libselinux: lazy init

Revive Steve Grubb's patch for libselinux lazy init and extend it to
address not only the reading of /etc/selinux/config but also probing
for /selinux/class and reading of /selinux/mls.  This should reduce the
need for dontaudit rules for programs that link with libselinux and it
should reduce unnecessary overhead.

I did not convert init_selinuxmnt over to lazy init since the functions
that use selinux_mnt are not localized, and it only requires stat'ing
of /selinux in the common case.

I couldn't see a valid reason why we needed fini_obj_class_compat(), as
the existence of /selinux/class will only change across a reboot with
different kernel versions.  fini_context_translations() already had a
comment saying that it was unnecessary as well.

Before:
$ strace ls 2> err
$ grep selinux err
open("/lib/libselinux.so.1", O_RDONLY)  = 3
open("/etc/selinux/config", O_RDONLY|O_LARGEFILE) = 3
statfs64("/selinux", 84, {f_type=0xf97cff8c, f_bsize=4096, f_blocks=0, f_bfree=0, f_bavail=0, f_files=0, f_ffree=0, f_fsid={0, 0}, f_namelen=255, f_frsize=4096}) = 0
stat64("/selinux/class", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
open("/selinux/mls", O_RDONLY|O_LARGEFILE) = 3

After:
$ strace ls 2> err
$ grep selinux err
open("/lib/libselinux.so.1", O_RDONLY)  = 3
statfs64("/selinux", 84, {f_type=0xf97cff8c, f_bsize=4096, f_blocks=0, f_bfree=0, f_bavail=0, f_files=0, f_ffree=0, f_fsid={0, 0}, f_namelen=255, f_frsize=4096}) = 0

Original-patch-by:  Steve Grubb <linux_4ever@yahoo.com>
Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>

0 files changed, 0 insertions, 0 deletions