But that's trivially done: it doesn't even have to be thread-specific, so
it can be just a global entry anywhere in the process data structures.
This is just a random sanity check thing, after all. It doesn't have to be
system-global or even per-cpu. The only really important thing is that
"gettimeofday()" should return monotonically increasing data - and if it
doesn't, the vsyscall would have to ask why (sometimes it's fine, if
somebody did a settimeofday, but usually it's a sign of trouble).
But yes, it's certainly a lot more complex than just doing it in a
controlled system call environment. Which is why I think vsyscalls are
eventually not worth it.
Linus
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