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.

1 files changed, 0 insertions, 2 deletions

diff --git a/htl/Makefile b/htl/Makefile
index 38d9f8c590..9adc95e07f 100644
--- a/htl/Makefile
+++ b/htl/Makefile
@@ -132,8 +132,6 @@ libpthread-routines := pt-attr pt-attr-destroy pt-attr-getdetachstate	    \
 	sem-post sem-timedwait sem-trywait sem_unlink			    \
 	sem-wait sem-waitfast						    \
 									    \
-	shm-directory							    \
-									    \
 	cancellation							    \
 	cthreads-compat							    \
 	herrno								    \