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today's leftovers

Submitted by Roy Schestowitz on Thursday 4th of August 2022 09:56:46 AM Filed under
Misc
  • Steam Deck: You Can Finally Order it in Japan. Through Komodo, not Steam. With Higher Pricing. And No Availability Window. - Boiling Steam

    Have you heard about the new and trending JavaScript library called React.js? It’s so cool that it has been extensively used by developers to create interactive User Interfaces and components in their applications. The React library is also a great choice when you want to build fast and scalable apps with a component-based approach. If you haven’t started using it yet, it’s time you start learning. In this blog post, we will show you how to set up a React development environment on your Mac computer. Read on!

  • Docker and the OCI container ecosystem

    Docker has transformed the way many people develop and deploy software. It wasn't the first implementation of containers on Linux, but Docker's ideas about how containers should be structured and managed were different from its predecessors. Those ideas matured into industry standards, and an ecosystem of software has grown around them. Docker continues to be a major player in the ecosystem, but it is no longer the only whale in the sea — Red Hat has also done a lot of work on container tools, and alternative implementations are now available for many of Docker's offerings.

  • Stuffing the return stack buffer [LWN.net]

    "Retbleed" is the name given to a class of speculative-execution vulnerabilities involving return instructions. Mitigations for Retbleed have found their way into the mainline kernel but, as of this writing, some remaining problems have kept them from the stable update releases. Mitigating Retbleed can impede performance severely, especially on some Intel processors. Thomas Gleixner and Peter Zijlstra think they have found a better way that bypasses the existing mitigations and misleads the processor's speculative-execution mechanisms instead.

    If a CPU is to speculate past a return instruction, it must have some idea of where the code will return to. In recent Intel processors, there is a special hidden data structure called the "return stack buffer" (RSB) that caches return addresses for speculation. The RSB can hold 16 entries, so it must drop the oldest entries if a call chain goes deeper than that. As that deep call chain returns, the RSB can underflow. One might think that speculation would just stop at that point but, instead, the CPU resorts to other heuristics, including predicting from the branch history buffer. Alas, techniques for mistraining the branch history buffer are well understood at this point.

    As a result, long call chains in the kernel are susceptible to speculative-execution attacks. On Intel processors starting with the Skylake generation, the only way to prevent such attacks is to turn on the indirect branch restricted speculation (IBRS) CPU "feature", which was added by Intel early in the Spectre era. IBRS works, but it has the unwelcome side effect of reducing performance by as much as 30%. For some reason, users lack enthusiasm for this solution.

  • Support for Intel's Linear Address Masking [LWN.net]

    A 64-bit pointer can address a lot of memory — far more than just about any application could ever need. As a result, there are bits within that pointer that are not really needed to address memory, and which might be put to other needs. Storing a few bits of metadata within a pointer is a common enough use case that multiple architectures are adding support for it at the hardware level. Intel is no exception; support for its "Linear Address Masking" (LAM) feature has been slowly making its way toward the mainline kernel.

    CPUs can support this metadata by simply masking off the relevant bits before dereferencing a pointer. Naturally, every CPU vendor has managed to support this feature differently. Arm's top-byte ignore feature allows the most-significant byte of the address to be used for non-pointing purposes; it has been supported by the Linux kernel since 5.4 came out in 2019. AMD's "upper address ignore" feature, instead, only allows the seven topmost bits to be used in this way; support for this feature was proposed earlier this year but has not yet been accepted.

    One of the roadblocks in the AMD case is that this feature would allow the creation of valid user-space pointers that have the most-significant bit set. In current kernels, only kernel-space addresses have that bit set, and an unknown amount of low-level code depends on that distinction. The consequences of confusing user-space and kernel-space addresses could be severe and contribute to the ongoing CVE-number shortage, so developers are nervous about any feature that could cause such confusion to happen. Quite a bit of code would likely have to be audited to create any level of confidence that allowing user-space addresses with that bit set would not open up a whole set of security holes.

  • BSD Now 466: cat(1)’s efficiency

    Contributing to Open Source Beyond Software Development, bringing TLS 1.3 to the Internet of Old Things, How efficient can cat(1) be, boost the speed of Unix shell programs, Running FreeBSD VNET Jails on AWS EC2 with Bastille, and more

  • The Linux Link Tech Show Episode 965
  • Linux Around The World: Denmark - LinuxLinks

    We cover events and user groups that are running in Denmark. This article forms part of our Linux Around The World series.

»

More in Tux Machines

today's howtos

  • How to Change Comment Color in Vim – Fix Unreadable Blue Color

    Are you annoyed about the comment color in vim? The dark blue color of the comment is often hard to read. In this tutorial, we learn how to change the comment color in Vim. There are few methods we can use to look vim comment very readable.

  • How to Add Repository to Debian

    APT checks the health of all the packages, and dependencies of the package before installing it. APT fetches packages from one or more repositories. A repository (package source) is basically a network server. The term "package" refers to an individual file with a .deb extension that contains either all or part of an application. The normal installation comes with default repositories configured, but these contain only a few packages out of an ocean of free software available. In this tutorial, we learn how to add the package repository to Debian.

  • Making a Video of a Single Window

    I recently wanted to send someone a video of a program doing some interesting things in a single X11 window. Recording the whole desktop is easy (some readers may remember my post on Aeschylus which does just that) but it will include irrelevant (and possibly unwanted) parts of the screen, leading to unnecessarily large files. I couldn't immediately find a tool which did what I wanted on OpenBSD [1] but through a combination of xwininfo, FFmpeg, and hk I was able to put together exactly what I needed in short order. Even better, I was able to easily post-process the video to shrink its file size, speed it up, and contort it to the dimension requirements of various platforms. Here's a video straight out of the little script I put together: [...]

  • Things You Can And Can’t Do

    And it got me thinking about what you can and can’t do — what you do and don’t have control over.

  • allow-new-zones in BIND 9.16 on CentOS 8 Stream under SELinux

    We run these training systems with SELinux enabled (I wouldn’t, but my colleague likes it :-), and that’s the reason I aborted the lab: I couldn’t tell students how to solve the cause other than by disabling SELinux entirely, but there wasn’t enough time for that.

  • Will the IndieWeb Ever Become Mainstream?

    This is an interesting question, thanks for asking it, Jeremy. I do have some history with the IndieWeb, and some opinions, so let’s dive in.

    The short answer to the question is a resounding no, and it all boils down to the fact that the IndieWeb is really complicated to implement, so it will only ever appeal to developers.

  • How to Install CUPS Print Server on Ubuntu 22.04

    If your business has multiple personal computers in the network which need to print, then we need a device called a print server. Print server act intermediate between PC and printers which accept print jobs from PC and send them to respective printers. CUPS is the primary mechanism in the Unix-like operating system for printing and print services. It can allow a computer to act as a Print server. In this tutorial, we learn how to set up CUPS print server on Ubuntu 22.04.

Open Hardware: XON/XOFF and Raspberry Pi Pico

  • From XON/XOFF to Forward Incremental Search

    In the olden days of computing, software flow control with control codes XON and XOFF was a necessary feature that dumb terminals needed to support. When a terminal received more data than it could display, there needed to be a way for the terminal to tell the remote host to pause sending more data. The control code 19 was chosen for this. The control code 17 was chosen to tell the remote host to resume transmission of data.

  • Raspberry Pi Pico Used in Plug and Play System Monitor | Tom's Hardware

    Dmytro Panin is at it again, creating a teeny system monitor for his MacBook from scratch with help from our favorite microcontroller, the Raspberry Pi Pico. This plug-and-play system monitor (opens in new tab) lets him keep a close eye on resource usage without having to close any windows or launch any third-party programs. The device is Pico-powered and plugs right into the MacBook to function. It has a display screen that showcases a custom GUI featuring four bar graphs that update in real-time to show the performance of different components, including the CPU, GPU, memory, and SSD usage. It makes it possible to see how hard your PC is running at a glance.

Security Leftovers

How to Apply Accent Colour in Ubuntu Desktop

A step-by-step tutorial on how to apply accent colour in Ubuntu desktop (GNOME) with tips for Kubuntu and others. Read more

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