From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
To: Blaisorblade <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>, Andi Kleen <ak@suse.de>,
user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [uml-devel] [PATCH] x86_64 32-bit ptrace mangles sixth systemcall argument
Date: Mon, 12 Mar 2007 11:42:47 +0100 [thread overview]
Message-ID: <45F52EA7.2090605@fujitsu-siemens.com> (raw)
In-Reply-To: <200703092250.48861.blaisorblade@yahoo.it>
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.
Bodo
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next prev parent reply other threads:[~2007-03-12 10:43 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-31 22:45 [uml-devel] [PATCH] x86_64 32-bit ptrace mangles sixth system call argument Jeff Dike
2007-02-02 17:48 ` Blaisorblade
2007-02-02 20:12 ` Jeff Dike
2007-03-05 23:03 ` Blaisorblade
2007-03-05 23:10 ` Jeff Dike
2007-03-05 23:26 ` Blaisorblade
2007-03-09 21:50 ` Blaisorblade
2007-03-12 10:42 ` Bodo Stroesser [this message]
2007-03-12 22:12 ` [uml-devel] [PATCH] x86_64 32-bit ptrace mangles sixth systemcall argument Blaisorblade
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