Building a Custom Programming Language and OS with OCaml, LLVM, and Generative AI

Building a Custom Programming Language and OS with OCaml, LLVM, and Generative AI

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  Createyourownprogramming Createyourownprogramming languageandOSusingOCaml, languageandOSusingOCaml, LLVM,andGenerativeAI-- LLVM,andGenerativeAI-- accessibletoeveryone accessibletoeveryone Kiwamu Okabe github.com/takibi-lang/takibi
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  Welovebuildingoperatingsystems But the traditionalimplementation language is a problem: C language gives the kernel complete control + C language gives the kernel almost no proof = one bad access can corrupt the entire system We wanted a language designed for the place where a crash is least recoverable. Could more kernel failures become compile-time errors? 2 / 15 OCaml Meeting 2026 in Tokyo 2
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  WhyOCaml+LLVM+GenerativeAI? Ingredient Role OCaml Makesyntax and static semantics explicit and changeable LLVM Produce real native code without writing machine backends Generative AI Implement enough compiler and kernel code to test ideas end-to-end The LLVM project officially maintains OCaml bindings. LLVM IR is still hard. AI made it easy. 3 / 15 OCaml Meeting 2026 in Tokyo 3
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  Thesetup,keepsthehumanontheloop Linux Desktop devcontainer Takibi toolchain RaspberryPi 5 USB storage (ext2) Memory Takibi kernel AI Agents Internet AI coding CLIs Claude Code · Codex · Copilot Ethernet validate httpd TCP/IP stack UART monitor logs UART monitor SWD memory + debug OpenOCD + GDB SWD debug interface hardware memory access Takibi compiler OCaml + LLVM kernel image BusyBox (httpd) UART driver 4 / 15 OCaml Meeting 2026 in Tokyo 4
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  Demo 0:00 / 0:55 5/ 15 OCaml Meeting 2026 in Tokyo 5
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  Thekernelisthelanguage-designworkload 1 AI implements a realkernel path 2 Repeated Takibi code patterns expose missing guarantees 3 The OCaml compiler learns a checked abstraction 4 The next kernel path becomes safer and simpler 6 / 15 OCaml Meeting 2026 in Tokyo 6
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  Ctechnique:describeNICstatewithbooleans frame->valid = true; frame->tx_in_flight= true; frame->released = false; The representation also permits contradictions: frame->valid && frame->released frame->tx_in_flight && frame->available Every caller must remember which combinations are legal. The compiler sees only fields and integers. 7 / 15 OCaml Meeting 2026 in Tokyo 7
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  Takibitechnique1:theNICisacapabilitystate machine NetRxCanAcquire -> NetRxValidated[desc] -> NetRxReplyReady[desc] ->NetTxInFlight[desc] -> NetRxCanAcquire fn net_transmit(reply: sink NetRxReplyReady[desc]) -> NetTxInFlight[desc]; fn net_tx_complete(in_flight: sink NetTxInFlight[desc]) -> NetRxCanAcquire !{may_block}; Each transition consumes the previous state with sink . 8 / 15 OCaml Meeting 2026 in Tokyo 8
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  MakeinvalidNICstatesunrepresentable The type checkerprevents: releasing the same RX frame twice; transmitting before validation; reacquiring a descriptor before TX completes; forgetting to return an active descriptor to DMA. detect an invalid state later C flags make the invalid state impossible Takibi types The capability types add no new descriptor identity at runtime. 9 / 15 OCaml Meeting 2026 in Tokyo 9
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  Ctechnique:returnapointerintoanRXbuffer uint8_t *packet =net_rx_frame(frame); net_rx_release(frame); /* DMA owns it again */ parse(packet); /* use after release */ The pointer still looks valid. Its type does not remember: the available length; the descriptor it came from; when ownership returned to DMA. 10 / 15 OCaml Meeting 2026 in Tokyo 10
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  Takibitechnique2:tietheslicetodescriptor authority fn net_rx_frame(frame: borrowNetRxValidated[desc]) -> [u8; 1514..] @ desc; The result carries two proofs: at least 1514 bytes are available + the slice is derived from descriptor desc let packet = net_rx_frame(frame); let ready = net_rx_release(frame); parse(packet); // compile error 11 / 15 OCaml Meeting 2026 in Tokyo 11
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  AproblemeventheAIcouldnotsolve:STM32 UART AI: "Serial outputis lost while using the SD card." It kept investigating symptoms. Human: Our UART is polling, while the SD card uses DMA. ChibiOS/RT normally uses DMA and interrupts for both. What happens if we change UART to DMA + IRQ? AI: Implemented it, tested it on the board -- problem solved. 12 / 15 OCaml Meeting 2026 in Tokyo 12
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  Anotherblindway:kernelprintfdebugging AI: Added moreand more kernel-side prints to infer userspace behavior. Human: If we need to know what BusyBox does, why not read the BusyBox source? AI: Read the actual userspace implementation -- problem solved. more observability is not always more understanding The human changed the source of evidence, not the amount of logging. 13 / 15 OCaml Meeting 2026 in Tokyo 13
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  TheoneOCaml-sideroughedge:DWARF Takibi emits DWARFand supports source debugging through GDB. LLVM's OCaml bindings still lack convenient APIs for: dbg.value locations for SSA and entry parameter values; DISubrange construction for natural fixed-array display. Takibi currently works around those gaps with debug-only allocas, volatile preservation stores, and GDB artificial arrays. We would like to contribute these capabilities upstream. Details: Takibi's open DWARF issues 14 / 15 OCaml Meeting 2026 in Tokyo 14
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  OCaml+LLVM+GenerativeAI OCaml+LLVM+GenerativeAI makesthestackaccessible makesthestackaccessible I tried theexperiment: github.com/takibi-lang/takibi Question today's architectural assumptions. Design your language and your OS with OCaml. Perhaps design the CPU too, with Hardcaml. OCamlmakesambitioussystemsexperiments ordinary.