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    Subject[patch] vsyscall feature

    On Tue, 22 Feb 2000, Dean Gaudet wrote:

    > out of curiosity, has the fast syscall and fast gettimeofday stuff
    > with the nifty kernel-supplied code page made it into the
    > kernel/glibc/etc?

    nope, 2.5 stuff. You can check out the 2.3.32 patch (which has a working
    purely-user-space times() syscall) at:

    Documentation/syscall.txt has the design:

    + 'x86 Virtual System Call Interface', Ingo Molnar <>
    + The point is to have an extensible system call interface. The kernel
    + provides a generic entry point, which is a readonly user-visible page
    + range. User-space does not know about the internals of this entry
    + point, it's a simple generic function call.

    there are several 'trampoline pages' (both data and code) which are
    'dual-mapped': kernel-space has a read-write mapping to the data page,
    user-space only has a read-only mapping. This is how sys_times() works.

    it's in the prototype stage, but pretty promising IMO, will post a
    finished patch once the 2.5 is branched off.

    -- mingo

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