[Help]How to update the section content during the assemble?

[Terry Guo <flameroc at gmail dot com>]

Hi there,

Currently the gas will emit the obj attribute section and then do
relaxation. But my target will adjust some target attributes during
the relaxation, so I want to update the already generated attribute
section after relaxation.

Currently I am using the md_post_relax_hook with following code (in
pseudo code):

attribute_sec = bfd_get_section_by_name (abfd, sec_name);
size = bfd_elf_obj_attr_size (abfd);
seginfo = seg_info (attr_sec);

//generate new frag for updated target attributes.
fragS *newf = frag_alloc (ob);
bfd_elf_set_obj_attr_contents (abfd, (bfd_byte *)newf->fr_literal, size);

//link attribute section with this new frag and discard the old one
seginfo->frchainP->frch_root = newf;
seginfo->frchainP->frch_last = newf;

But it doesn't work. I think I am not understanding this frag stuff
very clearly. What's the correct way to do so? Please help.

BR,
Terry