base: new interface for textual output

Issue #1942

repos/base-fiasco/src/core/target.inc

@@ -9,6 +9,7 @@ SRC_CC      += stack_area.cc \
                cpu_session_component.cc \
                cpu_session_support.cc \
                dataspace_component.cc \
+               default_log.cc \
                dump_alloc.cc \
                io_mem_session_component.cc \
                io_mem_session_support.cc \
@@ -64,6 +65,7 @@ vpath io_mem_session_support.cc   $(GEN_CORE_DIR)
 vpath signal_source_component.cc  $(GEN_CORE_DIR)
 vpath trace_session_component.cc  $(GEN_CORE_DIR)
 vpath dataspace_component.cc      $(GEN_CORE_DIR)
+vpath default_log.cc              $(GEN_CORE_DIR)
 vpath dump_alloc.cc               $(GEN_CORE_DIR)
 vpath stack_area.cc               $(GEN_CORE_DIR)
 vpath pager_ep.cc                 $(GEN_CORE_DIR)

repos/base-foc/src/core/target.inc

@@ -12,6 +12,7 @@ SRC_CC      += stack_area.cc \
                cpu_session_component.cc \
                cpu_session_support.cc \
                dataspace_component.cc \
+               default_log.cc \
                dump_alloc.cc \
                io_mem_session_component.cc \
                io_mem_session_support.cc \
@@ -52,6 +53,7 @@ vpath cpu_session_component.cc    $(GEN_CORE_DIR)
 vpath cpu_session_support.cc      $(GEN_CORE_DIR)
 vpath dataspace_component.cc      $(GEN_CORE_DIR)
 vpath dump_alloc.cc               $(GEN_CORE_DIR)
+vpath default_log.cc              $(GEN_CORE_DIR)
 vpath io_mem_session_component.cc $(GEN_CORE_DIR)
 vpath io_mem_session_support.cc   $(GEN_CORE_DIR)
 vpath main.cc                     $(GEN_CORE_DIR)

repos/base-hw/lib/mk/core.inc

@@ -22,6 +22,7 @@ SRC_CC += core_region_map.cc
 SRC_CC += core_mem_alloc.cc
 SRC_CC += core_rpc_cap_alloc.cc
 SRC_CC += dataspace_component.cc
+SRC_CC += default_log.cc
 SRC_CC += dump_alloc.cc
 SRC_CC += io_mem_session_component.cc
 SRC_CC += io_mem_session_support.cc

repos/base-linux/src/core/target.mk

@@ -26,6 +26,7 @@ SRC_CC        = main.cc \
                 thread_linux.cc \
                 stack_area.cc \
                 core_printf.cc \
+                default_log.cc \
                 env_reinit.cc \
                 thread.cc thread_myself.cc
 
@@ -49,6 +50,7 @@ vpath platform_services.cc        $(GEN_CORE_DIR)
 vpath signal_source_component.cc  $(GEN_CORE_DIR)
 vpath trace_session_component.cc  $(GEN_CORE_DIR)
 vpath core_rpc_cap_alloc.cc       $(GEN_CORE_DIR)
+vpath default_log.cc              $(GEN_CORE_DIR)
 vpath core_printf.cc              $(BASE_DIR)/src/lib/base
 vpath thread.cc                   $(BASE_DIR)/src/lib/base
 vpath thread_myself.cc            $(BASE_DIR)/src/lib/base

repos/base-linux/src/lib/lx_hybrid/lx_hybrid.cc

@@ -19,6 +19,7 @@
 
 /* base-internal includes */
 #include <base/internal/native_thread.h>
+#include <base/internal/globals.h>
 
 
 extern "C" int raw_write_str(const char *str);
@@ -109,6 +110,7 @@ void Genode::call_global_static_constructors() { }
 
 int main()
 {
+	Genode::init_log();
 	Genode::bootstrap_component();
 
 	/* never reached */

repos/base-nova/src/core/target.inc

@@ -12,6 +12,7 @@ SRC_CC       = stack_area.cc \
                cpu_session_extension.cc \
                cpu_session_support.cc \
                dataspace_component.cc \
+               default_log.cc \
                dump_alloc.cc \
                echo.cc \
                io_mem_session_component.cc \
@@ -61,6 +62,7 @@ vpath io_mem_session_component.cc  $(GEN_CORE_DIR)
 vpath io_mem_session_support.cc    $(GEN_CORE_DIR)
 vpath dataspace_component.cc       $(GEN_CORE_DIR)
 vpath core_mem_alloc.cc            $(GEN_CORE_DIR)
+vpath default_log.cc               $(GEN_CORE_DIR)
 vpath dump_alloc.cc                $(GEN_CORE_DIR)
 vpath platform_services.cc         $(GEN_CORE_DIR)/spec/x86
 vpath stack_area.cc                $(GEN_CORE_DIR)

repos/base-okl4/src/core/target.inc

@@ -12,6 +12,7 @@ SRC_CC += stack_area.cc \
           cpu_session_component.cc \
           cpu_session_support.cc \
           dataspace_component.cc \
+          default_log.cc \
           dump_alloc.cc \
           io_mem_session_component.cc \
           io_mem_session_support.cc \
@@ -60,6 +61,7 @@ vpath dataspace_component.cc      $(GEN_CORE_DIR)
 vpath core_mem_alloc.cc           $(GEN_CORE_DIR)
 vpath core_rpc_cap_alloc.cc       $(GEN_CORE_DIR)
 vpath dump_alloc.cc               $(GEN_CORE_DIR)
+vpath default_log.cc              $(GEN_CORE_DIR)
 vpath stack_area.cc               $(GEN_CORE_DIR)
 vpath pager_ep.cc                 $(GEN_CORE_DIR)
 vpath %.cc                        $(REP_DIR)/src/core

repos/base-pistachio/src/core/target.inc

@@ -11,6 +11,7 @@ SRC_CC       = stack_area.cc \
                cpu_session_component.cc \
                cpu_session_platform.cc \
                dataspace_component.cc \
+               default_log.cc \
                dump_alloc.cc \
                io_mem_session_component.cc \
                io_mem_session_support.cc \
@@ -59,6 +60,7 @@ vpath signal_source_component.cc  $(GEN_CORE_DIR)
 vpath trace_session_component.cc  $(GEN_CORE_DIR)
 vpath dataspace_component.cc      $(GEN_CORE_DIR)
 vpath dump_alloc.cc               $(GEN_CORE_DIR)
+vpath default_log.cc              $(GEN_CORE_DIR)
 vpath core_rpc_cap_alloc.cc       $(GEN_CORE_DIR)
 vpath core_region_map.cc          $(GEN_CORE_DIR)
 vpath stack_area.cc               $(GEN_CORE_DIR)

repos/base-sel4/lib/mk/core_printf.mk

@@ -1,5 +1,6 @@
-SRC_CC   = core_printf.cc
+SRC_CC   = core_printf.cc default_log.cc
-INC_DIR += $(REP_DIR)/src/include
+INC_DIR += $(REP_DIR)/src/include $(BASE_DIR)/src/include
 LIBS    += syscall
 
 vpath core_printf.cc $(BASE_DIR)/src/lib/base
+vpath default_log.cc $(BASE_DIR)/src/core

repos/base/include/base/log.h

@@ -0,0 +1,109 @@
+/*
+ * \brief  LOG output functions
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__BASE__LOG_H_
+#define _INCLUDE__BASE__LOG_H_
+
+#include <base/output.h>
+#include <base/lock.h>
+
+namespace Genode { class Log; }
+
+
+/**
+ * Interface for writing output to the component's LOG session
+ *
+ * The LOG session is not used directly by the 'log', 'warning', and
+ * 'error' functions. They access the LOG indirectly via this interface
+ * instead, which ensures the proper synchronization of the output in the
+ * presence of multiple threads and to apply distinguishable colors to the
+ * different types of messages.
+ */
+class Genode::Log
+{
+	public:
+
+		/**
+		 * Type of message
+		 */
+		enum Type { LOG, WARNING, ERROR };
+
+	private:
+
+		Lock    _lock;
+		void    _acquire(Type);
+		void    _release();
+		Output &_output;
+
+		/**
+		 * Helper for the sequential output of a variable list of arguments
+		 */
+		template <typename HEAD, typename... TAIL>
+		void _output_args(Output &output, HEAD && head, TAIL &&... tail)
+		{
+			print(output, head);
+			_output_args(output, tail...);
+		}
+
+		template <typename LAST>
+		void _output_args(Output &output, LAST && last) { print(output, last); }
+
+	public:
+
+		Log(Output &output) : _output(output) { }
+
+		template <typename... ARGS>
+		void output(Type type, ARGS &&... args)
+		{
+			/*
+			 * This function is being inlined. Hence, we try to keep it as
+			 * small as possible. For this reason, the lock operations are
+			 * performed by the '_acquire' and '_release' functions instead of
+			 * using a lock guard.
+			 */
+			_acquire(type);
+			_output_args(_output, args...);
+			_release();
+		}
+
+		/**
+		 * Return component-global singleton instance of the 'Log'
+		 */
+		static Log &log();
+};
+
+
+namespace Genode {
+
+	/**
+	 * Write 'args' as a regular message to the log
+	 */
+	template <typename... ARGS>
+	void log(ARGS &&... args) { Log::log().output(Log::LOG, args...); }
+
+
+	/**
+	 * Write 'args' as a warning message to the log
+	 */
+	template <typename... ARGS>
+	void warning(ARGS &&... args) { Log::log().output(Log::WARNING, args...); }
+
+
+	/**
+	 * Write 'args' as an error message to the log
+	 */
+	template <typename... ARGS>
+	void error(ARGS &&... args) { Log::log().output(Log::ERROR, args...); }
+}
+
+#endif /* _INCLUDE__BASE__LOG_H_ */

repos/base/include/base/output.h

@@ -0,0 +1,154 @@
+/*
+ * \brief  Interface for textual output
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__BASE__OUTPUT_H_
+#define _INCLUDE__BASE__OUTPUT_H_
+
+#include <util/string.h>
+#include <base/stdint.h>
+
+namespace Genode { struct Output; }
+
+
+struct Genode::Output
+{
+	/**
+	 * Output single character
+	 */
+	virtual void out_char(char) = 0;
+
+	/**
+	 * Output string
+	 *
+	 * \param n  maximum number of characters to output
+	 *
+	 * The output stops on the first occurrence of a null character in the
+	 * string or after 'n' characters.
+	 *
+	 * The default implementation uses 'out_char'. This method may be
+	 * overridden by the backend for improving efficiency.
+	 */
+	virtual void out_string(char const *str, size_t n = ~0UL);
+};
+
+
+namespace Genode {
+
+	/**
+	 * Print null-terminated string
+	 */
+	void print(Output &output, char const *);
+
+	/**
+	 * Print pointer value
+	 */
+	void print(Output &output, void const *);
+
+	/**
+	 * Print arbitrary pointer types
+	 *
+	 * This function template takes precedence over the one that takes a
+	 * constant object reference as argument.
+	 */
+	template <typename T>
+	static inline void print(Output &output, T *ptr)
+	{
+		print(output, (void const *)ptr);
+	}
+
+	/**
+	 * Print unsigned long value
+	 */
+	void print(Output &output, unsigned long);
+
+	/**
+	 * Print unsigned integer value
+	 */
+	static inline void print(Output &output, unsigned value)
+	{
+		print(output, (unsigned long)value);
+	}
+
+	/**
+	 * Print signed long value
+	 */
+	void print(Output &output, long);
+
+	/**
+	 * Print signed integer value
+	 */
+	static inline void print(Output &output, int value)
+	{
+		print(output, (long)value);
+	}
+
+	/**
+	 * Print signed long long value
+	 */
+	void print(Output &output, long long);
+
+	/**
+	 * Helper for the hexadecimal output of integer values
+	 *
+	 * To output an integer value as hexadecimal number, the value can be
+	 * wrapped into an 'Hex' object, thereby selecting the corresponding
+	 * overloaded 'print' function below.
+	 */
+	struct Hex
+	{
+		enum Prefix { PREFIX, OMIT_PREFIX };
+		enum Pad    { PAD,    NO_PAD };
+
+		unsigned long const value;
+		size_t        const digits;
+		Prefix        const prefix;
+		Pad           const pad;
+
+		/**
+		 * Constructor
+		 *
+		 * \param prefix  by default, the value is prepended with the prefix
+		 *                '0x'. The prefix can be suppressed by specifying
+		 *                'OMIT_PREFIX' as argument.
+		 * \param pad     by default, leading zeros are stripped from the
+		 *                output. If set to 'PAD', the leading zeros will be
+		 *                printed.
+		 */
+		template <typename T>
+		explicit Hex(T value, Prefix prefix = PREFIX, Pad pad = NO_PAD)
+		: value(value), digits(2*sizeof(T)), prefix(prefix), pad(pad) { }
+	};
+
+	/**
+	 * Print hexadecimal number
+	 */
+	void print(Output &output, Hex const &);
+
+	/**
+	 * Print information about object 'obj'
+	 *
+	 * The object type must provide a const 'print(Output &)' method that
+	 * produces the textual representation of the object.
+	 *
+	 * In contrast to overloads of the 'Genode::print' function, the 'T::print'
+	 * method is able to access object-internal state, which can thereby be
+	 * incorporated into the textual output.
+	 */
+	template <typename T>
+	static inline void print(Output &output, T const &obj)
+	{
+		obj.print(output);
+	}
+}
+
+#endif /* _INCLUDE__BASE__OUTPUT_H_ */

repos/base/lib/mk/base-common.inc

@@ -11,11 +11,13 @@ SRC_CC += slab.cc
 SRC_CC += allocator_avl.cc
 SRC_CC += heap.cc sliced_heap.cc
 SRC_CC += console.cc
+SRC_CC += output.cc
 SRC_CC += child.cc
 SRC_CC += child_process.cc
 SRC_CC += elf_binary.cc
 SRC_CC += ipc.cc
 SRC_CC += lock.cc
+SRC_CC += log.cc
 SRC_CC += rpc_entrypoint.cc
 SRC_CC += signal.cc signal_common.cc
 SRC_CC += sleep.cc

repos/base/lib/mk/base.inc

@@ -1,4 +1,4 @@
-SRC_CC += log_console.cc
+SRC_CC += log_console.cc default_log.cc
 SRC_CC += env_deprecated.cc stack_area.cc env_reinit.cc
 SRC_CC += rpc_cap_alloc.cc
 

repos/base/src/core/default_log.cc

@@ -0,0 +1,51 @@
+/*
+ * \brief  Access to the core's log facility
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <base/log.h>
+#include <base/printf.h>
+
+/* base-internal includes */
+#include <base/internal/globals.h>
+#include <base/internal/output.h>
+#include <base/internal/unmanaged_singleton.h>
+
+using namespace Genode;
+
+
+static Log *log_ptr;
+
+
+Log &Log::log() { return *log_ptr; }
+
+
+void Genode::init_log()
+{
+	/* ignore subsequent calls */
+	if (log_ptr)
+		return;
+
+	/*
+	 * Currently, we still rely on the old format-string support and
+	 * produce output via 'core_printf.cc'.
+	 */
+	struct Write_fn { void operator () (char const *s) { printf("%s", s); } };
+
+	typedef Buffered_output<512, Write_fn> Buffered_log_output;
+
+	static Buffered_log_output *buffered_log_output =
+		unmanaged_singleton<Buffered_log_output>(Write_fn());
+
+	log_ptr = unmanaged_singleton<Log>(*buffered_log_output);
+}
+

repos/base/src/core/main.cc

@@ -16,6 +16,7 @@
 #include <base/sleep.h>
 #include <base/service.h>
 #include <base/child.h>
+#include <base/log.h>
 #include <rm_session/connection.h>
 #include <pd_session/connection.h>
 #include <rom_session/connection.h>
@@ -225,7 +226,7 @@ int main()
 	 */
 	inhibit_tracing = true;
 
-	PINF("Genode %s", Genode::version_string);
+	log("Genode ", Genode::version_string);
 
 	PDBG("--- create local services ---");
 

repos/base/src/include/base/internal/globals.h

@@ -26,6 +26,7 @@ namespace Genode {
 	extern Ram_session *env_stack_area_ram_session;
 
 	void init_signal_thread();
+	void init_log();
 }
 
 #endif /* _INCLUDE__BASE__INTERNAL__GLOBALS_H_ */

repos/base/src/include/base/internal/output.h

@@ -0,0 +1,160 @@
+/*
+ * \brief  Internal utilities used for implementing the 'Output' funtions
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__BASE__INTERNAL__OUTPUT_H_
+#define _INCLUDE__BASE__INTERNAL__OUTPUT_H_
+
+
+#include <base/output.h>
+
+using namespace Genode;
+
+
+/**
+ * Convert digit to ASCII value
+ */
+static inline char ascii(int digit, int uppercase = 0)
+{
+	if (digit > 9)
+		return digit + (uppercase ? 'A' : 'a') - 10;
+
+	return digit + '0';
+}
+
+
+/**
+ * Output signed value with the specified base
+ */
+template <typename T, typename OUT_CHAR_FN>
+static inline void out_signed(T value, unsigned base, OUT_CHAR_FN const &out_char)
+{
+	/**
+	 * for base 8, the number of digits is the number of value bytes times 3
+	 * at a max, because 0xff is 0o377 and accumulating this implies a
+	 * strictly decreasing factor
+	 */
+	char buf[sizeof(value)*3];
+
+	/* set flag if value is negative */
+	int neg = value < 0 ? 1 : 0;
+
+	/* get absolute value */
+	value = value < 0 ? -value : value;
+
+	int i = 0;
+
+	/* handle zero as special case */
+	if (value == 0)
+		buf[i++] = ascii(0);
+
+	/* fill buffer starting with the least significant digits */
+	else
+		for (; value > 0; value /= base)
+			buf[i++] = ascii(value % base);
+
+	/* add sign to buffer for negative values */
+	if (neg)
+		out_char('-');
+
+	/* output buffer in reverse order */
+	for (; i--; )
+		out_char(buf[i]);
+}
+
+
+/**
+ * Output unsigned value with the specified base and padding
+ */
+template <typename T, typename OUT_CHAR_FN>
+static inline void out_unsigned(T value, unsigned base, int pad,
+                                OUT_CHAR_FN const &out_char)
+{
+	/**
+	 * for base 8, the number of digits is the number of value bytes times 3
+	 * at a max, because 0xff is 0o377 and accumulating this implies a
+	 * strictly decreasing factor
+	 */
+	char buf[sizeof(value)*3];
+
+	int i = 0;
+
+	/* handle zero as special case */
+	if (value == 0) {
+		buf[i++] = ascii(0);
+		pad--;
+	}
+
+	/* fill buffer starting with the least significant digits */
+	for (; value > 0; value /= base, pad--)
+		buf[i++] = ascii(value % base);
+
+	/* add padding zeros */
+	for (; pad-- > 0; )
+		out_char(ascii(0));
+
+	/* output buffer in reverse order */
+	for (; i--; )
+		out_char(buf[i]);
+}
+
+
+namespace Genode { template <size_t, typename> class Buffered_output; }
+
+
+/**
+ * Implementation of the output interface that buffers characters
+ *
+ * \param BUF_SIZE  maximum number of characters to buffer before writing
+ * \param WRITE_FN  functor called to writing the buffered characters to a
+ *                  backend.
+ *
+ * The 'WRITE_FN' functor is called with a null-terminated 'char const *'
+ * as argument.
+ */
+template <size_t BUF_SIZE, typename BACKEND_WRITE_FN>
+class Genode::Buffered_output : public Output
+{
+	private:
+
+		BACKEND_WRITE_FN _write_fn;
+		char             _buf[BUF_SIZE];
+		unsigned         _num_chars = 0;
+
+		void _flush()
+		{
+			/* null-terminate string */
+			_buf[_num_chars] = 0;
+			_write_fn(_buf);
+
+			/* restart with empty buffer */
+			_num_chars = 0;
+		}
+
+	public:
+
+		Buffered_output(BACKEND_WRITE_FN const &write_fn) : _write_fn(write_fn) { }
+
+		void out_char(char c) override
+		{
+			/* ensure enough buffer space for complete escape sequence */
+			if ((c == 27) && (_num_chars + 8 > BUF_SIZE)) _flush();
+
+			_buf[_num_chars++] = c;
+
+			/* flush immediately on line break */
+			if (c == '\n' || _num_chars >= sizeof(_buf) - 1)
+				_flush();
+		}
+};
+
+#endif /* _INCLUDE__BASE__INTERNAL__OUTPUT_H_ */

repos/base/src/lib/base/console.cc

@@ -17,9 +17,13 @@
  * under the terms of the GNU General Public License version 2.
  */
 
+/* Genode includes */
 #include <base/console.h>
 #include <base/stdint.h>
 
+/* base-internal includes */
+#include <base/internal/output.h>
+
 using namespace Genode;
 
 
@@ -138,93 +142,6 @@ class Format_command
 };
 
 
-/**
- * Convert digit to ASCII value
- */
-static char ascii(int digit, int uppercase = 0)
-{
-	if (digit > 9)
-		return digit + (uppercase ? 'A' : 'a') - 10;
-
-	return digit + '0';
-}
-
-
-/**
- * Output signed value with the specified base
- */
-template <typename T>
-void Console::_out_signed(T value, unsigned base)
-{
-	/**
-	 * for base 8, the number of digits is the number of value bytes times 3
-	 * at a max, because 0xff is 0o377 and accumulating this implies a
-	 * strictly decreasing factor
-	 */
-	char buf[sizeof(value)*3];
-
-	/* set flag if value is negative */
-	int neg = value < 0 ? 1 : 0;
-
-	/* get absolute value */
-	value = value < 0 ? -value : value;
-
-	int i = 0;
-
-	/* handle zero as special case */
-	if (value == 0)
-		buf[i++] = ascii(0);
-
-	/* fill buffer starting with the least significant digits */
-	else
-		for (; value > 0; value /= base)
-			buf[i++] = ascii(value % base);
-
-	/* add sign to buffer for negative values */
-	if (neg)
-		_out_char('-');
-
-	/* output buffer in reverse order */
-	for (; i--; )
-		_out_char(buf[i]);
-}
-
-
-/**
- * Output unsigned value with the specified base and padding
- */
-template <typename T>
-void Console::_out_unsigned(T value, unsigned base, int pad)
-{
-	/**
-	 * for base 8, the number of digits is the number of value bytes times 3
-	 * at a max, because 0xff is 0o377 and accumulating this implies a
-	 * strictly decreasing factor
-	 */
-	char buf[sizeof(value)*3];
-
-	int i = 0;
-
-	/* handle zero as special case */
-	if (value == 0) {
-		buf[i++] = ascii(0);
-		pad--;
-	}
-
-	/* fill buffer starting with the least significant digits */
-	for (; value > 0; value /= base, pad--)
-		buf[i++] = ascii(value % base);
-
-	/* add padding zeros */
-	for (; pad-- > 0; )
-		_out_char(ascii(0));
-
-	/* output buffer in reverse order */
-	for (; i--; )
-		_out_char(buf[i]);
-}
-
-
 void Console::_out_string(const char *str)
 {
 	if (!str)
@@ -292,15 +209,18 @@ void Console::vprintf(const char *format, va_list list)
 			case Format_command::INT:
 
 				if (cmd.length == Format_command::LONG_LONG)
-					_out_signed<long long>(numeric_arg, cmd.base);
+					out_signed<long long>(numeric_arg, cmd.base,
+					                      [&] (char c) { _out_char(c); });
 				else
-					_out_signed<long>(numeric_arg, cmd.base);
+					out_signed<long>(numeric_arg, cmd.base,
+					                 [&] (char c) { _out_char(c); });
 				break;
 
 			case Format_command::UINT:
 
 				if (cmd.length == Format_command::LONG_LONG) {
-					_out_unsigned<unsigned long long>(numeric_arg, cmd.base, cmd.padding);
+					out_unsigned<unsigned long long>(numeric_arg, cmd.base, cmd.padding,
+					                                 [&] (char c) { _out_char(c); });
 					break;
 				}
 
@@ -308,7 +228,8 @@ void Console::vprintf(const char *format, va_list list)
 
 			case Format_command::PTR:
 
-				_out_unsigned<unsigned long>(numeric_arg, cmd.base, cmd.padding);
+				out_unsigned<unsigned long>(numeric_arg, cmd.base, cmd.padding,
+				                            [&] (char c) { _out_char(c); });
 				break;
 
 			case Format_command::CHAR:

repos/base/src/lib/base/default_log.cc

@@ -0,0 +1,51 @@
+/*
+ * \brief  Access to the component's LOG session
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <base/log.h>
+#include <log_session/log_session.h>
+
+/* base-internal includes */
+#include <base/internal/globals.h>
+#include <base/internal/output.h>
+#include <base/internal/unmanaged_singleton.h>
+
+using namespace Genode;
+
+
+static Log *log_ptr;
+
+
+Log &Log::log() { return *log_ptr; }
+
+
+extern "C" int stdout_write(const char *s);
+
+
+void Genode::init_log()
+{
+	/* ignore subsequent calls */
+	if (log_ptr)
+		return;
+
+	struct Write_fn { void operator () (char const *s) { stdout_write(s); } };
+
+	typedef Buffered_output<Log_session::MAX_STRING_LEN, Write_fn>
+	        Buffered_log_output;
+
+	static Buffered_log_output *buffered_log_output =
+		unmanaged_singleton<Buffered_log_output>(Write_fn());
+
+	log_ptr = unmanaged_singleton<Log>(*buffered_log_output);
+}
+

repos/base/src/lib/base/log.cc

@@ -0,0 +1,44 @@
+/*
+ * \brief  Access to the component's LOG session
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <base/log.h>
+
+using namespace Genode;
+
+
+void Log::_acquire(Type type)
+{
+	_lock.lock();
+
+	/*
+	 * Mark warnings and errors via distinct colors.
+	 */
+	switch (type) {
+	case LOG:                                              break;
+	case WARNING: _output.out_string("\033[34mWarning: "); break;
+	case ERROR:   _output.out_string("\033[31mError: ");   break;
+	};
+}
+
+
+void Log::_release()
+{
+	/*
+	 * Reset color and add newline
+	 */
+	_output.out_string("\033[0m\n");
+
+	_lock.unlock();
+}
+

repos/base/src/lib/base/output.cc

@@ -0,0 +1,83 @@
+/*
+ * \brief  Textual output functions
+ * \author Norman Feske
+ * \date   2016-05-03
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <base/output.h>
+
+/* base-internal includes */
+#include <base/internal/output.h>
+
+using namespace Genode;
+
+
+/************
+ ** Output **
+ ************/
+
+void Output::out_string(char const *str, size_t n)
+{
+	if (!str)
+		return;
+
+	while (*str && n--) out_char(*str++);
+}
+
+
+/******************************
+ ** Print function overloads **
+ ******************************/
+
+void Genode::print(Output &output, char const *str)
+{
+	if (!str)
+		output.out_string("<null-string>");
+	else
+		while (*str) output.out_char(*str++);
+}
+
+
+void Genode::print(Output &output, void const *ptr)
+{
+	print(output, Hex(reinterpret_cast<addr_t>(ptr)));
+}
+
+
+void Genode::print(Output &output, unsigned long value)
+{
+	out_unsigned<unsigned long>(value, 10, 0, [&] (char c) { output.out_char(c); });
+}
+
+
+void Genode::print(Output &output, long value)
+{
+	out_signed<long>(value, 10, [&] (char c) { output.out_char(c); });
+}
+
+
+void Genode::print(Output &output, long long value)
+{
+	out_signed<long long>(value, 10, [&] (char c) { output.out_char(c); });
+}
+
+
+void Genode::print(Output &output, Hex const &value)
+{
+	if (value.prefix == Hex::PREFIX)
+		output.out_string("0x");
+
+	size_t const pad_len = value.pad ? value.digits : 0;
+
+	out_unsigned<unsigned long>(value.value, 16, pad_len,
+	                            [&] (char c) { output.out_char(c); });
+}
+

repos/base/src/lib/startup/init_main_thread.cc

@@ -19,8 +19,12 @@
 #include <base/printf.h>
 #include <base/thread.h>
 
+/* base-internal includes */
+#include <base/internal/globals.h>
+
 using namespace Genode;
 
+
 addr_t init_main_thread_result;
 
 extern void init_exception_handling();
@@ -89,6 +93,7 @@ extern "C" void init_main_thread()
 	 * destructor won't be registered for the atexit routine.
 	 */
 	(void*)env();
+	init_log();
 
 	/* initialize exception handling */
 	init_exception_handling();