nitro_enclaves: Add logic for getting the enclave image load info

nitro_enclaves: Add logic for getting the enclave image load info

Before setting the memory regions for the enclave, the enclave image
needs to be placed in memory. After the memory regions are set, this
memory cannot be used anymore by the VM, being carved out.

Add ioctl command logic to get the offset in enclave memory where to
place the enclave image. Then the user space tooling copies the enclave
image in the memory using the given memory offset.

Changelog

v9 -> v10

* Update commit message to include the changelog before the SoB tag(s).

v8 -> v9

* No changes.

v7 -> v8

* Add custom error code for incorrect enclave image load info flag.

v6 -> v7

* No changes.

v5 -> v6

* Check for invalid enclave image load flags.

v4 -> v5

* Check for the enclave not being started when invoking this ioctl call.
* Remove log on copy_from_user() / copy_to_user() failure.

v3 -> v4

* Use dev_err instead of custom NE log pattern.
* Set enclave image load offset based on flags.
* Update the naming for the ioctl command from metadata to info.

v2 -> v3

* No changes.

v1 -> v2

* New in v2.

Reviewed-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Andra Paraschiv <andraprs@amazon.com>
Link: https://lore.kernel.org/r/20200921121732.44291-11-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>