exec_blob Directory Reference

Directory dependency graph for exec_blob:

Directories
	copy_file_blob
	demo_blob_1
	demo_blob_2

Detailed Description

`exec_blob` Tools

As a somewhat last-resort for missing functionality, and/or for dynamic on-orbit data analysis, it could be helpful to load a machine code file from the filesystem into a buffer in memory, and then execute it as though it's a function.

This functionality is fairly risky (though not too bad, due to safety features like the 2 layers of watchdogs), and decently challenging to use.

• Related to: https://github.com/CalgaryToSpace/CTS-SAT-1-OBC-Firmware/issues/573

Status

Basic demo blobs work reliably and safely, so this feature will be included in the firmware in case it is needed.

Guide

1. Duplicate demo_blob_2/ to start your own blob/script/payload.
2. Modify blob_main.c to implement whatever you wish.
3. Use the arm-none-eabi-nm -n CTS-SAT-1_FW.elf | grep function_or_variable_name command to get addresses of functions in the main firmware.
   • Be sure to add one to the address of functions (make the address odd).
4. Run make clean && make
5. Convert the blob.bin output file to hex and upload it using fs_write_file_hex(...), or use the bulk file uplink procedure.
6. Verify the hash with the SHA256 telecommand.
7. Run the exec_blob_from_fs telecommand to run the new blob.
   • The blob is triggered with the remaining/unused argument: exec_blob_from_fs(blob_filename.bin,0,this_argument_is_passed_as_arg_str_to_blob)

Other Notes

• When using where_to_load_arg_1=1 or 2, MPI data collection may not work well while using this feature (though will return to normal after the completion of exec_blob_from_fs), as we use the giant MPI buffer to store the blob/program.
  • Using where_to_load_arg_1=0 allows MPI operations to work as normal.
• This feature is "secure" because uplinks are validated/authenticated by HMAC in the AX100 transceiver.