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[PATCH] Fix writing object contents above 4GB in tekhex format

Jens Remus jremus@linux.ibm.com
Thu Oct 24 08:22:20 GMT 2024 
Hello Alan!

On 24.10.2024 09:33, Alan Modra wrote:
> On Wed, Oct 23, 2024 at 06:04:34PM +0200, Jens Remus wrote:
>> On 23.10.2024 17:10, Dani Szebenyi wrote:
...>>>    bfd/tekhex.c | 4 ++--
>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/bfd/tekhex.c b/bfd/tekhex.c
>>> index 96022c585ab..46f40b19817 100644
>>> --- a/bfd/tekhex.c
>>> +++ b/bfd/tekhex.c
>>> @@ -719,11 +719,11 @@ writevalue (char **dst, bfd_vma value)
>>>      int len;
>>>      int shift;
>>> -  for (len = 8, shift = 28; shift; shift -= 4, len--)
>>> +  for (len = 16, shift = 60; shift; shift -= 4, len--)
>>>        {
>>>          if ((value >> shift) & 0xf)
>>>    	{
>>> -	  *p++ = len + '0';
>>> +	  *p++ = digs[len & 0xf];
>>>    	  while (len)
>>>    	    {
>>>    	      *p++ = digs[(value >> shift) & 0xf];
>>
>> Looks good to me! Hope Nick/Alan agree.
> 
> Um, no.  You'll get undefined behaviour when bfd_vma is 32 bits.

Aww, I did not think of that.

> Huh, and it looks like the function is broken in other ways.  If, for
> example, "value" is 3 you'll get the same output as "value" 0.

Good catch!

> So I rewrote it and decided I ought to test it..
> 
> echo -n "123" > bin
> binutils/objcopy -I binary bin -O tekhex xxx
> binutils/objdump -s xxx
> binutils/objdump: xxx: file format not recognized

Dani did not notice when testing his use use case in GDB (dump tekhex ...).

> Oh great, let's see what is going on.  After debugging a little,
> I see we have a problem with *ABS* symbols, and after fixing that,
> the tekhex file created above:
> %47621103132330000000000000000000000000000000000000000000000000000000000
> %103EB5.data11013
> %1F3015.data40_binary_bin_star10
> %1E3C85.data4F_binary_bin_end13
> %1F3585*ABS*20_binary_bin_size13
> %0781010
> 
> now can be dumped.
> binutils/objdump -sx xxx
> 
> xxx:     file format tekhex
> xxx
> architecture: UNKNOWN!, flags 0x00000010:
> HAS_SYMS
> start address 0x00000000
> 
> Sections:
> Idx Name          Size      VMA       LMA       File off  Algn
>    0 .data         00000003  00000000  00000000  00000000  2**0
>                    CONTENTS, ALLOC, LOAD, DATA
> SYMBOL TABLE:
> 00000000 g       .data _binary_bin_star
> 00000003 g       .data _binary_bin_end
> 00000003 g       *ABS* _binary_bin_size
> 
> 
> Contents of section .data:
>   0000 313233                               123

Awesome, thank you!

> 	* tekhex.c (first_phase): Handle *ABS* symbols.
> 	(writevalue): Rewrite.
> 
> diff --git a/bfd/tekhex.c b/bfd/tekhex.c
> index 96022c585ab..16e8e185572 100644
> --- a/bfd/tekhex.c
> +++ b/bfd/tekhex.c
> @@ -395,7 +395,7 @@ first_phase (bfd *abfd, int type, char *src, char * src_end)
>   	  if (!n)
>   	    return false;
>   	  memcpy (n, sym, len + 1);
> -	  section = bfd_make_section (abfd, n);
> +	  section = bfd_make_section_old_way (abfd, n);
>   	  if (section == NULL)
>   	    return false;
>   	}
> @@ -719,24 +719,13 @@ writevalue (char **dst, bfd_vma value)
>     int len;
>     int shift;
>   
> -  for (len = 8, shift = 28; shift; shift -= 4, len--)
> -    {
> -      if ((value >> shift) & 0xf)
> -	{
> -	  *p++ = len + '0';
> -	  while (len)
> -	    {
> -	      *p++ = digs[(value >> shift) & 0xf];
> -	      shift -= 4;
> -	      len--;
> -	    }
> -	  *dst = p;
> -	  return;
> +  for (len = BFD_ARCH_SIZE / 4, shift = len * 4 - 4; len > 1; shift -= 4, len--)
> +    if ((value >> shift) & 0xf)
> +      break;
>   
> -	}
> -    }
> -  *p++ = '1';
> -  *p++ = '0';
> +  *p++ = digs[len & 0xf];
> +  for (; len; shift -= 4, len--)
> +    *p++ = digs[(value >> shift) & 0xf];
>     *dst = p;
>   }

Looks good to me. I see you already commited your patch. Thank you for 
taking care!

Regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303) and z/VSE Support
+49-7031-16-1128 Office
jremus@de.ibm.com

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