Re: faking time

[Pavel Machek <pavel@suse.cz>]

Hi!
> > > Here's an LD_PRELOAD shared library that will do the trick... just
> > > export the environment variable FAKETIME with the time that you'd
> > > like, and then export the LD_PRELOAD environment variable to point
> > > that the faketime.so library, and then execute your program.  All
> > > programs that have these two environment variables set will have their
> > > time faked out accordingly.
> >
> > But note that this doesn't work with programs linked statically. If
> > you must fool one of those, ptrace() is the only way to do it without
> > some sort of kernel patch or module I think.

subterfugue.sf.net can do this. It has ready-to-use timeshift/timemultiply
module.

> it's in alpha stages right now, but it seems pretty stable so far (It
> Works For Me - i run it regularly on all of my machines). note that we
> currently support only logging system calls (a-la strace) and failing
> them with a user given parameter- rewriting system call parameters will
> require additional hackery, but not too much of it - on the order of one
> day of work. volunteers are welcome.

Why do you need kernel module at all?

BTW syscall rewriting is pretty hard (subterfugue solves that, but it definitely
took more than a day.

Imagine open('/foo/bar')

you rewrite it to open('/funny/bar')

then another thread comes and rewrites it back to '/foo/bar'.

Or imagine open(address in read-only memory).
								Pavel

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