glibc/sysdeps/pthread/sem_unlink.c
Florian Weimer e9fed2438a linux: Require /dev/shm as the shared memory file system
Previously, glibc would pick an arbitrary tmpfs file system from
/proc/mounts if /dev/shm was not available.  This could lead to
an unsuitable file system being picked for the backing storage for
shm_open, sem_open, and related functions.

This patch introduces a new function, __shm_get_name, which builds
the file name under the appropriate (now hard-coded) directory.  It is
called from the various shm_* and sem_* function.  Unlike the
SHM_GET_NAME macro it replaces, the callers handle the return values
and errno updates.  shm-directory.c is moved directly into the posix
subdirectory because it can be implemented directly using POSIX
functionality.  It resides in libc because it is needed by both
librt and nptl/htl.

In the sem_open implementation, tmpfname is initialized directly
from a string constant.  This happens to remove one alloca call.

Checked on x86_64-linux-gnu.
2021-02-08 14:10:42 -03:00

43 lines
1.3 KiB
C

/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <semaphore.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "semaphoreP.h"
#include <shm-directory.h>
int
sem_unlink (const char *name)
{
struct shmdir_name dirname;
if (__shm_get_name (&dirname, name, true) != 0)
{
__set_errno (ENOENT);
return -1;
}
/* Now try removing it. */
int ret = unlink (dirname.name);
if (ret < 0 && errno == EPERM)
__set_errno (EACCES);
return ret;
}