Tools Used in 6.828

You'll use two sets of tools in this class: an x86 emulator, QEMU, for running your kernel; and a compiler toolchain, including assembler, linker, C compiler, and debugger, for compiling and testing your kernel. This page has the information you'll need to download and install your own copies. This class assumes familiarity with Unix commands throughout.

We highly recommend using a Debathena machine, such as, to work on the labs. If you use the MIT Athena machines that run Linux, then all the software tools you will need for this course are located in the 6.828 locker: just type 'add -f 6.828' to get access to them.

If you don't have access to a Debathena machine, we recommend you use a virtual machine with Linux. If you really want to, you can build and install the tools on your own machine. We have instructions below for Unix and MacOS computers.

It should be possible to get this development environment running under windows with the help of Cygwin. Install cygwin, and be sure to install the flex and bison packages (they are under the development header).

For an overview of useful commands in the tools used in 6.828, see the lab tools guide.

Compiler Toolchain

A "compiler toolchain" is the set of programs, including a C compiler, assemblers, and linkers, that turn code into executable binaries. You'll need a compiler toolchain that generates code for 32-bit Intel architectures ("x86" architectures) in the ELF binary format.

Test Your Compiler Toolchain

Modern Linux and BSD UNIX distributions already provide a toolchain suitable for 6.828. To test your distribution, try the following commands:

% objdump -i

The second line should say elf32-i386.

% gcc -m32 -print-libgcc-file-name

The command should print something like /usr/lib/gcc/i486-linux-gnu/version/libgcc.a or /usr/lib/gcc/x86_64-linux-gnu/version/32/libgcc.a

If both these commands succeed, you're all set, and don't need to compile your own toolchain.

If the gcc command fails, you may need to install a development environment. On Ubuntu Linux, try this:

% sudo apt-get install -y build-essential gdb

On 64-bit machines, you may need to install a 32-bit support library. The symptom is that linking fails with error messages like "__udivdi3 not found" and "__muldi3 not found". On Ubuntu Linux, try this to fix the problem:

% sudo apt-get install gcc-multilib

Using a Virtual Machine

Otherwise, the easiest way to get a compatible toolchain is to install a modern Linux distribution on your computer. With platform virtualization, Linux can cohabitate with your normal computing environment. Installing a Linux virtual machine is a two step process. First, you download the virtualization platform.

VirtualBox is a little slower and less flexible, but free!

Once the virtualization platform is installed, download a boot disk image for the Linux distribution of your choice.

This will download a file named something like ubuntu-10.04.1-desktop-i386.iso. Start up your virtualization platform and create a new (32-bit) virtual machine. Use the downloaded Ubuntu image as a boot disk; the procedure differs among VMs but is pretty simple. Type objdump -i, as above, to verify that your toolchain is now set up. You will do your work inside the VM.

Building Your Own Compiler Toolchain

This will take longer to set up, but give slightly better performance than a virtual machine, and lets you work in your own familiar environment (Unix/MacOS). (We believe the instructions work for MacOS too, but haven't confirmed recently. If it works, let's us know.)

You can use your own tool chain by adding the following line to conf/


We assume that you are installing the toolchain into /usr/local. You will need a fair amount of disk space to compile the tools (around 1GiB). If you don't have that much space, delete each directory after its make install step.

Download the following packages:

(You may also use newer versions of these packages.) Unpack and build the packages. The green bold text shows you how to install into /usr/local, which is what we recommend. To install into a different directory, $PFX, click herenote the differences in lighter type (hide). If you have problems, see below.

tar xjf gmp-5.0.2.tar.bz2 cd gmp-5.0.2 ./configure --prefix=/usr/local--prefix=$PFX make make install # This step may require privilege (sudo make install) cd .. tar xjf mpfr-3.0.1.tar.bz2 cd mpfr-3.0.1 ./configure --prefix=/usr/local--prefix=$PFX --with-gmp=$PFX make make install # This step may require privilege (sudo make install) cd .. tar xzf mpc-0.9.tar.gz cd mpc-0.9 ./configure --prefix=/usr/local--prefix=$PFX --with-gmp=$PFX --with-mpfr=$PFX make make install # This step may require privilege (sudo make install) cd .. tar xjf binutils-2.21.1.tar.bz2 cd binutils-2.21.1 ./configure --prefix=/usr/local--prefix=$PFX --target=i386-jos-elf --disable-werror make make install # This step may require privilege (sudo make install) cd .. i386-jos-elf-objdump -i # Should produce output like: # BFD header file version (GNU Binutils) 2.21.1 # elf32-i386 # (header little endian, data little endian) # i386... tar xjf gcc-core-4.6.1.tar.bz2 cd gcc-4.6.1 mkdir build # GCC will not compile correctly unless you build in a separate directory cd build ../configure --prefix=/usr/local--prefix=$PFX --with-gmp=$PFX --with-mpfr=$PFX --with-mpc=$PFX \ --target=i386-jos-elf --disable-werror \ --disable-libssp --disable-libmudflap --with-newlib \ --without-headers --enable-languages=c
MAC OS X 10.7 "LION" NOTE: The default clang compiler on Mac OS X 10.7 cannot build a working version of GCC. Use the following configure line to work around the problem (this has reported to work with OS X 10.9.4 withXCode 5.1.1 and its Command Line Tools package (for gcc): ../configure --prefix=/usr/local--prefix=$PFX --with-gmp=$PFX --with-mpfr=$PFX --with-mpc=$PFX \ --target=i386-jos-elf --disable-werror \ --disable-libssp --disable-libmudflap --with-newlib \ --without-headers --enable-languages=c \ CC=/usr/bin/gcc-4.2 \ make all-gcc make install-gcc # This step may require privilege (sudo make install-gcc) make all-target-libgcc make install-target-libgcc # This step may require privilege (sudo make install-target-libgcc) cd ../.. i386-jos-elf-gcc -v # Should produce output like: # Using built-in specs. # COLLECT_GCC=i386-jos-elf-gcc # COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/i386-jos-elf/4.6.1/lto-wrapper # Target: i386-jos-elf tar xjf gdb-7.3.1.tar.bz2 cd gdb-7.3.1 ./configure --prefix=/usr/local--prefix=$PFX --target=i386-jos-elf --program-prefix=i386-jos-elf- \ --disable-werror make all make install # This step may require privilege (sudo make install) cd ..


Q. I can't run make install because I don't have root permission on this machine.
A. Our instructions assume you are installing into the /usr/local directory. However, this may not be allowed in your environment. If you can only install code into your home directory, that's OK. In the instructions above, replace --prefix=/usr/local with --prefix=$HOME (and click here to update the instructions further). You will also need to change your PATH and LD_LIBRARY_PATH (Linux) or DYLD_LIBRARY_PATH (Mac OS X) environment variables, to inform your shell where to find the tools. For example:
export PATH=$HOME/bin:$PATH
Enter these lines in your ~/.bashrc file so you don't need to type them every time you log in.
Q. My build fails with an inscrutable message about "library not found".
A. You need to set your LD_LIBRARY_PATH (Linux) or DYLD_LIBRARY_PATH (Mac OS X) environment variable to include the libraries you built; see above. The environment variable must include the PREFIX/lib directory (for instance, /usr/local/lib).

QEMU Emulator

QEMU is a modern and fast PC emulator. QEMU version 2.3.0 is set up on Athena for x86 machines in the 6.828 locker (add -f 6.828)

Unfortunately, QEMU's debugging facilities, while powerful, are somewhat immature, so we highly recommend you use our patched version of QEMU instead of the stock version that may come with your distribution. The version installed on Athena is already patched. To build your own patched version of QEMU:

  1. Clone the IAP 6.828 QEMU git repository git clone -b 6.828-2.3.0
  2. On Linux, you may need to install several libraries. We have successfully built 6.828 QEMU on Debian/Ubuntu 16.04 after installing the following packages: libsdl1.2-dev, libtool-bin, libglib2.0-dev, libz-dev, and libpixman-1-dev.
  3. Configure the source code (optional arguments are shown in square brackets; replace PFX with a path of your choice)
    1. Linux: ./configure --disable-kvm [--prefix=PFX] [--target-list="i386-softmmu x86_64-softmmu"]
    2. OS X: ./configure --disable-kvm --disable-sdl [--prefix=PFX] [--target-list="i386-softmmu x86_64-softmmu"] The prefix argument specifies where to install QEMU; without it QEMU will install to /usr/local by default. The target-list argument simply slims down the architectures QEMU will build support for.
  4. Run make && make install

Questions or comments regarding 6.828? Send e-mail to the TAs at

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