[PATCH 4/5] libsframe: make flip_header version aware

[Indu Bhagat]

On 10/17/25 4:00 AM, Jens Remus wrote:
> Hello Indu!
> 
> On 10/17/2025 9:05 AM, Indu Bhagat via Binutils wrote:
>> Future versions of the format may have alternative representation of an
>> FDE.  As the format evolves, endian flipping will need to be version
>> aware.
>>
>> flip_header now takes the SFrame version as argument.  Currently unused,
>> this argument will be used later when we introduce SFrame V3.
>>
>> SFrame encoder, at the momemnt, writes the SFrame data in the most recent
>> format version by default.
>>
>> libsframe/
>>          * sframe.c (flip_header): Make version aware.
>>          (sframe_decode): Adjust usage of flup_header.
>>          (sframe_encoder_write): Likewise.
> 
>> diff --git a/libsframe/sframe.c b/libsframe/sframe.c
> 
>> +static int
>> +flip_header (char *buf, uint8_t ver ATTRIBUTE_UNUSED)
> 
> flip_header (char *buf, size_t size, uint8_t ver ATTRIBUTE_UNUSED)
> 

The decoder logic already checks this before invoking flipping. 
Similarly for encoder too, the malloc'd buffer does account for hdr 
size.  So, I think this is not necessary.

> Btw. how is passing VER into the helper expected to work?  Wouldn't it
> only be known in advance when encoding.  How would it work for decoding?
> 

I guess I just added the extra arg to flip_header for consistency and I 
thought its more flexible that way...

For decoder, we will indeed be passing the version value from the buffer 
as "flip_header (tempbuf, sfp->sfp_version))".  Similarly on the encoder 
side: even though we pass SFRAME_VERSION, this will be the same value as 
that in encoder header.

If the additional arg ver looks confusing for flip_header, we can remove 
it...

>> +{
>> +  /* SFrame header binary format has remained the same in SFRAME_VERSION_1,
>> +     SFRAME_VERSION_2.  */
>> +  sframe_header *sfh = (sframe_header *) buf;
> 
>    if (size < sizeof (sframe_header))
>      return SFRAME_ERR;
> 
> Or SFRAME_ERR_BUF_INVAL or the like.
> 
>> +  swap_thing (sfh->sfh_preamble.sfp_magic);
>> +  swap_thing (sfh->sfh_preamble.sfp_version);
>> +  swap_thing (sfh->sfh_preamble.sfp_flags);
>> +  swap_thing (sfh->sfh_abi_arch);
>> +  swap_thing (sfh->sfh_cfa_fixed_fp_offset);
>> +  swap_thing (sfh->sfh_cfa_fixed_ra_offset);
>> +  swap_thing (sfh->sfh_auxhdr_len);
>> +  swap_thing (sfh->sfh_num_fdes);
>> +  swap_thing (sfh->sfh_num_fres);
>> +  swap_thing (sfh->sfh_fre_len);
>> +  swap_thing (sfh->sfh_fdeoff);
>> +  swap_thing (sfh->sfh_freoff);
>> +
>> +  /* Alert for missing functionatlity.  Auxiliary header, if present, needs to
>> +     flipped based on per abi/arch semantics.  */
>> +  if (sfh->sfh_auxhdr_len)
>> +    return SFRAME_ERR;
>> +
>> +  return 0;
>>   }
> Thanks and regards,
> Jens