Re: SEC_NEVER_LOAD cleanup

[Kai Tietz <ktietz70@googlemail.com>]

2010/10/16 Alan Modra <amodra@gmail.com>:
> On Fri, Oct 15, 2010 at 09:54:18PM +0100, Dave Korn wrote:
>> >   .gnu_debuglink_overlay ALIGN(__section_alignment__) (NOLOAD):
>> >   {
>> >     BYTE(0) /* c */
>> >     BYTE(0) /* y */
>> >     BYTE(0) /* g */
>> >     BYTE(0) /* w */
>> >     BYTE(0) /* i */
>> >     BYTE(0) /* n */
>> >     BYTE(0) /* 1 */
>> >     BYTE(0) /* . */
>> >     BYTE(0) /* d */
>> >     BYTE(0) /* b */
>> >     BYTE(0) /* g */
>> >     BYTE(0) /* \0 */
>> >     LONG(0) /* checksum */
>> >   }
>
> Using your script with a small tweak for ELF gave me the same error.
>
>>   I think (haven't checked yet) that this looks like a consequence of the
>> ldlang.c changes.  Any thoughts on how to fix it?
>
> Like this, I think, just as we discard input sections and padding in
> noload sections.  Can you test this out for me on cygwin?
>
>        * ldwrite.c (build_link_order <lang_data_statement_enum>): Don't
>        output when section has no contents.
>        (build_link_order <lang_reloc_statement_enum>): Likewise.
>
> Index: ld/ldwrite.c
> ===================================================================
> RCS file: /cvs/src/src/ld/ldwrite.c,v
> retrieving revision 1.32
> diff -u -p -r1.32 ldwrite.c
> --- ld/ldwrite.c        22 Sep 2010 14:20:24 -0000      1.32
> +++ ld/ldwrite.c        16 Oct 2010 01:26:37 -0000
> @@ -51,6 +51,11 @@ build_link_order (lang_statement_union_t
>        output_section = statement->data_statement.output_section;
>        ASSERT (output_section->owner == link_info.output_bfd);
>
> +       if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
> +             || ((output_section->flags & SEC_LOAD) != 0
> +                 && (output_section->flags & SEC_THREAD_LOCAL))))
> +         break;
> +
>        link_order = bfd_new_link_order (link_info.output_bfd, output_section);
>        if (link_order == NULL)
>          einfo (_("%P%F: bfd_new_link_order failed\n"));
> @@ -191,6 +196,11 @@ build_link_order (lang_statement_union_t
>        output_section = rs->output_section;
>        ASSERT (output_section->owner == link_info.output_bfd);
>
> +       if (!((output_section->flags & SEC_HAS_CONTENTS) != 0
> +             || ((output_section->flags & SEC_LOAD) != 0
> +                 && (output_section->flags & SEC_THREAD_LOCAL))))
> +         break;
> +
>        link_order = bfd_new_link_order (link_info.output_bfd, output_section);
>        if (link_order == NULL)
>          einfo (_("%P%F: bfd_new_link_order failed\n"));
>
> --
> Alan Modra
> Australia Development Lab, IBM
>

Well, this looks ok, too. But AFAICS it is touching just the surface.
My recent patch took care that for PE-COFF the content of the
debugging sections didn't got zero'ed. Maybe it is a general failure
to assume (at least for pe-coff, but maybe for elf, too) that NOLOAD
means to discard sections from linking?

Cheers,
Kai


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