Re: intercepting system calls?
Re: intercepting system calls?
- Subject: Re: intercepting system calls?
- From: Erik Paulson <email@hidden>
- Date: Mon, 23 Jan 2006 15:43:36 -0600
On Mon, Jan 23, 2006 at 01:30:31PM -0800, Mike Smith wrote:
>
> On Jan 23, 2006, at 12:02 PM, email@hidden wrote:
>
> >On Mon, Jan 23, 2006 at 01:00:26AM -0800, Mike Smith wrote:
> >>On Jan 22, 2006, at 12:02 PM, email@hidden
> >>wrote:
> >>
> >>>I want to be able to capture the I/O calls of an application and
> >>>then
> >>>ship them back over the network to be handled by another machine.
> >>
> >>There are plenty of examples of this in the system already;
> >>they're called
> >>"network filesystems". One of them is even called "the Network
> >>File System".
> >
> >A shared filesystem is great, if the administrators of both computers
> >agree to use the same shared filesystems. That usually doesn't happen
> >between institutions, for example.
>
> This sounds like an administrative misconception revolving around
> traditional
> use of network filesystems.
>
Hrm, without going way off-topic I don't think I can convince you
that my motivation is real - my simple attempt at it is: If I want
to use idle computers at the University of Illinois and I'm at the
University of Wisconsin, I either have to get the UofI to mount my
file systems, or copy the files down to the UofI, or interpose and
make the processes running at the UofI believe that they're running
at the UofW.
> You're already talking about running privileged code on the client
> system
> in order to intercept system calls;
No, I'm looking for an unprivileged interface. PTRACE_SYSCALL means that
I can run two processes as user 'nobody' - the first one is the actual
process that I want to run on idle computers at the UofI, and the second
process, also running as 'nobody', can trace the first process, and
if need be do an RPC back to a server running at the UofW. I don't want
to run privileged code on the UofI machines.
Such an unprivileged interface doesn't appear to exist, short of some
sort of binary rewriting or single stepping.
-Erik
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