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.
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.
>
> I don't think we need to check any alignment constraints here anymore.
>
> The summarize end result would be:
>
> static unsigned long sgx_get_unmapped_area(struct file *file,
> unsigned long addr,
> unsigned long len,
> unsigned long pgoff,
> unsigned long flags)
> {
> if (flags & MAP_PRIVATE)
> return -EINVAL;
>
> if (flags & MAP_FIXED)
> return addr;
>
> return current->mm->get_unmapped_area(file, addr, 2 * len, pgoff,
> flags);
> }
>
> /Jarkko
>
