Xen project Mailing List

Hi,

this time for real:

so I've been reading up on the task quite a bit now and I'd be thankful if you could clarify what exactly you're looking for with the execution path. The AFL-fuzzer seems to make use just of a rather simple representation of that (https://lwn.net/Articles/674854/), so you would just have to insert this snippet:

  cur_location = <COMPILE_TIME_RANDOM>;
  shared_mem[cur_location ^ prev_location]++; 
  prev_location = cur_location >> 1;

at every edge, i.e. into __sanitizer_cov_trace_pc, and somehow set up a shared memory section between kernel (where you'd run the fuzzer) and hypervisor. That might however just be true for AFL and not for other coverage-guided fuzzers, so maybe that's the problem. For the fuzzer to work I'd also have to implement some templates on what hypercalls are available and what arguments they expect, but that would still not fill three months, so I'm assuming that I'm fundamentally missing something here.

On another note, would it be possible to apply for a second project (Adding Floating Point support to Mini-OS) without having to do another patch?

I added Juergen Gross in the recipients for this. I'd still be prefer the fuzzing project in case I can figure out a useful proposal, but the idea for the floating point project seems much clearer, so I figured to have something along the following lines as my proposal (I also assumed that the template you provide [https://wiki.xen.org/wiki/GSoC_Student_Application_Template] is still active):

1) Personal Information

1.1) Full Name: Felix Ekkehard Schmoll

1.2) Email: eggi.innovations@xxxxxxxxx

1.4) Other applications: Not currently

1.5) Previous experience: No

1.6) Time commitment: full-time

1.7) Other programs: No

2) Preparation done so far

2.1) Hardware: Yes.

2.2) Ability to Build and Test: Yes.

2.4) Other: Did patches suggested bei Wei Liu to get familiar with the hypervisor in general (https://lists.xen.org/archives/html/xen-devel/2017-03/msg01450.html)

3) Proposed Project

3.1) Project Category for which you are applying Mini-OS

3.2) Title for your proposal Adding Floating Point Support to Mini-OS

3.3) Link to original proposal

https://wiki.xenproject.org/wiki/Outreach_Program_Projects#Adding_Floating_Point_support_to_Mini-OS

4) Implementation Plan

4.1) Detailed Problem Description (Provide a high-level overview textual description of the problem): Mini-OS is a small kernel provided as part of the Xen project that is mainly used for stub domains, allowing to outsource certain computations from dom0. Currently Mini-OS however doesn't support the use of floating point registers, meaning that userspace programs can't do floating-point computations if they are multi-threaded. This should be fixed.

4.2) Implementation Plan (Provide as much detail and organisation as you can. Discuss with your mentor. Make sure you build in sufficient time for learning and getting up to speed. The questions in section 2 will help you and are very valuable to create a plan): At first I will implement a test application and read up on the details of floating point support for x86 and ARM. I will then start with x86, make sure that the application runs and continue with ARM. Once that works too I will do some thorough testing.

4.3) Expected Outcomes/Goals: (List the main outcomes that you will deliver during the program - this does not have to be perfect. It is also a good idea to link to a discussion on the relevant public mailing list here to give us some context. As an aside, it will also help you as well. Set some minimum outcomes/goals and stretch outcomes/goals - these are nice to have's. If you have experience with or prefer agile development methodologies, write down what you would like to achieve in different scrums. That's perfectly OK: you may want to discuss with your mentor - he/she can act as product owner or scrum master if you want. Do agree with him/her upfront.)

Userspace-program to test functionality of floating point registers
Patch that implements functionality of floating point registers for x86 and ARM

4.4) Timeline (Be specific and as complete as you can. Discuss feasibility with your mentor. Build in some buffers and set some stretch goals. This will help you with progress and motivation! ):

Bonding Period

Follow mailing lists

Ask clarifying questions

Weeks 1-2/ May 30 - June 13

Reading into the kernel and how usually floating point operations are implemented

Read up on documentation (e.g. Intel Architecture Software Developer's Manual, Volume 1: Basic Architecture, Chapter 7 on the Floating-Point Unit)

Build example application based on where critical parts are identified

Weeks 3 - 4, June 14 - June 30

Implement on x86

Midterm deliverables

Test application using floating point registers

Weeks 5-6

Implement on ARM

Weeks 7-8

Buffer time

Weeks 9-10

Do thorough testing, consider edge cases, do stress testing, commit to source tree

4.5) Maintenance: I don't expect any maintenance to be required, the Mini-OS tree seems to be fairly stable.

5) Let us know how much help you need

5.1 Describe experience with Domain Support, Xen Hypervisor, The XAPI toolstack, Mirage OS, Windows PV Drivers, Embedded & Automotive Drivers (as appropriate): No previous experience

5.2) Other experience: describe relevant experience that you have (If possible, describe what uniquely qualifies you for this proposal): Took 15-410 at CMU, i.e. building a kernel from scratch in six weeks, involved ASM and obviously large amounts of kernel programming and used an x86 processor; notably the kernel did also not support floating point computations; also built a thread-library based on the kernel

5.3) Learning and support: describe the part(s) of the proposed plan do you expect to be most difficult ( Include the specific types of of mentor help you think you will need for the part(s): Understanding the specifics of the processor architectures might require some help, in case I have troubles with specific parts of the manuals. They're usually quite detailed though.

5.5) Describe the part(s) of the proposed plan do you expect to be easiest:

Building the user space application (user space is generally easier than kernel and you don't have to get any offsets right or alike)

Questions:

*What if the CPU doesn't have an FPU? Is that even possible for the given two architectures?

Any comments would be appreciated.

Felix

2017-03-22 12:21 GMT+01:00 Wei Liu <wei.liu2@xxxxxxxxxx>:

On Wed, Mar 22, 2017 at 10:54:38AM +0100, Felix Schmoll wrote:
>
> Got it working! Thanks for all the help, will look into the "actual" task
> now :D

That's good.

IIRC the application is now open. Don't forget to submit your proposal.

Wei.

>
> >
> > Wei.
> >

Re: [Xen-devel] [GSoC] GSoC Introduction : Fuzzing Xen hypercall interface

1) Personal Information

2) Preparation done so far

3) Proposed Project

4) Implementation Plan

5) Let us know how much help you need