Few considerations:

• MDEV-7011 statement timeouts. currently max_statement_time limit applies to CALL statement as a whole, not to individual statements in the stored procedure. That was done, precisely, because CALL is logged in the slow query log as a whole, that is, the logic is — we measure time for the CALL, not for statements inside it. If slow query log will contain statements from inside the stored procedure, we might want to change max_statement_time to match this behavior.
• MDEV-7444 currently audit plugin doesn't see statements inside the stored procedure, we might want to change this too
• slow log can record EXPLAIN output for statements. it needs to work for statements inside a procedure too

this is in Percona Server 5.5, 5.6 and 5.7 - we need to see this in MariaDB Server 10.2 please (https://www.percona.com/doc/percona-server/5.7/diagnostics/slow_extended.html)

This functionality is now pushed to bb-10.3-monty to be included in next 10.3 alpha.

The differences to the patch in Percona server are:

• Instead of adding a new variable for just logging to sp, I added two more general variables:
  log_slow_disable_statements and log_disable_statements, which allowed me to make the following variables
  obsolete: log_slow_slave_statements, log_slow_admin_statements. This allow the user to specify more exactly
  what should not be logged. 'admin', 'call', 'slave' and 'sp'.
• All the above variables are now session variables instead of global variables.
• Status in slow log now show correct information for SP statements. CALL's correctly accumulates information from all included statements (This was not the case with the Percona patch).

From the commit statement (I have omitted internal changes not relevant for end user):

New functionallity:

• Added new variables log_slow_disable_statements and log_disable_statements
  that can be used to disable logging of certain queries to slow and
  general log. Currently supported options are 'admin', 'call', 'slave'
  and 'sp'.
  Defaults are as before. Only 'sp' (stored procedure statements) is
  disabled for slow and general_log.
• Slow log to files now includes the following new information:
• When logging stored procedure statements the name of stored
  procedure is logged.
• Number of created tmp_tables, tmp_disk_tables and the space used
  by temporary tables.
• When logging 'call', the logged status now contains the sum of all
  included statements. Before only 'time' was correct.

Mapped some old variables to bitmaps (old variables can still be used)

• Variable 'log_queries_not_using_indexes' is mapped to
  log_slow_filter='not_using_index'
• Variable 'log_slow_slave_statements' is mapped to
  log_slow_disabled_statements='slave'
• Variable 'log_slow_admin_statements' is mapped to
  log_slow_disabled_statements='admin'
• All the above variables are changed to session variables from global
  variables

Fixed and pushed a long time ago