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Kernel: LWN's In-Depth Articles and AMD "Smart Trace Buffer" Feature Being Wired Up For Linux

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  • The intersection of modules, GKI, and rocket science [LWN.net]

    One does not normally expect a lot of controversy around a patch series that makes changes to platform-specific configurations and drivers. The furor over some work on the Samsung Exynos platform may thus be surprising. When one looks into the discussion, things become more clear; it mostly has to do with disagreements over the best ways to get hardware vendors to cooperate with the kernel development community.

    In mid-September, Will McVicker posted a brief series of changes for the Exynos configuration files; one week later, a larger, updated series followed. The purpose in both cases was to change a number of low-level system-on-chip (SoC) drivers to allow them to be built as loadable modules. That would seem like an uncontroversial change; it is normally expected that device drivers will be modular. But the situation is a little different for these low-level SoC drivers.

  • Pulling slabs out of struct page [LWN.net]

    For the time being, the effort to add the folio concept to the memory-management subsystem appears to be stalled, but appearances can be deceiving. The numerous folio discussions have produced a number of points of consensus, though; one of those is that far too much of the kernel has to work with page structures to get its job done. As an example of how a subsystem might be weaned off of struct page usage, Matthew Wilcox has split out the slab allocators in a 62-part patch set. The result may be a foreshadowing of changes to come in the memory-management subsystem.

    The kernel maintains one page structure for every physical page of memory that it manages. On a typical system with a 4KB page size, that means managing millions of those structures. A page structure tells the kernel about the state of the page it refers to: how it is being used, how many references to it exist, its position in various queues, and more. The required information varies depending on how any given page is being used at the moment; to accommodate this, struct page is a complicated mess of structures and unions. The current definition of struct page makes for good pre-Halloween reading, but those who truly want a good scare may want to see what it looked like before Wilcox cleaned things up for 4.18.

  • A rough start for ksmbd [LWN.net]

    Among the many new features pulled into the mainline during the 5.15 merge window is the ksmbd network filesystem server. Ksmbd implements the SMB protocol (also known as CIFS, though that name has gone out of favor) that is heavily used in the Windows world. The creation of an in-kernel SMB server is a bit surprising, given that Linux has benefited greatly from the user-space Samba solution since shortly after the beginning. There are reasons for this move but, in the short term at least, they risk being overshadowed by a worrisome stream of security-related problems in ksmbd.
    Why create an in-kernel SMB server at this point? In a sense, ksmbd is not meant to compete with Samba; indeed, it has been developed in cooperation with the Samba project. It is, however, meant to be a more performant and focused solution than Samba is; at this point, Samba includes a great deal of functionality beyond simple file serving. Ksmbd claims significant performance improvements on a wide range of benchmarks; the graphs on this page show a doubling of performance on some tests. An in-kernel server is an easier place to support variants like SMB Direct, which uses RDMA to transfer data between systems. By drawing more eyes to the code, merging into the mainline may also facilitate faster development in general. One other reason — which tends to be spoken rather more quietly — is that a new implementation can be licensed under GPLv2, while Samba is GPLv3.

    Ksmbd was first posted for review (as "cifsd") by Namjae Jeon in late March; the eighth revision came out just before the opening of the 5.15 merge window in late August. The last version received no review comments, but previous versions had clearly been looked at by a number of developers. Nobody objected when Steve French asked Linus Torvalds to pull ksmbd into the mainline on August 29.

  • Scrutinizing bugs found by syzbot

    The syzbot kernel-fuzzing system finds an enormous number of bugs, but, since many of them may seem to be of a relatively low severity, they have a lower priority when contending for the attention of developers. A talk at the recent Linux Security Summit North America reported on some research that dug further into the bugs that syzbot has found; the results are rather worrisome. Rather than a pile of difficult- or impossible-to-exploit bugs, there are numerous, more serious problems lurking within.

    [...]

    The first speaker on day one of the summit was Xiaochen Zou, a PhD student at the University of California, Riverside, who described a tool that he and his colleagues have been running on bugs that syzbot—which uses the syzkaller coverage-guided fuzzer—has reported in the Linux kernel. Over the last four years, syzbot has reported around 4000 bugs, of which 3000 have been fixed. There are eight categories that these bugs mainly fall into, but only some of those categories represent security bugs, he said. These are classic, severe kernel security holes, such as use after free, double free, and out-of-bounds writes; they are mostly found by the Kernel Address Sanitizer (KASAN) as part of syzkaller runs.

  • AMD "Smart Trace Buffer" Feature Being Wired Up For Linux - Phoronix

    AMD patches this month have begun preparing support for a new CPU feature called Smart Trace Buffer (STB).

    Earlier this month the initial patch was posted for enabling AMD Smart Trace Buffer support on Linux as an extension to AMD's PMC kernel driver. This morning the STB enablement has already been revised in a second version of the patches.

More in Tux Machines

How new Linux users can increase their odds of success

The Linus Tech Tips YouTube channel has been putting out a series of videos called the Switching to Linux Challenge that has been causing a bit of a stir in the Linux community. I’ve been keeping an eye on these developments, and thought it was a good time to weigh in with my thoughts. This article focuses on how new Linux users can increase their odds for success — I have also written a companion article, “What desktop Linux needs to succeed in the mainstream”, which looks at the other side of the problem. Linux is, strictly speaking, an operating system kernel, which is a small component of a larger system. However, in the common usage, Linux refers to a family of operating systems which are based on this kernel, such as Ubuntu, Fedora, Arch Linux, Alpine Linux, and so on, which are referred to as distributions. Linux is used in other contexts, such as Android, but the common usage is generally limited to this family of Linux “distros”. Several of these distros have positioned themselves for various types of users, such as office workers or gamers. However, the most common Linux user is much different. What do they look like? The key distinction which sets Linux apart from more common operating systems like Windows and macOS is that Linux is open source. This means that the general public has access to the source code which makes it tick, and that anyone can modify it or improve it to suit their needs. However, to make meaningful modifications to Linux requires programming skills, so, consequentially, the needs which Linux best suits are the needs of programmers. Linux is the preeminent operating system for programmers and other highly technical computer users, for whom it can be suitably molded to purpose in a manner which is not possible using other operating systems. As such, it has been a resounding success on programmer’s workstations, on servers in the cloud, for data analysis and science, in embedded workloads like internet-of-things, and other highly technical domains where engineering talent is available and a profound level of customization is required. The Linux community has also developed Linux as a solution for desktop users, such as the mainstream audience of Windows and macOS. However, this work is mostly done by enthusiasts, rather than commercial entities, so it can vary in quality and generally any support which is available is offered on a community-run, best-effort basis. Even so, there have always been a lot of volunteers interested in this work — programmers want a working desktop, too. Programmers also want to play games, so there has been interest in getting a good gaming setup working on Linux. In the past several years, there has also been a commercial interest with the budget to move things forward: Valve Software. Valve has been instrumental in developing more sophisticated gaming support on Linux, and uses Linux as the basis of a commercial product, the Steam Deck Read more

today's leftovers

  • x86 Straight-Line Speculation Mitigation Patches Updated For Linux - Phoronix

    A year after Arm processors began mitigating straight-line speculation, Linux developers have been working on similar straight-line speculation mitigations for x86/x86_64 processors. The past few months we have been seeing Linux kernel and GCC and LLVM/Clang patches around straight-line speculation mitigation for Intel / AMD processors. The issue at hand is over processors speculatively executing instructions linearly in memory past an unconditional change in control flow.

  • EPEL 9 Ready To Provide Extra Packages For RHEL 9, CentOS Stream 9 - Phoronix

    launched and that effectively serving as the bleeding-edge of the RHEL9 upstream, EPEL 9 has already launched. Extra Packages for Enterprise Linux "EPEL" continues to provide a vast assortment of packages to complement the official packages in the RHEL/CentOS repository. EPEL packages continue to be derived from their Fedora counterpart and simply augment what is available to RHEL / CentOS (and Oracle Linux, et al) users.

  • Raku Advent Calendar: Day 5 – Santa Claus is Rakuing Along
  • There is a surge in Linux gamers with the release of Windows 11

    The surge can also be due to the Steam Deck effect.

  • XWayland Adds Support For Touchpad Gestures - Phoronix

    XWayland is increasingly great shape especially when it comes to fulfilling the needs of gamers with simply running games lacking native Wayland support with great speed. But when it comes to other use-cases there are occasionally gaps and areas not yet fulfilled by XWayland versus the conventional X.Org Server. One of the latest examples of a feature now correctly wired up is touchpad gesture handling. Should you be a fan of touchpad gestures, they should now be working under XWayland. Developer Povilas Kanapickas implemented support for touchpad gestures within the XWayland code that is now in the xserver Git tree. Povilas noted, "The implementation is relatively straightforward because both wayland and Xorg use libinput semantics for touchpad gestures."

  • 178: Blender 3.0, EndeavourOS, CentOS Stream 9, Steam Deck, NixOS, CrossOver | This Week in Linux

    On this episode of This Week in Linux, a brief note about Linus Tech Tips reaction videos, Blender 3.0, EndeavourOS, CentOS Stream 9, NixOS 21.11, Open 3D Engine, Heroic Games Launcher, Steam Deck, Fedora, Fedora Linux, Red Hat, RHEL, Ventoy 1.0.62, CrossOver 21.1, SDL 2.0.18, Xen Project 4.16, Tesseract 5.0, and Neovim 0.6.0. All that and much more on Your Weekly Source for Linux GNews!

Give your Terminal a Retro Look Using this Neat Application

Want to give your Terminal a retro look? This guide contains instructions to help you to install Cool Retro Terminal application in all Linux distributions. Read more

today's howtos

  • How To Install Apache Hadoop on Debian 11 - idroot

    In this tutorial, we will show you how to install Apache Hadoop on Debian 11. For those of you who didn’t know, Apache Hadoop is an open-source, Java-based software platform that manages data processing and storage for big data applications. It is designed to scale up from single servers to thousands of machines, each offering local computation and storage. This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo‘ to the commands to get root privileges. I will show you through the step-by-step installation of the Apache Hadoop on a Debian 11 (Bullseye).

  • What To Do After Installing Parabola KDE and GNOME System

    This is our recommended stuffs for you after finished Parabola GNU/Linux installation with either GNOME or KDE Desktop. Let's start it!

  • Install opensource CyberPanel on Almalinux | Rocky linux 8

    Looking for a free and open-source web hosting control panel? Then try out CyberPanel on AlmaLinux or Rocky Linux 8. It is a free alternative to the popular WHM Cpanel that comes with an OpenLiteSpeed Web server to provide the best possible performance. CyberPanel has a web-based, graphical, and user interactive Dashboard, from where we can access Users, Vhost Templates; multiple PHP Versions; MySQL Database, and more. It also offers a CLI tool that commands can be used on the Server terminal to perform various useful operations such as creating users, resetting permissions, and other tasks.

  • How to set up an SFTP server on Debian 11 Server – Citizix

    In this guide we are going to set up an sftp server on an Debian 11. We will also set up a form of chroot where users can only access sftp with the shared credentials. The File Transfer Protocol is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP isn’t popular today because it Lacks Security. When a file is sent using this protocol, the data, username, and password are all shared in plain text, which means a hacker can access this information with little to no effort. For data to be secure, you need to use an upgraded version of FTP like SFTP.

  • How to work with SFTP client in Linux – 10 sftp commands

    In this guide, we will learn how to do basic operations on an sftp server. The File Transfer Protocol is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP isn’t popular today because it Lacks Security. When a file is sent using this protocol, the data, username, and password are all shared in plain text, which means a hacker can access this information with little to no effort. For data to be secure, you need to use an upgraded version of FTP like SFTP.

  • Raspberry PI Pico Ethernet Port: adding the WIZNET Ethernet HAT

    Raspberry PI Pico works greatly to keep sensors measurements, combining/analyzing them and delivering data to external world. Adding an Etherneth port to Raspberry PI Pico with the WIZnet Ethernet HAT (based on W5100S chip) add a networking layer to improve communications