genode/os/src/app/cli_monitor/gdb_command.h

/*
 * \brief  Gdb command
 * \author Norman Feske
 * \author Christian Prochaska
 * \date   2013-03-18
 */

/*
 * Copyright (C) 2013 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 _GDB_COMMAND_H_
#define _GDB_COMMAND_H_

/* Genode includes */
#include <base/elf.h>
#include <os/attached_rom_dataspace.h>
#include <rom_session/connection.h>
#include <util/arg_string.h>
#include <util/xml_node.h>

/* local includes */
#include <child_registry.h>
#include <gdb_prefix.h>
#include <format_util.h>
#include <process_arg_registry.h>
#include <ram.h>

class Gdb_command_child : public Child
{
	private:

		Genode::Signal_context_capability _kill_gdb_sig_cap;
		Terminal::Session &_terminal;

		bool _kill_requested;

		void _kill_gdb()
		{
			_kill_requested = true;
			Genode::Signal_transmitter(_kill_gdb_sig_cap).submit();
		}

	public:

		Gdb_command_child(Ram                              &ram,
		                  char                       const *label,
		                  char                       const *binary,
		                  Genode::Cap_session              &cap_session,
		                  Genode::size_t                    ram_quota,
		                  Genode::size_t                    ram_limit,
		                  Genode::Signal_context_capability yield_response_sig_cap,
		                  Genode::Signal_context_capability kill_gdb_sig_cap,
		                  Terminal::Session                &terminal)
		: Child(ram, label, binary, cap_session, ram_quota, ram_limit,
		        yield_response_sig_cap),
		  _kill_gdb_sig_cap(kill_gdb_sig_cap),
		  _terminal(terminal),
		  _kill_requested(false)
		  { }

		bool kill_requested() const { return _kill_requested; }

		/*
		 * Check if GDB-related (Noux) session-requests will be successful.
		 * If not, terminate the subsystem and tell the user about it.
		 */
		Genode::Service *resolve_session_request(const char *service_name,
	                                             const char *args)
	    {
			if (_kill_requested)
				return 0;

			Genode::Service *service =
				Child::resolve_session_request(service_name, args);

			if (!service) {
				tprintf(_terminal, "Error: GDB subsystem session request for service '%s' failed\n",
				        service_name);
				PDBG("session request failed: service_name = %s, args = %s", service_name, args);
				_kill_gdb();
				return 0;
			}

			/* Find out if the session request comes from Noux */

			const char *noux_label_suffix = " -> noux";

			/* Arg::string() needs two extra bytes */
			size_t label_size = strlen(name()) + strlen(noux_label_suffix) + 2;

			char noux_label_buf[label_size];
			snprintf(noux_label_buf, sizeof(noux_label_buf),
			         "%s%s", name(), noux_label_suffix);

			char label_buf[label_size];
			Genode::Arg_string::find_arg(args, "label").string(label_buf,
			                                                   sizeof(label_buf),
			                                                   "");

			if (strcmp(label_buf, noux_label_buf, label_size) == 0) {
				/* Try to create and close the session */
				try {
					Genode::Session_capability s = service->session(args, Genode::Affinity());
					service->close(s);
				} catch (...) {
					tprintf(_terminal, "Error: GDB subsystem session request for service '%s' failed\n",
					        service_name);
					PDBG("session request failed: service_name = %s, args = %s", service_name, args);
					_kill_gdb();
					return 0;
				}
			}

			return service;
	    }

};


struct Gdb_command : Command
{
	typedef Genode::Xml_node                  Xml_node;
	typedef Genode::Signal_context_capability Signal_context_capability;

	struct Child_configuration_failed {}; /* exception */

	Ram                      &_ram;
	Child_registry           &_children;
	Genode::Cap_session      &_cap;
	Xml_node                  _config;
	Process_arg_registry     &_process_args;
	List<Argument>            _arguments;
	Signal_context_capability _yield_response_sigh_cap;
	Signal_context_capability _kill_gdb_sig_cap;

	Gdb_command(Ram &ram, Genode::Cap_session &cap, Child_registry &children,
	            Xml_node config, Process_arg_registry &process_args,
	            Signal_context_capability yield_response_sigh_cap,
	            Signal_context_capability kill_gdb_sig_cap)
	:
		Command("gdb", "create new subsystem with GDB"),
		_ram(ram), _children(children), _cap(cap), _config(config),
		_process_args(process_args),
		_yield_response_sigh_cap(yield_response_sigh_cap),
		_kill_gdb_sig_cap(kill_gdb_sig_cap)
	{
		/* scan config for possible subsystem arguments */
		try {
			Xml_node node = _config.sub_node("subsystem");
			for (;; node = node.next("subsystem")) {

				char name[Parameter::NAME_MAX_LEN];
				try { node.attribute("name").value(name, sizeof(name)); }
				catch (Xml_node::Nonexistent_attribute) {
					PWRN("Missing name in '<subsystem>' configuration");
					continue;
				}

				char   const *prefix     = "config: ";
				size_t const  prefix_len = strlen(prefix);

				char help[Parameter::SHORT_HELP_MAX_LEN + prefix_len];
				strncpy(help, prefix, ~0);
				try { node.attribute("help").value(help + prefix_len,
				                                   sizeof(help) - prefix_len); }
				catch (Xml_node::Nonexistent_attribute) {
					PWRN("Missing help in '<subsystem>' configuration");
					continue;
				}

				_arguments.insert(new Argument(name, help));
			}
		} catch (Xml_node::Nonexistent_sub_node) { /* end of list */ }

		add_parameter(new Parameter("--ram",       Parameter::NUMBER, "initial RAM quota"));
		add_parameter(new Parameter("--ram-limit", Parameter::NUMBER, "limit for expanding RAM quota"));
		add_parameter(new Parameter("--gdb-ram-preserve", Parameter::NUMBER,
		              "RAM quota which GDB monitor should preserve for itself (default: 5M)"));
		add_parameter(new Parameter("--verbose",   Parameter::VOID,   "show diagnostics"));
	}

	/**
	 * Lookup subsystem in config
	 */
	Xml_node _subsystem_node(char const *name)
	{
		Xml_node node = _config.sub_node("subsystem");
		for (;; node = node.next("subsystem")) {
			if (node.attribute("name").has_value(name))
				return node;
		}
	}

	/**
	 * Generate the config node for the GDB subsystem
	 */
	Xml_node _gdb_config_node(const char *binary_name,
	                          const char *target_config_addr,
	                          const size_t target_config_size,
	                          Genode::Number_of_bytes gdb_ram_preserve,
	                          Terminal::Session &terminal)
	{
		/* local exception types */
		struct Config_buffer_overflow { };
		struct Binary_elf_check_failed { };

		try {
			Genode::Attached_rom_dataspace gdb_command_config_ds("gdb_command_config");

			enum { CONFIG_BUF_SIZE = 4*1024 };
			static char config_buf[CONFIG_BUF_SIZE];

			int config_bytes_written = 0;

			/*
			 * Copy the first part of the config file template
			 */

			Xml_node init_config_node(gdb_command_config_ds.local_addr<const char>(),
				                      gdb_command_config_ds.size());

			Xml_node noux_node = init_config_node.sub_node("start");
			for (;; noux_node = noux_node.next("start"))
				if (noux_node.attribute("name").has_value("noux"))
					break;

			Xml_node noux_config_node = noux_node.sub_node("config");

			/* Genode::strncpy() makes the last character '\0', so we need to add 1 byte */
			size_t bytes_to_copy = (Genode::addr_t)noux_config_node.content_addr() -
				                   (Genode::addr_t)init_config_node.addr() + 1;

			if ((sizeof(config_buf) - config_bytes_written) < bytes_to_copy)
				throw Config_buffer_overflow();

			strncpy(&config_buf[config_bytes_written],
				    init_config_node.addr(),
				    bytes_to_copy);

			/* subtract the byte for '\0' again */
			config_bytes_written += bytes_to_copy - 1;

			/*
		 	 * Create the GDB arguments for breaking in 'main()'
		 	 */

			enum { GDB_MAIN_BREAKPOINT_ARGS_BUF_SIZE = 768 };
			static char gdb_main_breakpoint_args_buf[GDB_MAIN_BREAKPOINT_ARGS_BUF_SIZE];

			try {
				Genode::Attached_rom_dataspace binary_rom_ds(binary_name);
				Genode::Elf_binary elf_binary((Genode::addr_t)binary_rom_ds.local_addr<void>());

				if (elf_binary.is_dynamically_linked()) {

					snprintf(gdb_main_breakpoint_args_buf,
				         	 sizeof(gdb_main_breakpoint_args_buf),
				         	 "<arg value=\"-ex\" /><arg value=\"symbol-file /gdb/ld.lib.so\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"b call_program_main\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"c\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"delete 1\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"symbol-file /gdb/%s\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"b main()\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"set solib-search-path /gdb\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"sharedlibrary\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"c\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"delete 2\" />\n",
				          	  binary_name);
				} else {

					snprintf(gdb_main_breakpoint_args_buf,
				         	 sizeof(gdb_main_breakpoint_args_buf),
				         	 "<arg value=\"-ex\" /><arg value=\"symbol-file /gdb/%s\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"b main\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"c\" />\n \
				          	  <arg value=\"-ex\" /><arg value=\"delete 1\" />\n",
				          	  binary_name);
				}
			} catch (...) {
				throw Binary_elf_check_failed();
			}

			/*
			 * Insert the '<start>' node for 'noux'
			 */

			config_bytes_written += snprintf(&config_buf[config_bytes_written],
			                                 sizeof(config_buf) - config_bytes_written, "\n \
				<start name=\"/bin/%sgdb\">\n \
					<arg value=\"/gdb/%s\"/>\n \
					<arg value=\"-ex\" /><arg value=\"set interactive-mode off\" />\n \
					<arg value=\"-ex\" /><arg value=\"directory /gdb/src\" />\n \
					<arg value=\"-ex\" /><arg value=\"target remote /dev/gdb\" />\n \
					%s \
					<arg value=\"-ex\" /><arg value=\"set interactive-mode auto\" />\n \
				</start>",
				gdb_prefix,
				binary_name,
				gdb_main_breakpoint_args_buf);

			/*
			 * Copy the second part of the config file template
			 */

			Xml_node gdb_monitor_node = noux_node.next("start");

			/* Genode::strncpy() makes the last character '\0', so we need to add 1 byte */
			bytes_to_copy = (Genode::addr_t)gdb_monitor_node.content_addr() -
			                (Genode::addr_t)noux_config_node.content_addr() + 1;

			if ((sizeof(config_buf) - config_bytes_written) < bytes_to_copy)
				throw Config_buffer_overflow();

			strncpy(&config_buf[config_bytes_written],
				    noux_config_node.content_addr(),
				    bytes_to_copy);

			/* subtract the byte for '\0' again */
			config_bytes_written += bytes_to_copy - 1;

			/*
		 	 * Create a zero-terminated string for the GDB target config node
		 	 */

			char target_config[target_config_size + 1];
			if (target_config_addr)
				Genode::strncpy(target_config, target_config_addr, sizeof(target_config));
			else
				target_config[0] = '\0';

			/*
			 * Insert the '<config>' node for 'gdb_monitor'
			 */

			config_bytes_written += Genode::snprintf(&config_buf[config_bytes_written],
			                        (sizeof(config_buf) - config_bytes_written), "\n \
				<config>\n \
					<target name=\"%s\">\n \
						%s \
					</target>\n \
					<preserve name=\"RAM\" quantum=\"%zu\"/>\n \
				</config> \
			",
			binary_name,
			target_config,
			(size_t)gdb_ram_preserve);

			/*
			 * Copy the third (and final) part of the config file template
			 */

			/* Genode::strncpy() makes the last character '\0', so we need to add 1 byte */
			bytes_to_copy = ((Genode::addr_t)init_config_node.addr() +
			                 init_config_node.size()) -
			                (Genode::addr_t)gdb_monitor_node.content_addr() + 1;

			if ((sizeof(config_buf) - config_bytes_written) < bytes_to_copy)
				throw Config_buffer_overflow();

			strncpy(&config_buf[config_bytes_written],
				    gdb_monitor_node.content_addr(),
				    bytes_to_copy);

			/* subtract the byte for '\0' again */
			config_bytes_written += bytes_to_copy - 1;

			return Xml_node(config_buf, config_bytes_written);

		} catch (Config_buffer_overflow) {
			tprintf(terminal, "Error: the buffer for the generated GDB "
			                  "subsystem configuration is too small.\n");
			throw Child_configuration_failed();
		} catch (Binary_elf_check_failed) {
			tprintf(terminal, "Error: could not determine link type of the "
			                  "GDB target binary.\n");
			throw Child_configuration_failed();
		}

	}

	void execute(Command_line &cmd, Terminal::Session &terminal)
	{
		/* check if the GDB-related ROM modules are available */
		try {
			Genode::Rom_connection gdb_command_config("gdb_command_config");
			Genode::Rom_connection terminal_crosslink("terminal_crosslink");
			Genode::Rom_connection noux("noux");
			Genode::Rom_connection gdb_monitor("gdb_monitor");
		} catch (Genode::Rom_connection::Rom_connection_failed) {
			tprintf(terminal, "Error: The 'gdb' command needs the following ROM "
			                  "modules (of which some are currently missing): "
			                  "gdb_command_config, terminal_crosslink, noux, ",
			                  "gdb_monitor\n");
			return;
		}

		Genode::Number_of_bytes ram = 0;
		Genode::Number_of_bytes ram_limit = 0;
		Genode::Number_of_bytes gdb_ram_preserve = 10*1024*1024;

		char name[128];
		name[0] = 0;
		if (cmd.argument(0, name, sizeof(name)) == false) {
			tprintf(terminal, "Error: no configuration name specified\n");
			return;
		}

		char buf[128];
		if (cmd.argument(1, buf, sizeof(buf))) {
			tprintf(terminal, "Error: unexpected argument \"%s\"\n", buf);
			return;
		}

		/* check if a configuration for the subsystem exists */
		try { _subsystem_node(name); }
		catch (Xml_node::Nonexistent_sub_node) {
			tprintf(terminal, "Error: no configuration for \"%s\"\n", name);
			return;
		}

		/* read default RAM quota from config */
		try {
			Xml_node rsc = _subsystem_node(name).sub_node("resource");
			for (;; rsc = rsc.next("resource")) {
				if (rsc.attribute("name").has_value("RAM")) {
					rsc.attribute("quantum").value(&ram);

					if (rsc.has_attribute("limit"))
						rsc.attribute("limit").value(&ram_limit);
					break;
				}
			}
		} catch (...) { }

		cmd.parameter("--ram",       ram);
		cmd.parameter("--ram-limit", ram_limit);
		cmd.parameter("--gdb-ram-preserve", gdb_ram_preserve);

		/* account for cli_monitor local metadata */
		size_t preserve_ram = 100*1024;
		if ((ram + preserve_ram) > Genode::env()->ram_session()->avail()) {
			tprintf(terminal, "Error: RAM quota exceeds available quota\n");
			return;
		}

		bool const verbose = cmd.parameter_exists("--verbose");

		/*
		 * Determine binary name
		 *
		 * Use subsystem name by default, override with '<binary>' declaration.
		 */
		char binary_name[128];
		strncpy(binary_name, name, sizeof(binary_name));
		try {
			Xml_node bin = _subsystem_node(name).sub_node("binary");
			bin.attribute("name").value(binary_name, sizeof(binary_name));
		} catch (...) { }

		/* generate unique child name */
		char label[Child_registry::CHILD_NAME_MAX_LEN];
		_children.unique_child_name(name, label, sizeof(label));

		tprintf(terminal, "starting new subsystem '%s'\n", label);

		if (verbose) {
			tprintf(terminal, "  RAM quota: ");
			tprint_bytes(terminal, ram);
			tprintf(terminal,"\n");
			if (ram_limit) {
				tprintf(terminal, "  RAM limit: ");
				tprint_bytes(terminal, ram_limit);
				tprintf(terminal,"\n");
			}
			tprintf(terminal, "     binary: %s\n", binary_name);
		}

		Child *child = 0;
		try {

			/* create child configuration */
			const char *target_config_addr = 0;
			size_t target_config_size = 0;
			try { 
				Xml_node target_config_node = _subsystem_node(name).sub_node("config");
				target_config_addr = target_config_node.addr();
				target_config_size = target_config_node.size();
			} catch (...) { }

			Xml_node config_node = _gdb_config_node(binary_name,
			                                        target_config_addr,
			                                        target_config_size,
			                                        gdb_ram_preserve,
			                                        terminal);

			/* create child */
			child = new (Genode::env()->heap())
				Gdb_command_child(_ram, label, "init", _cap, ram, ram_limit,
				                  _yield_response_sigh_cap, _kill_gdb_sig_cap,
				                  terminal);

			/* configure child */
			try {
				child->configure(config_node.addr(), config_node.size());
				if (verbose)
					tprintf(terminal, "     config: inline\n");
			} catch (...) {
				if (verbose)
					tprintf(terminal, "     config: none\n");
			}

		}
		catch (Child_configuration_failed) {
			return;
		}
		catch (Genode::Rom_connection::Rom_connection_failed) {
			tprintf(terminal, "Error: could not obtain ROM module \"%s\"\n",
				    binary_name);
			return;
		}
		catch (Child::Quota_exceeded) {
			tprintf(terminal, "Error: insufficient memory, need ");
			tprint_bytes(terminal, ram + Child::DONATED_RAM_QUOTA);
			tprintf(terminal, ", have ");
			tprint_bytes(terminal, Genode::env()->ram_session()->avail());
			tprintf(terminal, "\n");
			return;
		}
		catch (Genode::Allocator::Out_of_memory) {
			tprintf(terminal, "Error: could not allocate meta data, out of memory\n");
			return;
		}

		_process_args.list.insert(&child->argument);
		_children.insert(child);
		child->start();
	}

	List<Argument> &arguments() { return _arguments; }
};

#endif /* _GDB_COMMAND_H_ */