Re: [RFC] c/r: prctl: Add ability to set new mm_struct::exe_file v3

[Oleg Nesterov <oleg@redhat.com>]

On 03/08, Cyrill Gorcunov wrote:
>
> On Thu, Mar 08, 2012 at 08:05:34PM +0100, Oleg Nesterov wrote:
> ...
> > >
> > > Yes, exactly, I need to remove old mappings first (because VMAs
> > > we're about to restore may intersect with current map the host
> > > program has). And yes, once they all are removed I don't have
> > > /proc/pid/exe anymore. That's why I need num_exe_file_vmas == 0
> > > case.
> >
> > OK, in this case PR_SET_MM_EXE_FILE should probably fail if
> > mm->num_exe_file_vmas != 0 ? This way it would be more or less
> > consistent or at least understandable. Just we add the new
> > special case: num_exe_file_vmas == 0 but exe_file != NULL
> > because c/r people are crazy.
> >
>
> Sure, I can drop num_exe_file_vmas != 0 case and refuse to
> setup new exe symlink if there some VM_EXECUTABLE remains
> unmapped. Sounds good?

Personally I like this. This is simple and _understable_, even
if ->num_exe_file_vmas has no meaning after PR_SET_MM_EXE.

But please-please document the new special case in the changelog.

Oleg.