add README + fix compile script + add GCC's dependencies installation
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Yann MAGNIN
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# sh-elf-vhex - modified GCC for the Vhex kernel projet
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---
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## Context
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This project was born following the discovery of a limitation with GCC on the
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SuperH architecture
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(see on this subject from 2 years ago:
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https://gcc.gnu.org/legacy-ml/gcc-help/current/000075.html).
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The generation of dynamic libraries is blocked by GCC (the `--shared` flag is ignored),
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because the `sh3eb-elf` target (the one used for cross-compiling on Casio calculators),
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does not support this functionality.
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I am currently building a kernel of a Casio's calculator for a graduation
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project and I need this functionality. I had discovered, thanks to Lephenixnoir,
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that we could generate 'shared' libraries by using directly `ld` with a custom
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linker script, but this workaround was of short duration. Indeed, we are
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dependent on a library called `libgcc`, which provide some useful critical
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primitives and which is generated only statically (therefore with
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non-relocatable code), which broke all shared object file generated with this
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dependencie (and a lot of cases can involve this librarie).
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With the help of Lephenixnoir, we tried to add a target for the
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superH architecture called `sh-elf-vhex`, allowing us to enable these features
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and that's what we finally came up with.
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This repository gathers only the files that we had to modify for
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`binutils` and` GCC`, as well as scripts to automate the installation of this
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particular GCC.
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---
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## Build
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The build is relatively simple and can be done in two different ways: you can
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use the `compile.sh` script which is at the root of the repository:
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```bash
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./compile /your/installation/path
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```
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Or you can use the `giteapc` tool, created by Lephenixnoir:
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```bash
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giteapc install sh-elf-vhex
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```
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It takes about twenty minutes for the build.
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---
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## Technical notes
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The GCC build takes much longer than the `sh3eb-elf` target because we have two
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stages for the GCC build. In order, we have:
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* download + configuration of binutils sources
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* download + configuration of GCC sources
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* compilation of binutils
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* compilation of GCC (stage-1) without enabling the shared library functionality
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* compilation of OpenLibM (a dependency of our standard C library)
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* compilation of fxlibc, our custom C standard library
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* compilation of GCC (stage-2) with activation of the shared library fonctionality
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* installation of our C library
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* compilation of the shared libgcc
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As for the details of the `sh-elf-vhex` target that we created:
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* machine-specific features:
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* (`t-slibgcc`) compilation of the shared libgcc
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* (`t-libgcc-pic`) the compilation of the libgcc in PIC
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* (`t-fdpbit`) compilation of the library for emulated floating point numbers
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* global configuration:
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* only C is supported
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* only big endian encoding is supported
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* we use the stdint header from `newlib`. Otherwise, the generation of `stdint.h` is incomplete
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* we only target the SH4A-NOFPU processor (no backward compatibility with the SH3 assembler)
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* each public symbol begins with an underscore
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* by default, we link our own C library to each generation of an object file
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* we do not provide a specialized default linker script (for the moment)
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---
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## Special thanks
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A big thanks to Lephenixnoir who helped me a lot for the modification of the
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sources and made this project possible!
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14
compile.sh
14
compile.sh
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@ -1,9 +1,13 @@
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#! /usr/bin/env bash
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echo "Compil and install binutils"
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cd scripts/binutils
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./configure.sh --version=2.37 && ./build.sh && ./install.sh --prefix=/tmp
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# check mandatory args
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if [[ $# -eq 0 ]]; then
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echo "missing install path prefix !" >&2
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exit 1
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fi
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cd scripts/binutils
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./configure.sh --version=2.37 && ./build.sh && ./install.sh --prefix="$1"
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echo "Compil and install GCC"
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cd ../gcc
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./configure.sh --version=11.2.0 && ./build.sh && ./install.sh --prefix=/tmp
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./configure.sh --version=11.2.0 && ./build.sh && ./install.sh --prefix="$1"
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@ -130,9 +130,12 @@ ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ld sh-elf-vhex/bin/ld
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ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ar sh-elf-vhex/bin/ar
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ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ranlib sh-elf-vhex/bin/ranlib
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# patch OpenLibM building error (which search for sh-elf-vhex-ar)
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# Patch OpenLibM building error (which search for sh-elf-vhex-ar)
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ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ar sh-elf-vhex/bin/sh-elf-vhex-ar
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# Install dependencies
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./gcc/contrib/download_prerequisites
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# Cache management
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if [[ "$cache" == 'false' ]]; then
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