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e9fed2438a
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.
63 lines
1.8 KiB
C
63 lines
1.8 KiB
C
/* shm_open -- open a POSIX shared memory object. Generic POSIX file version.
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Copyright (C) 2001-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <unistd.h>
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#if ! _POSIX_MAPPED_FILES
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# include <rt/shm_open.c>
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#else
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# include <errno.h>
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# include <fcntl.h>
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# include <pthread.h>
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# include <shm-directory.h>
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/* Open shared memory object. */
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int
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shm_open (const char *name, int oflag, mode_t mode)
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{
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struct shmdir_name dirname;
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if (__shm_get_name (&dirname, name, false) != 0)
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{
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__set_errno (EINVAL);
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return -1;
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}
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oflag |= O_NOFOLLOW | O_CLOEXEC;
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/* Disable asynchronous cancellation. */
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int state;
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pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state);
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int fd = open (dirname.name, oflag, mode);
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if (fd == -1 && __glibc_unlikely (errno == EISDIR))
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/* It might be better to fold this error with EINVAL since
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directory names are just another example for unsuitable shared
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object names and the standard does not mention EISDIR. */
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__set_errno (EINVAL);
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pthread_setcancelstate (state, NULL);
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return fd;
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}
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#endif /* _POSIX_MAPPED_FILES */
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