Microsoft change removed from Linux over Intel CPU issues
Intel and AMD engineers have stepped in at the eleventh hour to deal with a code contribution from a Microsoft developer that could have broken Linux 6.13 on some systems.
The change, made in the autumn, was a useful improvement at face value. It was a modification to Linux x86_64 to use large read-only execute (ROX) pages for caching executable pages. The theory was that the alteration would result in increased performance.
However, the code caused problems on some setups and an urgent patch from Intel's Peter Zijlstra was committed yesterday to disable it. The stable release of the 6.13 kernel was due this coming weekend.
Zijlstra wrote: "The whole module_writable_address() nonsense made a giant mess of alternative.c, not to mention it still contains bugs -- notable (sic) some of the CFI variants crash and burn.
Control Flow Integrity (CFI) is an anti-malware technology aimed at preventing attackers from redirecting the control flow of a program. The change can cause issues on some CFI-enabled setups and reports have included Intel Alder Lake-powered machines failing to resume from hibernation.
Update
More here:
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Microsoft pulls a Windows as it breaks Linux on Intel CPUs and angers AMD in the process
Earlier today, we reported about a happy and content Linus Torvalds, who is offering to make a guitar pedal for one of the lucky Linux devs out there since he is pleased with how things have been this holiday season and the progress with the Linux kernel version 6.13.
Unfortunately for Torvalds, a Microsoft-contributed change nearly ruined it, but Intel and AMD had intervened just in time to save the day.
The change in question was related to a ARCH_HAS_EXECMEM_ROX kernel configuration, which would allow caching of executable memory (EXECMEM) with read-only execute (ROX) permissions. It was being added as a performance improvement feature on Linux 6.13 for x86_64/ AMD64, ie, 64-bit AMD and Intel CPUs.
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Microsoft Breaks Linux Again
One more:
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Linux Developers scramble to solve last minute bug for GNU/Linux 6.13
In this video, we take a look at a bug that was introduced by a Abusive Monopolist Microsoft engineer into the GNU/Linux kernel that had to be patched at the eleventh hour before GNU/Linux 6.13 is released.
Another one:
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Intel and AMD rescue Linux 6.13 after Microsoft developer mistakes
Engineers from Intel and AMD have stepped in at the last minute to address a code bug from a Microsoft developer that could have broken Linux 6.13 on some systems.
The change, made in the fall, appeared to be a helpful improvement at first glance. It involved modifying Linux x86_64 to use large read-only executable (ROX) pages to cache executable pages. The theory was that this modification would provide better performance.
Late:
"Microsoft Change Removed From Linux Over Intel CPU Issues", discussed here.
Later:
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Intel & AMD Devs Address Bad Linux Kernel Code From Microsoft Dev
Intel and AMD developers fixed a major issue in the Linux 6.13 release, an issue that was caused by a bad commit from a Microsoft developer.
A Microsoft developer submitted code months ago that was designed to improve performance by changing how CPUs cache executable pages. The code was designed to use large read-only execute (ROX) pages instead of the current method.
Unfortunately, the code interfered with Control Clow Integrity (CFI), an anti-malware feature that is critical to maintaining Linux security.
Intel engineer Peter Zijlstra submitted a commit that that rolled back the code. He acknowledged the Microsoft developer has been working to fix the issue, but felt time had run out in order to finalize work on 6.13.