Re: linux-next: add utrace tree

From: Thomas Gleixner
Date: Sun Jan 24 2010 - 11:38:01 EST

On Sat, 23 Jan 2010, Frank Ch. Eigler wrote:
> On Sat, Jan 23, 2010 at 07:04:01AM +0100, Ingo Molnar wrote:
> > [...] Also, if any systemtap person is interested in helping us
> > create a more generic filter engine out of the current ftrace filter
> > engine (which is really a precursor of a safe, sandboxed in-kernel
> > script engine), that would be excellent as well. [...]
> Thank you for the invitation.
> > More could be done - a simple C-like set of function perhaps - some minimal
> > per probe local variable state, etc. (perhaps even looping as well, with a
> > limit on number of predicament executions per filter invocation.)
> Yes, at some point when such bytecode intepreter gets rich enough, one
> may not need the translated-to-C means of running scripts.
> > ( _Such_ a facility, could then perhaps be used to allow applications access
> > to safe syscall sandboxing techniques: i.e. a programmable seccomp concept
> > in essence, controlled via ASCII space filter expressions [...]
> > IMHO that would be a superior concept for security modules too [...]
> >
> > [...] specific functionality with an immediately visible upside,
> > with no need for opaque hooks.
> This OTOH seem like rather a stretch. If one claims that "opaque
> hooks" are bad, so instead have hooks that jump not to auditable C
> code but an bytecode interpreter? And have the bytecodes be uploaded
> from userspace? How is this supposed to produce "transparency" from
> the kernel/hook point of view?

Simply because the kernel controls which byte code is executed and has
control over the functionality behind it. That makes the hooks well
defined and transparent.


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