Current pselect(3) is implemented in usermode and thus vulnerable to

well-known race condition, which elimination was the reason for the
function appearance in first place. If sigmask supplied as argument to
pselect() enables a signal, the signal might be delivered before thread
called select(2), causing lost wakeup. Reimplement pselect() in kernel,
making change of sigmask and sleep atomic.

Since signal shall be delivered to the usermode, but sigmask restored,
set TDP_OLDMASK and save old mask in td_oldsigmask. The TDP_OLDMASK
should be cleared by ast() in case signal was not gelivered during
syscall execution.

Reviewed by:	davidxu
Tested by:	pho
MFC after:	1 month

3 files changed, 6 insertions, 79 deletions

diff --git a/lib/libc/gen/pselect.c b/lib/libc/gen/pselect.c
deleted file mode 100644
index 28066a2..0000000
--- a/lib/libc/gen/pselect.c
+++ /dev/null
@@ -1,78 +0,0 @@
-/*
- * Copyright 2000 Massachusetts Institute of Technology
- *
- * Permission to use, copy, modify, and distribute this software and
- * its documentation for any purpose and without fee is hereby
- * granted, provided that both the above copyright notice and this
- * permission notice appear in all copies, that both the above
- * copyright notice and this permission notice appear in all
- * supporting documentation, and that the name of M.I.T. not be used
- * in advertising or publicity pertaining to distribution of the
- * software without specific, written prior permission.  M.I.T. makes
- * no representations about the suitability of this software for any
- * purpose.  It is provided "as is" without express or implied
- * warranty.
- *
- * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
- * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
- * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
- * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
- * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-#include "namespace.h"
-#include <sys/select.h>
-#include <sys/time.h>
-
-#include <errno.h>
-#include <signal.h>
-#include "un-namespace.h"
-
-__weak_reference(__pselect, pselect);
-
-/*
- * Emulate the POSIX 1003.1g-2000 `pselect' interface.  This is the
- * same as the traditional BSD `select' function, except that it uses
- * a timespec rather than a timeval, doesn't modify the timeout argument,
- * and allows the user to specify a signal mask to apply during the select.
- */
-int
-__pselect(int count, fd_set * __restrict rfds, fd_set * __restrict wfds, 
-	fd_set * __restrict efds, const struct timespec * __restrict timo, 
-	const sigset_t * __restrict mask)
-{
-	sigset_t omask;
-	struct timeval tvtimo, *tvp;
-	int rv, sverrno;
-
-	if (timo) {
-		TIMESPEC_TO_TIMEVAL(&tvtimo, timo);
-		tvp = &tvtimo;
-	} else
-		tvp = 0;
-
-	if (mask != 0) {
-		rv = _sigprocmask(SIG_SETMASK, mask, &omask);
-		if (rv != 0)
-			return rv;
-	}
-
-	rv = _select(count, rfds, wfds, efds, tvp);
-	if (mask != 0) {
-		sverrno = errno;
-		_sigprocmask(SIG_SETMASK, &omask, (sigset_t *)0);
-		errno = sverrno;
-	}
-
-	return rv;
-}
diff --git a/lib/libc/sys/Symbol.map b/lib/libc/sys/Symbol.map
index c834a25..ce6f32a 100644
--- a/lib/libc/sys/Symbol.map
+++ b/lib/libc/sys/Symbol.map
@@ -211,6 +211,7 @@ FBSD_1.0 {
 	posix_openpt;
 	preadv;
 	profil;
+	pselect;
 	ptrace;
 	pwritev;
 	quotactl;
@@ -781,6 +782,8 @@ FBSDprivate_1.0 {
 	__sys_preadv;
 	_profil;
 	__sys_profil;
+	_pselect;
+	__sys_pselect;
 	_ptrace;
 	__sys_ptrace;
 	_pwritev;
diff --git a/lib/libthr/thread/thr_syscalls.c b/lib/libthr/thread/thr_syscalls.c
index d05d68b..92670a9 100644
--- a/lib/libthr/thread/thr_syscalls.c
+++ b/lib/libthr/thread/thr_syscalls.c
@@ -104,6 +104,8 @@ extern int	__sys_accept(int, struct sockaddr *, socklen_t *);
 extern int	__sys_connect(int, const struct sockaddr *, socklen_t);
 extern int	__sys_fsync(int);
 extern int	__sys_msync(void *, size_t, int);
+extern int	__sys_pselect(int, fd_set *, fd_set *, fd_set *,
+			const struct timespec *, const sigset_t *);
 extern int	__sys_poll(struct pollfd *, unsigned, int);
 extern ssize_t	__sys_recv(int, void *, size_t, int);
 extern ssize_t	__sys_recvfrom(int, void *, size_t, int, struct sockaddr *, socklen_t *);
@@ -394,7 +396,7 @@ ___pselect(int count, fd_set *rfds, fd_set *wfds, fd_set *efds,
 	int ret;
 
 	_thr_cancel_enter(curthread);
-	ret = __pselect(count, rfds, wfds, efds, timo, mask);
+	ret = __sys_pselect(count, rfds, wfds, efds, timo, mask);
 	_thr_cancel_leave(curthread);
 
 	return (ret);