# Analyzing the Linux boot process (opensource.com)

Post Syndicated from corbet original https://lwn.net/Articles/744528/rss

Alison Chaiken looks
in detail at how the kernel boots
on opensource.com.
Besides starting buggy spyware, what function does early boot
firmware serve? The job of a bootloader is to make available to a newly
powered processor the resources it needs to run a general-purpose operating
system like Linux. At power-on, there not only is no virtual memory, but no
DRAM until its controller is brought up.

# Eevee gained 2791 experience points

Post Syndicated from Eevee original https://eev.ee/blog/2018/01/15/eevee-gained-2791-experience-points/

Eevee grew to level 31!

A year strongly defined by mixed success! Also, a lot of video games.

I ran three game jams, resulting in a total of 157 games existing that may not have otherwise, which is totally mindblowing?!

For GAMES MADE QUICK???, glip and I made NEON PHASE, a short little exploratory platformer. Honestly, I should give myself more credit for this and the rest of the LÖVE games I’ve based on the same codebase — I wove a physics engine (and everything else!) from scratch and it has held up remarkably well for a variety of different uses.

I successfully finished an HD version of Isaac’s Descent using my LÖVE engine, though it doesn’t have anything new over the original and I’ve only released it as a tech demo on Patreon.

For Strawberry Jam (NSFW!) we made fox flux (slightly NSFW!), which felt like a huge milestone: the first game where I made all the art! I mean, not counting Isaac’s Descent, which was for a very limited platform. It’s a pretty arbitrary milestone, yes, but it feels significant. I’ve been working on expanding the game into a longer and slightly less buggy experience, but the art is taking the longest by far. I must’ve spent weeks on player sprites alone.

We then set about working on Bolthaven, a sequel of sorts to NEON PHASE, and got decently far, and then abandond it. Oops.

We then started a cute little PICO-8 game, and forgot about it. Oops.

I was recruited to help with Chaos Composer, a more ambitious game glip started with someone else in Unity. I had to get used to Unity, and we squabbled a bit, but the game is finally about at the point where it’s “playable” and “maps” can be designed? It’s slightly on hold at the moment while we all finish up some other stuff, though.

We made a birthday game for two of our friends whose birthdays were very close together! Only they got to see it.

For Ludum Dare 38, we made Lunar Depot 38, a little “wave shooter” or whatever you call those? The AI is pretty rough, seeing as this was the first time I’d really made enemies and I had 72 hours to figure out how to do it, but I still think it’s pretty fun to play and I love the circular world.

I made Roguelike Simulator as an experiment with making something small and quick with a simple tool, and I had a lot of fun! I definitely want to do more stuff like this in the future.

And now we’re working on a game about Star Anise, my cat’s self-insert, which is looking to have more polish and depth than anything we’ve done so far! We’ve definitely come a long way in a year.

Somewhere along the line, I put out a call for a “potluck” project, where everyone would give me sprites of a given size without knowing what anyone else had contributed, and I would then make a game using only those sprites. Unfortunately, that stalled a few times: I tried using the Phaser JS library, but we didn’t get along; I tried LÖVE, but didn’t know where to go with the game; and then I decided to use this as an experiment with procedural generation, and didn’t get around to it. I still feel bad that everyone did work for me and I didn’t follow through, but I don’t know whether this will ever become a game.

veekun, alas, consumed months of my life. I finally got Sun and Moon loaded, but it took weeks of work since I was basically reinventing all the tooling we’d ever had from scratch, without even having most of that tooling available as a reference. It was worth it in the end, at least: Ultra Sun and Ultra Moon only took a few days to get loaded. But veekun itself is still missing some obvious Sun/Moon features, and the whole site needs an overhaul, and I just don’t know if I want to dedicate that much time to it when I have so much other stuff going on that’s much more interesting to me right now.

I finally turned my blog into more of a website, giving it a neat front page that lists a bunch of stuff I’ve done. I made a release category at last, though I’m still not quite in the habit of using it.

I wrote some blog posts, of course! I think the most interesting were JavaScript got better while I wasn’t looking and Object models. I was also asked to write a couple pieces for money for a column that then promptly shut down.

On a whim, I made a set of Eevee mugshots for Doom, which I think is a decent indication of my (pixel) art progress over the year?

I started idchoppers, a Doom parsing and manipulation library written in Rust, though it didn’t get very far and I’ve spent most of the time fighting with Rust because it won’t let me implement all my extremely bad ideas. It can do a couple things, at least, like flip maps very quickly and render maps to SVG.

I did toy around with music a little, but not a lot.

I wrote two short twines for Flora. They’re okay. I’m working on another; I think it’ll be better.

I didn’t do a lot of art overall, at least compared to the two previous years; most of my art effort over the year has gone into fox flux, which requires me to learn a whole lot of things. I did dip my toes into 3D modelling, most notably producing my current Twitter banner as well as this cool Star Anise animation. I wouldn’t mind doing more of that; maybe I’ll even try to make a low-poly pixel-textured 3D game sometime.

I restarted my book with a much better concept, though so far I’ve only written about half a chapter. Argh. I see that the vast majority of the work was done within the span of a single week, which is bad since that means I only worked on it for a week, but good since that means I can actually do a pretty good amount of work in only a week. I also did a lot of squabbling with tooling, which is hopefully mostly out of the way now.

My computer broke? That was an exciting week.

A lot of stuff, but the year as a whole still feels hit or miss. All the time I spent on veekun feels like a black void in the middle of the year, which seems like a good sign that I maybe don’t want to pour even more weeks into it in the near future.

Mostly, I want to do: more games, more art, more writing, more music.

I want to try out some tiny game making tools and make some tiny games with them — partly to get exposure to different things, partly to get more little ideas out into the world regularly, and partly to get more practice at letting myself have ideas. I have a couple tools in mind and I guess I’ll aim at a microgame every two months or so? I’d also like to finish the expanded fox flux by the end of the year, of course, though at the moment I can’t even gauge how long it might take.

I seriously lapsed on drawing last year, largely because fox flux pixel art took me so much time. So I want to draw more, and I want to get much faster at pixel art. It would probably help if I had a more concrete goal for drawing, so I might try to draw some short comics and write a little visual novel or something, which would also force me to aim for consistency.

I want to work on my book more, of course, but I also want to try my hand at a bit more fiction. I’ve had a blast writing dialogue for our games! I just shy away from longer-form writing for some reason — which seems ridiculous when a large part of my audience found me through my blog. I do think I’ve had some sort of breakthrough in the last month or two; I suddenly feel a good bit more confident about writing in general and figuring out what I want to say? One recent post I know I wrote in a single afternoon, which virtually never happens because I keep rewriting and rearranging stuff. Again, a visual novel would be a good excuse to practice writing fiction without getting too bogged down in details.

And, ah, music. I shy heavily away from music, since I have no idea what I’m doing, and also I seem to spend a lot of time fighting with tools. (Surprise.) I tried out SunVox for the first time just a few days ago and have been enjoying it quite a bit for making sound effects, so I might try it for music as well. And once again, visual novel background music is a pretty low-pressure thing to compose for. Hell, visual novels are small games, too, so that checks all the boxes. I guess I’ll go make a visual novel.

Here’s to twenty gayteen!

# timeShift(GrafanaBuzz, 1w) Issue 29

Post Syndicated from Blogs on Grafana Labs Blog original https://grafana.com/blog/2018/01/12/timeshiftgrafanabuzz-1w-issue-29/

### Welcome to TimeShift

intro paragraph

#### Latest Stable Release

Grafana 4.6.3 is now available. Latest bugfixes include:

• Gzip: Fixes bug Gravatar images when gzip was enabled #5952
• Alert list: Now shows alert state changes even after adding manual annotations on dashboard #99513
• Alerting: Fixes bug where rules evaluated as firing when all conditions was false and using OR operator. #93183
• Cloudwatch: CloudWatch no longer display metrics’ default alias #101514, thx @mtanda

#### From the Blogosphere

Graphite 1.1: Teaching an Old Dog New Tricks: Grafana Labs’ own Dan Cech is a contributor to the Graphite project, and has been instrumental in the addition of some of the newest features. This article discusses five of the biggest additions, how they work, and what you can expect for the future of the project.

Instrument an Application Using Prometheus and Grafana: Chris walks us through how easy it is to get useful metrics from an application to understand bottlenecks and performace. In this article, he shares an application he built that indexes your Gmail account into Elasticsearch, and sends the metrics to Prometheus. Then, he shows you how to set up Grafana to get meaningful graphs and dashboards.

Visualising Serverless Metrics With Grafana Dashboards: Part 3 in this series of blog posts on “Monitoring Serverless Applications Metrics” starts with an overview of Grafana and the UI, covers queries and templating, then dives into creating some great looking dashboards. The series plans to conclude with a post about setting up alerting.

Huawei FAT WLAN Access Points in Grafana: Huawei’s FAT firmware for their WLAN Access points lacks central management overview. To get a sense of the performance of your AP’s, why not quickly create a templated dashboard in Grafana? This article quickly steps your through the process, and includes a sample dashboard.

#### Grafana Plugins

Lots of updated plugins this week. Plugin authors add new features and fix bugs often, to make your plugin perform better – so it’s important to keep your plugins up to date. We’ve made updating easy; for on-prem Grafana, use the Grafana-cli tool, or update with 1 click if you’re using Hosted Grafana.

UPDATED PLUGIN

Clickhouse Data Source – The Clickhouse Data Source plugin has been updated a few times with small fixes during the last few weeks.

• Fix for quantile functions
• Allow rounding with round option for both time filters: $from and $to

UPDATED PLUGIN

Zabbix App – The Zabbix App had a release with a redesign of the Triggers panel as well as support for Multiple data sources for the triggers panel

UPDATED PLUGIN

OpenHistorian Data Source – this data source plugin received some new query builder screens and improved documentation.

UPDATED PLUGIN

BT Status Dot Panel – This panel received a small bug fix.

UPDATED PLUGIN

Carpet Plot Panel – A recent update for this panel fixes a D3 import bug.

#### Upcoming Events

In between code pushes we like to speak at, sponsor and attend all kinds of conferences and meetups. We also like to make sure we mention other Grafana-related events happening all over the world. If you’re putting on just such an event, let us know and we’ll list it here.

Women Who Go Berlin: Go Workshop – Monitoring and Troubleshooting using Prometheus and Grafana | Berlin, Germany – Jan 31, 2018: In this workshop we will learn about one of the most important topics in making apps production ready: Monitoring. We will learn how to use tools you’ve probably heard a lot about – Prometheus and Grafana, and using what we learn we will troubleshoot a particularly buggy Go app.

FOSDEM | Brussels, Belgium – Feb 3-4, 2018: FOSDEM is a free developer conference where thousands of developers of free and open source software gather to share ideas and technology. There is no need to register; all are welcome.

Jfokus | Stockholm, Sweden – Feb 5-7, 2018:
Carl Bergquist – Quickie: Monitoring? Not OPS Problem

Why should we monitor our system? Why can’t we just rely on the operations team anymore? They use to be able to do that. What’s currently changing? Presentation content: – Why do we monitor our system – How did it use to work? – Whats changing – Why do we need to shift focus – Everyone should be on call. – Resilience is the goal (Best way of having someone care about quality is to make them responsible).

Jfokus | Stockholm, Sweden – Feb 5-7, 2018:
Leonard Gram – Presentation: DevOps Deconstructed

What’s a Site Reliability Engineer and how’s that role different from the DevOps engineer my boss wants to hire? I really don’t want to be on call, should I? Is Docker the right place for my code or am I better of just going straight to Serverless? And why should I care about any of it? I’ll try to answer some of these questions while looking at what DevOps really is about and how commodisation of servers through “the cloud” ties into it all. This session will be an opinionated piece from a developer who’s been on-call for the past 6 years and would like to convince you to do the same, at least once.

Stockholm Metrics and Monitoring | Stockholm, Sweden – Feb 7, 2018:
Observability 3 ways – Logging, Metrics and Distributed Tracing

Let’s talk about often confused telemetry tools: Logging, Metrics and Distributed Tracing. We’ll show how you capture latency using each of the tools and how they work differently. Through examples and discussion, we’ll note edge cases where certain tools have advantages over others. By the end of this talk, we’ll better understand how each of Logging, Metrics and Distributed Tracing aids us in different ways to understand our applications.

OpenNMS – Introduction to “Grafana” | Webinar – Feb 21, 2018:
IT monitoring helps detect emerging hardware damage and performance bottlenecks in the enterprise network before any consequential damage or disruption to business processes occurs. The powerful open-source OpenNMS software monitors a network, including all connected devices, and provides logging of a variety of data that can be used for analysis and planning purposes. In our next OpenNMS webinar on February 21, 2018, we introduce “Grafana” – a web-based tool for creating and displaying dashboards from various data sources, which can be perfectly combined with OpenNMS.

GrafanaCon EU | Amsterdam, Netherlands – March 1-2, 2018:
Lock in your seat for GrafanaCon EU while there are still tickets avaialable! Join us March 1-2, 2018 in Amsterdam for 2 days of talks centered around Grafana and the surrounding monitoring ecosystem including Graphite, Prometheus, InfluxData, Elasticsearch, Kubernetes, and more.

We have some exciting talks lined up from Google, CERN, Bloomberg, eBay, Red Hat, Tinder, Automattic, Prometheus, InfluxData, Percona and more! Be sure to get your ticket before they’re sold out.

#### Tweet of the Week

We scour Twitter each week to find an interesting/beautiful dashboard and show it off! #monitoringLove

Nice hack! I know I like to keep one eye on server requests when I’m dropping beats. 😉

#### Grafana Labs is Hiring!

We are passionate about open source software and thrive on tackling complex challenges to build the future. We ship code from every corner of the globe and love working with the community. If this sounds exciting, you’re in luck – WE’RE HIRING!

Check out our

#### How are we doing?

Thanks for reading another issue of timeShift. Let us know what you think! Submit a comment on this article below, or post something at our community forum.

Follow us on Twitter, like us on Facebook, and join the Grafana Labs community.

# [$] A look at the handling of Meltdown and Spectre Post Syndicated from jake original https://lwn.net/Articles/743363/rss The Meltdown/Spectre debacle has, deservedly, reached the mainstream press and, likely, most of the public that has even a remote interest in computers and security. It only took a day or so from the accelerated disclosure date of January 3—it was originally scheduled for January 9—before the bugs were making big headlines. But Spectre has been known for at least six months and Meltdown for nearly as long—at least to some in the industry. Others that were affected were completely blindsided by the announcements and have joined the scramble to mitigate these hardware bugs before they bite users. Whatever else can be said about Meltdown and Spectre, the handling (or, in truth, mishandling) of this whole incident has been a horrific failure. # Wanted: Sales Engineer Post Syndicated from Yev original https://www.backblaze.com/blog/wanted-sales-engineer/ At inception, Backblaze was a consumer company. Thousands upon thousands of individuals came to our website and gave us$5/mo to keep their data safe. But, we didn’t sell business solutions. It took us years before we had a sales team. In the last couple of years, we’ve released products that businesses of all sizes love: Backblaze B2 Cloud Storage and Backblaze for Business Computer Backup. Those businesses want to integrate Backblaze deeply into their infrastructure, so it’s time to hire our first Sales Engineer!

Company Description:
Founded in 2007, Backblaze started with a mission to make backup software elegant and provide complete peace of mind. Over the course of almost a decade, we have become a pioneer in robust, scalable low cost cloud backup. Recently, we launched B2 – robust and reliable object storage at just $0.005/gb/mo. Part of our differentiation is being able to offer the lowest price of any of the big players while still being profitable. We’ve managed to nurture a team oriented culture with amazingly low turnover. We value our people and their families. Don’t forget to check out our “About Us” page to learn more about the people and some of our perks. We have built a profitable, high growth business. While we love our investors, we have maintained control over the business. That means our corporate goals are simple – grow sustainably and profitably. Some Backblaze Perks: • Competitive healthcare plans • Competitive compensation and 401k • All employees receive Option grants • Unlimited vacation days • Strong coffee • Fully stocked Micro kitchen • Catered breakfast and lunches • Awesome people who work on awesome projects • Childcare bonus • Normal work hours • Get to bring your pets into the office • San Mateo Office – located near Caltrain and Highways 101 & 280. Backblaze B2 cloud storage is a building block for almost any computing service that requires storage. Customers need our help integrating B2 into iOS apps to Docker containers. Some customers integrate directly to the API using the programming language of their choice, others want to solve a specific problem using ready made software, already integrated with B2. At the same time, our computer backup product is deepening it’s integration into enterprise IT systems. We are commonly asked for how to set Windows policies, integrate with Active Directory, and install the client via remote management tools. We are looking for a sales engineer who can help our customers navigate the integration of Backblaze into their technical environments. Are you 1/2” deep into many different technologies, and unafraid to dive deeper? Can you confidently talk with customers about their technology, even if you have to look up all the acronyms right after the call? Are you excited to setup complicated software in a lab and write knowledge base articles about your work? Then Backblaze is the place for you! Enough about Backblaze already, what’s in it for me? In this role, you will be given the opportunity to learn about the technologies that drive innovation today; diverse technologies that customers are using day in and out. And more importantly, you’ll learn how to learn new technologies. Just as an example, in the past 12 months, we’ve had the opportunity to learn and become experts in these diverse technologies: • How to setup VM servers for lab environments, both on-prem and using cloud services. • Create an automatically “resetting” demo environment for the sales team. • Setup Microsoft Domain Controllers with Active Directory and AD Federation Services. • Learn the basics of OAUTH and web single sign on (SSO). • Archive video workflows from camera to media asset management systems. • How upload/download files from Javascript by enabling CORS. • How to install and monitor online backup installations using RMM tools, like JAMF. • Tape (LTO) systems. (Yes – people still use tape for storage!) How can I know if I’ll succeed in this role? You have: • Confidence. Be able to ask customers questions about their environments and convey to them your technical acumen. • Curiosity. Always want to learn about customers’ situations, how they got there and what problems they are trying to solve. • Organization. You’ll work with customers, integration partners, and Backblaze team members on projects of various lengths. You can context switch and either have a great memory or keep copious notes. Your checklists have their own checklists. You are versed in: • The fundamentals of Windows, Linux and Mac OS X operating systems. You shouldn’t be afraid to use a command line. • Building, installing, integrating and configuring applications on any operating system. • Debugging failures – reading logs, monitoring usage, effective google searching to fix problems excites you. • The basics of TCP/IP networking and the HTTP protocol. • Novice development skills in any programming/scripting language. Have basic understanding of data structures and program flow. • Your background contains: • Bachelor’s degree in computer science or the equivalent. • 2+ years of experience as a pre or post-sales engineer. • The right extra credit: There are literally hundreds of previous experiences you can have had that would make you perfect for this job. Some experiences that we know would be helpful for us are below, but make sure you tell us your stories! • Experience using or programming against Amazon S3. • Experience with large on-prem storage – NAS, SAN, Object. And backing up data on such storage with tools like Veeam, Veritas and others. • Experience with photo or video media. Media archiving is a key market for Backblaze B2. • Program arduinos to automatically feed your dog. • Experience programming against web or REST APIs. (Point us towards your projects, if they are open source and available to link to.) • Experience with sales tools like Salesforce. • 3D print door stops. • Experience with Windows Servers, Active Directory, Group policies and the like. • What’s it like working with the Sales team? The Backblaze sales team collaborates. We help each other out by sharing ideas, templates, and our customer’s experiences. When we talk about our accomplishments, there is no “I did this,” only “we”. We are truly a team. We are honest to each other and our customers and communicate openly. We aim to have fun by embracing crazy ideas and creative solutions. We try to think not outside the box, but with no boxes at all. Customers are the driving force behind the success of the company and we care deeply about their success. If this all sounds like you: 1. Send an email to [email protected] with the position in the subject line. 2. Tell us a bit about your Sales Engineering experience. 3. Include your resume. The post Wanted: Sales Engineer appeared first on Backblaze Blog | Cloud Storage & Cloud Backup. # [$] Is it time for open processors?

Post Syndicated from corbet original https://lwn.net/Articles/743602/rss

The disclosure of the Meltdown and Spectre
vulnerabilities
has brought a
new level of attention to the security bugs that can lurk at the hardware
level. Massive amounts of work have gone into improving the (still poor)
security of our software, but all of that is in vain if the hardware gives
away the game. The CPUs that we run in our systems are highly proprietary
and have been shown to contain unpleasant surprises (the Intel management
engine, for example). It is thus natural to wonder whether it is time to
make a move to open-source hardware, much like we have done with our
software. Such a move may well be possible, and it would certainly offer
some benefits, but it would be no panacea.

# Physics cheats

Post Syndicated from Eevee original https://eev.ee/blog/2018/01/06/physics-cheats/

Anonymous asks:

something about how we tweak physics to “work” better in games?

Ho ho! Work. Get it? Like in physics…?

## Hitboxes

Hitbox” is perhaps not the most accurate term, since the shape used for colliding with the environment and the shape used for detecting damage might be totally different. They’re usually the same in simple platformers, though, and that’s what most of my games have been.

The hitbox is the biggest physics fudge by far, and it exists because of a single massive approximation that (most) games make: you’re controlling a single entity in the abstract, not a physical body in great detail.

That is: when you walk with your real-world meat shell, you perform a complex dance of putting one foot in front of the other, a motion you spent years perfecting. When you walk in a video game, you press a single “walk” button. Your avatar may play an animation that moves its legs back and forth, but since you’re not actually controlling the legs independently (and since simulating them is way harder), the game just treats you like a simple shape. Fairly often, this is a box, or something very box-like.

Since the player has no direct control over the exact placement of their limbs, it would be slightly frustrating to have them collide with the world. This is especially true in cases like the above, where the tail and left ear protrude significantly out from the main body. If that Eevee wanted to stand against a real-world wall, she would simply tilt her ear or tail out of the way, so there’s no reason for the ear to block her from standing against a game wall. To compensate for this, the ear and tail are left out of the collision box entirely and will simply jut into a wall if necessary — a goofy affordance that’s so common it doesn’t even register as unusual. As a bonus (assuming this same box is used for combat), she won’t take damage from projectiles that merely graze past an ear.

(One extra consideration for sprite games in particular: the hitbox ought to be horizontally symmetric around the sprite’s pivot — i.e. the point where the entity is truly considered to be standing — so that the hitbox doesn’t abruptly move when the entity turns around!)

### Corners

Treating the player (and indeed most objects) as a box has one annoying side effect: boxes have corners. Corners can catch on other corners, even by a single pixel. Real-world bodies tend to be a bit rounder and squishier and this can tolerate grazing a corner; even real-world boxes will simply rotate a bit.

Ah, but in our faux physics world, we generally don’t want conscious actors (such as the player) to rotate, even with a realistic physics simulator! Real-world bodies are made of parts that will generally try to keep you upright, after all; you don’t tilt back and forth much.

One way to handle corners is to simply remove them from conscious actors. A hitbox doesn’t have to be a literal box, after all. A popular alternative — especially in Unity where it’s a standard asset — is the pill-shaped capsule, which has semicircles/hemispheres on the top and bottom and a cylindrical body in 3D. No corners, no problem.

Of course, that introduces a new problem: now the player can’t balance precariously on edges without their rounded bottom sliding them off. Alas.

If you’re stuck with corners, then, you may want to use a corner bump, a term I just made up. If the player would collide with a corner, but the collision is only by a few pixels, just nudge them to the side a bit and carry on.

When the corner is horizontal, this creates stairs! This is, more or less kinda, how steps work in Doom: when the player tries to cross from one sector into another, if the height difference is 24 units or less, the game simply bumps them upwards to the height of the new floor and lets them continue on.

Implementing this in a game without Doom’s notion of sectors is a little trickier. In fact, I still haven’t done it. Collision detection based on rejection gets it for free, kinda, but it’s not very deterministic and it breaks other things. But that’s a whole other post.

## Gravity

Gravity is pretty easy. Everything accelerates downwards all the time. What’s interesting are the exceptions.

### Jumping

Jumping is a giant hack.

Think about how actual jumping works: you tense your legs, which generally involves bending your knees first, and then spring upwards. In a platformer, you can just leap whenever you feel like it, which is nonsense. Also you go like twenty feet into the air?

Worse, most platformers allow variable-height jumping, where your jump is lower if you let go of the jump button while you’re in the air. Normally, one would expect to have to decide how much force to put into the jump beforehand.

But of course this is about convenience of controls: when jumping is your primary action, you want to be able to do it immediately, without any windup for how high you want to jump.

(And then there’s double jumping? Come on.)

Air control is a similar phenomenon: usually you’d jump in a particular direction by controlling how you push off the ground with your feet, but in a video game, you don’t have feet! You only have the box. The compromise is to let you control your horizontal movement to a limit degree in midair, even though that doesn’t make any sense. (It’s way more fun, though, and overall gives you more movement options, which are good to have in an interactive medium.)

Air control also exposes an obvious place that game physics collide with the realistic model of serious physics engines. I’ve mentioned this before, but: if you use Real Physics™ and air control yourself into a wall, you might find that you’ll simply stick to the wall until you let go of the movement buttons. Why? Remember, player movement acts as though an external force were pushing you around (and from the perspective of a Real™ physics engine, this is exactly how you’d implement it) — so air-controlling into a wall is equivalent to pushing a book against a wall with your hand, and the friction with the wall holds you in place. Oops.

### Ground sticking

Another place game physics conflict with physics engines is with running to the top of a slope. On a real hill, of course, you land on top of the slope and are probably glad of it; slopes are hard to climb!

In a video game, you go flying. Because you’re a box. With momentum. So you hit the peak and keep going in the same direction. Which is diagonally upwards.

### Projectiles

To make them more predictable, projectiles generally aren’t subject to gravity, at least as far as I’ve seen. The real world does not have such an exemption. The real world imposes gravity even on sniper rifles, which in a video game are often implemented as an instant trace unaffected by anything in the world because the bullet never actually exists in the world.

## Resistance

Ah. Welcome to hell.

### Water

Water is an interesting case, and offhand I don’t know the gritty details of how games implement it. In the real world, water applies a resistant drag force to movement — and that force is proportional to the square of velocity, which I’d completely forgotten until right now. I am almost positive that no game handles that correctly. But then, in real-world water, you can push against the water itself for movement, and games don’t simulate that either. What’s the rough equivalent?

The Sonic Physics Guide suggests that Sonic handles it by basically halving everything: acceleration, max speed, friction, etc. When Sonic enters water, his speed is cut; when Sonic exits water, his speed is increased.

That last bit feels validating — I could swear Metroid Prime did the same thing, and built my own solution around it, but couldn’t remember for sure. It makes no sense, of course, for a jump to become faster just because you happened to break the surface of the water, but it feels fantastic.

The thing I did was similar, except that I didn’t want to add a multiplier in a dozen places when you happen to be underwater (and remember which ones need it to be squared, etc.). So instead, I calculate everything completely as normal, so velocity is exactly the same as it would be on dry land — but the distance you would move gets halved. The effect seems to be pretty similar to most platformers with water, at least as far as I can tell. It hasn’t shown up in a published game and I only added this fairly recently, so I might be overlooking some reason this is a bad idea.

(One reason that comes to mind is that velocity is now a little white lie while underwater, so anything relying on velocity for interesting effects might be thrown off. Or maybe that’s correct, because velocity thresholds should be halved underwater too? Hm!)

Notably, air is also a fluid, so it should behave the same way (just with different constants). I definitely don’t think any games apply air drag that’s proportional to the square of velocity.

### Friction

Friction is, in my experience, a little handwaved. Probably because real-world friction is so darn complicated.

Consider that in the real world, we want very high friction on the surfaces we walk on — shoes and tires are explicitly designed to increase it, even. We move by bracing a back foot against the ground and using that to push ourselves forward, so we want the ground to resist our push as much as possible.

In a game world, we are a box. We move by being pushed by some invisible outside force, so if the friction between ourselves and the ground is too high, we won’t be able to move at all! That’s complete nonsense physically, but it turns out to be handy in some cases — for example, highish friction can simulate walking through deep mud, which should be difficult due to fluid drag and low friction.

But the best-known example of the fakeness of game friction is video game ice. Walking on real-world ice is difficult because the low friction means low grip; your feet are likely to slip out from under you, and you’ll simply fall down and have trouble moving at all. In a video game, you can’t fall down, so you have the opposite experience: you spend most of your time sliding around uncontrollably. Yet ice is so common in video games (and perhaps so uncommon in places I’ve lived) that I, at least, had never really thought about this disparity until an hour or so ago.

### Game friction vs real-world friction

Real-world friction is a force. It’s the normal force (which is the force exerted by the object on the surface) times some constant that depends on how the two materials interact.

Force is mass times acceleration, and platformers often ignore mass, so friction ought to be an acceleration — applied against the object’s movement, but never enough to push it backwards.

I haven’t made any games where variable friction plays a significant role, but my gut instinct is that low friction should mean the player accelerates more slowly but has a higher max speed, and high friction should mean the opposite. I see from my own source code that I didn’t even do what I just said, so let’s defer to some better-made and well-documented games: Sonic and Doom.

In Sonic, friction is a fixed value subtracted from the player’s velocity (regardless of direction) each tic. Sonic has a fixed framerate, so the units are really pixels per tic squared (i.e. acceleration), multiplied by an implicit 1 tic per tic. So far, so good.

But Sonic’s friction only applies if the player isn’t pressing or . Hang on, that isn’t friction at all; that’s just deceleration! That’s equivalent to jogging to a stop. If friction were lower, Sonic would take longer to stop, but otherwise this is only tangentially related to friction.

(In fairness, this approach would decently emulate friction for non-conscious sliding objects, which are never going to be pressing movement buttons. Also, we don’t have the Sonic source code, and the name “friction” is a fan invention; the Sonic Physics Guide already uses “deceleration” to describe the player’s acceleration when turning around.)

Okay, let’s try Doom. In Doom, the default friction is 90.625%.

Hang on, what?

Yes, in Doom, friction is a multiplier applied every tic. Doom runs at 35 tics per second, so this is a multiplier of 0.032 per second. Yikes!

This isn’t anything remotely like real friction, but it’s much easier to implement. With friction as acceleration, the game has to know both the direction of movement (so it can apply friction in the opposite direction) and the magnitude (so it doesn’t overshoot and launch the object in the other direction). That means taking a semi-costly square root and also writing extra code to cap the amount of friction. With a multiplier, neither is necessary; just multiply the whole velocity vector and you’re done.

There are some downsides. One is that objects will never actually stop, since multiplying by 3% repeatedly will never produce a result of zero — though eventually the speed will become small enough to either slip below a “minimum speed” threshold or simply no longer fit in a float representation. Another is that the units are fairly meaningless: with Doom’s default friction of 90.625%, about how long does it take for the player to stop? I have no idea, partly because “stop” is ambiguous here! If friction were an acceleration, I could divide it into the player’s max speed to get a time.

All that aside, what are the actual effects of changing Doom’s friction? What an excellent question that’s surprisingly tricky to answer. (Note that friction can’t be changed in original Doom, only in the Boom port and its derivatives.) Here’s what I’ve pieced together.

Doom’s “friction” is really two values. “Friction” itself is a multiplier applied to moving objects on every tic, but there’s also a move factor which defaults to $$\frac{1}{32} = 0.03125$$ and is derived from friction for custom values.

Every tic, the player’s velocity is multiplied by friction, and then increased by their speed times the move factor.

$$v(n) = v(n – 1) \times friction + speed \times move factor$$

Eventually, the reduction from friction will balance out the speed boost. That happens when $$v(n) = v(n – 1)$$, so we can rearrange it to find the player’s effective max speed:

$$v = v \times friction + speed \times move factor \\ v – v \times friction = speed \times move factor \\ v = speed \times \frac{move factor}{1 – friction}$$

For vanilla Doom’s move factor of 0.03125 and friction of 0.90625, that becomes:

$$v = speed \times \frac{\frac{1}{32}}{1 – \frac{29}{32}} = speed \times \frac{\frac{1}{32}}{\frac{3}{32}} = \frac{1}{3} \times speed$$

Curiously, “speed” is three times the maximum speed an actor can actually move. Doomguy’s run speed is 50, so in practice he moves a third of that, or 16⅔ units per tic. (Of course, this isn’t counting SR40, a bug that lets Doomguy run ~40% faster than intended diagonally.)

So now, what if you change friction? Even more curiously, the move factor is calculated completely differently depending on whether friction is higher or lower than the default Doom amount:

$$move factor = \begin{cases} \frac{133 – 128 \times friction}{544} &≈ 0.244 – 0.235 \times friction & \text{ if } friction \ge \frac{29}{32} \\ \frac{81920 \times friction – 70145}{1048576} &≈ 0.078 \times friction – 0.067 & \text{ otherwise } \end{cases}$$

That’s pretty weird? Complicating things further is that low friction (which means muddy terrain, remember) has an extra multiplier on its move factor, depending on how fast you’re already going — the idea is apparently that you have a hard time getting going, but it gets easier as you find your footing. The extra multiplier maxes out at 8, which makes the two halves of that function meet at the vanilla Doom value.

That very top point corresponds to the move factor from the original game. So no matter what you do to friction, the move factor becomes lower. At 0.85 and change, you can no longer move at all; below that, you move backwards.

From the formula above, it’s easy to see what changes to friction and move factor will do to Doomguy’s stable velocity. Move factor is in the numerator, so increasing it will increase stable velocity — but it can’t increase, so stable velocity can only ever decrease. Friction is in the denominator, but it’s subtracted from 1, so increasing friction will make the denominator a smaller value less than 1, i.e. increase stable velocity. Combined, we get this relationship between friction and stable velocity.

As friction approaches 1, stable velocity grows without bound. This makes sense, given the definition of $$v(n)$$ — if friction is 1, the velocity from the previous tic isn’t reduced at all, so we just keep accelerating freely.

All of this is why I’m wary of using multipliers.

Anyway, this leaves me with one last question about the effects of Doom’s friction: how long does it take to reach stable velocity? Barring precision errors, we’ll never truly reach stable velocity, but let’s say within 5%. First we need a closed formula for the velocity after some number of tics. This is a simple recurrence relation, and you can write a few terms out yourself if you want to be sure this is right.

$$v(n) = v_0 \times friction^n + speed \times move factor \times \frac{friction^n – 1}{friction – 1}$$

Our initial velocity is zero, so the first term disappears. Set this equal to the stable formula and solve for n:

$$speed \times move factor \times \frac{friction^n – 1}{friction – 1} = (1 – 5\%) \times speed \times \frac{move factor}{1 – friction} \\ friction^n – 1 = -(1 – 5\%) \\ n = \frac{\ln 5\%}{\ln friction}$$

Speed” and move factor disappear entirely, which makes sense, and this is purely a function of friction (and how close we want to get). For vanilla Doom, that comes out to 30.4, which is a little less than a second. For other values of friction:

As friction increases (which in Doom terms means the surface is more slippery), it takes longer and longer to reach stable speed, which is in turn greater and greater. For lesser friction (i.e. mud), stable speed is lower, but reached fairly quickly. (Of course, the extra “getting going” multiplier while in mud adds some extra time here, but including that in the graph is a bit more complicated.)

I think this matches with my instincts above. How fascinating!

What’s that? This is way too much math and you hate it? Then don’t use multipliers in game physics.

## Uh

That was a hell of a diversion!

I guess the goofiest stuff in basic game physics is really just about mapping player controls to in-game actions like jumping and deceleration; the rest consists of hacks to compensate for representing everything as a box.

# Kroah-Hartman: Meltdown and Spectre Linux Kernel Status

Post Syndicated from corbet original https://lwn.net/Articles/743383/rss

Here’s an
update from Greg Kroah-Hartman
on the kernel’s response to Meltdown and
Spectre. “If you rely on any other kernel tree other than 4.4, 4.9, or 4.14 right now, and you do not have a distribution supporting you, you are out of luck. The lack of patches to resolve the Meltdown problem is so minor compared to the hundreds of other known exploits and bugs that your kernel version currently contains. You need to worry about that more than anything else at this moment, and get your systems up to date first.

Also, go yell at the people who forced you to run an obsoleted and insecure
kernel version, they are the ones that need to learn that doing so is a
totally reckless act.”

# More details about mitigations for the CPU Speculative Execution issue (Google Security Blog)

Post Syndicated from jake original https://lwn.net/Articles/743269/rss

One of the main concerns about the mitigations for the Meltdown/Spectre speculative execution bugs has been performance. The Google Security Blog is reporting negligible performance impact on Google systems for two of the mitigations (kernel page-table isolation and Retpoline): “In response to the vulnerabilities that were discovered we developed a novel mitigation called “Retpoline” — a binary modification technique that protects against “branch target injection” attacks. We shared Retpoline with our industry partners and have deployed it on Google’s systems, where we have observed negligible impact on performance.
In addition, we have deployed Kernel Page Table Isolation (KPTI) — a general purpose technique for better protecting sensitive information in memory from other software running on a machine — to the entire fleet of Google Linux production servers that support all of our products, including Search, Gmail, YouTube, and Google Cloud Platform.
There has been speculation that the deployment of KPTI causes significant performance slowdowns. Performance can vary, as the impact of the KPTI mitigations depends on the rate of system calls made by an application. On most of our workloads, including our cloud infrastructure, we see negligible impact on performance.

# Three new stable kernels

Post Syndicated from jake original https://lwn.net/Articles/743246/rss

Greg Kroah-Hartman has announced the release of the 4.14.12, 4.9.75, and 4.4.110 stable kernels. The bulk of the
changes are either to fix the mitigations for Meltdown/Spectre (in 4.14.12) or to backport
those mitigations (in the two older kernels). There are apparently known (or
suspected) problems with
each of the releases, which Kroah-Hartman is hoping to get shaken out in
the near term. For example, the 4.4.110 announcement warns: “But be
careful, there have been some reports of problems with this
release during the -rc review cycle. Hopefully all of those issues are
now resolved.

So please test, as of right now, it should be ‘bug compatible’ with the
‘enterprise’ kernel releases with regards to the Meltdown bug and proper
support on all virtual platforms (meaning there is still a vdso issue
that might trip up some old binaries, again, please test!)”

# timeShift(GrafanaBuzz, 1w) Issue 28

Post Syndicated from Blogs on Grafana Labs Blog original https://grafana.com/blog/2018/01/05/timeshiftgrafanabuzz-1w-issue-28/

Happy new year! Grafana Labs is getting back in the swing of things after taking some time off to celebrate 2017, and spending time with family and friends. We’re diligently working on the new Grafana v5.0 release (planning v5.0 beta release by end of January), which includes a ton of new features, a new layout engine, and a polished UI. We’d love to hear your feedback!

#### Latest Stable Release

Grafana 4.6.3 is now available. Latest bugfixes include:

• Gzip: Fixes bug Gravatar images when gzip was enabled #5952
• Alert list: Now shows alert state changes even after adding manual annotations on dashboard #99513
• Alerting: Fixes bug where rules evaluated as firing when all conditions was false and using OR operator. #93183
• Cloudwatch: CloudWatch no longer display metrics’ default alias #101514, thx @mtanda

#### From the Blogosphere

Why Observability Matters – Now and in the Future: Our own Carl Bergquist teamed up with Neil Gehani, Director of Product at Weaveworks to discuss best practices on how to get started with monitoring your application and infrastructure. This video focuses on modern containerized applications instrumented to use Prometheus to generate metrics and Grafana to visualize them.

How to Install and Secure Grafana on Ubuntu 16.04: In this tutorial, you’ll learn how to install and secure Grafana with a SSL certificate and a Nginx reverse proxy, then you’ll modify Grafana’s default settings for even tighter security.

Monitoring Informix with Grafana: Ben walks us through how to use Grafana to visualize data from IBM Informix and offers a practical demonstration using Docker containers. He also talks about his philosophy of sharing dashboards across teams, important metrics to collect, and how he would like to improve his monitoring stack.

Monitor your hosts with Glances + InfluxDB + Grafana: Glances is a cross-platform system monitoring tool written in Python. This article takes you step by step through the pieces of the stack, installation, confirguration and provides a sample dashboard to get you up and running.

#### GrafanaCon Tickets are Going Fast!

Lock in your seat for GrafanaCon EU while there are still tickets avaialable! Join us March 1-2, 2018 in Amsterdam for 2 days of talks centered around Grafana and the surrounding monitoring ecosystem including Graphite, Prometheus, InfluxData, Elasticsearch, Kubernetes, and more.

We have some exciting talks lined up from Google, CERN, Bloomberg, eBay, Red Hat, Tinder, Fastly, Automattic, Prometheus, InfluxData, Percona and more! You can see the full list of speakers below, but be sure to get your ticket now.

#### GrafanaCon EU will feature talks from:

“Google Bigtable”
Misha Brukman
PROJECT MANAGER,
GOOGLE CLOUD
GOOGLE

“Monitoring at Bloomberg”
Stig Sorensen
HEAD OF TELEMETRY
BLOOMBERG

“Monitoring at Bloomberg”
Sean Hanson
SOFTWARE DEVELOPER
BLOOMBERG

“Monitoring Tinder’s Billions of Swipes with Grafana”
Utkarsh Bhatnagar
SR. SOFTWARE ENGINEER
TINDER

“Grafana at CERN”
Borja Garrido
PROJECT ASSOCIATE
CERN

“Monitoring the Huge Scale at Automattic”
Abhishek Gahlot
SOFTWARE ENGINEER
Automattic

“Real-time Engagement During the 2016 US Presidential Election”
Anna MacLachlan
CONTENT MARKETING MANAGER
Fastly

“Real-time Engagement During the 2016 US Presidential Election”
Gerlando Piro
FRONT END DEVELOPER
Fastly

“Grafana v5 and the Future”
Torkel Odegaard
CREATOR | PROJECT LEAD
GRAFANA

“Prometheus for Monitoring Metrics”
Brian Brazil
FOUNDER
ROBUST PERCEPTION

“What We Learned Integrating Grafana with Prometheus”
Peter Zaitsev
CO-FOUNDER | CEO
PERCONA

“The Biz of Grafana”
Raj Dutt
CO-FOUNDER | CEO
GRAFANA LABS

“What’s New In Graphite”
Dan Cech
DIR, PLATFORM SERVICES
GRAFANA LABS

“The Design of IFQL, the New Influx Functional Query Language”
Paul Dix
CO-FOUNTER | CTO
INFLUXDATA

“Writing Grafana Dashboards with Jsonnet”
Julien Pivotto
OPEN SOURCE CONSULTANT
INUITS

“Monitoring AI Platform at eBay”
Deepak Vasthimal
MTS-2 SOFTWARE ENGINEER
EBAY

“Running a Power Plant with Grafana”
Ryan McKinley
DEVELOPER
NATEL ENERGY

“Performance Metrics and User Experience: A “Tinder” Experience”
Susanne Greiner
DATA SCIENTIST
WÜRTH PHOENIX S.R.L.

“Analyzing Performance of OpenStack with Grafana Dashboards”
Alex Krzos
SENIOR SOFTWARE ENGINEER
RED HAT INC.

“Storage Monitoring at Shell Upstream”
Arie Jan Kraai
STORAGE ENGINEER
SHELL TECHNICAL LANDSCAPE SERVICE

“The RED Method: How To Instrument Your Services”
Tom Wilkie
FOUNDER
KAUSAL

“Grafana Usage in the Quality Assurance Process”
Andrejs Kalnacs
LEAD SOFTWARE DEVELOPER IN TEST
EVOLUTION GAMING

“Using Prometheus and Grafana for Monitoring my Power Usage”
Erwin de Keijzer
LINUX ENGINEER
SNOW BV

“Weather, Power & Market Forecasts with Grafana”
Max von Roden
DATA SCIENTIST
ENERGY WEATHER

“Weather, Power & Market Forecasts with Grafana”
Steffen Knott
HEAD OF IT
ENERGY WEATHER

“Inherited Technical Debt – A Tale of Overcoming Enterprise Inertia”
Jordan J. Hamel
HEAD OF MONITORING PLATFORMS
AMGEN

“Grafanalib: Dashboards as Code”
Jonathan Lange
VP OF ENGINEERING
WEAVEWORKS

“The Journey of Shifting the MQTT Broker HiveMQ to Kubernetes”
Arnold Bechtoldt
SENIOR SYSTEMS ENGINEER
INOVEX

“Graphs Tell Stories”
Blerim Sheqa
SENIOR DEVELOPER
NETWAYS

[email protected] or How to Store Millions of Metrics per Second”
Vladimir Smirnov
SYSTEM ADMINISTRATOR
Booking.com

#### Upcoming Events:

In between code pushes we like to speak at, sponsor and attend all kinds of conferences and meetups. We also like to make sure we mention other Grafana-related events happening all over the world. If you’re putting on just such an event, let us know and we’ll list it here.

FOSDEM | Brussels, Belgium – Feb 3-4, 2018: FOSDEM is a free developer conference where thousands of developers of free and open source software gather to share ideas and technology. There is no need to register; all are welcome.

Jfokus | Stockholm, Sweden – Feb 5-7, 2018:
Carl Bergquist – Quickie: Monitoring? Not OPS Problem

Why should we monitor our system? Why can’t we just rely on the operations team anymore? They use to be able to do that. What’s currently changing? Presentation content: – Why do we monitor our system – How did it use to work? – Whats changing – Why do we need to shift focus – Everyone should be on call. – Resilience is the goal (Best way of having someone care about quality is to make them responsible).

Jfokus | Stockholm, Sweden – Feb 5-7, 2018:
Leonard Gram – Presentation: DevOps Deconstructed

What’s a Site Reliability Engineer and how’s that role different from the DevOps engineer my boss wants to hire? I really don’t want to be on call, should I? Is Docker the right place for my code or am I better of just going straight to Serverless? And why should I care about any of it? I’ll try to answer some of these questions while looking at what DevOps really is about and how commodisation of servers through “the cloud” ties into it all. This session will be an opinionated piece from a developer who’s been on-call for the past 6 years and would like to convince you to do the same, at least once.

#### Tweet of the Week

We scour Twitter each week to find an interesting/beautiful dashboard and show it off! #monitoringLove

Awesome! Let us know if you have any questions – we’re happy to help out. We also have a bunch of screencasts to help you get going.

#### Grafana Labs is Hiring!

We are passionate about open source software and thrive on tackling complex challenges to build the future. We ship code from every corner of the globe and love working with the community. If this sounds exciting, you’re in luck – WE’RE HIRING!

Check out our

#### How are we doing?

That’s a wrap! Let us know what you think about timeShift. Submit a comment on this article below, or post something at our community forum. See you next year!

Follow us on Twitter, like us on Facebook, and join the Grafana Labs community.

# Backblaze Cloud Backup Release 5.2

Post Syndicated from Yev original https://www.backblaze.com/blog/backblaze-cloud-backup-release-5-2/

We’re pleased to start the year off the right way, with an update to Backblaze Cloud Backup, version 5.2! This is a smaller release, but does increase backup speeds, optimizes the backup client, and addresses a few minor bugs that we’re excited to lay to rest.

What’s New

• Increased transmission speed of files between 30MB and 400MB+.
• Optimized indexing to decrease system resource usage and lower the performance impact on computers that are backing up to Backblaze.
• Adjusted external hard drive monitoring and increased the speed of indexing.
• Changed copyright to 2018.

Release Version Number:

• Mac — 5.2.0
• PC — 5.2.0

Clients:
Backblaze Personal Backup
Backblaze Business Backup

Availability:
January 4, 2018

Upgrade Methods:

• Immediately as a download from: files.backblaze.com
• Rolling out soon when performing a “Check for Updates” (right-click on the Backblaze icon and then select “Check for Updates”).
• Rolling out soon as a download from: https://secure.backblaze.com/update.htm.
• Rolling out soon as the default download from: www.backblaze.com.
• Auto-update will begin in a couple of weeks.

Cost:
This is a free update for all Backblaze Cloud Backup consumer and business customers and active trial users.

The post Backblaze Cloud Backup Release 5.2 appeared first on Backblaze Blog | Cloud Storage & Cloud Backup.

# The Raspberry Pi PiServer tool

Post Syndicated from Gordon Hollingworth original https://www.raspberrypi.org/blog/piserver/

As Simon mentioned in his recent blog post about Raspbian Stretch, we have developed a new piece of software called PiServer. Use this tool to easily set up a network of client Raspberry Pis connected to a single x86-based server via Ethernet. With PiServer, you don’t need SD cards, you can control all clients via the server, and you can add and configure user accounts — it’s ideal for the classroom, your home, or an industrial setting.

## Client? Server?

Before I go into more detail, let me quickly explain some terms.

• Server — the server is the computer that provides the file system, boot files, and password authentication to the client(s)
• Client — a client is a computer that retrieves boot files from the server over the network, and then uses a file system the server has shared. More than one client can connect to a server, but all clients use the same file system.
• User – a user is a user name/password combination that allows someone to log into a client to access the file system on the server. Any user can log into any client with their credentials, and will always see the same server and share the same file system. Users do not have sudo capability on a client, meaning they cannot make significant changes to the file system and software.

## I see no SD cards

Last year we described how the Raspberry Pi 3 Model B can be booted without an SD card over an Ethernet network from another computer (the server). This is called network booting or PXE (pronounced ‘pixie’) booting.

Why would you want to do this?

• A client computer (the Raspberry Pi) doesn’t need any permanent storage (an SD card) to boot.
• You can network a large number of clients to one server, and all clients are exactly the same. If you log into one of the clients, you will see the same file system as if you logged into any other client.
• The server can be run on an x86 system, which means you get to take advantage of the performance, network, and disk speed on the server.

Sounds great, right? Of course, for the less technical, creating such a network is very difficult. For example, there’s setting up all the required DHCP and TFTP servers, and making sure they behave nicely with the rest of the network. If you get this wrong, you can break your entire network.

## PiServer to the rescue

To make network booting easy, I thought it would be nice to develop an application which did everything for you. Let me introduce: PiServer!

PiServer has the following functionalities:

• It automatically detects Raspberry Pis trying to network boot, so you don’t have to work out their Ethernet addresses.
• It sets up a DHCP server — the thing inside the router that gives all network devices an IP address — either in proxy mode or in full IP mode. No matter the mode, the DHCP server will only reply to the Raspberry Pis you have specified, which is important for network safety.
• It creates user names and passwords for the server. This is great for a classroom full of Pis: just set up all the users beforehand, and everyone gets to log in with their passwords and keep all their work in a central place. Moreover, users cannot change the software, so educators have control over which programs their learners can use.
• It uses a slightly altered Raspbian build which allows separation of temporary spaces, doesn’t have the default ‘pi’ user, and has LDAP enabled for log-in.

## What can I do with PiServer?

#### Serve a whole classroom of Pis

In a classroom, PiServer allows all files for lessons or projects to be stored on a central x86-based computer. Each user can have their own account, and any files they create are also stored on the server. Moreover, the networked Pis doesn’t need to be connected to the internet. The teacher has centralised control over all Pis, and all Pis are user-agnostic, meaning there’s no need to match a person with a computer or an SD card.

#### Build a home server

PiServer could be used in the home to serve file systems for all Raspberry Pis around the house — either a single common Raspbian file system for all Pis or a different operating system for each. Hopefully, our extensive OS suppliers will provide suitable build files in future.

#### Use it as a controller for networked Pis

In an industrial scenario, it is possible to use PiServer to develop a network of Raspberry Pis (maybe even using Power over Ethernet (PoE)) such that the control software for each Pi is stored remotely on a server. This enables easy remote control and provisioning of the Pis from a central repository.

## How to use PiServer

#### The client machines

So that you can use a Pi as a client, you need to enable network booting on it. Power it up using an SD card with a Raspbian Lite image, and open a terminal window. Type in

echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt

and press Return. This adds the line program_usb_boot_mode=1 to the end of the config.txt file in /boot. Now power the Pi down and remove the SD card. The next time you connect the Pi to a power source, you will be able to network boot it.

#### The server machine

As a server, you will need an x86 computer on which you can install x86 Debian Stretch. Refer to Simon’s blog post for additional information on this. It is possible to use a Raspberry Pi to serve to the client Pis, but the file system will be slower, especially at boot time.

Make sure your server has a good amount of disk space available for the file system — in general, we recommend at least 16Gb SD cards for Raspberry Pis. The whole client file system is stored locally on the server, so the disk space requirement is fairly significant.

Next, start PiServer by clicking on the start icon and then clicking Preferences > PiServer. This will open a graphical user interface — the wizard — that will walk you through setting up your network. Skip the introduction screen, and you should see a screen looking like this:

If you’ve enabled network booting on the client Pis and they are connected to a power source, their MAC addresses will automatically appear in the table shown above. When you have added all your Pis, click Next.

On the Add users screen, you can set up users on your server. These are pairs of user names and passwords that will be valid for logging into the client Raspberry Pis. Don’t worry, you can add more users at any point. Click Next again when you’re done.

The Add software screen allows you to select the operating system you want to run on the attached Pis. (You’ll have the option to assign an operating system to each client individually in the setting after the wizard has finished its job.) There are some automatically populated operating systems, such as Raspbian and Raspbian Lite. Hopefully, we’ll add more in due course. You can also provide your own operating system from a local file, or install it from a URL. For further information about how these operating system images are created, have a look at the scripts in /var/lib/piserver/scripts.

Once you’re done, click Next again. The wizard will then install the necessary components and the operating systems you’ve chosen. This will take a little time, so grab a coffee (or decaffeinated drink of your choice).

When the installation process is finished, PiServer is up and running — all you need to do is reboot the Pis to get them to run from the server.

## Shooting troubles

If you have trouble getting clients connected to your network, there are a fewthings you can do to debug:

1. If some clients are connecting but others are not, check whether you’ve enabled the network booting mode on the Pis that give you issues. To do that, plug an Ethernet cable into the Pi (with the SD card removed) — the LEDs on the Pi and connector should turn on. If that doesn’t happen, you’ll need to follow the instructions above to boot the Pi and edit its /boot/config.txt file.
2. If you can’t connect to any clients, check whether your network is suitable: format an SD card, and copy bootcode.bin from /boot on a standard Raspbian image onto it. Plug the card into a client Pi, and check whether it appears as a new MAC address in the PiServer GUI. If it does, then the problem is a known issue, and you can head to our forums to ask for advice about it (the network booting code has a couple of problems which we’re already aware of). For a temporary fix, you can clone the SD card on which bootcode.bin is stored for all your clients.

If neither of these things fix your problem, our forums are the place to find help — there’s a host of people there who’ve got PiServer working. If you’re sure you have identified a problem that hasn’t been addressed on the forums, or if you have a request for a functionality, then please add it to the GitHub issues.

The post The Raspberry Pi PiServer tool appeared first on Raspberry Pi.

# Some notes on Meltdown/Spectre

Post Syndicated from Robert Graham original http://blog.erratasec.com/2018/01/some-notes-on-meltdownspectre.html

I thought I’d write up some notes.

You don’t have to worry if you patch. If you download the latest update from Microsoft, Apple, or Linux, then the problem is fixed for you and you don’t have to worry. If you aren’t up to date, then there’s a lot of other nasties out there you should probably also be worrying about. I mention this because while this bug is big in the news, it’s probably not news the average consumer needs to concern themselves with.

This will force a redesign of CPUs and operating systems. While not a big news item for consumers, it’s huge in the geek world. We’ll need to redesign operating systems and how CPUs are made.

Don’t worry about the performance hit. Some, especially avid gamers, are concerned about the claims of “30%” performance reduction when applying the patch. That’s only in some rare cases, so you shouldn’t worry too much about it. As far as I can tell, 3D games aren’t likely to see less than 1% performance degradation. If you imagine your game is suddenly slower after the patch, then something else broke it.

This wasn’t foreseeable. A common cliche is that such bugs happen because people don’t take security seriously, or that they are taking “shortcuts”. That’s not the case here. Speculative execution and timing issues with caches are inherent issues with CPU hardware. “Fixing” this would make CPUs run ten times slower. Thus, while we can tweek hardware going forward, the larger change will be in software.

There’s no good way to disclose this. The cybersecurity industry has a process for coordinating the release of such bugs, which appears to have broken down. In truth, it didn’t. Once Linus announced a security patch that would degrade performance of the Linux kernel, we knew the coming bug was going to be Big. Looking at the Linux patch, tracking backwards to the bug was only a matter of time. Hence, the release of this information was a bit sooner than some wanted. This is to be expected, and is nothing to be upset about.

It helps to have a name. Many are offended by the crassness of naming vulnerabilities and giving them logos. On the other hand, we are going to be talking about these bugs for the next decade. Having a recognizable name, rather than a hard-to-remember number, is useful.

Should I stop buying Intel? Intel has the worst of the bugs here. On the other hand, ARM and AMD alternatives have their own problems. Many want to deploy ARM servers in their data centers, but these are likely to expose bugs you don’t see on x86 servers. The software fix, “page table isolation”, seems to work, so there might not be anything to worry about. On the other hand, holding up purchases because of “fear” of this bug is a good way to squeeze price reductions out of your vendor. Conversely, later generation CPUs, “Haswell” and even “Skylake” seem to have the least performance degradation, so it might be time to upgrade older servers to newer processors.

Intel misleads. Intel has a press release that implies they are not impacted any worse than others. This is wrong: the “Meltdown” issue appears to apply only to Intel CPUs. I don’t like such marketing crap, so I mention it.

Statements from companies:

# Why Meltdown exists

Post Syndicated from Robert Graham original http://blog.erratasec.com/2018/01/why-meltdown-exists.html

So I thought I’d answer this question. I’m not a “chipmaker”, but I’ve been optimizing low-level assembly x86 assembly language for a couple of decades.

The tl;dr version is this: the CPUs have no bug. The results are correct, it’s just that the timing is different. CPU designers will never fix the general problem of undetermined timing.
CPUs are deterministic in the results they produce. If you add 5+6, you always get 11 — always. On the other hand, the amount of time they take is non-deterministic. Run a benchmark on your computer. Now run it again. The amount of time it took varies, for a lot of reasons.
That CPUs take an unknown amount of time is an inherent problem in CPU design. Even if you do everything right, “interrupts” from clock timers and network cards will still cause undefined timing problems. Therefore, CPU designers have thrown the concept of “deterministic time” out the window.
The biggest source of non-deterministic behavior is the high-speed memory cache on the chip. When a piece of data is in the cache, the CPU accesses it immediately. When it isn’t, the CPU has to stop and wait for slow main memory. Other things happening in the system impacts the cache, unexpectedly evicting recently used data for one purpose in favor of data for another purpose.
Hackers love “non-deterministic”, because while such things are unknowable in theory, they are often knowable in practice.
That’s the case of the granddaddy of all hacker exploits, the “buffer overflow”. From the programmer’s perspective, the bug will result in just the software crashing for undefinable reasons. From the hacker’s perspective, they reverse engineer what’s going on underneath, then carefully craft buffer contents so the program doesn’t crash, but instead continue to run the code the hacker supplies within the buffer. Buffer overflows are undefined in theory, well-defined in practice.
Hackers have already been exploiting this defineable/undefinable timing problems with the cache for a long time. An example is cache timing attacks on AES. AES reads a matrix from memory as it encrypts things. By playing with the cache, evicting things, timing things, you can figure out the pattern of memory accesses, and hence the secret key.
Such cache timing attacks have been around since the beginning, really, and it’s simply an unsolvable problem. Instead, we have workarounds, such as changing our crypto algorithms to not depend upon cache, or better yet, implement them directly in the CPU (such as the Intel AES specialized instructions).
What’s happened today with Meltdown is that incompletely executed instructions, which discard their results, do affect the cache. We can then recover those partial/temporary/discarded results by measuring the cache timing. This has been known for a while, but we couldn’t figure out how to successfully exploit this, as this paper from Anders Fogh reports. Hackers fixed this, making it practically exploitable.
As a CPU designer, Intel has few good options.
Fixing cache timing attacks is an impossibility. They can do some tricks, such as allowing some software to reserve part of the cache for private use, for special crypto operations, but the general problem is unsolvable.
Fixing the “incomplete results” problem from affecting the cache is also difficult. Intel has the fastest CPUs, and the reason is such speculative execution. The other CPU designers have the same problem: fixing the three problems identified today would cause massive performance issues. They’ll come up with improvements, probably, but not complete solutions.
Instead, the fix is within the operating system. Frankly, it’s a needed change that should’ve been done a decade ago. They’ve just been putting it off because of the performance hit. Now that the change has been forced to happen, CPU designers will probably figure out ways to mitigate the performance cost.
Thus, the Intel CPU you buy a year from now will have some partial fixes for these exactly problems without addressing the larger security concerns. They will also have performance enhancements to make the operating system patches faster.
But the underlying theoretical problem will never be solved, and is essentially unsolvable.

# The disclosure on the processor bugs

Post Syndicated from corbet original https://lwn.net/Articles/742744/rss

The rumored bugs in Intel (and beyond) processors have now been disclosed:
they are called Meltdown and
Spectre
, and have the requisite cute logos. Stay tuned for more.

See also: this Project
Zero
blog post. “Variants of this issue are known to affect many
modern processors, including certain processors by Intel, AMD and ARM. For
a few Intel and AMD CPU models, we have exploits that work against real
software. We reported this issue to Intel, AMD and ARM on
2017-06-01.

See also: this
Google blog posting
on how it affects users of Google products in
particular. “[Android] devices with the latest security update are
protected. Furthermore, we are unaware of any successful reproduction of
this vulnerability that would allow unauthorized information disclosure on
ARM-based Android devices. Supported Nexus and Pixel devices with the
latest security update are protected.

# A press release from Intel

Post Syndicated from corbet original https://lwn.net/Articles/742714/rss

Intel has responded
to reports of security issues in its processors:

Recent reports that these exploits are caused by a “bug” or a
“flaw” and are unique to Intel products are incorrect. Based on the
analysis to date, many types of computing devices — with many
different vendors’ processors and operating systems — are
susceptible to these exploits.

Intel is committed to product and customer security and is working
closely with many other technology companies, including AMD, ARM
Holdings and several operating system vendors, to develop an
industry-wide approach to resolve this issue promptly and
constructively. Intel has begun providing software and firmware
updates to mitigate these exploits. Contrary to some reports, any
performance impacts are workload-dependent, and, for the average
computer user, should not be significant and will be mitigated over
time.

Stay tuned, there is certainly more to come.

# [\$] Statistics for the 4.15 kernel

Post Syndicated from corbet original https://lwn.net/Articles/742672/rss

The 4.15 kernel is likely to require a relatively long development cycle as
a result of the post-rc5 merge of the kernel
page-table isolation
patches. That said, it should be in something
close to its final form, modulo some inevitable bug fixes. The development
statistics for this kernel release look fairly normal, but they do reveal an
unexpectedly busy cycle overall.

# Announcing the OpenWrt/LEDE merge

Post Syndicated from ris original https://lwn.net/Articles/742708/rss

The OpenWrt and LEDE projects have announced
their unification
under the OpenWrt name. The old OpenWrt CC 15.05
release series will receive a limited amount of security and bug fixes, but
the current LEDE 17.01 series is the most up-to-date. “The merged
project will use the code base of the former LEDE project. OpenWrt specific
patches not present in the LEDE repository but meeting LEDEs code quality
requirements got integrated into the new tree. The source code will be
hosted at git.openwrt.org with a
continuously synchronized mirror hosted at Github. The original OpenWrt
codebase has been archived on
Github
for future reference.