通过arm c内联汇编程序在内存中操作数组

问题描述

  
您应该将％[ptrToSmpl] >方括号内 - 你想要加载/存储/注入寄存器中的地址。
 
 
 
这个 ldr r2 ，％[ptrToSmpl] 被翻译成 ldr r2，rX   - 废话
 
 
 
  ldr r2，[％[ptrToSmpl]]   ldr r2，[rX]   - 正确 
 
 
此外 - 当你覆盖编译器放在那里的时候，你应该把r2放到破坏寄存器列表中。在最后一个（第三个）冒号后面加上r2（带引号）。
 
int smplSize = 48;
int Smpl[48];

for(int i = 0; i < smplSize; i++) Smpl[i] = 0x0;
Smpl[smplSize-1] = 0x1;

int *ptrToSmpl = &Smpl[0];

printf("Sample @%p of Size %i :\n",(void*)ptrToSmpl,smplSize);

asm volatile(

             "@ ------------------------------------------------- \n"
             "@ Invert the sample \n"
             "@ ------------------------------------------------- \n"

            //"0:                \n"
            "ldr r2,[r3] \n"
            //"cmp r2,#0x1          \n"
            //"bne 1f             \n"
            "add r2,#0x1       \n"

            //"add r2,#0x1          \n"
            "str r2,[r3]        \n"

            //"ldr r1, .0             \n"
            //"bx  r1             \n"
            //"1:                \n"


            :
            : "r"   (ptrToSmpl)
            : "r3", "memory"

             );

printf("Sample[0] = %i" , Smpl[0]);
Edit:
As you can see I want to manipulate a variable of an array via the inline assembler on arm, but I always get a segfault. How can I access the memory without segfault?
printf("Hello inline asmTest start!\n\n");

int smplSize = 48;
int Smpl[48];

for(int i = 0; i < smplSize; i++) Smpl[i] = 0x0;
Smpl[smplSize-1] = 0x1;

int *ptrToSmpl = &Smpl[0];

printf("Sample @%p of Size %i :\n",(void*)ptrToSmpl,smplSize);

asm volatile(

             "@ ------------------------------------------------- \n"
             "@ Invert the sample \n"
             "@ ------------------------------------------------- \n"

            //"0:                \n"

            "ldr r2,%[ptrToSmpl] \n"
            //"cmp r2,#0x1          \n"
            //"bne 1f             \n"
            "add r2,#0x1       \n"

            //"add r2,#0x1          \n"
            "str r2,%[ptrToSmpl]        \n"

            //"ldr r1, .0             \n"
            //"bx  r1             \n"
            //"1:                \n"


            :
            : [ptrToSmpl]"r"   (ptrToSmpl)
            :

             );

printf("Sample[0] = %i" , Smpl[0]);
Ok, I did so, but now I get a "/tmp/cczQDyiw.s|72|Error: internal_relocation (type: OFFSET_IMM) not fixed up|" when compiling it.
BTW: Can I "org [Adress of the programm]" the inline asm code ?
printf("Hello inline asmTest start!\n\n");

int smplSize = 48;
int Smpl[48];

for(int i = 0; i < smplSize; i++) Smpl[i] = 0x0;
Smpl[smplSize-1] = 0x1;

int *ptrToSmpl = &Smpl[0];

printf("Sample @%p of Size %i :\n",(void*)ptrToSmpl,smplSize);

asm volatile(

             "@ ------------------------------------------------- \n"
             "@ Invert the sample \n"
             "@ ------------------------------------------------- \n"

            "init:                \n"
            "ldr   r0,%[ptrToSmpl] \n"

            "loop :                 \n"
            "ldr r4,[r0]        \n"
            "cmp r4,#0x0          \n"
            "bne  end             \n"

            "add r4,#0x1          \n"
            "str r4,[r0]        \n"

            "add r0,#0x1       \n"


            "b  loop             \n"
            "end:                \n"


            :
            : [ptrToSmpl]"r"   (ptrToSmpl)
            :  "r0" , "r4", "memory"

             );

printf("Sample[0] = %i" , Smpl[0]);
Edit 2:
As you can see above theres still a bug in the adressing I think.The error message now is:"/tmp/ccE69oZd.s|75|Error: undefined symbol r6 used as an immediate value|"but there's no r6 anywhere.
 解决方案 
You should put %[ptrToSmpl] inside square brackets - you want to load/store from/to the address that is in the register.
This ldr r2,%[ptrToSmpl] gets translated into ldr r2,rX - nonsense
This ldr r2,[%[ptrToSmpl]]  ldr r2,[rX] - correct
Moreover - you should put r2 into the list of clobbered registers, as you overwrite what compiler puts there. Add "r2" (with quotes) after the last (third) colon.
                        
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