Re: [Gcl-devel] ghci on arm

[Camm Maguire]

Greetings!  GCL has a working native linker now on armel and armhf.  We
have a generic elf relocation file, with machine specific headers
implementing only those relocs output by gcc.  I can step you through
the code if interested.

For example, here is the core file for elf32_arm, which should be almost
readable: 

#define R_ARM_THM_CALL        10
#define R_ARM_CALL 28
#define R_ARM_V4BX 40
#define R_ARM_THM_MOVW_ABS_NC 47
#define R_ARM_THM_MOVW_ABS    48
    case R_ARM_THM_CALL: 
      s+=a; 
      if (ELF_ST_TYPE(sym->st_info)==STT_FUNC) s|=1; 
      s-=p+4; /*FIXME maybe drop 4 and add_val below*/
      s=((long)s>>1); 
      massert(!(abs(s)&0xffc00000));  
      store_val(where,MASK(11),s>>11); 
      store_val(where,MASK(11)<<16,(s&0x7ff)<<16); 
      break; 
    case R_ARM_THM_MOVW_ABS_NC:
      s+=a;
      if (ELF_ST_TYPE(sym->st_info)==STT_FUNC) s|=1;
      s&=0xffff;
      s=((s>>12)&0xf)|(((s>>11)&0x1)<<10)|((s&0xff)<<16)|(((s>>8)&0x7)<<28);
      add_vals(where,~0L,s);
      break;
    case R_ARM_THM_MOVW_ABS:
      s+=a;
      s>>=16;
      s=((s>>12)&0xf)|(((s>>11)&0x1)<<10)|((s&0xff)<<16)|(((s>>8)&0x7)<<28);
      add_vals(where,~0L,s);
      break;
    case R_ARM_CALL:
      add_vals(where,MASK(24),((long)(s+a-p))>>2);
      break;
    case R_ARM_ABS32:
      add_val(where,~0L,s+a);
      break;
    case R_ARM_V4BX:
      add_val(where,~0L,s+a);
      break;


I've found the quickest way to implement these is to make a simple a.out
file with ld -R <main program> <foo.o> and reverse engineer, looking at
binutils and some platform docs as necessary.

I'm missing ia64 only -- any help here?

Take care,



Clint Adams <address@hidden> writes:

> On Tue, Jan 10, 2012 at 03:17:41PM -0500, Ben Gamari wrote:
>> If anyone knows people experienced in ARM linker implementation, then feel
>> free to send them my way. At this point I'm at the difficult point of
>> figuring out why some relocation (plural?) sends the CPU to the
>> middle of nowhere. I've had next to no experience with linker
>> implementation in general, much less the mess that seems to be ARM, so
>> feedback from someone with some experience in this field would be
>> definitely appreciated. As Karel said, there is no Haskell code here at
>> all; strictly C.
>
> Maybe Camm has dealt with something similar already and can offer
> some insight?
>
>
>
>

-- 
Camm Maguire                                        address@hidden
==========================================================================
"The earth is but one country, and mankind its citizens."  --  Baha'u'llah