[cryptolib] csrng driver

This commit introduces the a driver for the software instance of the
csrng. The driver interface supports regular DRBG functions, i.e.
instantiate, reseed, update and generate functions.

The focus of this commit is functionality, so there are a few things
that will be addressed in future commits:

- Handling of blocking operations. This is currently an area where we
  need to come up with a strategy for the crypto library as indefinite
  blocking operations may need an unconditional timeout when called in
  higher application layers.
- alert and state checks.

Signed-off-by: Miguel Osorio <[email protected]>

sw/device/lib/crypto/drivers/BUILD

@@ -20,6 +20,21 @@ cc_library(
     ],
 )
 
+opentitan_functest(
+    name = "aes_test",
+    srcs = ["aes_test.c"],
+    verilator = verilator_params(
+        timeout = "long",
+    ),
+    deps = [
+        ":aes",
+        "//sw/device/lib/base:macros",
+        "//sw/device/lib/base:memory",
+        "//sw/device/lib/testing/test_framework:check",
+        "//sw/device/lib/testing/test_framework:ottf_main",
+    ],
+)
+
 cc_library(
     name = "kmac",
     srcs = ["kmac.c"],
@@ -58,21 +73,6 @@ opentitan_functest(
     ],
 )
 
-opentitan_functest(
-    name = "aes_test",
-    srcs = ["aes_test.c"],
-    verilator = verilator_params(
-        timeout = "long",
-    ),
-    deps = [
-        ":aes",
-        "//sw/device/lib/base:macros",
-        "//sw/device/lib/base:memory",
-        "//sw/device/lib/testing/test_framework:check",
-        "//sw/device/lib/testing/test_framework:ottf_main",
-    ],
-)
-
 cc_library(
     name = "entropy",
     srcs = ["entropy.c"],

sw/device/lib/crypto/drivers/entropy.c

@@ -158,7 +158,7 @@ status_t entropy_csrng_generate_data_get(uint32_t *buf, size_t len) {
     // Block until there is more data available in the genbits buffer. CSRNG
     // generates data in 128bit chunks (i.e. 4 words).
     static_assert(kEntropyCsrngBitsBufferNumWords == 4,
-      "kEntropyCsrngBitsBufferNumWords must be a power of 2.");
+                  "kEntropyCsrngBitsBufferNumWords must be a power of 2.");
     if (i & (kEntropyCsrngBitsBufferNumWords - 1)) {
       uint32_t reg;
       do {