On Wed, Jun 19, 2019 at 07:08:53AM -0700, Sean Christopherson wrote:
> On Wed, Jun 19, 2019 at 04:24:05PM +0300, Jarkko Sakkinen wrote:
> > On Mon, 2019-06-17 at 15:24 -0700, Sean Christopherson wrote:
> > > {
> > > - if (len < 2 * PAGE_SIZE || len & (len - 1) || flags & MAP_PRIVATE)
> > > + if (flags & MAP_PRIVATE)
> > > + return -EINVAL;
> > > +
> > > + if (flags & MAP_FIXED)
> > > + return addr;
> > > +
> > > + if (len < 2 * PAGE_SIZE || len & (len - 1))
> > > return -EINVAL;
> > >
> > > addr = current->mm->get_unmapped_area(file, addr, 2 * len, pgoff,
> >
> > Just sanity checking that for MAP_FIXED case the mm checks that the area is
> > unmapped before calling this?
>
> No, straight MAP_FIXED unmaps any existing mappings. The NOREPLACE variant
> fails with -EEXIST if there are existing mappings.
Ah so it was [1]!
> The MAP_FIXED behavior is actually useful, bordering on mandatory, for the
> new flow. It allows the loader to keep its initial mmap(PROT_NONE) of
> ELRANGE while (re)mapping the individual enclave sections, e.g. to prevent
> a different aspect of the process from mapping the require ELRANGE.
Yeah, totally agree.
[1] http://man7.org/linux/man-pages/man2/mmap.2.html
/Jarkko
