Re: add closefrom() call


On Fri, 6 Jul 2007, LI Xin wrote:

Joerg Sonnenberger wrote:

On Wed, Jul 04, 2007 at 08:27:49PM -0400, Ighighi Ighighi wrote:

The closefrom() call, available in Solaris, is present in NetBSD since version 3.0. It is implemented with the F_CLOSEM fcntl() available since version 2.0.

You could also add a system call like it was done in DragonFly. That might be even simpler to implement.

Here is my implementation for FreeBSD. Some difference between my and DragonFly's implementation:

- closefrom(-1) would be no-op on DragonFly, my version would close all
open files (From my understanding of OpenSolaris's userland
implementation, this is Solaris's behavior).
- my version closefrom(very_big_fd) would result in EBADF. I am not
very sure whether this is correct, but it does not hurt for applications
that thinks closefrom() would return void.

To RW: I have not found a suitable audit event for this, should I create a new event?

Solaris side-steps this issue by simply auditing the individual close() system calls. My preference would be that we implement this in user space also, which would likewise generate a series of audit events, one for each system call. The procfs optimization they use (I wonder -- is it really an optimization?) won't work for us, however. Do you think that there's a strong motivation to provide a closefrom(2) system call, rather than a closefrom(3) library call? This would let us neatly avoid the question you've posed :-).

Robert N M Watson
Computer Laboratory
University of Cambridge
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