Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!pt.cs.cmu.edu!spice.cs.cmu.edu!af
From: af@spice.cs.cmu.edu (Alessandro Forin)
Newsgroups: comp.os.mach
Subject: Re: execve in Mach 2.5
Summary: The beauties of merging pears and apples
Message-ID: <8252@pt.cs.cmu.edu>
Date: 2 Mar 90 15:27:08 GMT
References: <77747@tut.cis.ohio-state.edu>
Distribution: usa
Organization: Carnegie-Mellon University, CS/RI
Lines: 29

In article <77747@tut.cis.ohio-state.edu>, philk@tictoc.cis.ohio-state.edu (Phillip E Krueger) writes:
> Under Mach 2.5, what task does execve belong to (i.e. what task and
> thread are considered current when execve is executed)?  The mach task?
> The user task whose thread called it?
> 
> Thanks,
>   -- Phil

Mach 2.5 supports Unix in-kernel.  This means that the Mach abstractions 
_and_ the Unix abstractions co-exist, and each one tries very hard not to
interfere with the other.

The Unix semantics is provided by equating

	Unix-process ==  This-thread + Its-task

which in the case of execve means:
	1) terminate all other threads in the same task of the invoking
	   thread
	2) reshape the task's address space as described in the executable
	   image (text+data+implicit-stack)
	3) restart this thread at the PC defined in the executable image.

Additional clarifications:
1- the relation thread->task never changes once established (at thread
   creation time)
2- Unix primitives never take Mach entities as parameters

sandro-