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+/*
+ * Copyright (c) 2011-2013, Chris Johns <chrisj@rtems.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/**
+ * @mainpage RTEMS Linker Tools
+ *
+ * The RTEMS Linker is a suite of tools that create and manage @subpage rtems-apps
+ * that are dynamically loadable by the @subpage rtems-rtl on target
+ * hardware. The target code uses the standard `dlopen`, `dlclose` type calls
+ * to load and manage modules, object files or archives on the target at
+ * runtime. The RTEMS Linker forms a part of this process by helping managing
+ * the object files, libraries and applications on a host machine. This host
+ * processing simplifies the demands on the target and avoids wastefull excess
+ * of files and data that may not be used at runtime.
+ *
+ * These tools are written in C++ with some 3rd party packages in C. The
+ * license for this RTEMS Tools code is a BSD type open source license. The
+ * package includes code from:
+ *
+ * -# @b efltoolchain - http://sourceforge.net/apps/trac/elftoolchain/
+ * -# @b libiberty - Libiberty code from GCC (GPL)
+ * -# @b fastlz - http://fastlz.org/
+ *
+ * The project uses a C++ demangler and PEX code from the GCC project. This
+ * code is GPL making this project GPL. A platform independent way to execute
+ * sub-processes and capture the output that is not GPL is most welcome.
+ *
+ * @subpage build-me details building this package with @subpage waf.
+ *
+ * The tools provided are:
+ *
+ * - @subpage rtems-ld
+ * - @subpage rtems-syms
+ * - @subpage rtems-rap
+ *
+ * ____________________________________________________________________________
+ * @copyright
+ * Copyright (c) 2011-2013, Chris Johns <chrisj@rtems.org>
+ * @copyright
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ * @copyright
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+/**
+ * @page rtems-apps RTEMS Applications
+ *
+ * The RTEMS Linker and @ref rtems-rtl provides RTEMS with the ability to
+ * support applications loaded and linked at runtime. RTEMS is a single address
+ * space real-time operating system designed for embedded systems that are
+ * statically linked therefore the idea of applications requires some extra
+ * understanding when applied to RTEMS. They are not essential, rather they are
+ * important in a range of systems that have the resources available to support
+ * them.
+ *
+ * Applications allow:
+ *
+ * - A team to create a single verified base kernel image that is used by all
+ *   team developers. This kernel could be embedded on the target hardware and
+ *   applications loaded over a network. The verified kernel binary used during
+ *   development can be shipped without being changed.
+ *
+ * - Layered applications designed as modules that are loaded at runtime to
+ *   create a specific target environment for a specific system. This approach
+ *   allows development of modules that become verified components. An example
+ *   is the NASA Core Flight Executive.
+ *
+ * - Runtime configuration and loading of features or drivers based on
+ *   configuration data or detected hardware. This is important if your target
+ *   hardware has an external bus such as PCI. You can add a new driver to a
+ *   system without needing to rebuild the kernel and application lowering the
+ *   verify and validation costs. If these are high the savings can be
+ *   substantial.
+ *
+ * RTEMS is a single address space operating system therefore any code loaded
+ * is loaded into that address space. This means applications are not operating
+ * in a separate protected address space you typically get with host type
+ * operating systems. You need to control and manage what you allow to load on
+ * your system. This is no differerent to how single image RTEMS are currently
+ * created and managed. The point being RTEMS applications only changes the way
+ * you package and maintain your applications and do not provide any improved
+ * security or protection. You need to do this as your currently do with
+ * testing and careful design.
+ *
+ * RTEMS is statically linked to a fixed address and does not support dynamic
+ * ELF files. Dynamic ELF files are designed for use in virtual memory
+ * protected address space operating systems. They contain Position Independent
+ * Code (PIC) code, Procedure Linkage Tables (PLT) and Global Offset Tables
+ * (GOT) and are effective in not only allowing dynamic linking at runtime but
+ * also the sharing of the code between separate process address spaces. Using
+ * virtual memory and a memory management unit, a protected address space
+ * operating system can efficiently share code between processes with minimal
+ * performance overhead. RTEMS has no such need because it is a single address
+ * space and all code is shared therefore ELF dynamic files only add complexity
+ * and performance overhead. This means RTEMS needs a target based run-time
+ * link editor that can relocate and fix up static code when loading it and
+ * RTEMS loadable files need to contain the symbols and relocation records to
+ * allow relocation to happen.
+ *
+ * The @ref rtems-rtl supports the followiing file formats:
+ *
+ * -# Relocatable ELF (ELF)
+ * -# RTEMS Application (RAP)
+ * -# Archive (AR) Libraries with GNU extensions
+ *
+ * ### Relocation ELF Files
+ *
+ * The @ref rtems-rtl can load standard relocatable ELF format files. They can
+ * be stripped or unstripped. This ELF file is the standard output from the
+ * compiler and is contained in the standard libraries.
+ *
+ * ### RTEMS Application (RAP) Files.
+ *
+ * The @ref rtems-rtl can load RAP format files. This format is RTEMS specific
+ * and is designed to minimise the overhead and resources needed to load the
+ * file on the target. A RAP file is compressed using LZ77 compression and
+ * contains only the following sections:
+ *
+ * - `.text` - The executable code section.
+ * - `.const` - The constants and strings section.
+ * - `.ctor` - The constructor table section.
+ * - `.dtor` - The destructor table section.
+ * - `.data` - The initialised data section.
+ *
+ * The `.bss` uninitialised data section is only a size. A RAP file also
+ * contains a symbol string table and symbol table that are directly loadable
+ * into into the target memory. Finally the RAP contains the relocation
+ * records. The format is structured so it can be read and processed as a
+ * stream with the need to seek on the file.
+ *
+ * The @ref rtems-ld can output RAP format files suitable for loading. It will
+ * take the object files from the command line and the referenced files from
+ * the libraries and merge all the sections, symbols and relocation records to
+ * create the RAP format file.
+ *
+ * RAP format files are the most efficient way to load applications or modules
+ * because all object files are merged into an single image. Each file loaded
+ * on the target has and overhead therefore lowering the number of files loaded
+ * lowers the overhead. You could also use the standard linker to incrementally
+ * link the command line object files to archieve the same effect.
+ *
+ * ### Archive (AR) Library Files
+ *
+ * The @ref rtems-rtl can load from archive ior library type files. The file
+ * name syntax lets a user reference a file in an archive. The format is:
+ *
+ * @par
+ * `libme.a:foo.o@12345`
+ *
+ * where `libme.a` is the archive file name, `foo.o` is the file in the archive
+ * and `@12345` is optionally the offset in the archive where the file
+ * starts. The optional offset helps speed up load by avoiding the file name
+ * table search. If the archive is stable and known the offset will be
+ * fixed. If the file is located at the offset the file name table is searched.
+ *
+ * At this point in time only ELF files can be loaded from archives. Loading of
+ * RAP format files is planned.
+ *
+ * ## An Application
+ *
+ * Applications are created the same way you create standard host type
+ * programs. You compile the source files and link them using the @ref
+ * rtems-ld.
+ *
+ * @code
+ * $ rtems-ld --base my-rtems foo.o bar.o -o my-app.rap -L /lib/path -lstuff
+ * @endcode
+ *
+ * The command line of the @ref rtems-ld is similar to a standard linker with
+ * some extra features specific to RTEMS. You provide a list of object files,
+ * libraries and library paths plus you need to provide the RTEMS kernel image
+ * you will use to load the application. The RTEMS kernel image provides the
+ * symbols in the kernel to the linker. Errors will be generated if symbols are
+ * not located.
+ *
+ * The linker can output a archive of ELF files, a RAP file for a text script
+ * of files that need to be loaded.
+ *
+ * The script lets you load and link the application at runtime on the
+ * target. You need to copy the libraries referenced to the target.
+ *
+ * If you break your application into separate modules and each module
+ * references a symbol in a library that is not in the base image the linker
+ * will include the object file containing the symbol into each application
+ * module. This is only of concern for the RAP format because it merges the
+ * object files together. With the archive and scripts the loader will not load
+ * object files with duplicate symbols.
+ *
+ * @note In time the linker will gain an option to not pull object modules from
+ *       libraries into the RAP file. Another option will be added that will
+ *       copy referenced library object files into a target library all
+ *       application modules can share.
+ *
+ * ## Linking
+ *
+ * The @ref rtems-ld places the command line object files in the output image
+ * and any reference object files found in libraries. If a symbol is located in
+ * the kernel base image it is not searched for in the libraries.
+ *
+ * The architecture is automatically detected by inspecting the first object
+ * file passed on the command line. All future object files loaded must match
+ * the architecture for an error is raised. The linker supports all
+ * architectures in a single binrary. It is not like the GNU tools which are
+ * specific to an architecture.
+ *
+ * The linker needs to be able to locate the C compiler for the architecture
+ * being linked. The compiler can be in the path for a command line option can
+ * explicitly set the compiler. The compiler is used to locate the standard
+ * libraries such as the C library.
+ *
+ *
+ */
+
+/**
+ * @page rtems-rtl RTEMS Target Link Editor
+ *
+ * The RTEMS Target link editor is a C module you link to the RTEMS kernel to
+ * provide the `dlopen`, `dlclose` etc family of calls. This code is a stand
+ * alone project:
+ *
+ * @par
+ * http://git.rtems.org/chrisj/rtl.git
+ */
+
+/**
+ * @page build-me Building The RTEMS Linker
+ *
+ * This package is written in C++ therefore you need a current working C++
+ * compiler for your host. The GCC or clang compilers can be used and clang was
+ * used during the development. The build system is @ref waf.
+ *
+ * -# Clone the git repository:
+ * @code
+ * $ git clone http://git.rtems.org/chrisj/rtl-host.git rtl-host.git
+ * @endcode
+ * -# Configure with the default C++ compiler, default options, and an install
+ * prefix of `$HOME/development/rtems/4.11`:
+ * @code
+ * $ waf configure --prefix=$HOME/development/rtems/4.11
+ * @endcode
+ * With @ref waf you build in the source directory and the @ref waf script
+ * (`wscript`) will create a host specific directory. On MacOS the output is in
+ * `build-darwin`. If you clean the build tree by deleting this directly you
+ * will need to run the configure stage again.
+ * @note The nominal RTEMS prefix is `/opt/rtems-4.11` where `4.11` is the
+ *       version of RTEMS you are building the tools for. If you are using
+ *       RTEMS 4.10 or a different version please use that version number. I
+ *       always work under my home directory and under the `development/rtems`
+ *       tree and then use the version number.
+ * -# Build the tools:
+ * @code
+ * $ waf
+ * @endcode
+ * -# Install the tools to the configured prefix:
+ * @code
+ * $ waf install
+ * @endcode
+ *
+ * You will now have the tools contained in this package build and installed.
+ *
+ * At this stage of the project's development there are no tests. I am wondering
+ * if this could be a suitable GSoC project.
+ *
+ * To build with `clang` use the documented @ref waf method:
+ * @code
+ * $ CC=clang waf configure --prefix=$HOME/development/rtems/4.11
+ * @endcode
+ *
+ * You can add some extra options to @ref waf's configure to change the
+ * configuration. The options are:
+ * @code
+ * --rtems-version=RTEMS_VERSION
+ *                       Set the RTEMS version
+ * --c-opts=C_OPTS       Set build options, default: -O2.
+ * --show-commands       Print the commands as strings.
+ * @endcode
+ *
+ * - @b --rtems-version Set the RTEMS version number.
+ * Not used.
+ * - @b --c-opts Set the C and C++ compiler flags the tools are built with. For
+ * example to disable all optimization flags to allow better debugging do:
+ * @code
+ * $ waf configure --prefix=$HOME/development/rtems/4.11 --c-opts=
+ * @endcode
+ * - @b --show-commands Prints the command string used to the invoke the
+ *   compiler or linker. @ref waf normally prints a summary type line.
+ *
+ */
+
+/**
+ * @page waf Waf
+ *
+ * It is best you install waf by just downloading it from the Waf project
+ * website:
+ *
+ * @par
+ * http://code.google.com/p/waf/
+ *
+ * Waf is a Python program so you will also need to have a current Python
+ * version installed and in your path.
+ *
+ * I download the latest "run from writable folder" version named single waf
+ * file from http://code.google.com/p/waf/downloads/list to `$HOME/bin` and
+ * symlink it to `waf`. The directory `$HOME/bin` is in my path.
+ *
+ * @code
+ * $ cd $HOME/bin
+ * $ curl http://waf.googlecode.com/files/waf-1.7.9 > waf-1.7.9
+ *   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
+ *                                  Dload  Upload   Total   Spent    Left  Speed
+ * 100 90486  100 90486    0     0  39912      0  0:00:02  0:00:02 --:--:-- 79934
+ * $ rm -f waf
+ * $ chmod +x waf-1.7.9
+ * $ ln -s waf-1.7.9 waf
+ * $ ./waf --version
+ * waf 1.7.9 (9e92489dbc008e4abae9c147b1d63b48296797c2)
+ * @endcode
+ */
+
+/**
+ * @page rtems-ld RTEMS Linker
+ *
+ * The RTEMS Linker is a single tool that lets you create applications. It is a
+ * special kind of linker and does not perform all the functions found in a
+ * normal linker. RAP format output performs a partial increment link.
+ *
+ * ## Command
+ *
+ * `rtems-ld [options] objects`
+ *
+ * ## Options
+ *
+ * - @e Help (@b -h @b --help): \n
+ *   Print the command line help then exit.
+ *
+ * - @e Version (@b -V @b --version): \n
+ *   Print the linker's version then exit.
+ *
+ * - @e Verbose (@b -v @b --verbose): \n
+ *   Control the trace output level. The RTEMS linker is always built with
+ *   trace logic. The more times this appears on the command the more detailed
+ *   the output becomes. The amount of output can be large at higher levels.
+ *
+ * - @e Warnings (@b -w @--warn): \n
+ *   Print warnings.
+ *
+ * - @e Map (@b -M @b --map): \n
+ *   Generate map output to stdout.
+ *
+ * - @e Output (@b -o @b --output): \n
+ *   Set the output file name.
+ *
+ * - @e Output @e Format (@b -O @b --out-format): \n
+ *   Set the output format. The valid formats are:
+ *    Format     | Description
+ *    -----------|----------------------------------------
+ *    @b rap     |RTEMS application (LZ77, single image)
+ *    @b elf     |ELF application (script, ELF files)
+ *    @b script  |Script format (list of object files)
+ *    @b archive |Archive format (collection of ELF files)
+ *
+ * - @e Library @e Path (@b -L @b --lib-path): \n
+ *   Add a library path. More than one path can be added with multiple library
+ *   path options.
+ *
+ * - @e Library (@b -l @b --lib): \n
+ *   Add a library. More than one library can be added with multiple library
+ *   paths.
+ *
+ * - @e No @e Standard @e Libraries (@b -n @b --no-stdlibs): \n
+ *   Do not search the standard libraries. The linker uses the architecture C
+ *   compiler to locate the installed standard libraries and these are
+ *   automatically searched. If this option is used the C compiler is not
+ *   called and the libraries are not added to the search list.
+ *
+ * - @e Entry @e Point (@b -e @b --entry): \n
+ *   Set the entry point. This is used with the RAP format and defaults to
+ *   `rtems`. The entry point is called when a RAP file is loaded by the
+ *   target RAP loader.
+ *
+ * - @e Define @e Symbol (@b -d @b --define): \n
+ *   Add a symbol to the symbol table. More than one symbol can be added
+ *   with multiple define options.
+ *
+ * - @e Undefined @e Symbol (@b -u @b --undefined): \n
+ *   Add an undefined symbol to the undefined symbol list. More than one
+ *   undefined symbol can be added with multiple undefined options. This
+ *   options will pull specific code into the output image.
+ *
+ * - @e RTEMS @e Kernel (@b -b @b --base): \n
+ *   Set the RTEMS kernel image. This is the ELF file of the RTEMS kernel
+ *   that will load the output from the linker. The RTEMS kernel is the
+ *   @e base module or image. The linker does not pull the symbol from a
+ *   library if the symbol is found in the base module. The kernel will
+ *   load the target symbol table with these symbols so they can be
+ *   resolved at runtime.
+ *
+ * - @e Architecture @e C @e Compiler (@b -C @b --cc): \n
+ *   Set the architecture's C compiler. This is used to find the standard
+ *   libraries.
+ *
+ * - @e Tool @e Prefix (@b -E @b --exec-prefix): \n
+ *   Set the tool prefix. The tool prefix is the architecture and this is
+ *   normally automatically set by inspecting the first object file
+ *   loaded. This option allows the automatic detection to be overridden.
+ *
+ * - @e Machine @e Architecture (@b -a @b --march): \n
+ *   Set the machine architecture.
+ *
+ * - @e Machine @e CPU (@b -c @b --mcpu): \n
+ *   Set the machine architecture's CPU.
+ */
+
+/**
+ * @page rtems-syms RTEMS Symbols Utility
+ *
+ * The symbols tool lets you see symbols in various RTEMS support file formats.
+ */
+
+/**
+ * @page rtems-rap RTEMS Application (RAP) Utility
+ *
+ * The symbols tool lets you see symbols in various RTEMS support file formats.
+ */