xv6-extensions

A collection of extensions to xv6, the ANSI C reimplementation of Dennis Ritchie's and Ken Thompson's Unix Version 6. These extensions include:

• A CPU scheduler supporting two pricing schemes similar to those used by AWS and other cloud services: reserved processes and spot processes. The former is implemented with a lottery scheduler.
• A few modern virtual memory features, including:
  • Null-pointer dereference handling.
  • A stack rearrangement, with the stack placed at the high end of the address space.
• Kernel threads.
• Protection from data corruption via the addition of file checksums.

Getting Started

To run xv6, I suggest that you install the QEMU PC emulator. You can get a version of QEMU with patched debugging facilities from the IAP 6.828 crew at MIT. To build your own patched version of QEMU, do the following:

1. Clone the IAP 6.828 QEMU git repository

$ git clone http://web.mit.edu/ccutler/www/qemu.git -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)

   • Linux:

   $ ./configure --disable-kvm [--prefix=PFX] [--target-list="i386-softmmu x86_64-softmmu"]
   

   • 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

To simulate one of the xv6 extensions in this repository, do the following:

1. Clone or download this repository.
2. Navigate to the src directory of the repository.

$ cd /path/to/repository/xv6-extensions/src

3. Choose which extension you want to emulate. E.g., if you want to simulate the kernel thread extension of xv6, we would proceed as follows:

$ cd xv6-kernel

4. Run the QEMU emulator.

$ make qemu

5. Test it out!