Read 'main()' function arguments from config file

This patch reads program arguments from the config file and makes them
available to the application via the 'argc' and 'argv' arguments of the
'main()' function. The configuration syntax looks like this:

<config>
	<arg value="...">
	<arg value="...">
        ...
</config>

The 'value' attribute of the first <arg> node becomes 'argv[0]' and so on.

Fixes #184.

base-linux/src/platform/lx_hybrid.cc

@@ -48,6 +48,16 @@ __attribute__((constructor(101))) void lx_hybrid_init()
 	lx_environ = environ;
 }
 
+/*
+ * Dummy symbols to let generic tests programs (i.e., 'test-config_args') link
+ * successfully. Please note that such programs are not expected to work when
+ * built as hybrid Linux/Genode programs because when using the glibc startup
+ * code, we cannot manipulate argv prior executing main. However, by defining
+ * these symbols, we prevent the automated build bot from stumbling over such
+ * binaries.
+ */
+char **genode_argv = 0;
+int    genode_argc = 1;
 
 /************
  ** Thread **

os/lib/mk/config_args.mk

@@ -0,0 +1,3 @@
+SRC_CC = config_args.cc
+
+vpath %.cc $(REP_DIR)/src/lib/config_args

os/run/config_args.run

@@ -0,0 +1,42 @@
+build "core init drivers/timer test/config_args"
+
+create_boot_directory
+
+install_config {
+	<config>
+		<parent-provides>
+			<service name="ROM"/>
+			<service name="RAM"/>
+			<service name="CPU"/>
+			<service name="RM"/>
+			<service name="CAP"/>
+			<service name="PD"/>
+			<service name="IRQ"/>
+			<service name="IO_PORT"/>
+			<service name="SIGNAL"/>
+			<service name="LOG"/>
+		</parent-provides>
+		<default-route>
+			<any-service> <parent/> <any-child/> </any-service>
+		</default-route>
+		<start name="timer">
+			<resource name="RAM" quantum="1M"/>
+			<provides><service name="Timer"/></provides>
+		</start>
+		<start name="test-config_args">
+			<resource name="RAM" quantum="10M"/>
+			<config>
+				<arg value="test-config_args"/>
+				<arg value="-testarg"/>
+			</config>
+		</start>
+	</config>
+}
+
+build_boot_image "core init timer test-config_args"
+
+append qemu_args "-nographic -m 64"
+
+run_genode_until {--- end of config args test ---} 10
+
+puts "Test succeeded"

os/src/lib/config_args/config_args.cc

@@ -0,0 +1,68 @@
+/*
+ * \brief   Read program arguments from the config file
+ * \date    2012-04-19
+ * \author  Christian Prochaska
+ */
+
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#include <os/config.h>
+
+using namespace Genode;
+
+
+/* external symbols provided by Genode's startup code */
+extern char **genode_argv;
+extern int    genode_argc;
+
+
+__attribute__((constructor))
+void init_config_args(void)
+{
+	int argc = 0;
+	static char **argv;
+
+	/* count the number of arguments */
+	try {
+		Xml_node arg_node = config()->xml_node().sub_node("arg");
+		for (;;) {
+			/* check if the 'value' attribute exists */
+			arg_node.attribute("value");
+			argc++;
+			arg_node = arg_node.next("arg");
+		}
+	}
+	catch (Config::Invalid) { return; }
+	catch (Xml_node::Nonexistent_sub_node) { }
+	catch (Xml_node::Nonexistent_attribute)
+	{
+		PERR("<arg> node has no 'value' attribute, ignoring further <arg> nodes");
+	}
+
+	if (argc == 0)
+		return;
+
+	argv = (char**)env()->heap()->alloc(argc * sizeof(char*));
+
+	/* read the arguments */
+	Xml_node arg_node = config()->xml_node().sub_node("arg");
+	try {
+		for (int i = 0; i < argc; i++) {
+			static char buf[512];
+			arg_node.attribute("value").value(buf, sizeof(buf));
+			size_t arg_size = strlen(buf) + 1;
+			argv[i] = (char*)env()->heap()->alloc(arg_size);
+			strncpy(argv[i], buf, arg_size);
+			arg_node = arg_node.next("arg");
+		}
+	} catch (Xml_node::Nonexistent_sub_node) { }
+
+	/* register command-line arguments at Genode's startup code */
+	genode_argc = argc;
+	genode_argv = argv;
+}

os/src/test/config_args/main.cc

@@ -0,0 +1,42 @@
+/*
+ * \brief  'main()' arguments test
+ * \author Christian Prochaska
+ * \date   2012-04-19
+ *
+ */
+
+/*
+ * Copyright (C) 2012 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.
+ */
+
+#include <base/printf.h>
+#include <util/string.h>
+
+using namespace Genode;
+
+int main(int argc, char **argv)
+{
+	printf("--- config args test started ---\n");
+
+	if (argc != 2) {
+		PERR("Error: argc is not as expected");
+		return -1;
+	}
+
+	if (strcmp(argv[0], "test-config_args") != 0) {
+		PERR("Error: argv[0] is not as expected");
+		return -1;
+	}
+
+	if (strcmp(argv[1], "-testarg") != 0) {
+		PERR("Error: argv[1] is not as expected");
+		return -1;
+	}
+
+	printf("--- end of config args test ---\n");
+
+	return 0;
+}

os/src/test/config_args/target.mk

@@ -0,0 +1,3 @@
+TARGET = test-config_args
+LIBS   = env config_args
+SRC_CC = main.cc