2010-04-09 Doug Kwan <dougkwan@google.com>
* layout.cc (Layout::choose_output_section): Handle script section
types.
(Layout::make_output_section_for_script): Add section type parameter.
Handle script section types.
* layout.h (Layout::make_output_section_for_script): Add section
type parameter.
* output.cc (Output_section::Output_section): Initialize data member
is_noload_.
(Output_section::do_reset_address_and_file_offset): Do not set address
to 0 if section is a NOLOAD section.
* output.h (Output_section::is_noload): New method.
(Output_section::set_is_noload): Ditto.
(Output_section::is_noload_): New data member.
* script-c.h (Script_section_type): New enum type.
(struct Parser_output_section_header): Add new file section_type.
* script-sections.cc (Sections_element::output_section_name): Add
parameter for returning script section type.
(Output_section_definition::output_section_name): Ditto.
(Output_section_definition::section_type)P; New method.
(Output_section_definiton::script_section_type_name): Ditto.
(Output_section_definition::script_section_type_): New data member.
(Output_section_definition::Output_section_definition): Initialize
data member Output_section_definition::script_section_type_.
(Output_section_definition::create_sections): Pass script section type
to Layout::make_output_section_for_script.
(Output_section_definition::output_section_name): Return script
section type to caller.
(Output_section_definition::set_section_address): Do not advance
dot value and load address if section type is NOLOAD. Set address
of NOLOAD sections regardless of section flags.
(Output_section_definition::print): Print section type if it is
not SCRIPT_SECTION_TYPE_NONE.
(Output_section_definition::section_type): New method.
(Output_section_definition::script_section_type_name): Ditto.
(Script_sections::output_section_name): Add new parameter
PSECTION_TYPE for returning script section type. Pass it to
section elements. Handle discard sections.
(Sort_output_sections::operator()): Handle NOLOAD sections.
* script-sections.h (Script_sections::Section_type): New enum type.
(Script_sections::output_section_name): Add a new parameter for
returning script section type.
* script.cc (script_keyword_parsecodes): Add keywords COPY, DSECT,
INFO and NOLOAD.
* yyscript.y (union): Add new field SECTION_TYPE.
(COPY, DSECT, INFO, NOLOAD): New tokens.
(opt_address_and_section_type): Change type to output_section_header.
(section_type): New non-terminal
(section_header): Handle section type.
(opt_address_and_section_type): Return section type value.
gold is an ELF linker. It is intended to have complete support for
ELF and to run as fast as possible on modern systems. For normal use
it is a drop-in replacement for the older GNU linker.
gold is part of the GNU binutils. See ../binutils/README for more
general notes, including where to send bug reports.
gold was originally developed at Google, and was contributed to the
Free Software Foundation in March 2008. At Google it was designed by
Ian Lance Taylor, with major contributions by Cary Coutant, Craig
Silverstein, and Andrew Chatham.
The existing GNU linker manual is intended to be accurate
documentation for features which gold supports. gold supports most of
the features of the GNU linker for ELF targets. Notable
omissions--features of the GNU linker not currently supported in
gold--are:
* MEMORY regions in linker scripts
* MRI compatible linker scripts
* cross-reference reports (--cref)
* various other minor options
Notes on the code
=================
These are some notes which may be helpful to people working on the
source code of gold itself.
gold is written in C++. It is a GNU program, and therefore follows
the GNU formatting standards as modified for C++. Source documents in
order of decreasing precedence:
http://www.gnu.org/prep/standards/
http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/C++STYLE
http://www.zembu.com/eng/procs/c++style.html
The linker is intended to have complete support for cross-compilation,
while still supporting the normal case of native linking as fast as
possible. In order to do this, many classes are actually templates
whose parameter is the ELF file class (e.g., 32 bits or 64 bits). The
C++ code is the same, but we don't pay the execution time cost of
always using 64-bit integers if the target is 32 bits. Many of these
class templates also have an endianness parameter: true for
big-endian, false for little-endian.
The linker is multi-threaded. The Task class represents a single unit
of work. Task objects are stored on a single Workqueue object. Tasks
communicate via Task_token objects. Task_token objects are only
manipulated while holding the master Workqueue lock. Relatively few
mutexes are used.
Build requirements
==================
The gold source code uses templates heavily. Building it requires a
recent version of g++. g++ 4.0.3 is known to work. g++ 3.2 and g++
3.4.3 are known to fail.
The linker script parser uses features which are only in newer
versions of bison. bison 2.3 is known to work. bison 1.26 is known
to fail. If you are building gold from an official binutils release,
the bison output should already be included.
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