exec.c

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/*
 * 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,
};