gold input section handling

[Ian Lance Taylor]

David Miller <davem@davemloft.net> writes:

> From: Ian Lance Taylor <iant@google.com>
> Date: Mon, 14 Apr 2008 09:45:05 -0700
>
>> Because the Linux kernel is not reliable about setting section flags
>> in assembler source, gold has exceptions such that it will combine
>> sections with zero flags with sections with non-zero flags if they
>> have the same name.
>> 
>> Because gcc uses an optimization for the .eh_frame section, making it
>> read-only possible and read-write when necessary, gold has an
>> exception for the .eh_frame section.
>
> I think the fact that gold needs two exceptions already, and we know
> of other cases that break, are good indications that it may not be
> tenable, in the end, to enforce this rule.
>
> There seems to be quite some precendence of using different section
> flags in different instances of a section.

I saw your later post, but this seems like a reasonable argument to
me.  I changed gold so that it ignores SHF_WRITE and SHF_EXECINSTR
when merging sections.  It still pays attention to SHF_ALLOC, except
for sections with zero flags.

I committed the attached patch.

Ian


2008-04-14  Ian Lance Taylor  <iant@google.com>

	* layout.cc (Layout::Layout): Initialize sections_are_attached_.
	(Layout::get_output_section): Ignore SHF_WRITE and SHF_EXECINSTR
	in the name/type/flags to section mapping.  Don't call
	allocate_output_section.
	(Layout::choose_output_section): Change parameter from adjust_name
	to is_input_section.  Don't permit input sections after sections
	are attached to segments.  Don't call allocate_output_section.
	(Layout::layout_eh_frame): Call update_flags_for_input_section,
	not write_enable_output_section.
	(Layout::make_output_section): Don't push to
	unattached_section_list_ nor call attach_to_segment.  Call
	attach_section_to_segment if sections are attached.
	(Layout::attach_sections_to_segments): New function.
	(Layout::attach_section_to_segment): New function.
	(Layout::attach_allocated_section_to_segment): Rename from
	attach_to_segment.  Remove flags parameter.
	(Layout::allocate_output_section): Remove function.
	(Layout::write_enable_output_section): Remove function.
	* layout.h (class Layout): Update for above changes.  Add new
	field sections_are_attached_.
	* output.h (Output_section::update_flags_for_input_section): New
	function.
	* output.cc (Output_section::add_input_section): Call
	update_flags_for_input_section.
	* gold.cc (queue_middle_tasks): Call attach_sections_to_segments.


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