1. 环境搭建
# rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# cargo
cargo install cross
cargo install cargo-make
# 增加平台
rustup target add armv7-unknown-linux-musleabihf
rustup target add arm-unknown-linux-gnueabihf
# Supports Pi 0/1
rustup target add arm-unknown-linux-gnueabihf
# Supports Pi 2/3/4
rustup target add armv7-unknown-linux-gnueabihf
2. 编译
查看 rustc 支持的目标平台：
> rustc --print target-list | pr -tw120 --output-tabs=' 1' --columns 3
aarch64-apple-darwin i586-unknown-linux-gnu riscv64gc-unknown-none-elf
aarch64-apple-ios i586-unknown-linux-musl riscv64imac-unknown-none-elf
aarch64-apple-ios-macabi i686-apple-darwin s390x-unknown-linux-gnu
aarch64-apple-ios-sim i686-linux-android s390x-unknown-linux-musl
aarch64-apple-tvos i686-pc-windows-gnu sparc-unknown-linux-gnu
aarch64-fuchsia i686-pc-windows-msvc sparc64-unknown-linux-gnu
aarch64-linux-android i686-unknown-freebsd sparc64-unknown-netbsd
aarch64-pc-windows-msvc i686-unknown-haiku sparc64-unknown-openbsd
aarch64-unknown-freebsd i686-unknown-linux-gnu sparcv9-sun-solaris
aarch64-unknown-hermit i686-unknown-linux-musl thumbv4t-none-eabi
aarch64-unknown-linux-gnu i686-unknown-netbsd thumbv6m-none-eabi
aarch64-unknown-linux-gnu_ilp32 i686-unknown-openbsd thumbv7a-pc-windows-msvc
aarch64-unknown-linux-musl i686-unknown-uefi thumbv7a-uwp-windows-msvc
aarch64-unknown-netbsd i686-uwp-windows-gnu thumbv7em-none-eabi
aarch64-unknown-none i686-uwp-windows-msvc thumbv7em-none-eabihf
aarch64-unknown-none-softfloat i686-wrs-vxworks thumbv7m-none-eabi
aarch64-unknown-openbsd mips-unknown-linux-gnu thumbv7neon-linux-androideabi
aarch64-unknown-redox mips-unknown-linux-musl thumbv7neon-unknown-linux-gnueabihf
aarch64-uwp-windows-msvc mips-unknown-linux-uclibc thumbv7neon-unknown-linux-musleabihf
aarch64-wrs-vxworks mips64-unknown-linux-gnuabi64 thumbv8m.base-none-eabi
aarch64_be-unknown-linux-gnu mips64-unknown-linux-muslabi64 thumbv8m.main-none-eabi
aarch64_be-unknown-linux-gnu_ilp32 mips64el-unknown-linux-gnuabi64 thumbv8m.main-none-eabihf
arm-linux-androideabi mips64el-unknown-linux-muslabi64 wasm32-unknown-emscripten
arm-unknown-linux-gnueabi mipsel-sony-psp wasm32-unknown-unknown
arm-unknown-linux-gnueabihf mipsel-unknown-linux-gnu wasm32-wasi
arm-unknown-linux-musleabi mipsel-unknown-linux-musl x86_64-apple-darwin
arm-unknown-linux-musleabihf mipsel-unknown-linux-uclibc x86_64-apple-ios
armebv7r-none-eabi mipsel-unknown-none x86_64-apple-ios-macabi
armebv7r-none-eabihf mipsisa32r6-unknown-linux-gnu x86_64-apple-tvos
armv4t-unknown-linux-gnueabi mipsisa32r6el-unknown-linux-gnu x86_64-fortanix-unknown-sgx
armv5te-unknown-linux-gnueabi mipsisa64r6-unknown-linux-gnuabi64 x86_64-fuchsia
armv5te-unknown-linux-musleabi mipsisa64r6el-unknown-linux-gnuabi64 x86_64-linux-android
armv5te-unknown-linux-uclibceabi msp430-none-elf x86_64-pc-solaris
armv6-unknown-freebsd nvptx64-nvidia-cuda x86_64-pc-windows-gnu
armv6-unknown-netbsd-eabihf powerpc-unknown-linux-gnu x86_64-pc-windows-msvc
armv7-apple-ios powerpc-unknown-linux-gnuspe x86_64-sun-solaris
armv7-linux-androideabi powerpc-unknown-linux-musl x86_64-unknown-dragonfly
armv7-unknown-freebsd powerpc-unknown-netbsd x86_64-unknown-freebsd
armv7-unknown-linux-gnueabi powerpc-unknown-openbsd x86_64-unknown-haiku
armv7-unknown-linux-gnueabihf powerpc-wrs-vxworks x86_64-unknown-hermit
armv7-unknown-linux-musleabi powerpc-wrs-vxworks-spe x86_64-unknown-illumos
armv7-unknown-linux-musleabihf powerpc64-unknown-freebsd x86_64-unknown-l4re-uclibc
armv7-unknown-netbsd-eabihf powerpc64-unknown-linux-gnu x86_64-unknown-linux-gnu
armv7-wrs-vxworks-eabihf powerpc64-unknown-linux-musl x86_64-unknown-linux-gnux32
armv7a-none-eabi powerpc64-wrs-vxworks x86_64-unknown-linux-musl
armv7a-none-eabihf powerpc64le-unknown-linux-gnu x86_64-unknown-netbsd
armv7r-none-eabi powerpc64le-unknown-linux-musl x86_64-unknown-none-hermitkernel
armv7r-none-eabihf riscv32gc-unknown-linux-gnu x86_64-unknown-none-linuxkernel
armv7s-apple-ios riscv32gc-unknown-linux-musl x86_64-unknown-openbsd
asmjs-unknown-emscripten riscv32i-unknown-none-elf x86_64-unknown-redox
avr-unknown-gnu-atmega328 riscv32imac-unknown-none-elf x86_64-unknown-uefi
hexagon-unknown-linux-musl riscv32imc-unknown-none-elf x86_64-uwp-windows-gnu
i386-apple-ios riscv64gc-unknown-linux-gnu x86_64-uwp-windows-msvc
i586-pc-windows-msvc riscv64gc-unknown-linux-musl x86_64-wrs-vxworks
gateway-rs 使用到的平台
CROSS_TARGET = "arm-unknown-linux-gnueabihf" # raspberry pi 0 / 1
CROSS_TARGET = "armv7-unknown-linux-gnueabihf" # raspberry pi 2 / 3 / 4
CROSS_TARGET = "armv7-unknown-linux-musleabihf" # kerlink
CROSS_TARGET = "mipsel-unknown-linux-musl" # ramips
CROSS_TARGET = "mips-unknown-linux-musl"
CROSS_TARGET = "armv5te-unknown-linux-musleabi"
编译未通过
随便选择一个 target，尝试编译，但是报错，由于缺少工具链。参考 https://github.com/japaric/rust-cross 解决。
> cargo build --target armv7-unknown-linux-musleabihf --release
3. 配置交叉编译工具链
交叉编译工具链是一个麻烦事儿
命名规范
交叉编译工具链的命名规则为：arch [-vendor] [-os] [-(gnu)eabi]
- arch - 体系架构，如ARM，MIPS
- verdor - 工具链提供商
- os - 目标操作系统
- eabi - 嵌入式应用二进制接口
根据对操作系统的支持与否，ARM GCC可分为支持和不支持操作系统，如：
- arm-none-eabi：这个是没有操作系统的（bare metal），自然不可能支持那些跟操作系统关系密切的函数，比如fork。他使用的是newlib这个专用于嵌入式系统的C库。
- arm-none-linux-eabi：用于Linux的，使用Glibc
参考：https://blog.csdn.net/weixin_43997099/article/details/109087458
gcc-arm-linux-gnueabi 以及 gcc-arm-linux-gnueabihf 的区别
gcc-arm-linux-gnueabi is the cross-toolchain package for the armel architecture. This toolchain implies the EABI generated by gcc's -mfloat-abi=soft or -mfloat-abi=softfp options.
gcc-arm-linux-gnueabihf is the cross-toolchain package for the armhf architecture. This toolchain implies the EABI generated by the gcc -mfloat-abi=hard option.
hf 将开启硬件浮点指令，可能有厂家会从成本角度考虑阉割硬件浮点数预算的支持，这样就必须使用软件浮点数。
树莓派工具链
git clone --depth 1 https://github.com/raspberrypi/tools.git rpitools
~/tool/rpitools/arm-bcm2708/arm-linux-gnueabihf/bin
4. 为 DietPi 系统编译 gateway-rs
工具链
下载 rpi 官方的工具链，并添加环境变量。
PATH=...:...:/home/jp/tool/rpitools/arm-bcm2708/arm-rpi-4.9.3-linux-gnueabihf/bin/
修改 cargo 配置文件指定 linker 及其配置
仓库 .cargo/config.toml 路径下面有相关的配置文件。可以根据 target 准备编译选项和链接配置参数。增加如下配置：
...
# Pi 2/3/4
[target.armv7-unknown-linux-gnueabihf]
linker = "arm-linux-gnueabihf-gcc"
rustflags = [
"-C", "target-feature=+crt-static",
"-C", "link-args=-static",
]
...
编译并运行
> cargo build --target armv7-unknown-linux-gnueabihf --release
Compiling libc v0.2.94
Compiling proc-macro2 v1.0.26
Compiling unicode-xid v0.2.2
Compiling syn v1.0.72
Compiling cfg-if v1.0.0
Compiling autocfg v1.0.1
Compiling version_check v0.9.3
Compiling getrandom v0.2.2
...
...
...
Compiling tonic v0.4.3
Compiling gateway-rs v1.0.0-alpha.8 (/home/jp/helium/gateway-rs)
Finished release [optimized] target(s) in 1m 35s
上传 (使用 tar / pipe / ssh 方式进行)
> tar cf - ./target/armv7-unknown-linux-gnueabihf/release/helium_gateway | ssh root@192.168.0.21 "tar xf - -C ~"
运行
root@DietPi:~/target/armv7-unknown-linux-gnueabihf/release# ./helium_gateway -h
helium_gateway 1.0.0-alpha.8
Helium Light Gateway
USAGE:
helium_gateway [FLAGS] [OPTIONS] <SUBCOMMAND>
FLAGS:
--daemon Daemonize the application
-h, --help Prints help information
-V, --version Prints version information
OPTIONS:
-c <config> Configuration folder to use. default.toml will be loaded first and any custom settings in
settings.toml merged in [default: /etc/helium_gateway]
SUBCOMMANDS:
help Prints this message or the help of the given subcommand(s)
key Commands on gateway keys
server Run the gateway service
update Commands for gateway updates
注意：dietpi 一定需要增加静态编译的选项，否则编译后的镜像无法使用（可能是 dietpi 比较精简删掉了一些动态库，测试用的dietpi 版本 7.）
> ssh root@192.168.0.21 root@192.168.0.21's password: ───────────────────────────────────────────────────── DietPi v7.1.2 : 06:35 - Wed 05/12/21 ───────────────────────────────────────────────────── - Device model : RPi 3 Model B (aarch64) - CPU temp : 48'C : 118'F (Optimal temperature) - LAN IP : 192.168.0.21 (eth0) - MOTD : Did you know that you can run "dietpi-banner" to change its content? ───────────────────────────────────────────────────── DietPi Team : MichaIng (lead), Daniel Knight (founder), Joulinar (support) Image by : DietPi Core Team (pre-image: Raspberry Pi OS Lite (64-bit)) Web : https://dietpi.com | https://twitter.com/DietPi_ Patreon Legends : Camry2731 Contribute : https://dietpi.com/contribute.html DietPi Hosting : Powered by https://myvirtualserver.com dietpi-launcher : All the DietPi programs in one place. dietpi-config : Feature rich configuration tool for your device. dietpi-software : Select optimized software for installation. htop : Resource monitor. cpu : Shows CPU information and stats.
小贴士
pr
为了解决终端内容复制到 md 后格式混乱的问题（TAB 默认宽度不一样），help 文档不是很友好，就稍微阅读了一下 pr 的源码。
默认使用 TAB （8）进行排版， --output-tabs=' 1'（1前面有个空格） 选项可以强制使用空格输出。
pr 工具隶属于 gnu core utilities。
一个 windows 工具链下载站
https://gnutoolchains.com/raspberry/
神秘的 musl
官方网站：https://www.musl-libc.org/ / https://musl.libc.org/
musl is an implementation of the C standard library built on top of the Linux system call API, including interfaces defined in the base language standard, POSIX, and widely agreed-upon extensions. musl is ightweight, fast, simple, free, and strives to be correct in the sense of standards-conformance and safety.
标有 musl 字样的 target 表示的应该是有 musl libc 依赖的 gcc。而标有 gnu 字样的应该是以来 glibc 的库。 （仅为猜测）
限制 cargo 编译时的任务数
$ export CARGO_BUILD_JOBS = 1
$ cargo build