Re: Syscall table AKA hijacking syscalls

[stefan . eletzhofer]

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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