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The Fiasco µ-Kernel
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Building and Using the Fiasco µ-Kernel

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System Requirements

To compile Fiasco, you need:
  • The GNU C++ compiler, version 4.1, 4.2 or 4.3
  • GNU Binutils recent version.
    The only compilation environment we've tested is Linux/ELF on x86.
  • GNU Make. If GNU Make is not called `make' on your system, substitute its name in the examples below.
  • Perl version 5.6 or higher, needed for preprocessing.
  • Flex and Byacc. (If you don't have Byacc, but Bison, try setting "bison -y" in the L4 configuration menu under "Compilers and Tools". Other Yacc implementations might do it as well.)
  • Python2, needed for the configuration tool, available in the system as python.

To run Fiasco, you need:

  • A PC with an x86 CPU from i486 up. A Pentium-class CPU is recommended. Fiasco doesn't yet support SMP.
  • At least 2 MB of RAM. Fiasco currently can manage up to 1GB RAM.


The steps nessecary to build a Fiasco kernel are as follows:

  1. Get Fiasco and needed modules from our read-only SVN.

    How to get all the needed modules from our SVN is described on the Get DROPS page.

    a) Checkout the hello module to get everything (Recommended):

    The hello module contains more than what is actually needed, so don't be scared!

    b) If you're only interested in Fiasco itself (i.e. compile without Roottask, Sigma0, etc.), the following suffices:

    • l4/tool/preprocess
    • kernel/fiasco

    Don't call make in the l4/tool/preprocess directory, it won't work because of the missing l4 checkout and it's NOT necessary to build Fiasco!

  2. Check configuration. (Only needed when choosing 1a))
    Configure the L4 system libraries and support servers:
    make -C l4 O=/my-user-build-dir oldconfig
    Most likely you do not need to change anything, so oldconfig is ok. If you want to change something you may also take the config target.

    /my-user-build-dir is any directory you like. That's the location where any generated file will be put in.

  3. Compile the L4 system libraries and support servers.

    a) Compilation when you've checked out the whole L4 tree:

    cd l4
    make O=/my-user-build-dir
    This will build all packages that you have checked out and that are necessary to run Fiasco with some programs.

    b) When building Fiasco only:
    Nothing needs to be done here, proceed with the next point.

  4. Compile Fiasco.

    First, create a build directory using:
    cd kernel/fiasco
    make BUILDDIR=/my-kernel-build-dir
    The path given to make BUILDDIR= can either be absolute or relative to kernel/fiasco.

    Now change to your build directory to configure the kernel.

    cd /my-kernel-build-dir
    make menuconfig
    With make menuconfig the kernel configurator will be started. You can now configure your kernel. Use the 'h' key to get help, use the arrow keys to navigate through the menus and space to switch the options, use 'x' to save and exit.

    At this stage, your kernel should be properly configured, so you can proceed to building it:

    This should create a binary named `main' and symbolic link fiasco pointing to main.

    An even faster way to build a preconfigured fiasco kernel is to go to kernel/fiasco and call make fiasco:

    cd kernel/fiasco
    make fiasco
    This will build a fiasco kernel with the ia32-short template in the kernel/fiasco/build directory.

    If you're looking for Fiasco-UX (the Fiasco port to Linux User space), you probably want to take a look at its own page.

Booting Fiasco

To boot Fiasco, you need:
  • The bootstrap binary can be found at <builddir>/bin/$(ARCH)/bootstrap.
    $(ARCH) is something like x86_586 and $(L4API) is something like l4v2.

  • The Fiasco binary at /my-kernel-build-dir/fiasco.

  • The Sigma0 pager. It is the first user-level server started by Fiasco. Sigma0 has been built in step 2 in the previous section. Its binary can be found at <builddir>/bin/$(ARCH)/$(L4API)/sigma0.

  • The resource manager Roottask. Roottask is the second server started by Fiasco.

    Roottask also has been built in step 2 in the previous section. The Roottask binary can be found at <builddir>/bin/$(ARCH)/$(L4API)/roottask.

  • At least one L4 application program. For demonstration purposes, we will use the Hello World server which also has been built in step 2 in the previous section and can be found at <builddir>/bin/$(ARCH)/$(L4API)/hello.

    The L4Linux server is another very popular Fiasco application program.

  • The GRUB bootloader. I won't discuss here how to build and install GRUB; for information about that please visit the GRUB website.

    For the examples below, I'll assume you use the courtesy GRUB boot floppy we provide (see the download page for details).

  • A typical menu.lst file looks as follows:
    title hello world
    kernel (fd0)/bootstrap
    modaddr 0x02000000
    module (fd0)/fiasco -nokdb
    module (fd0)/sigma0
    module (fd0)/roottask
    module (fd0)/hello

When booted, you should see the hello word server repeatedly printing its thread id.

Some notes:

  • If you leave out the "-nokdb" option for Fiasco (see step 3 in the previous section), Fiasco would enter a kernel breakpoint at startup and try to connect to a remote GDB connected via a serial line (COM1).

  • Other Fiasco command line options are documented in the Fiasco online manual page.

Debugging Fiasco

Fiasco can be source-level-debugged using a remote debugger running on a second machine via a serial connection: Just connect one of your test machine's serial ports (default: COM1) to your development host using a null-modem cable. Edit fiasco/src/.gdbinit to match your host's serial port, add "-wait" to the boot option of your GRUB config file, reboot Fiasco, and start your GDB (or your favorite GDB-based debugger) when the "KDB: init" message appears. You can then set breakpoints, continue the execution, and even interrupt Fiasco by typing Control-C in the debugger.

Another way to debug Fiasco is using Fiasco's built-in low-level debugger. This debugger has its own manual, which you can find on the documentation page.

Developing for Fiasco

To develop applications for Fiasco, you can use the L4 development environment, including some libraries in l4/lib. The most important library is Libl4sys which provides C bindings for L4 system calls.

For more information, please visit the L4/x86 Developer's Resources page, and have a look at the Libl4sys manual pages.

If you are developing for L4, we also suggest that you subscribe to the L4-Hackers mailing list.

Reporting a bug in Fiasco

To report a bug in the Fiasco µ-kernel, please use the l4-hackers mailing list.

This document

If you have corrections or additions to this document, please send them to its current maintainer Adam. Thanks.

Last modified: Fri Mar 13 2009, 13.39:11 CET

Team Fiasco