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    1: **Contents**
    2: 
    3: [[!toc levels=2]]
    4: 
    5: This page is about rump kernels in NetBSD and assumes the reader knows
    6: the basics of rump kernels.  [General information
    7: about rump kernels](https://github.com/rumpkernel/wiki) is available elsewhere.
    8: 
    9: ## System security
   10: 
   11: File system drivers are vulnerable to consistency errors in
   12: file system images, see e.g.
   13: [here](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.114.4312)
   14: 
   15: What this vulnerability means is that whenever an untrusted file system
   16: image is mounted using an in-kernel driver, system compromise should be
   17: expected.  This untrusted images include for example ones on USB sticks.
   18: There are heavyweight workarounds for the problem, for example including
   19: virtual machines.
   20: 
   21: NetBSD allows transparently mounting an untrusted file system image by
   22: running the kernel driver in a rump kernel in userspace.  The driver
   23: is thus isolated and any damage that a malicious file system image
   24: can directly cause is restricted to a userspace process.  From a user
   25: perspective, mounting with the `-o rump` option is the only change
   26: required, or `rump` in `/etc/fstab`.  Notably, even though interacting
   27: with untrusted file systems will suffer from a minor performance penalty,
   28: the performance of mounts from trusted file systems is completely
   29: unaffected.
   30: 
   31: 
   32: ## Automated testing
   33: 
   34: The problems of automated kernel testing are documented for example in
   35: [The Design and Implementation of the Anykernel and Rump Kernels](http://lib.tkk.fi/Diss/2012/isbn9789526049175/isbn9789526049175.pdf).
   36: Rump kernels are used in the continuous tests run by the NetBSD project.
   37: See [Release Engineering Status Site](http://releng.NetBSD.org/) for the results or the NetBSD source tree
   38: under `src/tests` for the test programs themselves.
   39: 
   40: 
   41: ## Kernel development
   42: 
   43: On the flipside of testing is kernel development.  Rump kernels allow
   44: developing kernel drivers in a test-driven manner, including both unit
   45: tests and integration tests.  Since the iteration time with a rump
   46: kernel is in the subsecond range, the development process is smoother
   47: than with a virtual machine.  Also, the tests written during development
   48: can be entered into the automated tests (see above), and later used
   49: for further development.  This method avoids "throw-away" tests that
   50: are hardcoded for one virtual machine environment and unusable in both
   51: automated testing and further development done in another environment.
   52: 
   53: 
   54: ## Source Code
   55: 
   56: You can also [browse](http://cvsweb.NetBSD.org/bsdweb.cgi/src/) the
   57: source code history online. Code is found from all areas of the source
   58: tree. Some examples of where to look include
   59: [src/lib](http://cvsweb.NetBSD.org/bsdweb.cgi/src/lib/),
   60: [src/usr.bin](http://cvsweb.NetBSD.org/bsdweb.cgi/src/usr.bin/) and
   61: [src/sys/rump](http://cvsweb.NetBSD.org/bsdweb.cgi/src/sys/rump/).