12 KiB
1 mescc-tools-seed
This is where all the magic begins. We start with our hex0 and kaem seeds and bootstrap our way up to M2-Planet, a subset of C, and mes-m2, an independent port of GNU Mes to M2-Planet. The following steps are taken here:
- hex0 (seed)
- hex0 compiles hex1
- hex0 compiles catm
- hex1 compiles hex2 (v1)
- hex2 (v1) compiles M0
- M0 compiles cc_x86
- cc_x86 compiles M2-Planet (v1)
- M2-Planet (v1) compiles blood-elf (v1)
- M2-Planet (v1) compiles hex2 (final)
- M2-Planet (v1) compiles M1
- M2-Planet (v1) compiles kaem
- M2-Planet (v1) compiles blood-elf (final)
- M2-Planet (v1) compiles get_machine
- M2-Planet (v1) compiles M2-Planet (final)
This seems very intimidating, but becomes clearer when reading the source: https://github.com/oriansj/mescc-tools-seed/blob/master/x86/ (start at mescc-tools-seed-kaem.kaem).
From here, we can move on from the lowest level stuff.
2 mescc-tools-extra
mescc-tools and mes-m2 are the projects bootstrapped by mescc-tools-seed. However, we have some currently unmerged additions to mescc-tools that we require for this project, namely filesystem utilities cp and chown. This allows us to have one unified directory for our binaries. Futhermore, we also build fletcher16, a preliminary checksumming tool, that we use to ensure reproducibility and authenticity of generated binaries.
3 /after
We now move into the /after directory. As mescc-tools-seed has no concept of chdir() (not added until very late in mescc-tools-seed), we have to copy a lot of files into the root of the initramfs, making it very messy. We get into the move ordered directory /after here, copying over all of the required binaries from /.
4 mes
mes is a scheme interpreter. It runs the sister project mescc, which is a C compiler written in scheme, which links against the Mes C Library. All 3 are included in this same repository. Note that we are using the experimental wip-m2 branch to jump over the gap between M2-Planet and mes. There are two stages to this part:
- Compiling an initial mes using M2-Planet. Note that this is only the Mes interpreter, not the libc or anything else.
- We then use this to recompile the Mes interpreter as well as building the libc. This second interpreter is faster and less buggy. We need the libc to compile all the programs until we get glibc.
5 tinycc 0.9.26
tinycc is a minimal C compiler that aims to be small and fast. It complies with all C89 and most of C99 standards.
First, we compile janneke’s fork of tcc 0.9.26 using mescc, containing 27 patches to make it operate well in the bootstrap environment and make it compilable using mescc. This is a non-trivial process and as seen within tcc.kaem has many different parts within it: a. tcc 0.9.26 is first compiled using mescc. b. The mes libc is recompiled using tcc (mescc has a non-standard .a format), including some additions for later programs. c. tcc 0.9.26 is recompiled 5(!) times to add new features that are required for other features, namely long long and float. Each time, the libc is also recompiled.
6 tinycc 0.9.27
Now, we compile upstream tcc 0.9.27, the latest release of tinycc, using the final version of tcc 0.9.26. We then recompile the libc once more.
From this point onwards, until further notice, all programs are compiled using tinycc 0.9.27. Note that now we begin to delve into the realm of old GNU software, using older versions compilable by tinycc. Prior to this point, all tools have been adapted significantly for the bootstrap; now, we will be using old tooling instead.
7 sed 4.0.7
You are most likely aware of GNU sed, a line editor.
8 tar 1.12
GNU tar is the most common archive format used by software source code, often compressed also. To avoid continuing using submodules, we build GNU tar 1.12, the last version compilable by tinycc without significant patching.
9 gzip 1.2.4
gzip is the most common compression format used for software source code. It is luckily distributed as a barebones uncompressed .tar, which we extract and then build. We do require deletion of a few lines unsupported by mes libc.
Going forward, we can now use .tar.gz for source code.
10 patch 2.5.9
patch is a very useful tool at this stage, allowing us to make significantly more complex edits, including just changes to lines. Luckily, we are able to patch patch using sed only.
11 sha-2
sha-2 is a standalone external sha256sum implementation, originally as a library, but patched to have a command line interface. It is mostly output-compatible with sha256sum from coreutils. We use this in replacement of fletcher16.
12 Redo checksums using sha256sum
We have now just built sha256sum, which has a significantly (many orders of magnitude) lower collision rate than fletcher16, so we recheck all of the existing binaries using sha256sum.
13 patched mes-libc
Since patch is available at this point, we can apply additional fixes to mes-libc that are not included in the wip-m2 branch and recompile libc.
14 patched tinycc
In Guix, tinycc is patched to force static linking. Prior to this step, we have been forced to manually specify static linking for each tool. Now that we have patch, we can patch tinycc to force static linking and then recompile it.
Note that we have to do this using tinycc 0.9.26, as tinycc 0.9.27 cannot recompile itself for unknown reasons.
15 make 3.80
GNU make is now built so we have a more robust building system. make allows us to do things like define rules for files rather than writing complex kaem scripts.
16 bzip2 1.0.8
bzip2 is a compression format that compresses more than gzip. It is preferred where we can use it, and makes source code sizes smaller.
17 coreutils 5.0.0
GNU Coreutils is a collection of widely used utilities such as cat, chmod, chown, cp, install, ln, ls, mkdir, mknod, mv, rm, rmdir, tee, test, true, and many others.
A few of the utilities cannot be easily compiled with Mes C library, so we skip them.
The cp in this stage replaces the mescc-tools-extra cp.
18 heirloom devtools
lex and yacc from the Heirloom project. The Heirloom project is a collection of standard UNIX utilities derived from code by Caldera and Sun. Differently from the analogous utilities from the GNU project, they can be compiled with a simple Makefile.
19 bash 2.05b
GNU bash is the most well known shell and the most complex piece of software so far. However, it comes with a number of great benefits over kaem, including proper POSIX sh support, globbing, etc.
Bash ships with a bison pre-generated file here which we delete. Unfortunately, we have not bootstrapped bison but fortunately for us, heirloom yacc is able to cope here.
20 flex 2.5.11
flex is a tool for generating lexers or scanners: programs that recognize lexical patters.
Unfortunately flex also depends on itself for compiling its own scanner, so first flex 2.5.11 is compiled, with its scanner definition manually modified so that it can be processed by lex for the Heirloom project (the required modifications are mostly syntactical, plus a few workarounds to avoid some flex advanced features).
21 musl 1.1.24
musl is a C standard library that is lightweight, fast, simple, free, and strives to be correct in the sense of standards-conformance and safety. musl is used by some distributions of GNU/Linux as their C library. Our previous Mes C library was incomplete which prevented us from building many newer or more complex programs.
tcc has slight problems when building and linking musl, so we apply a few patches. In particular, we replace all weak symbols with strong symbols and will patch tcc in the next step to ignore duplicate symbols.
22 tcc 0.9.27 (musl)
We recompile tcc against musl. This is a two stage process. First we build tcc-0.9.27 that itself links to Mes C library but produces binaries linked to musl. Then we recompile newly produced tcc with itself. Interestingly, tcc-0.9.27 linked against musl is self hosting.
23 musl 1.1.24 (tcc-musl)
We now rebuild musl with tcc-musl of Part 22, which fixes a number of bugs, particularly regarding floats, in the first musl.
24 tcc 0.9.27 (musl v2)
Now that we have a ‘fixed’ musl, we now recompile tcc as tcc uses floats extensively.
25 bzip2 1.0.8
bzip2 is rebuilt unpatched with the new tcc and musl fixing issues with reading files from stdin that existed in the previous build.
26 m4 1.4.7
m4 is the first piece of software we need in the autotools suite, flex 2.6.4 and bison. It allows macros to be defined and files to be generated from those macros.
27 flex 2.6.14
We recompile unpatched GNU flex using older flex 2.5.11. This is again a two stage process, first compiling flex using scan.c (from scan.l) created by old flex, then recompile scan.c using the new version of flex to remove any buggy artifacts from the old flex.
28 bison 3.4.1
GNU bison is a parser generator. With m4 and flex we can now bootstrap it following https://gitlab.com/giomasce/bison-bootstrap. It’s a 3 stage process:
- Build bison using a handwritten grammar parser in C.
- Use bison from previous stage on a simplified bison grammar file.
- Build bison using original grammar file.
Finally we have a fully functional bison executable.
29 grep 2.4
GNU grep is a pattern matching utility. Is is not immediately needed but will be useful later for autotools.
30 diffutils 2.7
diffutils is useful for comparing two files. It is not immediately needed but is required later for autotools.
31 coreutils 5.0
coreutils is rebuilt against musl. Additional utilities are built including comm, expr, date, dd, sort, uname and uniq. This fixes a variety of issues with existing coreutils.
32 gawk 3.0.4
gawk is the GNU implementation of awk, yet another pattern matching and data extraction utility. It is also required for autotools.
33 perl 5.000
Perl is a general purpose programming language that is especially suitable for text processing. It is essential for autotools build system because automake and some other tools are written in Perl.
Perl itself is written in C but ships with some pre-generated files that need perl for processing, namely embed.h and keywords.h. To bootstrap Perl we will start with the oldest Perl 5 version which has the fewest number of pregenerated files. We reimplement two remaining perl scripts in awk and use our custom makefile instead of Perl’s pre-generated Configure script.
At this first step we build miniperl which is perl without support for loading modules.
34 perl 5.003
We now use perl from the previous stage to recreate pre-generated files that are shipped in perl 5.003. But for now we still need to use handwritten makefile instead of ./Configure script.
35 perl 5.004_05
Yet another version of perl; the last version buildable with 5.003.
36 perl 5.005_03
More perl! This is the last version buildable with 5.004. It also introduces the new pregenerated files regnodes.h and byterun.{h,c}.
37 perl 5.6.2
Even more perl. 5.6.2 is the last version buildable with 5.004.
38 autoconf 2.52
GNU Autoconf is a tool for producing configure scripts for building, installing and packaging software on computer systems where a Bourne shell is available.
At this stage we still do not have a working autotools system, so we manually install autoconf script and replace a few placeholder variables with sed.