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, 1 deletions

diff --git a/nptl/nptlfreeres.c b/nptl/nptlfreeres.c
index 77ad5b53ff..d295bcb3c3 100644
--- a/nptl/nptlfreeres.c
+++ b/nptl/nptlfreeres.c
@@ -27,6 +27,5 @@ __libpthread_freeres (void)
 {
   call_function_static_weak (__default_pthread_attr_freeres);
   call_function_static_weak (__nptl_stacks_freeres);
-  call_function_static_weak (__shm_directory_freeres);
   call_function_static_weak (__nptl_unwind_freeres);
 }