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141 lines
3.4 KiB
C++
141 lines
3.4 KiB
C++
/*
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* \brief Populate arguments and environment from config
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* \author Christian Prochaska
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* \date 2020-08-14
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*/
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/*
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* Copyright (C) 2020 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__LIBC__ARGS_H_
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#define _INCLUDE__LIBC__ARGS_H_
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/* Genode includes */
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#include <libc/component.h>
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#include <util/xml_node.h>
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/* libc includes */
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#include <stdlib.h> /* 'malloc' */
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static void populate_args_and_env(Libc::Env &env, int &argc, char **&argv, char **&envp)
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{
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using Genode::Xml_node;
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using Genode::Xml_attribute;
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env.config([&] (Xml_node const &node) {
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int envc = 0;
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/* count the number of arguments and environment variables */
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node.for_each_sub_node([&] (Xml_node const &node) {
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/* check if the 'value' attribute exists */
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if (node.has_type("arg") && node.has_attribute("value"))
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++argc;
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else
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if (node.has_type("env") && node.has_attribute("key") && node.has_attribute("value"))
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++envc;
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});
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if (argc == 0 && envc == 0) {
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/*
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* If argc is zero then argv is still a NULL-terminated array.
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*/
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static char const *args[] = { nullptr, nullptr };
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argc = 0;
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argv = (char**)&args;
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envp = &argv[1];
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return; /* from lambda */
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}
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/* arguments and environment are arranged System V style (but don't count on it) */
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argv = (char**)malloc((argc + envc + 2) * sizeof(char*));
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envp = &argv[argc+1];
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/* read the arguments */
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int arg_i = 0;
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int env_i = 0;
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node.for_each_sub_node([&] (Xml_node const &node) {
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/* insert an argument */
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if (node.has_type("arg")) {
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Xml_attribute attr = node.attribute("value");
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attr.with_raw_value([&] (char const *start, size_t length) {
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size_t const size = length + 1; /* for null termination */
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argv[arg_i] = (char *)malloc(size);
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Genode::copy_cstring(argv[arg_i], start, size);
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});
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++arg_i;
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}
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else
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/* insert an environment variable */
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if (node.has_type("env")) try {
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auto check_attr = [] (Xml_node node, auto key) {
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if (!node.has_attribute(key))
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Genode::warning("<env> node lacks '", key, "' attribute"); };
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check_attr(node, "key");
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check_attr(node, "value");
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Xml_attribute const key = node.attribute("key");
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Xml_attribute const value = node.attribute("value");
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using namespace Genode;
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/*
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* An environment variable has the form <key>=<value>, followed
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* by a terminating zero.
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*/
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size_t const var_size = key .value_size() + 1
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+ value.value_size() + 1;
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envp[env_i] = (char*)malloc(var_size);
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size_t pos = 0;
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/* append characters to env variable with zero termination */
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auto append = [&] (char const *s, size_t len) {
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if (pos + len >= var_size) {
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/* this should never happen */
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warning("truncated environment variable: ", node);
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return;
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}
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copy_cstring(envp[env_i] + pos, s, len + 1);
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pos += len;
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};
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key.with_raw_value([&] (char const *start, size_t length) {
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append(start, length); });
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append("=", 1);
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value.with_raw_value([&] (char const *start, size_t length) {
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append(start, length); });
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++env_i;
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}
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catch (Xml_node::Nonexistent_sub_node) { }
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catch (Xml_node::Nonexistent_attribute) { }
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});
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/* argv and envp are both NULL terminated */
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argv[arg_i] = NULL;
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envp[env_i] = NULL;
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});
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}
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#endif /* _INCLUDE__LIBC__ARGS_H_ */
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