lib/posix: populate environment variables from config

Parse ``<env key="..." value=".."/>`` nodes from the config ROM and
populate a list at the 'genode_envp' and 'environ' symbols.

Test script at run/libc_getenv.

Fix #2236

repos/libports/run/libc_getenv.run

@@ -0,0 +1,53 @@
+build "core init drivers/timer test/libc_getenv"
+
+create_boot_directory
+
+install_config {
+<config>
+	<parent-provides>
+		<service name="CPU"/>
+		<service name="LOG"/>
+		<service name="PD"/>
+		<service name="RAM"/>
+		<service name="RM"/>
+		<service name="ROM"/>
+	</parent-provides>
+	<default-route>
+		<any-service> <parent/> <any-child/> </any-service>
+	</default-route>
+	<start name="timer">
+		<resource name="RAM" quantum="2M"/>
+		<provides> <service name="Timer"/> </provides>
+	</start>
+	<start name="test-libc_getenv">
+		<resource name="RAM" quantum="4M"/>
+		<config>
+			<vfs> <dir name="dev"> <log/> </dir> </vfs>
+			<libc stdout="/dev/log"/>
+			<arg value="test-libc_getenv"/>
+			<arg value="foo"/>
+			<arg value="bar"/>
+			<arg value="baz"/>
+			<env key="foo" value="bar"/>
+			<env key="bar" value="foo"/>
+		</config>
+	</start>
+</config>
+}
+
+build_boot_image {
+	core init timer test-libc_getenv
+	ld.lib.so libc.lib.so libm.lib.so
+}
+
+append qemu_args " -nographic -m 64 "
+
+run_genode_until "child .* exited with exit value 0.*\n" 10
+
+grep_output {\[init -\> test-libc_getenv\]}
+
+compare_output_to {
+[init -> test-libc_getenv] foo="bar"
+[init -> test-libc_getenv] bar="foo"
+[init -> test-libc_getenv] baz="(null)"
+}

repos/libports/src/lib/posix/construct.cc

@@ -22,6 +22,8 @@ extern char **genode_argv;
 extern int    genode_argc;
 extern char **genode_envp;
 
+/* initial environment for the FreeBSD libc implementation */
+extern char **environ;
 
 /* provided by the application */
 extern "C" int main(int argc, char ** argv, char **envp);
@@ -34,40 +36,72 @@ void Libc::Component::construct(Libc::Env &env)
 
 	env.config([&] (Xml_node const &node) {
 		int argc = 0;
-		static char **argv;
+		int envc = 0;
+		char **argv;
+		char **envp;
 
-		/* count the number of arguments */
+		/* count the number of arguments and environment variables */
-		node.for_each_sub_node("arg", [&] (Xml_node const &arg_node) {
+		node.for_each_sub_node([&] (Xml_node const &node) {
 			/* check if the 'value' attribute exists */
-			if (arg_node.has_attribute("value"))
+			if (node.has_type("arg") && node.has_attribute("value"))
 				++argc;
+			else
+			if (node.has_type("env") && node.has_attribute("key") && node.has_attribute("value"))
+				++envc;
 		});
 
-		if (argc == 0)
+		if (argc == 0 && envc == 0)
-			return;
+			return; /* from lambda */
 
-		argv = (char**)malloc((argc + 1) * sizeof(char*));
+		/* arguments and environment are a contiguous array (but don't count on it) */
+		argv = (char**)malloc((argc + envc + 1) * sizeof(char*));
+		envp = &argv[argc];
 
 		/* read the arguments */
-		int i = 0;
+		int arg_i = 0;
-		node.for_each_sub_node("arg", [&] (Xml_node const &arg_node) {
+		int env_i = 0;
-			try {
+		node.for_each_sub_node([&] (Xml_node const &node) {
-				Xml_attribute attr = arg_node.attribute("value");
+			/* insert an argument */
+			if (node.has_type("arg")) try {
+				Xml_attribute attr = node.attribute("value");
+
 				Genode::size_t const arg_len = attr.value_size()+1;
-				argv[i] = (char*)malloc(arg_len);
+				char *arg = argv[arg_i] = (char*)malloc(arg_len);
-				attr.value(argv[i], arg_len);
+
-				++i;
+				attr.value(arg, arg_len);
+				++arg_i;
+
+			} catch (Xml_node::Nonexistent_sub_node) { }
+
+			else
+
+			/* insert an environment variable */
+			if (node.has_type("env")) try {
+				Xml_attribute key_attr = node.attribute("key");
+				Xml_attribute val_attr = node.attribute("value");
+
+				Genode::size_t const pair_len =
+					key_attr.value_size() +
+					val_attr.value_size() + 1;
+				char *env = envp[env_i] = (char*)malloc(pair_len);
+
+				Genode::size_t off = 0;
+				key_attr.value(&env[off], key_attr.value_size()+1);
+				off = key_attr.value_size();
+				env[off++] = '=';
+				val_attr.value(&env[off], val_attr.value_size()+1);
+				++env_i;
+
 			} catch (Xml_node::Nonexistent_sub_node) { }
 		});
 
-		argv[i] = nullptr;
+		envp[env_i] = NULL;
 
 		/* register command-line arguments at Genode's startup code */
 		genode_argc = argc;
 		genode_argv = argv;
+		genode_envp = environ = envp;
 	});
 
-	/* TODO: environment variables, see #2236 */
-
 	exit(main(genode_argc, genode_argv, genode_envp));
 }

repos/libports/src/test/libc_getenv/main.c

@@ -0,0 +1,26 @@
+/*
+ * \brief  Libc getenv(...) test
+ * \author Emery Hemingway
+ * \date   2017-01-24
+ */
+
+/*
+ * Copyright (C) 2017 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 <stdlib.h>
+#include <stdio.h>
+
+int main(int argc, char **argv)
+{
+	int i;
+	for (i = 1; i < argc; ++i) {
+		char const *key = argv[i];
+		printf("%s=\"%s\"\n", key, getenv(key));
+	}
+
+	return 0;
+}

repos/libports/src/test/libc_getenv/target.mk

@@ -0,0 +1,3 @@
+TARGET = test-libc_getenv
+SRC_C  = main.c
+LIBS   = posix

tool/autopilot.list

@@ -8,10 +8,12 @@ tar_rom
 noux
 noux_net_netcat
 libc_ffat
+libc_getenv
 libc_pipe
 libc_vfs
-libc_vfs_ram
+libc_vfs_ext2
 libc_vfs_fs
+libc_vfs_ram
 timed_semaphore
 signal
 sub_rm
@@ -41,7 +43,6 @@ part_blk
 xml_generator
 blk_cache
 rump_ext2
-libc_vfs_ext2
 thread
 pthread
 vbox_auto_win7