Prerequisites and Installation
The easiest way of hacking SWEB is by using Linux as development system and qemu as virtual machine for SWEB to run in. To compile and run SWEB you need the following components:
gcc (9 or newer)
g++ (9 or newer)
If you are using Ubuntu, all of them should be available as packages and you can install them with:
sudo apt install cmake qemu-system-x86 gcc g++ python build-essential.
In addition to the software requirements, you should possess a fair amount of programming knowledge in C and C++. Basic knowledge of the x86-architecture can also come in handy at times.
Preparing your build environment
SWEB supports compiling within the source directory or outside of the source directory. Compiling outside the source directory has several advantages (no binary files in the source directory, build environment in RAM, easy deletion of binary files with no risk of losing the source files, …).
As recommended here, we make
tmpfsdirectory (mount point). This way all data in
/tmp will reside in RAM. Open
/etc/fstaband look for a line containing
tmpfs /tmp tmpfs nodev,nosuid 0 0
If there is no such line, add the above line to
/etc/fstabbut make sure you don’t delete anything or your computer might not boot anymore.
After this change you need to restart your computer.
Compiling and running
Once you have the source code and all necessary tools, you are already ready to compile and run SWEB. Of course, it will not do anything terribly interesting, but you can verify that your toolchain is set up properly. To compile and run use
mkdir -p /tmp/sweb; cd /tmp/sweb; cmake /path/to/sourcecode/of/sweb; make; make qemu This first creates a folder
/tmp/sweb in which all object and binary files will be placed. We change into that directory and call
cmake /path/to/sourcecode/of/sweb. CMake generates the Makefile we use to compile SWEB.
make runs this generated Makefile and compiles SWEB. Finally
make qemuopens qemu and boots into SWEB which will run the
SWEB shell (see
userspace/tests/stdin-test.c). If you want to use bochs instead, type
make bochs, if you want to force qemu to use kvm, type
Aside: Which emulator to use? We recommend using qemu, as it is much faster than bochs. If you want to use emulated hardware which is not provided by qemu, you can of course try using a different emulator.
Do not call cmake in-source, i.e. do not type
cmake . in the source folder.
If you see other students using
cmake .in the source folder, please inform them that this is not recommended.
Once you entered
cmake . in the source folder, regular cmake calls (in a build folder, as described in this tutorial) will all fail. So, don’t do that. You will have to cleanup the repository by hand or by removing all untracked files with the slightly dangerous command
git clean -d -x which will also remove all files that you forgot to commit. Better just don’t call cmake like this at all to avoid problems.
cmake . in the build folder is totally fine (once you initialized the build folder).
Compilation or pre-boot issues
In case the compilation process fails, you are getting file system errors or if you are stuck while loading GRUB, try to rebuild the entire project:
make mrproper; make; make qemu
Note that there is a difference between