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【完整版】使用 Rust 进行嵌入式开发

文件 开发
2023-03-14 22:36:18 时间

作者：RT-Thread社区团队 liukang

原文链接：

https://club.rt-thread.org/ask/article/2944.html

本文转载自公众号：RTThread物联网操作系统 。原文链接：

https://mp.weixin.qq.com/s/9QGIM7xkjZNxI7SYj5kDlw

Rust 是什么

Rust 是一门赋予每个人 构建可靠且高效软件能力的语言。

  • 高性能：速度惊人且内存利用率极高
  • 可靠性：在编译期就能消除各种内存错误
  • 生产力：出色的文档，友好的编译器和清晰的错误提示信息

为什么要用 Rust 进行嵌入式开发

Rust 的设计理念：既要安全，也要高性能。Rust 的设计理念完全是嵌入式开发所需要的。

嵌入式软件在运行过程中出现问题，大部分是由于内存引起的。Rust 语言可以说是一门面向编译器的语言。在编译期间，就能够确保你安全地使用内存。

目前，嵌入式的主流开发语言还是 C 语言，不能上来就把底层的逻辑用 Rust 重新实现一遍。但是可以在 C 代码中嵌入 Rust 语言。

C 调用 Rust

在 C 代码中调用 Rust 代码，需要我们将 Rust 源代码打包为静态库文件。在 C 代码编译时，链接进去。

创建 lib 库

1、在 Clion 中使用 cargo init --lib rust_to_c 建立 lib 库。添加以下代码到 lib.rs 中，使用 Rust 语言计算两个整数的和：

#![no_std]
use core::panic::PanicInfo;

#[no_mangle]
pub extern "C" fn sum(a: i32, b: i32) -> i32 {
    a + b
}

#[panic_handler]
fn panic(_info:&PanicInfo) -> !{
    loop{}
}

在 Cargo.toml 文件中添加以下代码，生成静态库文件：

[lib]
name = "sum"
crate-type = ["staticlib"]
path = "src/lib.rs"

交叉编译

1、安装 armv7 target:

rustup target add armv7a-none-eabi

2、生成静态库文件：

PS C:UsersLiuKangDesktopRUST
ust_to_c> cargo build --target=armv7a-none-eabi --release --verbose
       Fresh rust_to_c v0.1.0 (C:UsersLiuKangDesktopRUST
ust_to_c)
    Finished release [optimized] target(s) in 0.01s

生成头文件

1、安装 cbindgen](https://github.com/eqrion/cbindgen)), cbindgen 从 rust 库生成 C/C++ 11 头文件：

cargo install --force cbindgen

2、在项目文件夹下新建文件 cbindgen.toml 文件：

3、生成头文件：

cbindgen --config cbindgen.toml --crate rust_to_c --output sum.h

调用 Rust 库文件

1、将生成的sum.h 以及 sum.a 文件放入 rt-threadspqemu-vexpress-a9applications 目录下

2、修改 SConscript 文件，添加静态库:

from building import *

cwd     = GetCurrentDir()
src     = Glob('*.c') + Glob('*.cpp')
CPPPATH = [cwd]

LIBS = ["libsum.a"]
LIBPATH = [GetCurrentDir()]

group = DefineGroup('Applications', src, depend = [''], CPPPATH = CPPPATH, LIBS = LIBS, LIBPATH = LIBPATH)

Return('group')

3、在 main 函数中调用 sum 函数, 并获取返回值

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <rtthread.h>
#include "sum.h"

int main(void)
{
    int32_t tmp;

    tmp = sum(1, 2);
    printf("call rust sum(1, 2) = %d
", tmp);

    return 0;
}

4、在 env 环境下，使用 scons 编译工程：

   LiuKang@DESKTOP-538H6DE D:
epogithub
t-threadspqemu-vexpress-a9
   $ scons -j6
   scons: Reading SConscript files ...
   scons: done reading SConscript files.

   scons: warning: you do not seem to have the pywin32 extensions installed;
   parallel (-j) builds may not work reliably with open Python files.
   File "D:softwareenv_released_1.2.0env	oolsPython27Scriptsscons.py", line 204, in <module>
   scons: Building targets ...
   scons: building associated VariantDir targets: build
   LINK rtthread.elf
   arm-none-eabi-objcopy -O binary rtthread.elf rtthread.bin
   arm-none-eabi-size rtthread.elf
  text    data     bss     dec     hex filename
628220    2148   86700  717068   af10c rtthread.elf
   scons: done building targets.

   LiuKang@DESKTOP-538H6DE D:
epogithub
t-threadspqemu-vexpress-a9
   $ qemu.bat
   WARNING: Image format was not specified for 'sd.bin' and probing guessed raw.
Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
Specify the 'raw' format explicitly to remove the restrictions.

 | /
   - RT -     Thread Operating System
/ |      4.0.4 build Jul 28 2021
2006 - 2021 Copyright by rt-thread team
   lwIP-2.1.2 initialized!
   [I/sal.skt] Socket Abstraction Layer initialize success.
   [I/SDIO] SD card capacity 65536 KB.
   [I/SDIO] switching card to high speed failed!
   call rust sum(1, 2) = 3
   msh />

加减乘除

1、在 lib.rs 文件中，使用 rust 语言实现加减乘除运算：

  #![no_std]
  use core::panic::PanicInfo;


  #[no_mangle]
  pub extern "C" fn add(a: i32, b: i32) -> i32 {
      a + b
  }

  #[no_mangle]
  pub extern "C" fn subtract(a: i32, b: i32) -> i32 {
      a - b
  }

  #[no_mangle]
  pub extern "C" fn multiply(a: i32, b: i32) -> i32 {
      a * b
  }

  #[no_mangle]
  pub extern "C" fn divide(a: i32, b: i32) -> i32 {
      a / b
  }

  #[panic_handler]
  fn panic(_info:&PanicInfo) -> !{
      loop{}
  }

2、生成库文件和头文件并放在 application 目录下

3、使用 scons 编译，链接时报错，在 rust github 仓库的 issues 中找到了 解决办法（https://github.com/rust-lang/compiler-builtins/issues/353） ：

   LINK rtthread.elf
   d:/software/env_released_1.2.0/env/tools/gnu_gcc/arm_gcc/mingw/bin/../lib/gcc/arm-none-eabi/5.4.1/armv7-ar/thumblibgcc.a(_arm_addsubdf3.o): In function `__aeabi_ul2d':
   (.text+0x304): multiple definition of `__aeabi_ul2d'
   applicationslibsum.a(compiler_builtins-9b744f6fddf5e719.compiler_builtins.20m0qzjq-cgu.117.rcgu.o):/cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.35/src/float/conv.rs:143: first defined here
   collect2.exe: error: ld returned 1 exit status
   scons: *** [rtthread.elf] Error 1
   scons: building terminated because of errors.

4、修改 rtconfig.py 文件， 添加链接参数 --allow-multiple-definition：

    DEVICE = ' -march=armv7-a -marm -msoft-float'
    CFLAGS = DEVICE + ' -Wall'
    AFLAGS = ' -c' + DEVICE + ' -x assembler-with-cpp -D__ASSEMBLY__ -I.'
    LINK_SCRIPT = 'link.lds'
    LFLAGS = DEVICE + ' -nostartfiles -Wl,--gc-sections,-Map=rtthread.map,-cref,-u,system_vectors,--allow-multiple-definition'+
                      ' -T %s' % LINK_SCRIPT

    CPATH = ''
    LPATH = ''

5、编译并运行 qemu：

   LiuKang@DESKTOP-538H6DE D:
epogithub
t-threadspqemu-vexpress-a9
   $ scons -j6
   scons: Reading SConscript files ...
   scons: done reading SConscript files.

   scons: warning: you do not seem to have the pywin32 extensions installed;
   parallel (-j) builds may not work reliably with open Python files.
   File "D:softwareenv_released_1.2.0env	oolsPython27Scriptsscons.py", line 204, in <module>
   scons: Building targets ...
   scons: building associated VariantDir targets: build
   LINK rtthread.elf
   arm-none-eabi-objcopy -O binary rtthread.elf rtthread.bin
   arm-none-eabi-size rtthread.elf
  text    data     bss     dec     hex filename
628756    2148   86700  717604   af324 rtthread.elf
   scons: done building targets.

   LiuKang@DESKTOP-538H6DE D:
epogithub
t-threadspqemu-vexpress-a9
   $ qemu.bat
   WARNING: Image format was not specified for 'sd.bin' and probing guessed raw.
    Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
    Specify the 'raw' format explicitly to remove the restrictions.

 | /
   - RT -     Thread Operating System
/ |      4.0.4 build Jul 28 2021
2006 - 2021 Copyright by rt-thread team
   lwIP-2.1.2 initialized!
   [I/sal.skt] Socket Abstraction Layer initialize success.
   [I/SDIO] SD card capacity 65536 KB.
   [I/SDIO] switching card to high speed failed!
   call rust sum(1, 2) = 3
   call rust subtract(2, 1) = 1
   call rust multiply(2, 2) = 4
   call rust divide(4, 2) = 2

Rust 调用 C

可以 在 C 代码中调用 Rust，那么在 Rust 中也可以调用 C 代码。我们在 Rust 代码中调用 rt_kprintf 函数：

修改 lib.rs 文件

    // 导入的 rt-thread 函数列表
    extern "C" {
        pub fn rt_kprintf(format: *const u8, ...);
    }

    #[no_mangle]
    pub extern "C" fn add(a: i32, b: i32) -> i32 {
        unsafe {
            rt_kprintf(b"this is from rust
" as *const u8);
        }
        a + b
    }

生成库文件

    cargo build --target=armv7a-none-eabi --release --verbose
       Compiling rust_to_c v0.1.0 (C:UsersLiuKangDesktopRUST
ust_to_c)
         Running `rustc --crate-name sum --edition=2018 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type staticlib --emit=dep-info,link -C opt-level=3 -C embed-bitcode=no -C metadata=a
    0723fa112c78339 -C extra-filename=-a0723fa112c78339 --out-dir C:UsersLiuKangDesktopRUST
ust_to_c	argetarmv7a-none-eabi
eleasedeps --target armv7a-none-eabi -L dependency=C:UsersLiuKangDesktopRUS
    T
ust_to_c	argetarmv7a-none-eabi
eleasedeps -L dependency=C:UsersLiuKangDesktopRUST
ust_to_c	arget
eleasedeps`
        Finished release [optimized] target(s) in 0.11s

运行

复制 rust 生成的库文件到 application 目录下。

    LiuKang@DESKTOP-538H6DE D:
epogithub
t-threadspqemu-vexpress-a9                                                       
    $ scons -j6                                                                                                             
    scons: Reading SConscript files ...                                                                                  
    scons: done reading SConscript files.                                                                                                     
    scons: warning: you do not seem to have the pywin32 extensions installed;                                                   
            parallel (-j) builds may not work reliably with open Python files.                                                  
    File "D:softwareenv_released_1.2.0env	oolsPython27Scriptsscons.py", line 204, in <module>                            
    scons: Building targets ...                                                                                                 
    scons: building associated VariantDir targets: build                                                                        
    LINK rtthread.elf                                                                                                           
    arm-none-eabi-objcopy -O binary rtthread.elf rtthread.bin                                                                   
    arm-none-eabi-size rtthread.elf                                                                                             
       text    data     bss     dec     hex filename                                                                            
     628812    2148   90796  721756   b035c rtthread.elf                                                                        
    scons: done building targets.                                                                                               

    LiuKang@DESKTOP-538H6DE D:
epogithub
t-threadspqemu-vexpress-a9                                                       
    $ qemu.bat                                                                                                                  
    WARNING: Image format was not specified for 'sd.bin' and probing guessed raw.                                               
             Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.    
             Specify the 'raw' format explicitly to remove the restrictions.                                                    

      | /                                                                                                                      
    - RT -     Thread Operating System                                                                                          
     / |      4.0.4 build Jul 28 2021                                                                                          
     2006 - 2021 Copyright by rt-thread team                                                                                    
    lwIP-2.1.2 initialized!                                                                                                     
    [I/sal.skt] Socket Abstraction Layer initialize success.                                                                    
    [I/SDIO] SD card capacity 65536 KB.                                                                                         
    [I/SDIO] switching card to high speed failed!                                                                               
    this is from rust                                                                                                           
    call rust sum(1, 2) = 3                                                                                           
    call rust subtract(2, 1) = 1                                                                                                
    call rust multiply(2, 2) = 4                                                                                                
    call rust divide(4, 2) = 2                                                                                     
    msh />

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