Re: syscall: sys_promote

[Qi Yong <qiyong@fc-cn.com>]

Ulrich Drepper wrote:

>On 8/29/05, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>  
>
>>Fixing it might be useful in some obscure cases anyway - POSIX threads
>>might benefit from it too, providing the functionality of changing all
>>thread uids at once isnt triggered for sensible threaded app behaviour.
>>    
>>
>
>I would very much like to see that fixed.  Currently we have to change
>the UIDs/GIDs at userlevel with cross-thread calls implemented via
>signals.  This is user observable which is not correct.  This is
>probably the last area where we're not 100% POSIX compliant.
>
>As for adding this proposed syscall: it can only lead to chaos.  All
>kinds of user code correctly so assumes the IDs don't change over the
>lifetime of a process.  The solution for the problem has been
>  
>
After a user shell is promoted to root, its prompt is still $ instead of 
#. But why do we care?

>mentioned as well: re-exec.  This will require some code rewrite on
>the side of the applications but any decent daemon is hopefully soon
>  
>

OK, so any decent processes should not break into other processes' 
address space.
And let us use non-preemptive multitasking?

>support re-exec anyway for another reason: re-randomization of the
>address space.  What good does address space randomization do if the
>machines and programs are so damn stable that they keep running for
>months at a time?  nscd supports this now and I think openssh as well.
>  
>