kernel: support log system for fatal errors

We introduce a new z_fatal_print() API and replace all
occurrences of exception handling code to use it.
This routes messages to the logging subsystem if enabled.
Otherwise, messages are sent to printk().

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

include/fatal.h

@@ -8,6 +8,7 @@
 #define ZEPHYR_INCLUDE_FATAL_H
 
 #include <arch/cpu.h>
+#include <toolchain.h>
 
 enum k_fatal_error_reason {
 	/** Generic CPU exception, not covered by other codes */
@@ -77,4 +78,27 @@ void k_sys_fatal_error_handler(unsigned int reason, const NANO_ESF *esf);
  */
 void z_fatal_error(unsigned int reason, const NANO_ESF *esf);
 
+/**
+ * Print messages related to an exception
+ *
+ * This ensures the following:
+ *  - The log system will enter panic mode if it is not already
+ *  - Messages will be sent to printk() or the log subsystem if it is enabled
+ *
+ * Log subsystem filtering is disabled.
+ * To conform with log subsystem semantics, newlines are automatically
+ * appended, invoke this once per line.
+ *
+ * @param fmt Format string
+ * @param ... Optional list of format arguments
+ *
+ * FIXME: Implemented in C file to avoid #include loops, disentangle and
+ * make this a macro
+ */
+#if defined(CONFIG_LOG) || defined(CONFIG_PRINTK)
+__printf_like(1, 2) void z_fatal_print(const char *fmt, ...);
+#else
+#define z_fatal_print(...) do { } while (false)
+#endif
+
 #endif /* ZEPHYR_INCLUDE_FATAL_H */