Profiling the Cryptech Alpha
============================

Origin
------

This code was copied from https://github.com/ErichStyger/mcuoneclipse.git,
directory `Examples/KDS/FRDM-K64F120M/FRDM-K64F_Profiling/Profiling`, commit
9b7eedddd8b24968128582aedc63be95b61f782c, dated Mon Jan 9 16:56:17 2017 +0100.

References
----------

I recommend reading both of these to understand how the profiling code works.

1. [Tutorial: Using GNU Profiling (gprof) with ARM Cortex-M](https://mcuoneclipse.com/2015/08/23/tutorial-using-gnu-profiling-gprof-with-arm-cortex-m/)

2. [Semihosting with ARM, GCC, and OpenOCD](http://bgamari.github.io/posts/2014-10-31-semihosting.html)

How to build
------------

From the top level, run

    $ make DO_PROFILING=1 hsm

By default, all code is profiled, *except* the profiling code itself,
because that would cause fatal recursion.

How to run
----------

You need to start OpenOCD on the host, and enable semihosting, at least
before you try to use it as a remote file system.

I recommend executing the following in the `projects/hsm` directory, so that
`gmon.out` ends up in the same directory as `hsm.elf`.

Start the debugger:

    $ ../../bin/debug hsm

In another window, connect to OpenOCD:

    $ telnet localhost 4444

In the OpenOCD console, enable semihosting:

    > arm semihosting enable
    > exit

Then connect to the Cryptech management console:

    $ cryptech_console

In the Cryptech console, type `profile start`, then start the unit test or
whatever will be exercising the hsm. Afterwards, in the console, type
`profile stop`.

After invoking `profile stop`, it can take several minutes to write
`gmon.out` over OpenOCD to the host.

In the `projects/hsm` directory, run `gprof` to analyse the `gmon.out` file:

    $ gprof hsm.elf >gprof.txt