%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% PAPER FOR: %% %% https://locos.codeberg.page/loco2024/ %% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% %% The first command in your LaTeX source must be the \documentclass %% command. %% %% For submission and review of your manuscript please change the %% command to \documentclass[manuscript, screen, review]{acmart}. %% %% When submitting camera ready or to TAPS, please change the command %% to \documentclass[sigconf]{acmart} or whichever template is required %% for your publication. %% %% \documentclass[sigconf]{acmart} %% For Unix quotes \usepackage{epigraph} \setlength{\epigraphrule}{0pt} %% \BibTeX command to typeset BibTeX logo in the docs \AtBeginDocument{% \providecommand\BibTeX{{% Bib\TeX}}} %% Rights management information. This information is sent to you %% when you complete the rights form. 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The command \citestyle{authoryear} switches to the %% "author year" style. %% %% If you are preparing content for an event %% sponsored by ACM SIGGRAPH, you must use the "author year" style of %% citations and references. %% Uncommenting %% the next command will enable that style. %%\citestyle{acmauthoryear} %% Easy way to write code inline \newcommand{\code}{\texttt} %% end of the preamble, start of the body of the document source. \begin{document} %% The "title" command has an optional parameter, %% allowing the author to define a "short title" to be used in page headers. \title{Simplifying modern computing by embracing the language} \subtitle{A case study using Scheme} %% %% The "author" command and its associated commands are used to define %% the authors and their affiliations. %% Of note is the shared affiliation of the first two authors, and the %% "authornote" and "authornotemark" commands %% used to denote shared contribution to the research. \author{Ekaitz Zárraga Río} %% \authornote{Both authors contributed equally to this research.} \email{ekaitz@elenq.tech} %% \affiliation{% %% \institution{Institute for Clarity in Documentation} %% \city{Dublin} %% \state{Ohio} %% \country{USA} %% } %% %% By default, the full list of authors will be used in the page %% headers. Often, this list is too long, and will overlap %% other information printed in the page headers. This command allows %% the author to define a more concise list %% of authors' names for this purpose. \renewcommand{\shortauthors}{Zárraga Río E.} %% The abstract is a short summary of the work to be presented in the %% article. \begin{abstract} %% TODO Computing, as any other field, evolved from the previous work on the matter. During its development huge advancements have been done in many areas but only some are in use today, due to the inertia industry already had, which forced some sort of retrocompatibility. In this document a new computing platform is presented, one that makes use of some of the ideas that did not reach the mainstream and uses our current computing capabilities in order to achieve a personal computing device that embraces the programming language. \end{abstract} %% Document outline: %% - Motivation: Simplification as a mean for more efficient computing and %% a more accessible manufacture. Modern computing systems are so complex %% that they require very good manufacturing to deal with the excessive %% computing waste. %% Also, maintenance should be reduced as much as possible, even leaving it %% in the hands of the user, as Oberon would, reducing the impact of the %% repairs, upgrades, and computing infrastructure needed for simple tasks. %% - Kernels, Unix %% - Interpreters %% - Shells %% - Are interpreters a kernel? %% - Removing layers instead of adding layers %% - Unikernels: Good idea but miss the target. %% Keywords. The author(s) should pick words that accurately describe %% the work being presented. Separate the keywords with commas. \keywords{Operating Systems, Programming Languages, Interpreters} %% A "teaser" image appears between the author and affiliation %% information and the body of the document, and typically spans the %% page. %% \begin{teaserfigure} %% \includegraphics[width=\textwidth]{sampleteaser} %% \caption{Seattle Mariners at Spring Training, 2010.} %% \Description{Enjoying the baseball game from the third-base %% seats. Ichiro Suzuki preparing to bat.} %% \label{fig:teaser} %% \end{teaserfigure} %% Dates for the article %% \received{20 February 2007} %% \received[revised]{12 March 2009} %% \received[accepted]{5 June 2009} %% This command processes the author and affiliation and title %% information and builds the first part of the formatted document. \maketitle \section{Context} %% We need to understand context ... All engineering decisions are taken in a context and those that are adopted by any industry are oftentimes driven by previous decisions taken in the same subject. Specifically, the computing industry, arguably due to its rapid emergence, has been heavily influenced by previous technology and \textit{backwards compatibility}. %% TODO: remove this and put some personal computing instead? \subsection{Von Neumann model} The von Neummann model introduced in 1945 proposes a general purpose device consisting of a \textit{Central Processing Unit} (CPU) and a \textit{Store}. The \textit{Store} is often implemented as a \textit{Random Access Memory} (RAM or, simply, \textit{memory}). In the von Neumann model the data and the program are both written to and read from the \textit{Store}. This fact imposes limitations in any design that aims to have direct access to memory and multitasking, as any running program could read and manipulate other running program's, and even manipulate its behavior, overwriting the program itself. \subsection{Unix's heritage} \epigraph{ Applicants must also have extensive knowledge of Unix, although they should have sufficiently good programming taste to not consider this an achievement. }{\textit{-- Hal Abelson}} Since its inception, Unix was a huge innovation in Operating Systems market. Its main features include \textit{multitasking} and \textit{multi-user} support, a programming interface, \textit{files as abstractions} for devices and other objects and a powerful \textit{shell} that facilitates program composition. In the Unix model, the Kernel, the core of the Operating System, is responsible for managing the hardware resources. For that job, it uses several concepts that systems designers and programmers are familiarized with and are discouraged to change. Those include \textit{virtual memory}, \textit{processes}, \textit{shared-memory threads}, \textit{hierarchical filesystems} and \textit{system calls}. The \textit{shell} is run as a userspace program that has the ability to launch other programs using an outdated fork+exec mechanism that encourages memory overshoot\cite{fork:Baumann}. The shell in Unix systems is optimized for text processing as, in McIlroy's words, \textit{"text streams [are] the universal interface"} \cite{QuarterCenturyUnix:Salus}. Userspace programs are loaded in and given access to \textit{virtual memory}, and they can only run the \textit{unprivileged} subset of the CPU instructions. For restricted operations, programs need to call the \textit{Kernel} using a \textit{system-call} that can be accepted or rejected by the latter, according to \textit{permissions} or resource availability. In order to achieve multitasking, many programs can be loaded in memory (\textit{processes}) simultaneously and the \textit{Kernel} \textit{schedules} which of the them will run at a given moment in time. % \paragraph{Concurrency} % If programs need to operate concurrently they can create many % \textit{processes} or use \textit{threads}. A \textit{thread} is a % lightweight version of a \textit{process} that shares the memory with the % \textit{process} that created it. Resource sharing in a concurrent system has % many security and reliability implications, and has proven to be a difficult % subject for computer programmers over the years % \cite{Threads:Lee}. % % %\subsubsection{Interpreters} % Interpreters, like one in the \textit{shell}, are a fundamental part of % modern day programming. Interpreters are run as userspace programs, acting as % a \textit{host} for the program they interpret. The interpreter effectively % hides the details of the Operating System, often even implementing a virtual % machine for that job, in order to provide \textit{portability} and % \textit{usability} to the programmers. That is why the most used and demanded % programming languages nowadays are interpreted \cite{PLCommunity:Tambad}. % Unix was marketed as a system for multiple languages / supports many % languages via interpreters that ease the development experience. Describe how % they work and why they are useful % Interpreters are programs that run in userspace \subsection{Computer hardware} Computer processors, often marketed as "\textit{general purpose}", are based on the von Neumann model\cite{LiberateFromVonNeumann:Backus}, a CPU and a Store that is, and designed for running an Operating System on them. They clearly separate \textit{privileged}, reserved for the kernel, and \textit{unprivileged} instructions, that any userspace program can use, in order to facilitate \textit{system-calls} and \textit{interrupt} and \textit{virtual memory} control. Contrary to what one could expect, improvements in the processor architectures come from specialization, instead of generalization, making processors heavily optimized machines for Operating Systems that follow the Unix model (including MS Windows), and a memory layout that resembles that of a \textit{C-like} program, which also comes from the days of Unix \cite{GeneralPurposeProcessor:Chisnall}, reducing the chance for other paradigms to succeed. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Simplification enables optimization} Choosing a language and committing to it enables aggressive simplification of the computing systems, taking advantage of that, many research areas open, most of them confront Unix's heritage and modern computing but which could provide a powerful but simple set of constructs that allow to create simple computers that can be maintained by an individual. \subsection{Embracing the language: Scheme} \textit{Scheme} is a simple language, with a minimal standard, but that enables a huge level of abstraction thanks to its minimal but powerful core concepts which are also present in mainstream programming languages today (Python, JavaScript). The \textit{Lisp} family of languages have proven to be flexible and powerful for system design \cite{LispMachine:Greenblatt} and particularly \textit{Scheme} has a long history of research in language and CPU design \cite{Lambda:Steele}. The nature of the Lisp family of languages also makes them suitable as file formats (sxml) for storage and configuration files, writing DSLs (language oriented programming), or extending the language (GOOPS, WISP) to the users' needs (Typed Racket, Kawa). This eliminates the need to rely on unstructured text. \subsection{An Operating System that embraces the language} An Operating System that embraces the language becomes a bare metal interpreter, eliminating the duplication of tasks present in Unix operating systems \cite{MIMOSA:Yvon}. The Operating System is just accessible in the runtime environment of the programs. \textit{System calls} become \textit{procedure calls}. The \textit{Shell} is a system \textit{REPL}, an interactive environment for programming that exposes Operating System's facilities. \subsubsection{Capability based security "lambda-style"} Most modern computers do not have more than a single user, but they preserve an antique user management system, inherited from Unix, recycled for program permissions. 3L \cite{3L:Hintz} explored an OS where permission control is reduced to \textit{environments} with access to a limited set of bindings \cite{securityKernelLambda:Rees}. A program can only access the bindings provided by the system, which also facilitates fine grained control letting the user replace system bindings by ad-hoc versions when needed. \subsubsection{Managed memory} Virtual memory is an attempt to isolate programs from each other and provide a permission system on top of a flawed von Neumann model but it is a leaky abstraction that can be exploited\cite{SpectreMeltdown:HillMasters}. Removing direct access to memory, replacing it with managed memory, removes the need of virtual memory and decouples underlying implementations from user programs. \subsubsection{Concurrency} Unix-style concurrency, reinforced by modern \textit{multi-core} CPU design and threads, is hard to reason about\cite{Threads:Lee}. A multitasking system can be approached in terms of \textit{Scheme}'s \textit{continuations}\cite{ContinuationsConcurrency:Hieb}, embracing its first-class constructs. \subsection{Computer hardware that embraces the language} Attempts have been done to run Scheme in a bare-metal environment using commodity hardware\cite{MIMOSA:Yvon}\cite{Loko:Weinholt}, but they do not take advantage of hardware optimized for \textit{Scheme}, which would provide huge performance benefits and simplify the interpreter and potentially the CPU. \subsubsection{Optimization for tree structures} \textit{Scheme} is profoundly based on the \textit{cons cell}, similar to a \textit{linked-list} node, and the data structures that can be created from it (\textit{lists} and \textit{trees}). Optimizing the CPU for that case, with fast lookups and \code{car} and \code{cdr} operations would impact its performance. This might require developing new caching and memory access mechanism, but could simplify the ones present in mainstream CPUs and reducing its security concerns. \subsubsection{CPU as a reducer} \textit{Scheme} supports many paradigms but the basis of the language is the expression reduction, in opposition to imperative language, where the basis is the \textit{statement}, that matches current processor architectures better. This opens a full research area, that was mainly abandoned after the modern CPU architectures flooded the market, but has a long history\cite{LiberateFromVonNeumann:Backus}. \subsubsection{Hardware garbage collection} When the whole system uses managed memory, the Garbage Collection, \textit{GC}, can be pushed down in the stack. Both Oberon\cite{Oberon:Wirth} and MIMOSA \cite{MIMOSA:Yvon} propose Garbage Collector as part of the Operating System. A computing device that embraces \textit{Scheme} in its core may take a more radical approach and involve the hardware in the Garbage Collection process. Hardware assisted GC has been proven to improve the performance of managed memory in von Neumann style processors \cite{HWAssistedGC:Maas} and Lisp Machines\cite{LispMachine:Greenblatt}. \subsubsection{Exploration via reconfigurable Hardware} % TODO LANGUAGE SKIM \cite{FPhardware:Stoye} tries to go for custom hardware, with a functional programming language and there have been more attempts \cite{LiberateFromVonNeumann:Backus}. Instead of making real machines, we could just go for FPGAs, they are powerful nowadays, and we could do it incrementally, as our language is simple and can be represented using imperative CPUs. Focusing on personal computing can be a extremely powerful way to explore optimization and simplification of computing systems to the point they can be run in custom unoptimized CPUs implemented in FPGAs \cite{Oberon:Wirth}. For our case, a FPGA facilitates the incremental testing and the evaluation of the impacts of the proposed optimizations. If a Hardware Description Language, \textit{HDL}, is provided with the system and the Operating System has support for Partial and Dynamic Reconfiguration\cite{FPGAReconf:Vipin}, the whole system can be updated together, improving the OS and the needed hardware at the same time. A \textit{rollback} system\cite{Guix:Courtes} could always recover the state of both hardware and software as if they were the same thing. The FPGAs are more power hungry and not as fast as ASICs but the reduction of complexity proposed in this paper should be enough for personal computing. Also, letting the user configure the CPU from the computer itself reduces the need for constant upgrades, uses commodity hardware instead of very specialized devices and reduces the chance of a supply chain attack in many levels \cite{riscvSelfHostingComputer:Somlo}. \section{Conclusion} This paper introduces a computing system that combines a reconfigurable CPU and a simplified approach to Operating System design that embraces the programming language \textit{Scheme} and proposes several optimizations and research areas that its design would enable. The cited literature demonstrates systems with a similar level of simplification to the one proposed in this document can be implemented and maintained by a single individual, meaning that the proposed computing system would be possibly created and maintained by anyone, down to the hardware, while keeping it secure, accessible and bootstrappable if carefully designed. %% TODO: mention FPGAs are commodity hardware today, and don't require %% special manufacturing facilities: autonomy and sovereignty %% TODO: only if cite vernacular programmers properly Literature also supports that extending the reach of the language enriches the relationship the user has with the computer. If the selected language is powerful in terms of the level of abstraction it can provide, like the one selected in this paper, it could become the only tool a user needs for every single administration task, including hardware upgrade or optimization, providing a solid foundation for more human-centered design where the antiquities from the times of Unix can be displaced. \clearpage %% The acknowledgments section is defined using the "acks" environment %% (and NOT an unnumbered section). This ensures the proper %% identification of the section in the article metadata, and the %% consistent spelling of the heading. %% \begin{acks} %% To Robert, for the bagels and explaining CMYK and color spaces. %% \end{acks} %% The next two lines define the bibliography style to be used, and %% the bibliography file. \bibliographystyle{ACM-Reference-Format} \bibliography{../../bibliography} %% If your work has an appendix, this is the place to put it. %% \appendix \end{document} \endinput