From 648fdbf86f8be96dc4b8d31a197a0faec44175c0 Mon Sep 17 00:00:00 2001
From: Yann MAGNIN <yann.magnin@protonmail.com>
Date: Wed, 17 Nov 2021 19:41:16 +0100
Subject: [PATCH] add README + fix compile script + add GCC's dependencies
 installation

---
 README.md                | 89 ++++++++++++++++++++++++++++++++++++++++
 compile.sh               | 14 ++++---
 scripts/gcc/configure.sh |  5 ++-
 3 files changed, 102 insertions(+), 6 deletions(-)
 create mode 100644 README.md

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..0a5d067
--- /dev/null
+++ b/README.md
@@ -0,0 +1,89 @@
+# sh-elf-vhex - modified GCC for the Vhex kernel projet
+
+---
+
+## Context
+
+This project was born following the discovery of a limitation with GCC on the
+SuperH architecture
+(see on this subject from 2 years ago:
+https://gcc.gnu.org/legacy-ml/gcc-help/current/000075.html).
+
+The generation of dynamic libraries is blocked by GCC (the `--shared` flag is ignored),
+because the `sh3eb-elf` target (the one used for cross-compiling on Casio calculators),
+does not support this functionality.
+
+I am currently building a kernel of a Casio's calculator for a graduation
+project and I need this functionality. I had discovered, thanks to Lephenixnoir,
+that we could generate 'shared' libraries by using directly `ld` with a custom
+linker script, but this workaround was of short duration. Indeed, we are
+dependent on a library called `libgcc`, which provide some useful critical
+primitives and which is generated only statically (therefore with
+non-relocatable code), which broke all shared object file generated with this
+dependencie (and a lot of cases can involve this librarie).
+
+With the help of Lephenixnoir, we tried to add a target for the
+superH architecture called `sh-elf-vhex`, allowing us to enable these features
+and that's what we finally came up with.
+
+This repository gathers only the files that we had to modify for
+`binutils` and` GCC`, as well as scripts to automate the installation of this
+particular GCC.
+
+---
+
+## Build
+
+The build is relatively simple and can be done in two different ways: you can
+use the `compile.sh` script which is at the root of the repository:
+
+```bash
+./compile /your/installation/path
+```
+
+Or you can use the `giteapc` tool, created by Lephenixnoir:
+
+```bash
+giteapc install sh-elf-vhex
+```
+
+It takes about twenty minutes for the build.
+
+---
+
+## Technical notes
+
+The GCC build takes much longer than the `sh3eb-elf` target because we have two
+stages for the GCC build. In order, we have:
+
+* download + configuration of binutils sources
+* download + configuration of GCC sources
+* compilation of binutils
+* compilation of GCC (stage-1) without enabling the shared library functionality
+* compilation of OpenLibM (a dependency of our standard C library)
+* compilation of fxlibc, our custom C standard library
+* compilation of GCC (stage-2) with activation of the shared library fonctionality
+* installation of our C library
+* compilation of the shared libgcc
+
+As for the details of the `sh-elf-vhex` target that we created:
+
+* machine-specific features:
+  * (`t-slibgcc`) compilation of the shared libgcc
+  * (`t-libgcc-pic`) the compilation of the libgcc in PIC
+  * (`t-fdpbit`) compilation of the library for emulated floating point numbers
+* global configuration:
+  * only C is supported
+  * only big endian encoding is supported
+  * we use the stdint header from `newlib`. Otherwise, the generation of `stdint.h` is incomplete
+  * we only target the SH4A-NOFPU processor (no backward compatibility with the SH3 assembler)
+  * each public symbol begins with an underscore
+  * by default, we link our own C library to each generation of an object file
+  * we do not provide a specialized default linker script (for the moment)
+
+---
+
+## Special thanks
+
+A big thanks to Lephenixnoir who helped me a lot for the modification of the
+sources and made this project possible!
diff --git a/compile.sh b/compile.sh
index 7d57b86..8e679b9 100755
--- a/compile.sh
+++ b/compile.sh
@@ -1,9 +1,13 @@
 #! /usr/bin/env bash
 
-echo "Compil and install binutils"
-cd scripts/binutils
-./configure.sh --version=2.37 && ./build.sh && ./install.sh --prefix=/tmp
+# check mandatory args
+if [[ $# -eq 0 ]]; then
+  echo "missing install path prefix !" >&2
+  exit 1
+fi
+
+cd scripts/binutils
+./configure.sh --version=2.37 && ./build.sh && ./install.sh --prefix="$1"
 
-echo "Compil and install GCC"
 cd ../gcc
-./configure.sh --version=11.2.0 && ./build.sh && ./install.sh --prefix=/tmp
+./configure.sh --version=11.2.0 && ./build.sh && ./install.sh --prefix="$1"
diff --git a/scripts/gcc/configure.sh b/scripts/gcc/configure.sh
index 2f791f0..089b10f 100755
--- a/scripts/gcc/configure.sh
+++ b/scripts/gcc/configure.sh
@@ -130,9 +130,12 @@ ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ld sh-elf-vhex/bin/ld
 ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ar sh-elf-vhex/bin/ar
 ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ranlib sh-elf-vhex/bin/ranlib
 
-# patch OpenLibM building error (which search for sh-elf-vhex-ar)
+# Patch OpenLibM building error (which search for sh-elf-vhex-ar)
 ln -sf $(pwd)/../binutils/bin/sh-elf-vhex-ar sh-elf-vhex/bin/sh-elf-vhex-ar
 
+# Install dependencies
+./gcc/contrib/download_prerequisites
+
 # Cache management
 
 if [[ "$cache" == 'false' ]]; then