On Sun, 2018-02-11 at 10:56 +0100, Bastian Blank wrote: > Moin > > After almost four years and due to recent changes in the syscall path, > I'd like to revisit our current handling of the x32 ABI. > > Currently we disable support for the x32 ABI on runtime, enabling it > needs a kernel command line parameter. This Debian specific change was > done due to concerns of ABI specific problems with the pretty new code. > > In 4.15.2 the syscall path was cleaned up. The so called "fast-path" > was dropped completely, it didn't provide much of a fast path anymore > because of the whole Spectre and Meltdown stuff. Also our patch made > inline patches of the fast path, to remove the overhead of the checks. > > I think after that four years we shoud revisit that change. Do we still > think x32 may be a problem? Yes, I think so. Some people try to sandbox applications with syscall blacklists that don't take x32 into account. This is obviously a bad idea since new syscalls are constantly being added, but that's the reality we have to work with. > Does the patch introduce runtime latency due to it's not longer > inline patched form? Yes, a little. Maybe I should update the slow path to use a static key. Ben. -- Ben Hutchings Sturgeon's Law: Ninety percent of everything is crap.
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