Re: [uml-devel] [PATCH] x86_64 32-bit ptrace mangles sixth systemcall argument

[Blaisorblade <blaisorblade@yahoo.it>]

On Monday 12 March 2007 11:42, Bodo Stroesser wrote:
> Blaisorblade wrote:
> > On Tuesday 06 March 2007 00:26, Blaisorblade wrote:
> >  > On Tuesday 06 March 2007 00:10, Jeff Dike wrote:
> >  > > On Tue, Mar 06, 2007 at 12:03:26AM +0100, Blaisorblade wrote:
> >  > > > > No, RCX corruption is different - that happens when a sysexit
> >
> > is done
> >
> >  > > > > from a system call where userspace wasn't prepared to save and
> >  > > > > restore RCX.  sigreturn is the best example.
> >  > > >
> >  > > > Hmm... we should finally fix that, at some point. Or... now that
> >  > > > you explain it this way, it could even seem unfixable... is it? Or
> >  > > > maybe sysreturn should become a syscall where the return must
> >  > > > happen
> >
> > through
> >
> >  > > > the slow return path (iret), if that exists for x86_64.
> >  > >
> >  > > This is fixed, and has been for a while.  The fix was, as you
> >  > > suggest, return through iret in this case.
> >
> > Hmm, return through IRET is implemented for sys_rt_sigreturn since 2.6.0
> > (with
> > a couple of changes, yeah, but...).
> >
> > Was the original Bodo's report bogus? No, he actually found a much harder
> > issue.
> >
> > I've attached the log of that IRC here for reference.
>
> I took a quick look into 2.6.21-rc3, arch/x86_64/entry.S. AFAICS, the
> problem I supposed in the IRC is fixed. Now a ptraced syscall always
> returns through IRET. Thus, *all* registers in user space exactly will have
> the contents, which the tracing process wrote at end of syscall.

About 32bit emulation (arch/x86_64/ia32/ia32entry.S), it too returns through 
IRET when ptrace is active. Ok.

Now it would then be time to look again at SKAS support? Well, nothing easy it 
seems - I've done a quick test of 32bit UML over 64bit host again and had no 
luck.
-- 
Inform me of my mistakes, so I can add them to my list!
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade
Chiacchiera con i tuoi amici in tempo reale! 
 http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com 


-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys-and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel