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/* Copyright (c) 2008, Tim Post <tinkertim@gmail.com>
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions are met:
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 *
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 * Redistributions of source code must retain the above copyright notice, this
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 * list of conditions and the following disclaimer.
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 *
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 * Redistributions in binary form must reproduce the above copyright notice,
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 * this list of conditions and the following disclaimer in the documentation
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 * and/or other materials provided with the distribution.
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 *
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 * Neither the name of the original program's authors nor the names of its
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 * contributors may be used to endorse or promote products derived from this
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 * software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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 * POSSIBILITY OF SUCH DAMAGE.
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 */
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/* The VERY basics of execute in place support. These are buggy, leaky
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 * and not nearly done. Only here for beta testing!! You were warned!!
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 * TODO:
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 * Hash command lookups to save time
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 * Create a running pointer to **path and advance/rewind it as we go */
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <fcntl.h>
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#ifndef HELENOS
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#include <linux/limits.h>
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#include <sys/errno.h>
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#include <sys/wait.h>
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#endif
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#include "config.h"
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#include "util.h"
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#include "exec.h"
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#include "errors.h"
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/* Easiest way to handle a shared + allocated string, a structure with
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 * one member is sort of silly :) */
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char *found;
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/* work-around for access() */
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unsigned int try_access(const char *f)
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{
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    int fd;
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    fd = open(f, O_RDONLY);
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    if (fd > 0) {
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        close(fd);
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        return 1;
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    } else
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        return 0;
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}
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/* Returns the full path of "cmd" if cmd is found, else just hand back
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 * cmd as it was presented */
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char *find_command(char *cmd)
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{
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    char *path_orig, *path_tok;
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    char *path[PATH_MAX];
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    int rc, n = 0, i = 0;
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    size_t x = strlen(cmd) + 2;
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    found = (char *)malloc(PATH_MAX);
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    /* The user has specified the full path, just give it back. Don't test it,
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     * they seem to know what they're doing. */
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    if (cmd[0] == '/' || cmd [0] == '.')
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        return (char *)cmd;
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#ifdef HELENOS
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    path_orig = PATH;
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#else
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    path_orig = getenv("PATH");
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    if (NULL == path_orig)
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        path_orig = PATH;
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#endif
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    path_tok = cli_strdup(path_orig);
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    /* Extract the PATH env to a path[] array */
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    path[n] = cli_strtok(path_tok, PATH_DELIM);
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    while (NULL != path[n]) {
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        if ((strlen(path[n]) + x ) > PATH_MAX) {
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            cli_error(CL_ENOTSUP,
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                "Segment %d of path is too large, search ends at segment %d",
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                n, n-1);
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            break;
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        }
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        path[++n] = cli_strtok(NULL, PATH_DELIM);
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    }
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    /* We now have n places to look for the command */
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    for (i=0; path[i]; i++) {
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        memset(found, 0, sizeof(found));
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        snprintf(found, PATH_MAX, "%s/%s", path[i], cmd);
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#ifdef HELENOS
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        rc = try_access(found);
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#else
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        rc = access(found, F_OK);
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#endif
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        if (rc >= 0) {
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            /* We found it */
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            free(path_tok);
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            return (char *) found;
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        }
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    }
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    /* We didn't find it, just give it back as-is. Could be an alias
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     * set in the parent shell */
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    free(path_tok);
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    return (char *) cmd;
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}
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#ifdef HELENOS
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task_id_t try_exec(char *cmd, char **argv)
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{
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    task_id_t tid;
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    char *tmp;
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    tmp = cli_strdup(find_command(cmd));
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    free(found);
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    tid = task_spawn((const char *)tmp, (const char **)argv);
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    free(tmp);
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    if (tid == 0)
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        /* HelenOS does not set errno, so all we can do is report
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         * a task ID of 0 as a generic failure. */
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        cli_error(CL_EEXEC, "Can not spawn %s", cmd);
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    return tid;
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}
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#else
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int try_exec(char *cmd, char **argv)
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{
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    char *tmp;
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    pid_t pid;
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    int status;
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    /* Copy the result of allocated 'found' */
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    tmp = cli_strdup(find_command(cmd));
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    /* free the pointer, no longer needed */
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    free(found);
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    if (-1 == (access(tmp, F_OK))) {
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        cli_error(CL_EFAIL,
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            "%s : No such external, modular or builtin command", tmp);
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        free(tmp);
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        return CL_EFAIL;
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    }
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    /* Create a child to run the program */
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    pid = fork();
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    if (pid == 0) {
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        execv(tmp, argv);
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        exit(errno);
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    } else if (pid > 0) {
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        /* Block until we get a PID (and result) */
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        wait(&status);
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        status = status / 256;
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    } else {
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        /* Could not fork, ulimit or out of memory */
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        cli_error(CL_ENOMEM, "Could not fork");
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        free(tmp);
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        return CL_ENOMEM;
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    }
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    free(tmp);
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    /* No need to go any further if status == 0 */
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    /*
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    if (status == 0)
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        return status;
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    */
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    /* Decode any errors from execv() (these explain themselves) */
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    switch (status) {
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    case ENOTDIR:
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        cli_error(CL_EFAIL, "%s : No such file or directory", tmp);
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        status = CL_EFAIL;
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        break;
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    case EISDIR:
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        cli_error(CL_EFAIL, "%s : Command is a directory", tmp);
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        status = CL_EFAIL;
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        break;
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    case EACCES:
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        cli_error(CL_EPERM, "%s :", tmp);
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        status = CL_EFAIL;
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        break;
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    case ENOMEM:
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        cli_error(CL_ENOMEM, "%s :", tmp);
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        status = CL_EFAIL;
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        break;
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    case ENAMETOOLONG:
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        cli_error(CL_EFAIL, "Argument list too long");
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        status = CL_EFAIL;
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        break;
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    case EFAULT:
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        cli_error(CL_EFAIL, "Invalid argument pointer\n(please report "
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            "this to %s)", PACKAGE_BUGREPORT);
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        status = CL_EFAIL;
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        break;
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    }
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    return status;
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}
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#endif /* HELENOS */