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/* upstart
*
* wrap_inotify.c - library to subvert inotify calls.
*
* Copyright 2013 Canonical Ltd.
* Author: James Hunt <james.hunt@canonical.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2, as
* published by the Free Software Foundation.
*
* 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.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/**
* = Description =
*
* The test_conf upstart test requires certain test scenarios to run in
* an environment where inotify(7) is not available/functional to force the
* underlying NIH library to perform a manual filesystem tree traversal.
*
* Since inotify limits are _per user_ and not _per process_, it is not
* possible to disable inotify on a system reliabliy for the duration
* of a test run since the test is at the mercy of other processes that
* are making inotify calls too.
*
* The only reliable method therefore is to "fake" the inotify calls
* using this library.
*
* To use this library:
*
* 1) Have the test code set the environment variable "INOTIFY_DISABLE" to
* any value to disable inotify, and unset the variable to leave it
* enabled.
*
* 2) Run the test code using LD_PRELOAD to force the dynamic
* link-loader to use these inotify definitions rather than those
* provided by libc:
*
* (LD_PRELOAD=/path/to/this/libary.so test_code)
*
* To convince yourself this library is being used, set "INOTIFY_DEBUG"
* to any value for some stdout debug messages.
**/
/* to ensure we get RTLD_NEXT */
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <sys/inotify.h>
#include <dlfcn.h>
/**
* Determine if inotify should be disabled.
**/
#define disable_inotify() \
(getenv ("INOTIFY_DISABLE"))
/**
* Determine if inotify debug should be displayed to stdout.
**/
#define debug_inotify() \
(getenv ("INOTIFY_DEBUG"))
/**
* debug_msg:
*
* If debug is enabled, display a message to stdout stating if inotify
* is enabled along with details of the called function.
**/
#define debug_msg() \
do { \
if (debug_inotify ()) { \
printf ("DEBUG:%s:%d: inotify %s\n", \
__func__, __LINE__, \
disable_inotify () \
? "disabled" : "enabled"); \
fflush (NULL); \
} \
} while (0)
int __wrap_inotify_init (void)
__attribute ((warn_unused_result, no_instrument_function));
int __wrap_inotify_add_watch (int fd, const char *pathname, uint32_t mask)
__attribute ((warn_unused_result, no_instrument_function));
int __wrap_inotify_rm_watch (int fd, int wd)
__attribute ((warn_unused_result, no_instrument_function));
int (*real_inotify_init_addr) (void);
int (*real_inotify_add_watch_addr) (int fd, const char *pathname, uint32_t mask);
int (*real_inotify_rm_watch_addr) (int fd, int wd);
int
__wrap_inotify_init (void)
{
if (disable_inotify ()) {
/* simulate reaching inotify instances user limit */
errno = EMFILE;
return -1;
}
*(void **)(&real_inotify_init_addr) = dlsym (RTLD_NEXT, "inotify_init");
assert (! dlerror ());
assert (real_inotify_init_addr);
return real_inotify_init_addr ();
}
int
__wrap_inotify_add_watch (int fd, const char *pathname, uint32_t mask)
{
if (disable_inotify ()) {
/* simulate reaching inotify watches user limit */
errno = ENOSPC;
return -1;
}
*(void **)(&real_inotify_add_watch_addr) = dlsym (RTLD_NEXT, "inotify_add_watch");
assert (! dlerror ());
assert (real_inotify_add_watch_addr);
return real_inotify_add_watch_addr (fd, pathname, mask);
}
int
__wrap_inotify_rm_watch (int fd, int wd)
{
if (disable_inotify ()) {
; /* not meaningful, so just pass through */
}
*(void **)(&real_inotify_rm_watch_addr) = dlsym (RTLD_NEXT, "inotify_rm_watch");
assert (! dlerror ());
assert (real_inotify_rm_watch_addr);
return real_inotify_rm_watch_addr (fd, wd);
}
int
inotify_init (void)
{
debug_msg ();
return __wrap_inotify_init ();
}
int
inotify_add_watch (int fd, const char *pathname, uint32_t mask)
{
debug_msg ();
return __wrap_inotify_add_watch (fd, pathname, mask);
}
int
inotify_rm_watch (int fd, int wd)
{
debug_msg ();
return __wrap_inotify_rm_watch (fd, wd);
}
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