Feeds

DragonFly BSD developer stung by Opteron bug

New 'Bulldozer' cores not affected

High performance access to file storage

Matthew Dillon, the lead developer behind the DragonFly BSD fork of the open source FreeBSD Unix variant, had some issues with crashes on Opteron-based systems running his operating system for more than a year - and now Advanced Micro Devices says it's a bug in earlier generations of Opteron processors.

The errata does not affect current Opteron 4200 and 6200 processors or the impending Opteron 3200 chips, all of which have a different microarchitecture based on the "Bulldozer" cores.

Dillon described the crashes he was seeing with Dragonfly BSD in a posting on his kernel list on Christmas Day, and said he had been bug hunting for more than a year.

The problem occurs with the cc1 C compiler in the open-source GNU gcc 4.4.7 compiler set. Dillon ran tests on Opteron and Phenon II machines as well as on Sandy Bridge Xeon E3 processors from Intel, and said he didn't see the issue on Intel iron and had discounted the OS as the source of the problem causing the crashes. On Monday, in another post, Dillon said that after reviewing his issues, AMD confirmed the bug and said that doing certain kinds of loop operations, the processor can incorrectly update some Opteron stack pointers.

AMD provided El Reg with the following statement about the bug:

A program exception has been identified in previous generations of the AMD Opteron processor that occurs in certain environments that leverage a very specific GCC compiler build. A workaround has been identified for the small segment of customers this could potentially impact.

It's also important to note the following:

  • Only one external software developer has reported this observation.
  • This could only impact previous generation products (codenames: "Barcelona," "Shanghai," "Istanbul," "Lisbon," and "Magny-Cours").
  • While there are millions of these processors in the field, no other cases have been reported.
  • To see this observation multiple events needed to happen concurrently and required a certain BSD-derivative environment (BSD is based on the Unix operating system) that uses a unique GCC compiler build.
  • This erratum CANNOT occur on AMD Opteron 3200, 4200 and 6200 ("Valencia" and "Interlagos") Series processors since it utilizes a different microarchitecture.

And finally and even more important for readers to understand, AMD and Intel post errata updates on a regular basis, the difference here is a developer with a blog and unique GCC compiler build uncovered it.

In the wake of that statement, AMD told Dillon that it would be updating its revision guides for its 10h and 12h processors to document this erratum, which has been given issue #721. At that time, AMD will provide a model-specific workaround to the issue, it said. ®

High performance access to file storage

More from The Register

next story
Android engineer: We DIDN'T copy Apple OR follow Samsung's orders
Veep testifies for Samsung during Apple patent trial
Windows 8.1, which you probably haven't upgraded to yet, ALREADY OBSOLETE
Pre-Update versions of new Windows version will no longer support patches
OpenSSL Heartbleed: Bloody nose for open-source bleeding hearts
Bloke behind the cockup says not enough people are helping crucial crypto project
Half of Twitter's 'active users' are SILENT STALKERS
Nearly 50% have NEVER tweeted a word
Windows XP still has 27 per cent market share on its deathbed
Windows 7 making some gains on XP Death Day
Internet-of-stuff startup dumps NoSQL for ... SQL?
NoSQL taste great at first but lacks proper nutrients, says startup cloud whiz
Microsoft lobs pre-release Windows Phone 8.1 at devs who dare
App makers can load it before anyone else, but if they do they're stuck with it
US taxman blows Win XP deadline, must now spend millions on custom support
Gov't IT likened to 'a Model T with a lot of things on top of it'
prev story

Whitepapers

Mainstay ROI - Does application security pay?
In this whitepaper learn how you and your enterprise might benefit from better software security.
Five 3D headsets to be won!
We were so impressed by the Durovis Dive headset we’ve asked the company to give some away to Reg readers.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Mobile application security study
Download this report to see the alarming realities regarding the sheer number of applications vulnerable to attack, as well as the most common and easily addressable vulnerability errors.