/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright 2019 OmniOS Community Edition (OmniOSce) Association.
 */

#pragma weak _isaexec = isaexec

#include "lint.h"
#include <sys/types.h>
#include <sys/systeminfo.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <limits.h>
#include <stdarg.h>
#include <stdlib.h>

/*
 * This is a utility routine to allow wrapper programs to simply
 * implement the isalist exec algorithms.  See PSARC/1997/220.
 */
int
isaexec(const char *execname, char *const *argv, char *const *envp)
{
        const char *fname;
        char *isalist;
        char *pathname;
        char *str;
        char *lasts;
        size_t isalen = 255;            /* wild guess */
        size_t len;
        int saved_errno;

        /*
         * Extract the isalist(7) for userland from the kernel.
         */
        isalist = malloc(isalen);
        do {
                long ret = sysinfo(SI_ISALIST, isalist, isalen);
                if (ret == -1l) {
                        free(isalist);
                        errno = ENOENT;
                        return (-1);
                }
                if (ret > isalen) {
                        isalen = ret;
                        isalist = reallocf(isalist, isalen);
                } else {
                        break;
                }
        } while (isalist != NULL);

        if (isalist == NULL) {
                /*
                 * Then either a malloc or a realloc failed.
                 */
                errno = EAGAIN;
                return (-1);
        }

        /*
         * Allocate a full pathname buffer.  The sum of the lengths of the
         * 'path' and isalist strings is guaranteed to be big enough.
         */
        len = strlen(execname) + isalen;
        if ((pathname = malloc(len)) == NULL) {
                free(isalist);
                errno = EAGAIN;
                return (-1);
        }

        /*
         * Break the exec name into directory and file name components.
         */
        (void) strcpy(pathname, execname);
        if ((str = strrchr(pathname, '/')) != NULL) {
                *++str = '\0';
                fname = execname + (str - pathname);
        } else {
                fname = execname;
                *pathname = '\0';
        }
        len = strlen(pathname);

        /*
         * For each name in the isa list, look for an executable file
         * with the given file name in the corresponding subdirectory.
         * If it's there, exec it.  If it's not there, or the exec
         * fails, then run the next version ..
         */
        str = strtok_r(isalist, " ", &lasts);
        saved_errno = ENOENT;
        do {
                (void) strcpy(pathname + len, str);
                (void) strcat(pathname + len, "/");
                (void) strcat(pathname + len, fname);
                if (access(pathname, X_OK) == 0) {
                        /*
                         * File exists and is marked executable.  Attempt
                         * to execute the file from the subdirectory,
                         * using the user-supplied argv and envp.
                         */
                        (void) execve(pathname, argv, envp);

                        /*
                         * If we failed to exec because of a temporary
                         * resource shortage, it's better to let our
                         * caller handle it (free memory, sleep for a while,
                         * or whatever before retrying) rather than drive
                         * on to run the "less capable" version.
                         */
                        if (errno == EAGAIN) {
                                saved_errno = errno;
                                break;
                        }
                }
        } while ((str = strtok_r(NULL, " ", &lasts)) != NULL);

        free(pathname);
        free(isalist);

        errno = saved_errno;
        return (-1);
}