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Latest LWN Articles About Linux (Paywall Has Just Expired)

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Linux
  • SPDX identifiers in the kernel

    Observers of the kernel's commit stream or mailing lists will have seen a certain amount of traffic referring to the addition of SPDX license identifiers to kernel source files. For many, this may be their first encounter with SPDX. But the SPDX effort has been going on for some years; this article describes SPDX, along with why and how the kernel community intends to use it.

    On its face, compliance with licenses like the GPL seems like a straightforward task. But it quickly becomes complicated for a company that is shipping a wide range of software, in various versions, in a whole set of different products. Compliance problems often come about not because a given company wants to flout a license, but instead because that company has lost track of which licenses it needs to comply with and for which versions of which software. SPDX has its roots in an effort that began in 2009 to help companies get a handle on what their compliance obligations actually are.

    It can be surprisingly hard to determine which licenses apply to a given repository full of software. The kernel's COPYING file states that it can be distributed under the terms of version 2 of the GNU General Public License. But many of the source files within the kernel tell a different story; some are BSD licensed, and many are dual-licensed. Some carry an exception to make it clear that user-space programs are not a derived product of the kernel. Occasionally, files with GPL-incompatible licenses have been found (and fixed).

  • 4.15 Merge window part 1

    When he released 4.14, Linus Torvalds warned that the 4.15 merge window might be shorter than usual due to the US Thanksgiving holiday. Subsystem maintainers would appear to have heard him; as of this writing, over 8,800 non-merge changesets have been pulled into the mainline since the opening of the 4.15 merge window. Read on for a summary of the most interesting changes found in that first set of patches.

  • 4.15 Merge window part 2

    Despite the warnings that the 4.15 merge window could be either longer or shorter than usual, the 4.15-rc1 prepatch came out right on schedule on November 26. Anybody who was expecting a quiet development cycle this time around is in for a surprise, though; 12,599 non-merge changesets were pulled into the mainline during the 4.15 merge window, 1,000 more than were seen in the 4.14 merge window. The first 8,800 of those changes were covered in this summary; what follows is a look at what came after.

  • BPF-based error injection for the kernel

    Diligent developers do their best to anticipate things that can go wrong and write appropriate error-handling code. Unfortunately, error-handling code is especially hard to test and, as a result, often goes untested; the code meant to deal with errors, in other words, is likely to contain errors itself. One way of finding those bugs is to inject errors into a running system and watching how it responds; the kernel may soon have a new mechanism for doing this sort of injection.

    As an example of error handling in the kernel, consider memory allocations. There are few tasks that can be performed in kernel space without allocating memory to work with. Memory allocation operations can fail (in theory, at least), so any code that contains a call to a function like kmalloc() must check the returned pointer and do the right thing if the requested memory was not actually allocated. But kmalloc() almost never fails in a running kernel, so testing the failure-handling paths is hard. It is probably fair to say that a large percentage of allocation-failure paths in the kernel have never been executed; some of those are certainly wrong.

  • Tools for porting drivers

    Out-of-tree drivers are a maintenance headache, since customers may want to use them in newer kernels. But even those drivers that get merged into the mainline may need to be backported at times. Coccinelle developer Julia Lawall introduced the audience at Open Source Summit Europe to some new tools that can help make both forward-porting and backporting drivers easier.

    She opened her talk by noting that she was presenting step one in her plans, she hoped to be able to report on step two next year some time. The problem she is trying to address is that the Linux kernel keeps moving on. A vendor might create a driver for the 4.4 kernel but, over the next six months, the kernel will have moved ahead by another two versions. There are lots of changes with each new kernel, including API changes that require driver changes to keep up.

    That means that vendors need to continually do maintenance on their drivers unless they get them upstream, where they will get forward-ported by the community. But the reverse problem is there as well: once a device becomes popular, customers may start asking for it to run with older kernels too. That means backporting.

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  • Brave Browser Team Up With Tor
     

    TOR [sic] or The Onion Router uses technology that separates your computer from the website you’re viewing by routing the network traffic through 3 seperate servers before it reaches your computer. That being said Brave Core Beta hasn’t been fully tested yet so “users should not rely on it for serious use just yet,” Brave said.

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  • Your RSS is grass: Mozilla euthanizes feed reader, Atom code in Firefox browser, claims it's old and unloved
    When Firefox 64 arrives in December, support for RSS, the once celebrated content syndication scheme, and its sibling, Atom, will be missing. "After considering the maintenance, performance and security costs of the feed preview and subscription features in Firefox, we’ve concluded that it is no longer sustainable to keep feed support in the core of the product," said Gijs Kruitbosch, a software engineer who works on Firefox at Mozilla, in a blog post on Thursday. RSS – which stands for Rich Site Summary, RDF Site Summary, or Really Simple Syndication, as you see fit – is an XML-based format for publishing and subscribing to web content feeds. It dates back to 1999 and for a time was rather popular, but been disappearing from a variety of applications and services since then. Mozilla appears to have gotten the wrecking ball rolling in 2011 when it removed the RSS button from Firefox. The explanation then was the same as it is now: It's just not very popular.
  • Cameron Kaiser: It's baaaaa-aaack: TenFourFox Intel
    It's back! It's undead! It's ugly! It's possibly functional! It's totally unsupported! It's ... TenFourFox for Intel Macs! Years ago as readers of this blog will recall, Claudio Leite built TenFourFox 17.0.2 for Intel, which the update check-in server shows some determined users are still running to this day on 10.5 and even 10.4 despite various problems such as issue 209. However, he didn't have time to maintain it, and a newer version was never built, though a few people since then have made various attempts and submitted some patches. One of these attempts is now far enough along to the point where I'm permitted to announce its existence. Riccardo Mottola has done substantial work on getting TenFourFox to build and run again on old Intel Macs with a focus on 32-bit compatibility, and his patches have been silently lurking in the source code repository for some time. Along with Ken Cunningham's additional work, who now also has a MacPorts portfile so you can build it yourself (PowerPC support in the portfile is coming, though you can still use the official instructions, of course), enough functions in the new Intel build that it can be used for basic tasks.

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