Re: Syscall table AKA hijacking syscalls

stefan.eletzhofer
2004-01-07T09:36:02Z

On Fri, Jan 02, 2004 at 04:38:27PM +0100, Libor Vanek wrote:
>
> >>I'm writing some project which needs to hijack some syscalls in VFS
> >>layer. AFAIK in 2.6 is this "not-wanted" solution (even that there are
> >>some very nasty ways of doing it - see
> >>http://mail.nl.linux.org/kernelnewbies/2002-12/msg00266.html )
> >>
> >>
> >
> >Why do you need to hijack system calls from a module? 99% of the
> >times, it's the wrong technical solution.
> >
> >
> I'm working on my diploma thesis which is adding snapshot capability
> into Linux VFS (so you can do directory based snapshots - not complete
> device, like in LVM). It'll consist of two separete modules:
> Snapshot module:
> - will hijack (one or another way) calls to open/move/unlink/mkdir/etc.
> syscall
> - when will detect change to selected directory (which I want to
> snapshot), it'll copy/move old file/directory to some temporary
> (selected when creating snapshot) - in fact - copy on write behaviour

Do it in userspace. Hack a nfs server.

>
> UnionFS module:
> - will place "temporary" directory with saved files/dirs "over" actual
> one and result will be read-only snapshot - this can be done without
> hijacking syscalls probably
> - something like overlay fs but a bit different
>
> --
>
> Libor Vanek
>
>
>
> -
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