arm 交叉编译 thumb 与 arm 指令的方法

• 本文实现了在 x86 的 ubuntu 的机器上，使用 arm-linux-gnueabihf-gcc 交叉编译链工具，编译出在 arm 开发板上可以运行的 thumb 指令集的可执行文件。后续会使用 vscode 使用网络进行远程调试。

1. 编译器 arm-linux-gnueabihf-gcc

# arm-linux-gnueabihf-gcc -v
Using built-in specs.
COLLECT_GCC=arm-linux-gnueabihf-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/arm-linux-gnueabihf/11/lto-wrapper
Target: arm-linux-gnueabihf
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 11.4.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-11 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --without-target-system-zlib --enable-multiarch --disable-sjlj-exceptions --with-arch=armv7-a+fp --with-float=hard --with-mode=thumb --disable-werror --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=arm-linux-gnueabihf --program-prefix=arm-linux-gnueabihf- --includedir=/usr/arm-linux-gnueabihf/include --with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04) 

ubuntu 中安装方法 sudo apt-get install binutils-arm-linux-gnueabi gcc-arm-linux-gnuabihf

2. 代码中实现

使用 __attribute__((target("thumb"))) void thumb_ins(void); 指定函数编译为 thumb 指令

//完整的 main.c 的示例
#include <stdio.h>

__attribute__((target("thumb"))) void thumb_ins(void);
void thumb_ins(void) {
	int ia = 0;
	int ib = 0;
	int ic = 0;

	while (1) {
		ia = 0;
		ib = 0;
		ic = 0xab;

		asm volatile ("mov r0, #1");
		asm volatile ("mov r4, #0");
		asm volatile ("cmp r4, #0");
		asm volatile ("itte  eq");
		asm volatile ("moveq r1, #55");
		asm volatile ("moveq r2, #66");
		asm volatile ("movne r2, #77");

		asm volatile ("mov %0, r1" : "=r" (ia));
		asm volatile ("mov %0, r2" : "=r" (ib));
		asm volatile ("mov %0, r0" : "=r" (ic));

		if ((ia != 55) || (ib != 66)) {
			printf("error!!!");
			printf(" ia %d ib %d  %d\r\n", ia, ib, ic);
		}
	}
}

int main(void)
{
  printf("I run!!! %s %s\r\n", __TIME__, __DATE__);

  while (1) {
    thumb_ins();
  }

  return 0;
}

3. 编译方法

• 编译指令 arm-linux-gnueabihf-gcc -g -static -mthumb-interwork -mthumb main.c
  
  参数解释：
  
  -g 添加调试信息
  
  -static 使用静态链接的方式
  
  -mthumb 使用 thumb 指令集
  
  -mthumb-interwork 支持 arm 与 thumb 混合
  

• 反汇编查看是否正确 arm-linux-gnueabihf-objdump -S a.out > a.asm

__attribute__((target("thumb"))) void thumb_ins(void);
void thumb_ins(void) {
   10438:	b580      	push	{r7, lr}
   1043a:	b084      	sub	sp, #16
   1043c:	af00      	add	r7, sp, #0
	int ia = 0;
   1043e:	2300      	movs	r3, #0
   10440:	607b      	str	r3, [r7, #4]
	int ib = 0;
   10442:	2300      	movs	r3, #0
   10444:	60bb      	str	r3, [r7, #8]
	int ic = 0;
   10446:	2300      	movs	r3, #0
   10448:	60fb      	str	r3, [r7, #12]

	while (1) {
		ia = 0;
   1044a:	2300      	movs	r3, #0
   1044c:	607b      	str	r3, [r7, #4]
		ib = 0;
   1044e:	2300      	movs	r3, #0
   10450:	60bb      	str	r3, [r7, #8]
		ic = 0xab;
   10452:	23ab      	movs	r3, #171	; 0xab
   10454:	60fb      	str	r3, [r7, #12]

		asm volatile ("mov r0, #1");
   10456:	f04f 0001 	mov.w	r0, #1
		asm volatile ("mov r4, #0");
   1045a:	f04f 0400 	mov.w	r4, #0
		asm volatile ("cmp r4, #0");
   1045e:	2c00      	cmp	r4, #0
		asm volatile ("itte  eq");
   10460:	bf06      	itte	eq
		asm volatile ("moveq r1, #55");
   10462:	2137      	moveq	r1, #55	; 0x37
		asm volatile ("moveq r2, #66");
   10464:	2242      	moveq	r2, #66	; 0x42
		asm volatile ("movne r2, #77");
   10466:	224d      	movne	r2, #77	; 0x4d

		asm volatile ("mov %0, r1" : "=r" (ia));
   10468:	460b      	mov	r3, r1
   1046a:	607b      	str	r3, [r7, #4]
		asm volatile ("mov %0, r2" : "=r" (ib));
   1046c:	4613      	mov	r3, r2
   1046e:	60bb      	str	r3, [r7, #8]
		asm volatile ("mov %0, r0" : "=r" (ic));
   10470:	4603      	mov	r3, r0
   10472:	60fb      	str	r3, [r7, #12]

		if ((ia != 55) || (ib != 66)) {
   10474:	687b      	ldr	r3, [r7, #4]
   10476:	2b37      	cmp	r3, #55	; 0x37
   10478:	d102      	bne.n	10480 <thumb_ins+0x48>
   1047a:	68bb      	ldr	r3, [r7, #8]
   1047c:	2b42      	cmp	r3, #66	; 0x42
   1047e:	d0e4      	beq.n	1044a <thumb_ins+0x12>
			printf("error!!!");
   10480:	4b06      	ldr	r3, [pc, #24]	; (1049c <thumb_ins+0x64>)
   10482:	447b      	add	r3, pc
   10484:	4618      	mov	r0, r3
   10486:	f004 fb67 	bl	14b58 <_IO_printf>
			printf(" ia %d ib %d  %d\r\n", ia, ib, ic);
   1048a:	68fb      	ldr	r3, [r7, #12]
   1048c:	68ba      	ldr	r2, [r7, #8]
   1048e:	6879      	ldr	r1, [r7, #4]
   10490:	4803      	ldr	r0, [pc, #12]	; (104a0 <thumb_ins+0x68>)
   10492:	4478      	add	r0, pc
   10494:	f004 fb60 	bl	14b58 <_IO_printf>
		ia = 0;
   10498:	e7d7      	b.n	1044a <thumb_ins+0x12>
   1049a:	bf00      	nop
   1049c:	0003f1be 	.word	0x0003f1be
   104a0:	0003f1ba 	.word	0x0003f1ba

000104a4 <main>:
	}
}

最后将 a.out 放入目标板卡使用 chmod +x 添加执行权限，即可运行。