We want to be able to revoke pci mmaps so that the same access rules
applies as for /dev/kmem. Revoke support for devmem was added in
3234ac66 ("/dev/mem: Revoke mappings when a driver claims the
region").

The simplest way to achieve this is by having the same filp->f_mapping
for all mappings, so that unmap_mapping_range can find them all, no
matter through which file they've been created. Since this must be set
at open time we need sysfs support for this.

Add an optional mapping parameter bin_attr, which is only consulted
when there's also an mmap callback, since without mmap support
allowing to adjust the ->f_mapping makes no sense.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201127164131.2244124-12-daniel.vetter@ffwll.ch