅ Framework	MEDIUM	2w
IPC: blackboard/buffer	✅ Implemented	LOW	1w
IPC: fastpath	⚠️ Framework	MEDIUM	2-3w
IPC: IVSHMEM	⚠️ Framework	MEDIUM	2-3w
Health monitoring	⚠️ Framework only	HIGH	3-4w
HM error recovery	❌ Stubs	HIGH	3-4w
KDEV device framework	⚠️ Skeleton	HIGH	6-8w
KDEV filesystem ops	❌ All stubs	HIGH	4-6w
VFS	⚠️ Framework only	HIGH	4-6w
seL4 capabilities	✅ Implemented	LOW	1-2w (wire to syscalls)
Capability-checked IPC	❌ Not wired	MEDIUM	2-3w
Device emulation	⚠️ Framework	MEDIUM	4-6w
Partition lifecycle	⚠️ Framework	MEDIUM	3-4w
Time partitioning	❌ Stubs	HIGH	3-4w
Trace	❌ All stubs	MEDIUM	2-3w
Monitoring	❌ All stubs	MEDIUM	2-3w
Signals	❌ Not implemented	HIGH	3-4w
Futex (ULOCK)	⚠️ Partial	MEDIUM	1-2w
TLS	⚠️ Basic register	MEDIUM	1-2w
POSIX ABI	⚠️ Stub-heavy	HIGH	6-8w
Guest VM management	⚠️ Framework	MEDIUM	3-4w
Live migration	⚠️ Framework	MEDIUM	4-6w
SMP (multi-core)	⚠️ Framework	HIGH	4-6w
PCI/PCIe	⚠️ Framework	MEDIUM	3-4w
Virtio	❌ Not present	HIGH	6-8w
Network stack	❌ Socket stubs	HIGH	8-10w

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6. SUMMARY SCORES

Syscall Parity

• 119/119 syscalls have handlers (100% table coverage)
• 41/119 have real implementations (34.5%)
• 78/119 are return-0 stubs (65.5%)
• 0 are sys_not_implemented

Subsystem Maturity

Subsystem	Maturity	Ready for demo?	Ready for production?
Scheduler	75%	✅ YES	❌ No
Memory	40%	✅ Boot only	❌ No
IPC	65%	✅ YES	❌ No
HM	25%	⚠️ Demo only	❌ No
KDEV	15%	⚠️ Skeleton	❌ No
VFS	10%	❌ No	❌ No
Capabilities	80%	✅ YES	⚠️ Partial
Signals	5%	❌ No	❌ No
Threading	45%	✅ Basic	❌ No
TLS	30%	⚠️ Basic	❌ No
Futex	25%	⚠️ Partial	❌ No
Partition mgmt	35%	⚠️ Parse only	❌ No
Device emu	20%	❌ No	❌ No
VMM	30%	⚠️ Framework	❌ No

Overall PikeOS 3-Layer Parity Estimate

Layer	Coverage
Layer 1: Microkernel (scheduler, IPC, memory, caps)	~55%
Layer 2: System services (HM, KDEV, VFS, partitions)	~20%
Layer 3: POSIX/runtime (signals, threading, futex, VFS)	~10%
Overall weighted parity	~28%

Prioritized Implementation Roadmap

1. Sprint 1 (2 weeks): Memory protection enforcement, futex wake_by_addr, wire caps to syscalls
2. Sprint 2 (3 weeks): HM error recovery, time partitioning enforcement, KDEV read/write
3. Sprint 3 (4 weeks): VFS implementation, KDEV filesystem ops, POSIX signal framework
4. Sprint 4 (4 weeks): Multi-core scheduling, device emulation, IVSHMEM/PCI live
5. Sprint 5 (6 weeks): POSIX ABI (fork/exec/wait), virtio, network stack

Estimated total to production-grade PikeOS parity: 19-24 engineer-weeks