Refactor shm_{open,unlink} code to separate Linux-specific directory choice from POSIX-generic code.

1 files changed, 63 insertions, 0 deletions

diff --git a/sysdeps/posix/shm-directory.h b/sysdeps/posix/shm-directory.h
new file mode 100644
index 0000000000..1c4d965b28
--- /dev/null
+++ b/sysdeps/posix/shm-directory.h
@@ -0,0 +1,63 @@
+/* Header for directory for shm/sem files.
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _SHM_DIRECTORY_H
+
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+extern const char *__shm_directory (size_t *len);
+
+/* This defines local variables SHM_DIR and SHM_DIRLEN, giving the
+   directory prefix (with trailing slash) and length (not including '\0'
+   terminator) of the directory used for shm files.  If that cannot be
+   determined, it sets errno to ENOSYS and returns RETVAL_FOR_INVALID.
+
+   This uses the local variable NAME as an lvalue, and increments it past
+   any leading slashes.  It then defines the local variable NAMELEN, giving
+   strlen (NAME) + 1.  If NAME is invalid, it sets errno to
+   ERRNO_FOR_INVALID and returns RETVAL_FOR_INVALID.  Finally, it defines
+   the local variable SHM_NAME, giving the absolute file name of the shm
+   file corresponding to NAME.  */
+
+#define SHM_GET_NAME(errno_for_invalid, retval_for_invalid)		      \
+  size_t shm_dirlen;							      \
+  const char *shm_dir = __shm_directory (&shm_dirlen);			      \
+  /* If we don't know what directory to use, there is nothing we can do.  */  \
+  if (__glibc_unlikely (shm_dir == NULL))				      \
+    {									      \
+      __set_errno (ENOSYS);						      \
+      return retval_for_invalid;					      \
+    }									      \
+  /* Construct the filename.  */					      \
+  while (name[0] == '/')						      \
+    ++name;								      \
+  size_t namelen = strlen (name) + 1;					      \
+  /* Validate the filename.  */						      \
+  if (namelen == 1 || namelen >= NAME_MAX || strchr (name, '/') != NULL)      \
+    {									      \
+      __set_errno (errno_for_invalid);					      \
+      return retval_for_invalid;					      \
+    }									      \
+  char *shm_name = __alloca (shm_dirlen + namelen);			      \
+  __mempcpy (__mempcpy (shm_name, shm_dir, shm_dirlen), name, namelen)
+
+#endif	/* shm-directory.h */