[crypto] Check if jittery clock is enabled

When using the CryptoLib, the jittery clock security function should
be enabled. This commit adds a function that checks if the JITTER_ENABLE
is set to kMultiBitBool4True.

Signed-off-by: Pascal Nasahl <[email protected]>

Author: nasahlpa

sw/device/silicon_creator/lib/drivers/BUILD

@@ -137,6 +137,21 @@ cc_test(
     ],
 )
 
+cc_library(
+    name = "clkmgr",
+    srcs = ["clkmgr.c"],
+    hdrs = [
+        "clkmgr.h",
+    ],
+    deps = [
+        "//hw/top:dt_clkmgr",
+        "//sw/device/lib/base:abs_mmio",
+        "//sw/device/lib/base:hardened",
+        "//sw/device/lib/base:macros",
+        "//sw/device/lib/base:multibits",
+    ],
+)
+
 dual_cc_library(
     name = "flash_ctrl",
     srcs = dual_inputs(

sw/device/silicon_creator/lib/drivers/clkmgr.c

@@ -0,0 +1,28 @@
+// Copyright lowRISC contributors (OpenTitan project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "sw/device/silicon_creator/lib/drivers/clkmgr.h"
+
+#include "hw/top/dt/dt_clkmgr.h"
+#include "sw/device/lib/base/abs_mmio.h"
+#include "sw/device/lib/base/multibits.h"
+
+#include "hw/top/clkmgr_regs.h"
+
+// Module ID for status codes.
+#define MODULE_ID MAKE_MODULE_ID('c', 'l', 'k')
+
+hardened_bool_t clkmgr_check_jittery_clk_en(void) {
+  uintptr_t clkmgr_base_addr = dt_clkmgr_primary_reg_block(kDtClkmgrAon);
+  uint32_t jittery_clk_en =
+      abs_mmio_read32(clkmgr_base_addr + CLKMGR_JITTER_ENABLE_REG_OFFSET);
+
+  // Check that the jittery clock is set to kMultiBitBool4True
+  if (launder32(jittery_clk_en) != kMultiBitBool4True) {
+    return kHardenedBoolFalse;
+  }
+  HARDENED_CHECK_EQ(jittery_clk_en, kMultiBitBool4True);
+
+  return kHardenedBoolTrue;
+}

sw/device/silicon_creator/lib/drivers/clkmgr.h

@@ -0,0 +1,31 @@
+// Copyright lowRISC contributors (OpenTitan project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_DRIVERS_CLKMGR_H_
+#define OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_DRIVERS_CLKMGR_H_
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "sw/device/lib/base/hardened.h"
+#include "sw/device/lib/base/macros.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Checks if the JITTER_ENABLE register of the CLKMGR is set to on.
+ *
+ * @return Whether the jittery clock is enabled.
+ */
+OT_WARN_UNUSED_RESULT
+hardened_bool_t clkmgr_check_jittery_clk_en(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_DRIVERS_CLKMGR_H_