在Rasperry pi中编译和运行ARM汇编thumb-2？

Question

我上了一个汇编类，结果发现我不能运行他们提供的汇编程序，因为它是兼容Windows 95的x.x

我正在运行Rasperry PI，可以通过以下方式轻松运行ARM代码的程序集

http://thinkingeek.com/2013/01/09/arm-assembler-raspberry-pi-chapter-1/

/* -- first.s */
/* This is a comment */
.global main /* 'main' is our entry point and must be global */
.func main   /* 'main' is a function */

main:          /* This is main */
    mov r0, #2 /* Put a 2 inside the register r0 */
    bx lr      /* Return from main */

$ as -o first.o first.s
$ gcc -o first first.o
$ ./first ; echo $?
2

但这是标准的ARM 32位设置，需要编译并运行thumb-2设置，例如：

    AREA PrintText, CODE, READONLY
SWI_WriteC  EQU &0     ;output character in r0 
SWI_Exit    EQU &11    ;finish program
        ENTRY

        BL  Print   ;call print subroutine
        =   "Text to print",&0a,&0d,0   
        ALIGN
        SWI     SWI_Exit    ;finish
Print       LDRB    r0,[r14], #1    ;get a character
        CMP     r0, #0      ;end mark NUL?
        SWINE   SWI_WriteC  ;if not, print
        BNE Print
        ADD r14, r14, #3    ; pass next word boundary
        BIC r14, r14, #3    ; round back to boundary
        MOV pc, r14     ;return
        END

有人知道我需要在Pi中做什么才能运行这个拇指风格吗？编辑：

对于上面的命令，我尝试添加-mthumb，但我不认为这是正确的，因为我没有看到任何变化。

作为-mthumb -o test.o test.s

Answer 1

看看你的汇编程序是否会采用下面这一行：

AREA PrintText, CODE, READONLY, THUMB

Answer 2

.code 32 @ stuff after this line is arm code

.globl hello_arm
hello_arm:  @an arm function


.thumb @stuff after this line is thumb

.thumb_func @the next function is a thumb function and called properly
.globl hello
hello: @ a thumb function