ele_concurrent_access
Overview
This application provides a demonstration of how the SSS API may be used concurrently from two cores. It demonstrates how initialization may be done independently on both cores and how to safely prepare input data into S200-accessible memory if used from the NBU core.
Access serialization
The S200 enclave supports receiving commands from multiple cores. For such cases, the S3MU driver functions for sending command messages and receiving response messages are wrapped in an S3MU-specific semaphore for command serialization between cores. This serialization is transparent to the driver’s user and the user does not need to manage this semaphore themselves.
However, on top of this there may be a need to serialize access to shared resources at the application layer, such as access to shared memory. Such a case is demonstrated by this application, in which the SEMA42 hardware semaphore is utilized.
Demo implementation components
The application is divided into three main components:
the primary core
main.cfile,the secondary core
main.cfile,and the
common_definitions.hfile.
The individual core’s main.c implementation files are specific to the given
core. Definitions in the common_definitions.h file are the same for both
cores and are included in both core’s binaries separately. These definitions
were placed in a single file to reduce code duplication. The common definitions
may differ in small ways between cores; please see the note below or the code
itself for concrete examples.
NOTE
This example showcases the requirement for buffers that are directly
accessed by the S200 to be placed into S200-accessible memory. Notably,
the S200 may only access Main-core memory and the shared memory between Main and
NBU core. Please note the code sections guarded by the
#if (defined(IS_RADIO_CORE) && (IS_RADIO_CORE > 0)) construct.
Building the application
This shows example how to build application for kw47evk board with cm33_core0 core_id.
Change the -b <board> parameter based on board you want to build.
Change the -Dcore_id=<core_id> parameter based on board core you want to build.
For these parameters please see attribute boards: in primary/example.yml.
west build --sysbuild examples/secure-subsystem_examples/ele_concurrent_access/primary --toolchain armgcc --config debug -b kw47evk -Dcore_id=cm33_core0