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- /*
- *
- * Copyright (c) 2003 The Regents of the University of California. All
- * rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * - Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * - Neither the name of the University nor the names of its
- * contributors may be used to endorse or promote products derived
- * from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
- * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
- /*
- * FUSD - The Framework for UserSpace Devices - Example program
- *
- * Jeremy Elson <jelson@circlemud.org>
- *
- * uid-filter. This program shows how you can use some of the
- * meta-data provided in the fusd_file_info structure to affect your
- * driver's behavior.
- *
- * In particular, this driver creates a device, /dev/my-pid, that can
- * not be read by anyone other than the driver owner (not even root!).
- * When you read from the device, it returns your PID to you.
- *
- * $Id: uid-filter.c 12351 2007-01-19 07:22:54Z xiphmont $
- */
- #include <stdio.h>
- #include <string.h>
- #include <errno.h>
- #include <unistd.h>
- #include "fusd.h"
- int do_close(struct fusd_file_info *file)
- {
- return 0; /* attempts to close the file always succeed */
- }
- /* EXAMPLE START uid-filter.c */
- int do_open(struct fusd_file_info *file)
- {
- /* If the UID of the process trying to do the read doesn't match the
- * UID of the owner of the driver, return -EPERM. If you run this
- * driver as a normal user, even root won't be able to read from the
- * device file created! */
- if (file->uid != getuid())
- return -EPERM;
- return 0;
- }
- ssize_t do_read(struct fusd_file_info *file, char *user_buffer,
- size_t user_length, loff_t *offset)
- {
- char buf[128];
- int len;
- /* The first read to the device returns a greeting. The second read
- * returns EOF. */
- if (*offset != 0)
- return 0;
- /* len gets set to the number of characters written to buf */
- len = sprintf(buf, "Your PID is %d. Have a nice day.\n", file->pid);
- /* NEVER return more data than the user asked for */
- if (user_length < len)
- len = user_length;
- memcpy(user_buffer, buf, len);
- *offset += len;
- return len;
- }
- /* EXAMPLE STOP uid-filter.c */
- int main(int argc, char *argv[])
- {
- struct fusd_file_operations fops = {
- open: do_open,
- read: do_read,
- close: do_close };
-
- if (fusd_register("/dev/my-pid", "misc", "my-pid", 0666, NULL, &fops) < 0)
- perror("Unable to register device");
- else {
- printf("/dev/my-pid should now exist - calling fusd_run...\n");
- fusd_run();
- }
- return 0;
- }
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