Linux 4.1 Brings Many Potentially Risky x86/ASM Changes

Written by Michael Larabel in Linux Kernel on 13 April 2015 at 12:27 PM EDT. 6 Comments
Another one of the Linux 4.1 pull requests sent in today by Ingo Molnar is for the x86/asm code.

There's a lot of new work that's gone into the Linux 4.1 kernel with this pull, which could potentially cause regressions, particularly with the Assembly code. The developers have tried testing the code on many different x86 boxes, but there's risk of regression when exposing the code to many more systems in the days and weeks ahead. Ingo explained:
- over 100 separate cleanups, restructuring changes, speedups and fixes in the x86 system call, irq, trap and other entry code, part of a heroic effort to deobfuscate a decade old spaghetti asm code and its C code dependencies. (Denys Vlasenko, Andy Lutomirski)

- alternatives code fixes and enhancements (Borislav Petkov)

- simplifications and cleanups to the compat code. (Brian Gerst)

- signal handling fixes and new x86 testcases. (Andy Lutomirski)

- various other fixes and cleanups

By their nature many of these changes are risky - we tried to test them well on many different x86 systems (there are no known regressions), and they are split up finely to help bisection - but there's still a fair bit of residual risk left so caveat emptor.
The full list of x86/asm changes for the Linux 4.1 merge window can be found via the pull request.
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