为什么要用Rust进行嵌入式开发

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：

 1#![no_std]
 2usecore::PanicInfo;
 3
 4#[no_mangle]
 5pubextern"C"fnsum(a:i32,b:i32)->i32{
 6a+b
 7}
 8
 9#[panic_handler]
10fnpanic(_info:&PanicInfo)->!{
11loop{}
12}

在 Cargo.toml 文件中添加以下代码，生成静态库文件：

1[lib]
2name="sum"
3crate-type=["staticlib"]
4path="src/lib.rs"

交叉编译

1、安装 armv7 target:

1rustuptargetaddarmv7a-none-eabi

2、生成静态库文件：

1PSC:UsersLiuKangDesktopRUST
ust_to_c>cargobuild--target=armv7a-none-eabi--release--verbose
2Freshrust_to_cv0.1.0(C:UsersLiuKangDesktopRUST
ust_to_c)
3Finishedrelease[optimized]target(s)in0.01s

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：

1cargoinstall--forcecbindgen

2、在项目文件夹下新建文件cbindgen.toml文件：

3、生成头文件：

1cbindgen--configcbindgen.toml--craterust_to_c--outputsum.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:

 1frombuildingimport*
 2
 3cwd=GetCurrentDir()
 4src=Glob('*.c')+Glob('*.cpp')
 5CPPPATH=[cwd]
 6
 7LIBS=["libsum.a"]
 8LIBPATH=[GetCurrentDir()]
 9
10group=DefineGroup('Applications',src,depend=[''],CPPPATH=CPPPATH,LIBS=LIBS,LIBPATH=LIBPATH)
11
12Return('group')

3、在 main 函数中调用 sum 函数, 并获取返回值

 1#include
 2#include
 3#include
 4#include
 5#include"sum.h"
 6
 7intmain(void)
 8{
 9int32_ttmp;
10
11tmp=sum(1,2);
12printf("callrustsum(1,2)=%d
",tmp);
13
14return0;
15}

4、在 env 环境下，使用 scons 编译工程：

 1LiuKang@DESKTOP-538H6DED:
epogithub
t-threadspqemu-vexpress-a9
 2$scons-j6
 3scons:ReadingSConscriptfiles...
 4scons:donereadingSConscriptfiles.
 5
 6scons:warning:youdonotseemtohavethepywin32extensionsinstalled;
 7parallel(-j)buildsmaynotworkreliablywithopenPythonfiles.
 8File"D:softwareenv_released_1.2.0env	oolsPython27Scriptsscons.py",line204,in<module>
 9scons:Buildingtargets...
10scons:buildingassociatedVariantDirtargets:build
11LINKrtthread.elf
12arm-none-eabi-objcopy-Obinaryrtthread.elfrtthread.bin
13arm-none-eabi-sizertthread.elf
14textdatabssdechexfilename
15628220214886700717068af10crtthread.elf
16scons:donebuildingtargets.
17
18LiuKang@DESKTOP-538H6DED:
epogithub
t-threadspqemu-vexpress-a9
19$qemu.bat
20WARNING:Imageformatwasnotspecifiedfor'sd.bin'andprobingguessedraw.
21Automaticallydetectingtheformatisdangerousforrawimages,writeoperationsonblock0willberestricted.
22Specifythe'raw'formatexplicitlytoremovetherestrictions.
23
24|/
25-RT-ThreadOperatingSystem
26/|4.0.4buildJul282021
272006-2021Copyrightbyrt-threadteam
28lwIP-2.1.2initialized!
29[I/sal.skt]SocketAbstractionLayerinitializesuccess.
30[I/SDIO]SDcardcapacity65536KB.
31[I/SDIO]switchingcardtohighspeedfailed!
32callrustsum(1,2)=3
33msh/>

加减乘除

1、在 lib.rs 文件中，使用 rust 语言实现加减乘除运算：

 1#![no_std]
 2usecore::PanicInfo;
 3
 4
 5#[no_mangle]
 6pubextern"C"fnadd(a:i32,b:i32)->i32{
 7a+b
 8}
 9
10#[no_mangle]
11pubextern"C"fnsubtract(a:i32,b:i32)->i32{
12a-b
13}
14
15#[no_mangle]
16pubextern"C"fnmultiply(a:i32,b:i32)->i32{
17a*b
18}
19
20#[no_mangle]
21pubextern"C"fndivide(a:i32,b:i32)->i32{
22a/b
23}
24
25#[panic_handler]
26fnpanic(_info:&PanicInfo)->!{
27loop{}
28}

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）：

1LINKrtthread.elf
2d:/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):Infunction`__aeabi_ul2d':
3(.text+0x304):multipledefinitionof`__aeabi_ul2d'
4applicationslibsum.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:firstdefinedhere
5collect2.exe:error:ldreturned1exitstatus
6scons:***[rtthread.elf]Error1
7scons:buildingterminatedbecauseoferrors.

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

1DEVICE='-march=armv7-a-marm-msoft-float'
2CFLAGS=DEVICE+'-Wall'
3AFLAGS='-c'+DEVICE+'-xassembler-with-cpp-D__ASSEMBLY__-I.'
4LINK_SCRIPT='link.lds'
5LFLAGS=DEVICE+'-nostartfiles-Wl,--gc-sections,-Map=rtthread.map,-cref,-u,system_vectors,--allow-multiple-definition'+
6'-T%s'%LINK_SCRIPT
7
8CPATH=''
9LPATH=''

5、编译并运行 qemu：

 1LiuKang@DESKTOP-538H6DED:
epogithub
t-threadspqemu-vexpress-a9
 2$scons-j6
 3scons:ReadingSConscriptfiles...
 4scons:donereadingSConscriptfiles.
 5
 6scons:warning:youdonotseemtohavethepywin32extensionsinstalled;
 7parallel(-j)buildsmaynotworkreliablywithopenPythonfiles.
 8File"D:softwareenv_released_1.2.0env	oolsPython27Scriptsscons.py",line204,in<module>
 9scons:Buildingtargets...
10scons:buildingassociatedVariantDirtargets:build
11LINKrtthread.elf
12arm-none-eabi-objcopy-Obinaryrtthread.elfrtthread.bin
13arm-none-eabi-sizertthread.elf
14textdatabssdechexfilename
15628756214886700717604af324rtthread.elf
16scons:donebuildingtargets.
17
18LiuKang@DESKTOP-538H6DED:
epogithub
t-threadspqemu-vexpress-a9
19$qemu.bat
20WARNING:Imageformatwasnotspecifiedfor'sd.bin'andprobingguessedraw.
21Automaticallydetectingtheformatisdangerousforrawimages,writeoperationsonblock0willberestricted.
22Specifythe'raw'formatexplicitlytoremovetherestrictions.
23
24|/
25-RT-ThreadOperatingSystem
26/|4.0.4buildJul282021
272006-2021Copyrightbyrt-threadteam
28lwIP-2.1.2initialized!
29[I/sal.skt]SocketAbstractionLayerinitializesuccess.
30[I/SDIO]SDcardcapacity65536KB.
31[I/SDIO]switchingcardtohighspeedfailed!
32callrustsum(1,2)=3
33callrustsubtract(2,1)=1
34callrustmultiply(2,2)=4
35callrustdivide(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

 1//导入的rt-thread函数列表
 2extern"C"{
 3pubfnrt_kprintf(format:*constu8,...);
 4}
 5
 6#[no_mangle]
 7pubextern"C"fnadd(a:i32,b:i32)->i32{
 8unsafe{
 9rt_kprintf(b"thisisfromrust
"as*constu8);
10}
11a+b
12}

生成库文件

1cargobuild--target=armv7a-none-eabi--release--verbose
2Compilingrust_to_cv0.1.0(C:UsersLiuKangDesktopRUST
ust_to_c)
3Running`rustc--crate-namesum--edition=2018src/lib.rs--error-format=json--json=diagnostic-rendered-ansi--crate-typestaticlib--emit=dep-info,link-Copt-level=3-Cembed-bitcode=no-Cmetadata=a
40723fa112c78339-Cextra-filename=-a0723fa112c78339--out-dirC:UsersLiuKangDesktopRUST
ust_to_c	argetarmv7a-none-eabi
eleasedeps--targetarmv7a-none-eabi-Ldependency=C:UsersLiuKangDesktopRUS
5T
ust_to_c	argetarmv7a-none-eabi
eleasedeps-Ldependency=C:UsersLiuKangDesktopRUST
ust_to_c	arget
eleasedeps`
6Finishedrelease[optimized]target(s)in0.11s

运行

复制 rust 生成的库文件到 application 目录下。

 1LiuKang@DESKTOP-538H6DED:
epogithub
t-threadspqemu-vexpress-a9
 2$scons-j6
 3scons:ReadingSConscriptfiles...
 4scons:donereadingSConscriptfiles.
 5scons:warning:youdonotseemtohavethepywin32extensionsinstalled;
 6parallel(-j)buildsmaynotworkreliablywithopenPythonfiles.
 7File"D:softwareenv_released_1.2.0env	oolsPython27Scriptsscons.py",line204,in<module>
 8scons:Buildingtargets...
 9scons:buildingassociatedVariantDirtargets:build
10LINKrtthread.elf
11arm-none-eabi-objcopy-Obinaryrtthread.elfrtthread.bin
12arm-none-eabi-sizertthread.elf
13textdatabssdechexfilename
14628812214890796721756b035crtthread.elf
15scons:donebuildingtargets.
16
17LiuKang@DESKTOP-538H6DED:
epogithub
t-threadspqemu-vexpress-a9
18$qemu.bat
19WARNING:Imageformatwasnotspecifiedfor'sd.bin'andprobingguessedraw.
20Automaticallydetectingtheformatisdangerousforrawimages,writeoperationsonblock0willberestricted.
21Specifythe'raw'formatexplicitlytoremovetherestrictions.
22
23|/
24-RT-ThreadOperatingSystem
25/|4.0.4buildJul282021
262006-2021Copyrightbyrt-threadteam
27lwIP-2.1.2initialized!
28[I/sal.skt]SocketAbstractionLayerinitializesuccess.
29[I/SDIO]SDcardcapacity65536KB.
30[I/SDIO]switchingcardtohighspeedfailed!
31thisisfromrust
32callrustsum(1,2)=3
33callrustsubtract(2,1)=1
34callrustmultiply(2,2)=4
35callrustdivide(4,2)=2
36msh/>

来源：

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

责任编辑：haq