libports: add vfs_jitterentropy library

This file system library uses the the jitterentropy library to provide
a rudimentary '/dev/random' device.

Fixes #1239.

repos/libports/lib/mk/vfs_jitterentropy.mk

@@ -0,0 +1,9 @@
+SRC_CC = vfs.cc
+
+INC_DIR += $(REP_DIR)/src/lib/vfs/jitterentropy
+
+LIBS  += libc jitterentropy
+
+vpath %.cc $(REP_DIR)/src/lib/vfs/jitterentropy
+
+SHARED_LIB = yes

repos/libports/src/lib/vfs/jitterentropy/vfs.cc

@@ -0,0 +1,36 @@
+/*
+ * \brief  Jitterentropy based random file system
+ * \author Josef Soentgen
+ * \date   2014-08-19
+ */
+
+/*
+ * Copyright (C) 2014 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 <libc-plugin/vfs.h>
+
+/* local includes */
+#include <vfs_jitterentropy.h>
+
+
+struct Jitterentropy_factory : Libc::File_system_factory
+{
+	Jitterentropy_factory() : File_system_factory("jitterentropy") { }
+
+	Vfs::File_system *create(Genode::Xml_node node)
+	{
+		return new (Genode::env()->heap()) Jitterentropy_file_system(node);
+	}
+};
+
+
+extern "C" Libc::File_system_factory *Libc_file_system_factory(void)
+{
+	static Jitterentropy_factory factory;
+	return &factory;
+}

repos/libports/src/lib/vfs/jitterentropy/vfs_jitterentropy.h

@@ -0,0 +1,101 @@
+/*
+ * \brief  Jitterentropy based random file system
+ * \author Josef Soentgen
+ * \date   2014-08-19
+ */
+
+/*
+ * Copyright (C) 2014 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 _JITTERENTROPY_FILE_SYSTEM_H_
+#define _JITTERENTROPY_FILE_SYSTEM_H_
+
+/* Genode includes */
+#include <util/xml_node.h>
+#include <vfs/single_file_system.h>
+
+/* jitterentropy includes */
+extern "C" {
+#include <jitterentropy.h>
+}
+
+class Jitterentropy_file_system : public Vfs::Single_file_system
+{
+	private:
+
+		struct rand_data *_ec_stir;
+		bool              _initialized;
+
+		bool _init_jitterentropy()
+		{
+			int err = jent_entropy_init();
+			if (err) {
+				PERR("jitterentropy library could not be initialized!");
+				return false;
+			}
+
+			/* use the default behaviour as specified in jitterentropy(3) */
+			_ec_stir = jent_entropy_collector_alloc(0, 0);
+			if (!_ec_stir) {
+				PERR("jitterentropy could not allocate entropy collector!");
+				return false;
+			}
+
+			return true;
+		}
+
+	public:
+
+		Jitterentropy_file_system(Genode::Xml_node config)
+		:
+			Single_file_system(NODE_TYPE_CHAR_DEVICE, name(), config),
+			_ec_stir(0),
+			_initialized(_init_jitterentropy())
+		{ }
+
+		~Jitterentropy_file_system()
+		{
+			if (_initialized)
+				jent_entropy_collector_free(_ec_stir);
+		}
+
+		static char const *name() { return "jitterentropy"; }
+
+
+		/********************************
+		 ** File I/O service interface **
+		 ********************************/
+
+		Write_result write(Vfs::Vfs_handle *, char const *, Genode::size_t count,
+		                   Genode::size_t &count_out) override
+		{
+			return WRITE_ERR_IO;
+		}
+
+		Read_result read(Vfs::Vfs_handle *vfs_handle, char *dst, Genode::size_t count,
+		                 Genode::size_t &out_count) override
+		{
+			if (!_initialized)
+				return READ_ERR_IO;
+
+			enum { MAX_BUF_LEN = 256 };
+			char buf[MAX_BUF_LEN];
+
+			size_t len = count > MAX_BUF_LEN ? MAX_BUF_LEN : count;
+
+			if (jent_read_entropy(_ec_stir, buf, len) < 0)
+				return READ_ERR_IO;
+
+			Genode::memcpy(dst, buf, len);
+
+			out_count = len;
+
+			return READ_OK;
+		}
+};
+
+#endif /* _JITTERENTROPY_FILE_SYSTEM_H_ */