Merge branch 'main' into bootstrap

hugo/content/posts/2023-10-08-guix-bootstrap.md

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+---
+lastmod: "2023-10-08T11:43:00.0000000+01:00"
+author: patrick
+categories:
+- programming
+date: "2023-10-18T11:43:00.0000000+01:00"
+title: The GUIX bootstrap
+summary: "Notes for a talk I gave at work on the GUIX bootstrap."
+---
+
+This is simply an outline, with no actual content.
+
+# Why bootstrap?
+
+* Auditing and security
+  * Seminal paper: [Reflections on Trusting Trust](https://www.cs.cmu.edu/~rdriley/487/papers/Thompson_1984_ReflectionsonTrustingTrust.pdf)
+
+# How is a system normally installed?
+
+* Massive binary blob (250MB of gcc, binutils etc) to start a bootstrap
+* Or an even massiver blob (Windows installer)
+
+# Necessary tools
+
+* A C compiler e.g. [TCC](https://bellard.org/tcc/)
+* Text manipulation e.g. `sed`
+
+# GUIX Full-Source Bootstrap
+
+[Official docs](https://guix.gnu.org/en/manual/devel/en/html_node/Full_002dSource-Bootstrap.html).
+
+## Stage-0
+
+[Main repo](https://github.com/oriansj/stage0-posix); [kaemfile](https://github.com/oriansj/stage0-posix-x86/blob/e86bf7d304bae5ce5ccc88454bb60cf0837e941f/mescc-tools-mini-kaem.kaem#L97).
+
+The kernel is trusted; eventually they would like to make no syscalls at all and run on bare metal.
+(GNU Guix bootstrap kernel is still 25MB.)
+
+* Base: a [tiny self-hosted assembler](https://github.com/oriansj/bootstrap-seeds/blob/master/POSIX/x86/hex0_x86.hex0) of 357 bytes, incredibly strict language, human-verifiable
+* [hex1](https://github.com/oriansj/stage0-posix-x86/blob/e86bf7d304bae5ce5ccc88454bb60cf0837e941f/hex1_x86.hex0): a slightly more powerful assembler, better hex parsing, single-character labels and some jumps
+* [hex2](https://github.com/oriansj/stage0-posix-x86/blob/e86bf7d304bae5ce5ccc88454bb60cf0837e941f/hex2_x86.hex1): an assembler with labels and absolute memory addresses
+* [catm](https://github.com/oriansj/stage0-posix-x86/blob/e86bf7d304bae5ce5ccc88454bb60cf0837e941f/catm_x86.hex2): an implementation of `cat`
+* [M0](https://github.com/oriansj/stage0-posix-x86/blob/e86bf7d304bae5ce5ccc88454bb60cf0837e941f/M0_x86.hex2): a C-style preprocessor and a bona-fide assembler which recognises a language you might recognise
+* [cc-x86](https://github.com/oriansj/stage0-posix-x86/blob/e86bf7d304bae5ce5ccc88454bb60cf0837e941f/cc_x86.M1): a C compiler! (only a subset of C though)
+* M2-Planet: a slightly better C compiler
+* [blood-elf-0](https://github.com/oriansj/mescc-tools/blob/master/blood-elf.c): writes [DWARF](https://en.wikipedia.org/wiki/DWARF) stubs for debug tables (but no actual implementation of those stubs)
+* M1: a better C compiler which is debuggable and implements some optimisations (TODO: example?)
+* Rebuild earlier inputs now that we have an optimising compiler
+* blood-elf again: provides implementations for the stubs `blood-elf-0` wrote (TODO: is that true? Understand the nature of the stubs and implementation)
+* A variety of nice things like `sha256sum`, `mkdir`, `untar`, primitive `cp`, `chmod`
+* [kaem](https://github.com/oriansj/kaem/tree/master): a tiny build system (anagram of `make`)
+
+## GNU Mes
+
+[Mes](https://www.gnu.org/software/mes/) is an intertwined pair of a C compiler and Scheme interpreter; its source is mirrored [on GitHub](https://github.com/gnu-mirror-unofficial/mes).
+It can be built with `kaem`, and the resulting C compiler can build [TCC](https://bellard.org/tcc/), which can then build early GCC, which can bootstrap later GCCs and hence support for other languages and architectures.
+
+As of a few years ago, they were experimenting with using the Mes Scheme compiler to compile [Gash](https://savannah.nongnu.org/projects/gash), an interpreted Scheme POSIX shell which could replace some of the binary blob.