gpxe/src/core/exec.c

/*
 * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <unistd.h>
#include <getopt.h>
#include <errno.h>
#include <assert.h>
#include <gpxe/tables.h>
#include <gpxe/command.h>
#include <gpxe/settings.h>

/** @file
 *
 * Command execution
 *
 */

/* Avoid dragging in getopt.o unless a command really uses it */
int optind;
int nextchar;

/**
 * Execute command
 *
 * @v command		Command name
 * @v argv		Argument list
 * @ret rc		Command exit status
 *
 * Execute the named command.  Unlike a traditional POSIX execv(),
 * this function returns the exit status of the command.
 */
int execv ( const char *command, char * const argv[] ) {
	struct command *cmd;
	int argc;

	/* Count number of arguments */
	for ( argc = 0 ; argv[argc] ; argc++ ) {}

	/* Sanity checks */
	if ( ! command ) {
		DBG ( "No command\n" );
		return -EINVAL;
	}
	if ( ! argc ) {
		DBG ( "%s: empty argument list\n", command );
		return -EINVAL;
	}

	/* Reset getopt() library ready for use by the command.  This
	 * is an artefact of the POSIX getopt() API within the context
	 * of Etherboot; see the documentation for reset_getopt() for
	 * details.
	 */
	reset_getopt();

	/* Hand off to command implementation */
	for_each_table_entry ( cmd, COMMANDS ) {
		if ( strcmp ( command, cmd->name ) == 0 )
			return cmd->exec ( argc, ( char ** ) argv );
	}

	printf ( "%s: command not found\n", command );
	return -ENOEXEC;
}

/**
 * Expand variables within command line
 *
 * @v command		Command line
 * @ret expcmd		Expanded command line
 *
 * The expanded command line is allocated with malloc() and the caller
 * must eventually free() it.
 */
static char * expand_command ( const char *command ) {
	char *expcmd;
	char *start;
	char *end;
	char *head;
	char *name;
	char *tail;
	int setting_len;
	int new_len;
	char *tmp;

	/* Obtain temporary modifiable copy of command line */
	expcmd = strdup ( command );
	if ( ! expcmd )
		return NULL;

	/* Expand while expansions remain */
	while ( 1 ) {

		head = expcmd;

		/* Locate opener */
		start = strstr ( expcmd, "${" );
		if ( ! start )
			break;
		*start = '\0';
		name = ( start + 2 );

		/* Locate closer */
		end = strstr ( name, "}" );
		if ( ! end )
			break;
		*end = '\0';
		tail = ( end + 1 );

		/* Determine setting length */
		setting_len = fetchf_named_setting ( name, NULL, 0 );
		if ( setting_len < 0 )
			setting_len = 0; /* Treat error as empty setting */

		/* Read setting into temporary buffer */
		{
			char setting_buf[ setting_len + 1 ];

			setting_buf[0] = '\0';
			fetchf_named_setting ( name, setting_buf,
					       sizeof ( setting_buf ) );

			/* Construct expanded string and discard old string */
			tmp = expcmd;
			new_len = asprintf ( &expcmd, "%s%s%s",
					     head, setting_buf, tail );
			free ( tmp );
			if ( new_len < 0 )
				return NULL;
		}
	}

	return expcmd;
}

/**
 * Split command line into argv array
 *
 * @v args		Command line
 * @v argv		Argument array to populate, or NULL
 * @ret argc		Argument count
 *
 * Splits the command line into whitespace-delimited arguments.  If @c
 * argv is non-NULL, any whitespace in the command line will be
 * replaced with NULs.
 */
static int split_args ( char *args, char * argv[] ) {
	int argc = 0;

	while ( 1 ) {
		/* Skip over any whitespace / convert to NUL */
		while ( isspace ( *args ) ) {
			if ( argv )
				*args = '\0';
			args++;
		}
		/* Check for end of line */
		if ( ! *args )
			break;
		/* We have found the start of the next argument */
		if ( argv )
			argv[argc] = args;
		argc++;
		/* Skip to start of next whitespace, if any */
		while ( *args && ! isspace ( *args ) ) {
			args++;
		}
	}
	return argc;
}

/**
 * Execute command line
 *
 * @v command		Command line
 * @ret rc		Command exit status
 *
 * Execute the named command and arguments.
 */
int system ( const char *command ) {
	char *args;
	int argc;
	int rc = 0;

	/* Perform variable expansion */
	args = expand_command ( command );
	if ( ! args )
		return -ENOMEM;

	/* Count arguments */
	argc = split_args ( args, NULL );

	/* Create argv array and execute command */
	if ( argc ) {
		char * argv[argc + 1];
		
		split_args ( args, argv );
		argv[argc] = NULL;

		if ( argv[0][0] != '#' )
			rc = execv ( argv[0], argv );
	}

	free ( args );
	return rc;
}

/**
 * The "echo" command
 *
 * @v argc		Argument count
 * @v argv		Argument list
 * @ret rc		Exit code
 */
static int echo_exec ( int argc, char **argv ) {
	int i;

	for ( i = 1 ; i < argc ; i++ ) {
		printf ( "%s%s", ( ( i == 1 ) ? "" : " " ), argv[i] );
	}
	printf ( "\n" );
	return 0;
}

/** "echo" command */
struct command echo_command __command = {
	.name = "echo",
	.exec = echo_exec,
};