Apache NuttX RTOS: Build Rust App for QEMU RISC-V 32-bit with Rust Custom Target. See https://lupyuen.github.io/articles/rust4

build-nuttx-rust-qemu-riscv32.sh

#!/usr/bin/env bash
#  Build NuttX for QEMU RISC-V 32-bit with Rust App

## TODO: Set PATH
export PATH="$HOME/xpack-riscv-none-elf-gcc-13.2.0-2/bin:$PATH"

set -e  #  Exit when any command fails
set -x  #  Echo commands

## Build NuttX
function build_nuttx {

  ## Go to NuttX Folder
  pushd ../nuttx

  ## Build NuttX
  make -j 8

  ## Return to previous folder
  popd
}

## Build Rust App for QEMU RISC-V 32-bit with Rust Custom Target
function build_rust_riscv32 {

  ## Go to NuttX Folder
  pushd ../nuttx

  ## Download our Custom Target for `riscv32gc`
  rm -f riscv32gc-unknown-none-elf.json
  wget https://raw.githubusercontent.com/lupyuen/nuttx-rust-app/main/riscv32gc-unknown-none-elf.json

  ## Custom Target needs Nightly Build of Rust Compiler
  rustup override set nightly
  rustup component add rust-src --toolchain nightly

  ## Verify our Custom Target, make sure it's OK
  rustc \
    --print cfg \
    --target riscv32gc-unknown-none-elf.json

  ## `cargo build` requires a Rust Project, so we create an empty one.
  rm -rf app
  cargo new app

  ## Build the Rust Core Library for `riscv32gc`
  ## Include the `alloc` library, which will support Heap Memory in future.
  ## Ignore the error: `can't find crate for std`
  pushd app
  cargo build \
    -Zbuild-std=core,alloc \
    --target ../riscv32gc-unknown-none-elf.json \
    || true
  popd

  ## Compile our Rust App with Rust Core Library for `riscv32gc`
  ## We changed the Target to `riscv32gc-unknown-none-elf.json`
  rustc \
    --target riscv32gc-unknown-none-elf.json \
    --edition 2021 \
    --emit obj \
    -g \
    -C panic=abort \
    -O \
    ../apps/examples/hello_rust/hello_rust_main.rs \
    -o ../apps/examples/hello_rust/*hello_rust.o \
    \
    -C incremental=app/target/riscv32gc-unknown-none-elf/debug/incremental \
    -L dependency=app/target/riscv32gc-unknown-none-elf/debug/deps \
    -L dependency=app/target/debug/deps \
    --extern noprelude:alloc=`ls app/target/riscv32gc-unknown-none-elf/debug/deps/liballoc-*.rlib` \
    --extern noprelude:compiler_builtins=`ls app/target/riscv32gc-unknown-none-elf/debug/deps/libcompiler_builtins-*.rlib` \
    --extern noprelude:core=`ls app/target/riscv32gc-unknown-none-elf/debug/deps/libcore-*.rlib` \
    -Z unstable-options

  ## NuttX Build need us to copy hello_rust.o to hello_rust_1.o
  cp \
    ../apps/examples/hello_rust/*hello_rust.o \
    ../apps/examples/hello_rust/*hello_rust_1.o

  ## Return to previous folder
  popd
}

## Obsolete: Fix the Rust Build for QEMU RISC-V 32-bit by patching the ELF Header
function old_build_rust_riscv32 {

  ## Add the Rust Target
  rustup target add riscv32i-unknown-none-elf

  ## Go to NuttX Folder
  pushd ../nuttx

  ## Patch the ELF Header, changing it from Software Floating-Point to Double Precision Hardware Floating-Point
  ## https://gist.github.com/lupyuen/7be4bedc6a109b2c3d1201aee6030428
  xxd -c 1 ../apps/examples/hello_rust/*hello_rust_1.o \
    | sed 's/00000024: 00/00000024: 04/' \
    | xxd -r -c 1 - /tmp/hello_rust_1.o
  cp /tmp/hello_rust_1.o ../apps/examples/hello_rust/*hello_rust_1.o

  ## Return to previous folder
  popd
}

## Pull updates
git pull && git status && hash1=`git rev-parse HEAD`
pushd ../apps
git pull && git status && hash2=`git rev-parse HEAD`
popd
echo NuttX Source: https://github.com/apache/nuttx/tree/$hash1 >nuttx.hash
echo NuttX Apps: https://github.com/apache/nuttx-apps/tree/$hash2 >>nuttx.hash

## Show the versions of GCC and Zig
riscv-none-elf-gcc -v

## Configure the NuttX Build
make distclean
tools/configure.sh rv-virt:nsh

## Enable the Hello Rust App
kconfig-tweak --enable CONFIG_EXAMPLES_HELLO_RUST

## Update the Kconfig Dependencies
make olddefconfig

## Build NuttX. Ignore the error: `can't link soft-float modules with double-float modules`
build_nuttx || true

## Build the Rust App with Custom Target
build_rust_riscv32
# Previously: old_build_rust_riscv32

## Link the Rust App with NuttX
build_nuttx

## Show the size
riscv-none-elf-size nuttx

## Export the Binary Image to nuttx.bin
riscv-none-elf-objcopy \
  -O binary \
  nuttx \
  nuttx.bin

## Copy the config
cp .config nuttx.config

## Dump the NuttX Kernel Disassembly to nuttx.S
riscv-none-elf-objdump \
  --syms --source --reloc --demangle --line-numbers --wide \
  --debugging \
  nuttx \
  >nuttx.S \
  2>&1

## Dump the Rust App Disassembly to hello_rust_1.S
riscv-none-elf-objdump \
  --syms --source --reloc --demangle --line-numbers --wide \
  --debugging \
  ../apps/examples/hello_rust/*1.o \
  >hello_rust_1.S \
  2>&1

## Check coding style
# ../nxstyle arch/risc-v/src/bl808/bl808_mm_init.c

## Start the emulator
qemu-system-riscv32 \
  -semihosting \
  -M virt,aclint=on \
  -cpu rv32 \
  -kernel nuttx \
  -nographic \
  -bios none