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    SubjectRe: Capabilities done right [diff against 2.3.1]
    -----BEGIN PGP SIGNED MESSAGE-----

    On Tue, 25 May 1999, Fred Reimer wrote:

    [-EACCES, -ECAP or SIGCAP]

    > Why not both? Why not return the syscall with failure (and appropriate
    > error code) AND send a signal. Signals are supposed to be async right? The
    > signal handler, for those cap aware future apps, could flip a flag that they
    > program can check after getting the failed syscall for more capability
    > specific information. Is this not doable? Or is it, just not desirable?

    Returning -EPERM and sending SIGCAP (non-fatal signal) has the
    disadvantage that the program cannot tell at the time the syscall returns
    what has happened, because signals are asynchronous.

    I see three options:

    return -ECAP: disadvantage: Non-aware apps wouldn't know about this error
    and assume wild things (or even break). advantage: Aware apps could know
    what happened without too much overhead.

    return -EACCES: advantage: Old apps know what happened. Disadvantage: New
    apps are unsure.

    send SIGCAP: advantage: ? disadvantage: Causes strange things if not
    properly caught.

    Simon

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