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SubjectRe: Capabilities done right [diff against 2.3.1]
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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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