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

[Jens Remus]

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)

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?

> +{
> +  /* 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
-- 
Jens Remus
Linux on Z Development (D3303)
+49-7031-16-1128 Office
jremus@de.ibm.com

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