Computer simulation, programming, software, technology, research, and more (since 2007)
I have had some annoying problems in recent months with my work laptop refusing to connect to certain WiFi login pages (more technically known as Captive Portals), essentially locking me out of the WiFi in certain places. Here is how I solved it.
Continue reading “Failing to See WiFi Login Page [Captive Portal] / Solved”
In this final part of my series on the history of reverse debugging I will look at the products that launched around the mid-2000s and that finally made reverse debugging available in a commercially packaged product and not just research prototypes. Part one of this series provided a background on the technology and part two discussed various research papers on the topic going back to the early 1970s. The first commercial product featuring reverse debugging was launched in 2003, and then there have been a steady trickle of new products up until today.
Originally published in January 2012. Post updated 2012-09-28 with a revised timeline for Lauterbach CTS. Post updated 2016-04-05 to include Mozilla RR. Post updated 2016-12-26 to add Simulics. Post updated 2017-10-08 to add Microsoft WinDbg. Post updated 2018-07-28 to add Borland Turbo Debugger.
I have an old Canon LIDE 30 scanner that I purchased sometime late in 2003. At that time, it was connected to a PC running Windows XP, and drivers worked just fine. However, after I got my new computer in early 2009, with Vista 64, there are no more drivers available. There is a funny way around this though, using a virtual machine.
In my series (well, I have one previous post about checkpointing) about misunderstood simulation technology items, the turn has come to the most difficult of all it seems: determinism. Determinism is often misunderstood as meaning “unchanging” or “constant” behavior of the simulation. People tend to assume that a deterministic simulation will not reveal errors due to nondeterministic behavior or races in the modeled system, which is a complete misunderstanding. Determinism is a necessary feature of any simulation system that wants to be really helpful to its users, not an evil that hides errors.
Continue reading “Simulation Determinism: Necessary or Evil?”
One thing that surprises me is how rare the feature of checkpointing or snapshotting is in the land of virtual platforms, despite the obvious benefits of that feature. Indeed, checkpointing was one of the first cool things demonstrated to me when I joined Virtutech back in 2002. Today, I could not ever imagine doing without it. Not having checkpointing is like having a word processor where you only get to save once, when your document is finished, with no option of saving intermediate states.
But not everyone seems to consider this an important feature, judging from its relative rarity in the world of EDA and virtual platforms. Why is this? Let’s look at some possible explanations.
Continue reading “Checkpointing: Meaningless, Difficult, or just Overlooked?”
It must have been Google Alerts that send me a link to the HOTOS 2007 (Hot Topics in Operating Systems) paper by Tal Garfinkel, Keith Adams, Andrew Warfield, and Jason Franklin called Compatibility is not Transparency: VMM Detection Myths and Realities. This paper is slightly less than a year old today, so it is old by blog standards and quite recent by research paper standards. It deals with the interesting problem of whether a virtual machine can be made undetectable by software running on it — and software that is trying to detect it. Their conclusion is that it is not feasible, and I agree with that. The reason WHY that is the case can use some more discussion, though… and here is my take on that issue from a Simics/embedded systems virtualization perspective.
Continue reading “VMM Detection Myths and Realities from a Simics and Embedded Perspective”