Wednesday, June 25, 2014

[HOWTO] build and run RTEMS on or1ksim

This post describes how to build, configure RTEMS to run on or1ksim emulator. Installing the tool-chain is a prerequisite before applying the steps in this post; if you have not already installed them, check out the steps here and do it. Once the tool-chain are installed and seen in the executable path, you may proceed with the following steps.

1- Set up the work space.

$ mkdir ~/rtems-dev
$ cd ~/rtems-dev

2- Clone my RTEMS project repo

This is temporary, by the end of the project, all the code at my repo should be upstreamed to RTEMS.

$ git clone
$ cd rtems-gsoc2014

3- Switch to or1k branch

I have created a branch for the project to help me with arranging and generating patches against master; meanwhile, keep master branch synchronized with remote.

$ git checkout or1k

4- bootstrap

$ bootstrap -p
$ bootstrap

5- Configuring and building 

$ cd ../
$ mkdir b-rtems
$ cd b-rtems
$ ../rtems-gsoc2014/configure --target=or1k-rtems4.11 --enable-rtemsbsp=or1k_or1ksim --disable-posix --disable-itron --disable-networking --disable-smp

You should get hello and ticker applications in their executable form. Other applications/tests will fail to compile because of other features/implementations that are not supported yet.

Running and debugging hello.exe

1- First you should have an or1ksim configuration script suitable for or1ksim BSP. This is the sim.cfg file I use at this stage of the project. It should be placed at your home directory. Note that as long as more features like: FP, cache manager, MMU manager are added, this file has to be changed to simulate these functionalists on or1ksim.

2- Run hello application on or1ksim.

The configuration file uses RSP (remote protocol) to enable GDB to connect to or1ksim. So, when running or1ksim, it reads configuration script, loads the program into the proper addresses, and waits for GDB to connect.

$ cd $HOME/rtems-dev/b-rtems/or1k-rtems4.11/c/or1k_or1ksim/testsuites/samples/hello/
$ or32-elf-sim -f ~/sim.cfg hello.exe

You should get something similar to the following picture:

3- Run GDB and connect to or1ksim 

From another terminal run GDB and connect to or1ksim

$ or1k-rtems4.11-gdb $HOME/rtems-dev/b-rtems/or1k-rtems4.11/c/or1k_or1ksim/testsuites/samples/hello/hello.exe

From gdb, attach it to or1ksim

(gdb) target remote :50001 
(gdb) continue

UART should emit the string output to or1ksim (and any other channel you provided in configuration script)


RTEMS kernel port for OpenRISC | Status Report - 25062014

As introduced before, this year I'm porting RTEMS to OpenRISC 1000 architecture during GSoC program. Other than getting the tool-chain built for RTEMS, the project is mainly about RTEMS kernel. In this post, I'll list the latest updates, concerning RTEMS kernel, that have been achieved so far. The current status is that RTEMS hello and ticker samples can run on or1ksim (see HOTWO build and run RTEMS for OpenRISC).

The code is in its earlier stages, and there is a lot more to do; though, the current code is fairly simple enough that allows anyone to build RTEMS and get hello and ticker samples exes. The project is spread out across RTEMS main components (directories):


Other than generic APIs, this directory should include shared stuff for any CPU that RTEMS supports; and now it includes or1k. Mainly, it provides details, definitions, configurations, and code for each CPU family for a given architecture. For or1k, the only family is OR1200. It contains processor configurations and properties embedded in .h, .c .S files like:
  • In which direction the stack grows. For or1200 the stack is growing down.
  • FP unit presence. There is no handling code for FP currently, it's on my TODO list.
  • Endianess. Big endian.
  • Context Control. This is a structure containing necessary processor context (registers) to be saved/retrieved during context switches. Currently, all general purpose registers are saved as well as supervision register; this is to be optimized in the future.
  • Processor definitions. This includes macros for first group of registers that all architectures should implement; most notably supervision register. 
  • Context Initialize. This function is implemented to support RTEMS multi-tasking. Initially, it sets elements of Context Control struct including: beginning address of the stack into sp (stack pointer) register and fp (frame pointer) register, loading lr (link register) and sr (supervision register). It's called part of the process of starting multi-tasking.
  • Context Switch. The most important function for multi-tasking. Functionality of context switching is supplied via an assembly file called or1k-context-switch.S. This file contains or1k assembly instructions for saving/restoring processor context. It's always invoked for any multi-tasking application.  

There is not any cache or MMU managers currently, this is on my TODO list.


libbsp is directory that includes every BSP (Board Support Package) for each architecture. For or1k, a new or1ksim BSP is added as an interface to or1k port; it's intended to run on or1ksim emulator. The new BSP contains:

start code

start code is the entry point for the program; it's resposible for providing abstract ISR handlers. For or1ksim, reset and timer handlers are the only statically installed handlers currently. _reset simply jumps to _start which does the following:
  1. Load stack and frame pointers.
  2. Clear .bss section. 
  3. Call bootcard function.
bootcard is a major part for linking BSPs and CPUKIT libraries, it acts as a coordinator from the beginning of initializing the board along with initializing RTEMS data structures, initializing drivers, multi-tasking, etc. The steps an application goes through from the time the first BSP code is executed until the first application task executes are illustrated in the following figure.


This is the linker script describing how the exe code will fit into memory, defining linker symbols that are used in other areas of RTEMS, and handling alignments. The structure of how or1ksim BSP utilizes memory is described in the following figure.

linker symbols 

linker-symbols.h externs all linker symbols for other RTEMS components that may use it. For example, this file is required for initializing context control (in cpukit), zeroing .bss section, and initializing stack and frame registers.

Console driver

Console driver is using UART. For or1ksim simulator, a configuration script is provided to map UART registers to base address 0x90000000. It's working on 115200 baud rate. The process of initializing the console driver includes initializing UART control. Also, the driver implements send_char(), which is used to implement printf, printk within higher layers. Currently, this is the only way we can get output to stdout. or1ksim can be configured to use xterm, tty0, or other channels for rx and/or tx.

Clock driver

Clock driver is essential for RTEMS scheduling purposes and some applications like ticker. The current clock driver implements initialization and tick facility. It should install the tick timer handler into the proper vector location and generate timer interrupt every N ticks. Number of ticks that fire an interrupt is calculated from some RTEMS configurations and the board frequency (100 MHz for or1ksim).  

The clock driver currently is not working in real-time, however, it makes multi-tasking and scheduling working. This issue is to be fixed soon. Also, on my TODO list, the implementation of RTEMS timer benchmark.


IRQ implementation is almost null; once creating IRQ manager for or1ksim (next task), I will generate patches for or1k port to RTEMS to be upstreamed.

In the following post, I will describe HOWTO get, configure, install, run, debug RTEMS application samples (hello and ticker) from my repo. Eventually (by the end of the project), all this code should be upstreamed to RTEMS so that anyone can build RTEMS for or1k like any other target.


Tuesday, June 24, 2014

[HOWTO] Build RTEMS tool-chain for OpenRISC targets

This post provides two methods of building RTEMS tool-chain for OpenRISC 1000 architecture: 1) building from RSB (RTEMS Source Builder) and 2) building each tool/program separately by downloading official tools' releases and apply our RTEMS specific patches to them. Merely, RSB is responsible for all the stuff including: setting up the environment, downloading releases, applying patches, configuring, building, and installing all the tools. The resulted tools should be program prefixed with or1k-rtems4.11-*. You may want to have a look at OpenRISC ELF GNU tool-chain; but note that RTEMS applications can't be built via these tools. The tool-chain has been tested and used on Fedora 20 and Ububtu 12.04 LTS. 

The tools/programs releases in the time being this post was written are:

  • binutils-2.24
  • gcc-4.8.2
  • newlib-2.1.0
  • gdb-7.7
  • or1ksim-github-head

Building RTEMS from RSB

Please have a look at RSB documentation here. It provides details in a thorough manner about RSB: how to download RSB, check environment, build RTEMS tool-chain for a specific target. Also, it gives a clear picture how RSB works internally.

1- Setup development and work space

$mkdir ~/rtems-dev
$cd ~/rtems-dev

2- Clone RSB 

$ git clone git://
$ cd rtems-source-builder

3- Check host environment

Check if host environment is setup correctly.
$ source-builder/sb-check
This command will tell you if any packages are required to be installed, if you miss any, please install them and try again, once every thing is Ok, you should have the following message:
$ source-builder/sb-check
RTEMS Source Builder environment is ok

 4- Building

$ cd rtems
$ ../source-builder/sb-set-builder --log=l-or1k.txt --prefix=$HOME/rtems-dev/rtems/4.11 \ 4.11/rtems-or1k

5- Check if all tools are installed successfully. You should get the following results

$ ls $HOME/rtems-dev/rtems/4.11
bin include lib libexec share or1k-rtems4.11
$ ls $HOME/development/rtems/4.11/bin

6- Add the newly installed tool-chain to the executable PATH

$ export PATH=$PATH:/$HOME/development/rtems/4.11/bin

Building RTEMS manually 

Currently, all or1k and RTEMS related patches are not upstreamed. So, we have to download official releases and apply patches to support or1k and RTEMS to them. I have worked on combining both or1k and RTEMS patches for all the tools against official tool releases. The following method of building the tools should be temporal. Eventually all patches including or1k and RTEMS should be upstreamed and tools should be built without patches provided here. 

1- Setup development and work space

$mkdir ~/rtems-dev
$cd ~/rtems-dev

2- Get the sources

3- Get the patches

Download all patches for the previous binutils, gcc, newlib, gdb releases from my repopreferably, the latest patches (with respect to commit time). Put them in the same directory. 

4- Unpack archives 

$ tar xf binutils*.tar.* 
$ tar xf gcc*.tar.* 
$ tar xf newlib*.tar.* 
$ tar xf gdb*.tar.

5- Apply patches

$ cd binutils-2.24
$ cat ../binutils*.diff | patch -p1
$ cd ../gcc-4.8.2
$ cat ../gcc*.diff | patch -p1
$ cd ../newlib-2.1.0$ cat ../newlib*.diff | patch -p1
$ cd ../gdb-7.7
cat ../gdb*.diff | patch -p1
 $ cd ../ 

6- Configure and build tools

  • Create build directories for all the tools
$ mkdir b-binutils b-gcc b-gdb

  • Configure and build binutils
$ cd b-binutils
$ ../binutils-2.24/configure --target=or1k-rtems4.11 --prefix=$HOME/rtems-dev/rtems/4.11
$ make
$ make install

  • Setup the PATH to include binutils binaries 
$ export PATH=$PATH:/$HOME/rtems-dev/rtems/4.11/bin

  • Link newlib into gcc directory
$ cd ../gcc-4.8.2/
$ ln -s ../newlib-2.1.0/newlib .

  • Configure and build gcc and newlib
$ cd ..
$ cd b-gcc
$ ../gcc-4.8.2/configure --target=or1k-rtems4.11 --prefix=$HOME/rtems-dev/rtems/4.11 --with-gnu-as --with-gnu-ld --enable-languages="c,c++" --enable-threads --disable-libssp --with-newlib --with-system-zlib --disable-libstdcxx-pch --disable-nls --without-included-gettext --disable-win32-registry --disable-lto --enable-newlib-io-c99-formats
$ make 
$ make install
  • Configure and build gdb
$ cd ../
$ cd b-gdb$ ../gdb-7.7/configure --target=or1k-rtems4.11 \
--prefix=$HOME/rtems-dev/rtems/4.11 \
--verbose --disable-nls \
--without-included-gettext \
--disable-win32-registry \
--disable-werror \
--disable-sim} \
--without-zlib \
--with-expat \
--with-python} \

Building or1ksim

You can follow instructions here to build and configure OpenRISC simulator- or1ksim. Patch for building or1ksim from RSB is on its way to be commited soon.

RTEMS (or1k-rtems4.11-*) tool-chain for OpenRISC | Status Report - 25062014

Part of my GSoC project: Porting RTEMS to OpenRISC, I worked on hacking GNU tools to be able to build these tools for RTEMS targeting OpenRISC 1000 (AKA OR1K) architecture. These tools include: binutils, GCC and GDB. Besides, I had to work on Newlib port for OR1K since RTEMS depends on it. or1ksim (OR1K main emulator) is also part of the tool-chain. Currently, all the tools are working fine.

First I will list the status of each tool/program separately. After that (in the next few posts), we will come to the process of building the tool-chain. The following descriptions are concerned with some specific releases:

  • binutils-2.24
  • gcc-4.8.2
  • newlib-2.1.0
  • gdb-7.7
  • or1ksim-github-head


There has a been a small patch for binutils to support building it for RTEMS. No big deal with it. Recently, supporting or1k for binutils has been upstreamed; so the next task for RTEMS is to push our patch for review and be upstream to binutils cvs repo.


RTEMS depends on Newlib as a library instead of the big libgcc one. Mainly, only Newlib/newlib is necessary for RTEMS. libgloss is not used because RTEMS should provide all the functions and systems calls there. There are some issues regarding Licences and a possibility that the or1k Newlib port may not be upstreamed consequently. Hence, I had to revert back to an old patch to avoid such conflicts. Also, I did not include all of libgloss code. Moreover, I had to write setjmp.S from scratch for the same reason.


Most of GCC work was about configurations. Some other definitions had to be added to include the proper headers for RTEMS and avoid others from OR1K. libgloss libraries for BSPs provided by OR1K are no longer linked by default (since RTEMS does not use any of them). To test my Newlib port, I had to link bare-metal applications with libnosys.a. Eventually GCC is working fine with Newlib.


A minimal effort was spent on GDB. It should be built without or1ksim embedded as built-in library. Instead, the current method of debugging with GDB, is to remotely attach it to or1ksim emulator via RSP protocol.


The OpenRISC simulator is just used as is from github. Anyone who uses or1ksim should provide a configuration script for his or her target. This is the current sim.cfg script I use to run or1ksim RTEMS BSP. It should be added to your home directory or the current directory you run the simulator from.

RSB (RTEMS Source Builder)

In the time being, all of the previous tools (excluding or1ksim) can be built from RSB; it's the latest modern tool RTEMS uses to build all the tool-chain for targets that RTEMS support. Therefor, I had to add support to RSB to build rtems4.11-or1k-* tool-chain. The patch for such a purpose is committed, so any one can clone RSB and build the entire tool-chain from it. Building the tool-chain from RSB is the easiest way.

In the next few posts, I will introduce some tutorials HOWTO build the tool-chain both manually and from RSB.


[1] Porting RTEMS to OpenRISC - Introduction 
[2] My github project repo (RTEMS).
[3] RTEMS or1k tool-chain status.
[4] HOWTO build or1k-rtems4.11 tool-chain.
[5] or1k/rtems related stuff.
[6] tool-chain patches