Re: [uml-devel] SYSEMU getting merged - but I'm in doubt

[Blaisorblade <blaisorblade@yahoo.it>]

On Wednesday 14 September 2005 13:48, Bodo Stroesser wrote:
> Bodo Stroesser wrote:
> > OTOH, if the new API would reuse the same ptrace code, check_sysemu of
> > the old
> > binaries will fail on i386

> > (and I hope on x86_64, too). 
Nobody implemented sysemu for x86_64, at least to my knowledge.

I hoped to finish skas first, but stopped on that problem.
> > That means, 
> > sysemu again
> > will be disabled. AFAICS, it will not refuse to run at all. (Not tested,
> > taken from
> > the code only)
> > On s390 the check even might succeed accidentally, but that's no
> > problem, as s390
> > isn't mainline yet, we can change check_sysemu() to avoid problems.
> > There will
> > never be an old binary for s390.

> Some more points:

> The new API must have PTRACE_SYSEMU _and_ PTRACE_SYSEMU_SINGLESTEP.
Granted.
> While with the old API SYSEMU_SINGLESTEP was inserted to improve security,
> with the new one it will be necessary to allow singlestepping of processes
> in UML-SKAS at all. Suppose a singlestepped userspace is stopped at a
> syscall interception. Now UML needs to restart it with SYSEMU for syscall
> emulation, but also wants to proceed with singlestepping. PTRACE_SYSEMU
> wouldn't do the job, as it starts userspace in "normal" mode, no
> singlestepping.
Hmm, I hadn't looked at this detail...
> Also, in tt new API's PTRACE_SYSEMU behaves as PTRACE_SYSCALL does, because
> tracer uses PTRACE_CONT after syscall interception. So tt (do_syscall(),
> ...) needs to be changed. PTRACE_SYSEMU_SINGLESTEP still should be used, as
> if it's name were PTRACE_SYSCALL_SINGLESTEP.
Ok, I think it's enough to warrant keeping the current behaviour and adding 
later an option, and/or removing it for now and merging it later.

Unless somebody manages to fix all this in time. I don't think I'm likely to 
accomplish this, sorry.
> 	Bodo

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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