diff --git a/mocks/common/tf_log.c b/mocks/common/tf_log.c
new file mode 100644
index 0000000..08d3cf4
--- /dev/null
+++ b/mocks/common/tf_log.c
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2017-2019, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdarg.h>
+#include <assert.h>
+#include <stdio.h>
+
+#include <common/debug.h>
+#include <plat/common/platform.h>
+
+/* Set the default maximum log level to the `LOG_LEVEL` build flag */
+static unsigned int max_log_level = LOG_LEVEL;
+
+/*
+ * The common log function which is invoked by TF-A code.
+ * This function should not be directly invoked and is meant to be
+ * only used by the log macros defined in debug.h. The function
+ * expects the first character in the format string to be one of the
+ * LOG_MARKER_* macros defined in debug.h.
+ */
+void tf_log(const char *fmt, ...)
+{
+	unsigned int log_level;
+	va_list args;
+	const char *prefix_str;
+
+	/* We expect the LOG_MARKER_* macro as the first character */
+	log_level = fmt[0];
+
+	/* Verify that log_level is one of LOG_MARKER_* macro defined in debug.h */
+	assert((log_level > 0U) && (log_level <= LOG_LEVEL_VERBOSE));
+	assert((log_level % 10U) == 0U);
+
+	if (log_level > max_log_level)
+		return;
+
+	prefix_str = plat_log_get_prefix(log_level);
+
+	while (*prefix_str != '\0') {
+		(void)putchar(*prefix_str);
+		prefix_str++;
+	}
+
+	va_start(args, fmt);
+	(void)vprintf(fmt + 1, args);
+	va_end(args);
+}
+
+/*
+ * The helper function to set the log level dynamically by platform. The
+ * maximum log level is determined by `LOG_LEVEL` build flag at compile time
+ * and this helper can set a lower (or equal) log level than the one at compile.
+ */
+void tf_log_set_max_level(unsigned int log_level)
+{
+	assert(log_level <= LOG_LEVEL_VERBOSE);
+	assert((log_level % 10U) == 0U);
+
+	/* Cap log_level to the compile time maximum. */
+	if (log_level <= (unsigned int)LOG_LEVEL)
+		max_log_level = log_level;
+}