Trying to prefetch code for encryption, specifically for ESP32

test_common.py

@@ -149,7 +149,7 @@ class UARTP:
                         return buf
 
 
-def run_nist_aead_test_line(dut, i, m, ad, k, npub, c):
+def run_nist_aead_test_line(dut, i, m, ad, k, npub, c=None):
     eprint()
     eprint("Count = %d" % i)
     eprint("   m = %s" % m.hex())
@@ -668,7 +668,39 @@ def run_nist_lws_aead_test(dut, vectors_file, build_dir,
     sys.stdout.write("Board prepared\n")
     sys.stdout.flush()
 
+    # For targets that support memory utilization testing, the RAM should now
+    # contain a known pattern pattern that is identical for all algorithms,
+    # minus the differences in static memory. Now we dump the RAM before and
+    # after running the first test vector, to measure how much of the memory
+    # was affected by one execution of encryption and decryption
+
     ram_dumps = [dut.dump_ram()]
+    if ram_dumps[0] is not None:
+        i, m, ad, k, npub, c = kat[0]
+        run_nist_aead_test_line(dut, i, m, ad, k, npub, c)
+        ram_dumps.append(dut.dump_ram())
+
+    # This is a dummy test to ensure the encryption and decryption code is in
+    # the cache for devices that make use of a slow flash for storing the code.
+    # The duration of this test is not measured.
+    # It uses the same length for the message and AD as the last line of the
+    # test vector file, which is assumed to be the longest.
+
+    i, m, ad, k, npub, c = kat[-1]
+    run_nist_aead_test_line(
+        dut,
+        -1,
+        b"m" * len(m),
+        b"a" * len(ad),
+        b"k" * len(k),
+        b"n" * len(npub),
+        None
+    )
+
+    # Now we do the encryption and decryption speed test. The tool object
+    # provides an abstraction to the logic analyzer that will check how long
+    # the encryption/decryption takes by mean of the CRYPTO_BUSY GPIO on the
+    # board.
 
     tool = LogicMultiplexerTimeMeasurements(logic_mask)
     try:
@@ -679,9 +711,6 @@ def run_nist_lws_aead_test(dut, vectors_file, build_dir,
             run_nist_aead_test_line(dut, i, m, ad, k, npub, c)
             tool.unarm()
 
-            if i == 1 and ram_dumps[0] is not None:
-                ram_dumps.append(dut.dump_ram())
-
     except Exception as ex:
         print("TEST FAILED")
         raise ex