Implement log framework
This patch gives users control over logging messages printed from the C
code using the LOG macros defined in debug.h Users now have the ability
to reduce the log_level at run time using the tf_log_set_max_level()
function. The default prefix string can be defined by platform by
overriding the `plat_log_get_prefix()` platform API which is also
introduced in this patch.
The new log framework results in saving of some RO data. For example,
when BL1 is built for FVP with LOG_LEVEL=LOG_LEVEL_VERBOSE, resulted
in saving 384 bytes of RO data and increase of 8 bytes of RW data. The
framework also adds about 108 bytes of code to the release build of FVP.
Fixes ARM-software/tf-issues#462
Change-Id: I476013d9c3deedfdd4c8b0b0f125665ba6250554
Co-authored-by: Eleanor Bonnici <Eleanor.bonnici@arm.com>
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
diff --git a/common/tf_log.c b/common/tf_log.c
new file mode 100644
index 0000000..54c0a43
--- /dev/null
+++ b/common/tf_log.c
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <debug.h>
+#include <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 ARM Trusted Firmware 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 && log_level <= LOG_LEVEL_VERBOSE);
+ assert(log_level % 10 == 0);
+
+ if (log_level > max_log_level)
+ return;
+
+ prefix_str = plat_log_get_prefix(log_level);
+
+ if (prefix_str != NULL)
+ tf_string_print(prefix_str);
+
+ va_start(args, fmt);
+ tf_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 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 % 10) == 0);
+
+ /* Cap log_level to the compile time maximum. */
+ if (log_level < LOG_LEVEL)
+ max_log_level = log_level;
+
+}