Fix known issues which blow up the process after dlopen("libthr.so")

(or loading a dso linked to libthr.so into process which was not
linked against threading library).

- Remove libthr interposers of the libc functions, including
  __error(). Instead, functions calls are indirected through the
  interposing table, similar to how pthread stubs in libc are already
  done.  Libc by default points either to syscall trampolines or to
  existing libc implementations.  On libthr load, libthr rewrites the
  pointers to the cancellable implementations already in libthr.  The
  interposition table is separate from pthreads stubs indirection
  table to not pull pthreads stubs into static binaries.

- Postpone the malloc(3) internal mutexes initialization until libthr
  is loaded.  This avoids recursion between calloc(3) and static
  pthread_mutex_t initialization.

- Reinstall signal handlers with wrapper on libthr load.  The
  _rtld_is_dlopened(3) is used to avoid useless calls to sigaction(2)
  when libthr is statically referenced from the main binary.

In the process, fix openat(2), swapcontext(2) and setcontext(2)
interposing.  The libc symbols were exported at different versions
than libthr interposers.  Export both libc and libthr versions from
libc now, with default set to the higher version from libthr.

Remove unused and disconnected swapcontext(3) userspace implementation
from libc/gen.

No objections from:	deischen
Tested by:	pho, antoine (exp-run) (previous versions)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

1 files changed, 95 insertions, 75 deletions

diff --git a/lib/libthr/thread/thr_sig.c b/lib/libthr/thread/thr_sig.c
index 57c9406..1ec64f0 100644
--- a/lib/libthr/thread/thr_sig.c
+++ b/lib/libthr/thread/thr_sig.c
@@ -38,6 +38,7 @@
 #include "un-namespace.h"
 #include "libc_private.h"
 
+#include "libc_private.h"
 #include "thr_private.h"
 
 /* #define DEBUG_SIGNAL */
@@ -54,24 +55,23 @@ struct usigaction {
 
 static struct usigaction _thr_sigact[_SIG_MAXSIG];
 
+static inline struct usigaction *
+__libc_sigaction_slot(int signo)
+{
+
+	return (&_thr_sigact[signo - 1]);
+}
+
 static void thr_sighandler(int, siginfo_t *, void *);
 static void handle_signal(struct sigaction *, int, siginfo_t *, ucontext_t *);
 static void check_deferred_signal(struct pthread *);
 static void check_suspend(struct pthread *);
 static void check_cancel(struct pthread *curthread, ucontext_t *ucp);
 
-int	___pause(void);
-int	_raise(int);
-int	__sigtimedwait(const sigset_t *set, siginfo_t *info,
-	const struct timespec * timeout);
 int	_sigtimedwait(const sigset_t *set, siginfo_t *info,
 	const struct timespec * timeout);
-int	__sigwaitinfo(const sigset_t *set, siginfo_t *info);
 int	_sigwaitinfo(const sigset_t *set, siginfo_t *info);
-int	___sigwait(const sigset_t *set, int *sig);
 int	_sigwait(const sigset_t *set, int *sig);
-int	__sigsuspend(const sigset_t *sigmask);
-int	_sigaction(int, const struct sigaction *, struct sigaction *);
 int	_setcontext(const ucontext_t *);
 int	_swapcontext(ucontext_t *, const ucontext_t *);
 
@@ -143,8 +143,8 @@ sigcancel_handler(int sig __unused,
 	errno = err;
 }
 
-typedef void (*ohandler)(int sig, int code,
-	struct sigcontext *scp, char *addr, __sighandler_t *catcher);
+typedef void (*ohandler)(int sig, int code, struct sigcontext *scp,
+    char *addr, __sighandler_t *catcher);
 
 /*
  * The signal handler wrapper is entered with all signal masked.
@@ -152,15 +152,19 @@ typedef void (*ohandler)(int sig, int code,
 static void
 thr_sighandler(int sig, siginfo_t *info, void *_ucp)
 {
-	struct pthread *curthread = _get_curthread();
-	ucontext_t *ucp = _ucp;
+	struct pthread *curthread;
+	ucontext_t *ucp;
 	struct sigaction act;
+	struct usigaction *usa;
 	int err;
 
 	err = errno;
-	_thr_rwl_rdlock(&_thr_sigact[sig-1].lock);
-	act = _thr_sigact[sig-1].sigact;
-	_thr_rwl_unlock(&_thr_sigact[sig-1].lock);
+	curthread = _get_curthread();
+	ucp = _ucp;
+	usa = __libc_sigaction_slot(sig);
+	_thr_rwl_rdlock(&usa->lock);
+	act = usa->sigact;
+	_thr_rwl_unlock(&usa->lock);
 	errno = err;
 	curthread->deferred_run = 0;
 
@@ -234,12 +238,12 @@ handle_signal(struct sigaction *actp, int sig, siginfo_t *info, ucontext_t *ucp)
 	 * so after setjmps() returns once more, the user code may need to
 	 * re-set cancel_enable flag by calling pthread_setcancelstate().
 	 */
-	if ((actp->sa_flags & SA_SIGINFO) != 0)
-		(*(sigfunc))(sig, info, ucp);
-	else {
-		((ohandler)(*sigfunc))(
-			sig, info->si_code, (struct sigcontext *)ucp,
-			info->si_addr, (__sighandler_t *)sigfunc);
+	if ((actp->sa_flags & SA_SIGINFO) != 0) {
+		sigfunc(sig, info, ucp);
+	} else {
+		((ohandler)sigfunc)(sig, info->si_code,
+		    (struct sigcontext *)ucp, info->si_addr,
+		    (__sighandler_t *)sigfunc);
 	}
 	err = errno;
 
@@ -395,9 +399,34 @@ check_suspend(struct pthread *curthread)
 }
 
 void
-_thr_signal_init(void)
+_thr_signal_init(int dlopened)
 {
-	struct sigaction act;
+	struct sigaction act, nact, oact;
+	struct usigaction *usa;
+	sigset_t oldset;
+	int sig, error;
+
+	if (dlopened) {
+		__sys_sigprocmask(SIG_SETMASK, &_thr_maskset, &oldset);
+		for (sig = 1; sig <= _SIG_MAXSIG; sig++) {
+			if (sig == SIGCANCEL)
+				continue;
+			error = __sys_sigaction(sig, NULL, &oact);
+			if (error == -1 || oact.sa_handler == SIG_DFL ||
+			    oact.sa_handler == SIG_IGN)
+				continue;
+			usa = __libc_sigaction_slot(sig);
+			usa->sigact = oact;
+			nact = oact;
+			remove_thr_signals(&usa->sigact.sa_mask);
+			nact.sa_flags &= ~SA_NODEFER;
+			nact.sa_flags |= SA_SIGINFO;
+			nact.sa_sigaction = thr_sighandler;
+			nact.sa_mask = _thr_maskset;
+			(void)__sys_sigaction(sig, &nact, NULL);
+		}
+		__sys_sigprocmask(SIG_SETMASK, &oldset, NULL);
+	}
 
 	/* Install SIGCANCEL handler. */
 	SIGFILLSET(act.sa_mask);
@@ -418,18 +447,20 @@ _thr_sigact_unload(struct dl_phdr_info *phdr_info)
 	struct pthread *curthread = _get_curthread();
 	struct urwlock *rwlp;
 	struct sigaction *actp;
+	struct usigaction *usa;
 	struct sigaction kact;
 	void (*handler)(int);
 	int sig;
  
 	_thr_signal_block(curthread);
 	for (sig = 1; sig <= _SIG_MAXSIG; sig++) {
-		actp = &_thr_sigact[sig-1].sigact;
+		usa = __libc_sigaction_slot(sig);
+		actp = &usa->sigact;
 retry:
 		handler = actp->sa_handler;
 		if (handler != SIG_DFL && handler != SIG_IGN &&
 		    __elf_phdr_match_addr(phdr_info, handler)) {
-			rwlp = &_thr_sigact[sig-1].lock;
+			rwlp = &usa->lock;
 			_thr_rwl_wrlock(rwlp);
 			if (handler != actp->sa_handler) {
 				_thr_rwl_unlock(rwlp);
@@ -455,7 +486,7 @@ _thr_signal_prefork(void)
 	int i;
 
 	for (i = 1; i <= _SIG_MAXSIG; ++i)
-		_thr_rwl_rdlock(&_thr_sigact[i-1].lock);
+		_thr_rwl_rdlock(&__libc_sigaction_slot(i)->lock);
 }
 
 void
@@ -464,7 +495,7 @@ _thr_signal_postfork(void)
 	int i;
 
 	for (i = 1; i <= _SIG_MAXSIG; ++i)
-		_thr_rwl_unlock(&_thr_sigact[i-1].lock);
+		_thr_rwl_unlock(&__libc_sigaction_slot(i)->lock);
 }
 
 void
@@ -472,8 +503,10 @@ _thr_signal_postfork_child(void)
 {
 	int i;
 
-	for (i = 1; i <= _SIG_MAXSIG; ++i)
-		bzero(&_thr_sigact[i-1].lock, sizeof(struct urwlock));
+	for (i = 1; i <= _SIG_MAXSIG; ++i) {
+		bzero(&__libc_sigaction_slot(i) -> lock,
+		    sizeof(struct urwlock));
+	}
 }
 
 void
@@ -481,84 +514,81 @@ _thr_signal_deinit(void)
 {
 }
 
-__weak_reference(___pause, pause);
-
 int
-___pause(void)
+__thr_pause(void)
 {
 	sigset_t oset;
 
 	if (_sigprocmask(SIG_BLOCK, NULL, &oset) == -1)
 		return (-1);
-	return (__sigsuspend(&oset));
+	return (__thr_sigsuspend(&oset));
 }
 
-__weak_reference(_raise, raise);
-
 int
-_raise(int sig)
+__thr_raise(int sig)
 {
-	return _thr_send_sig(_get_curthread(), sig);
-}
 
-__weak_reference(_sigaction, sigaction);
+	return (_thr_send_sig(_get_curthread(), sig));
+}
 
 int
-_sigaction(int sig, const struct sigaction * act, struct sigaction * oact)
+__thr_sigaction(int sig, const struct sigaction *act, struct sigaction *oact)
 {
 	struct sigaction newact, oldact, oldact2;
 	sigset_t oldset;
-	int ret = 0, err = 0;
+	struct usigaction *usa;
+	int ret, err;
 
 	if (!_SIG_VALID(sig) || sig == SIGCANCEL) {
 		errno = EINVAL;
 		return (-1);
 	}
 
-	if (act)
-		newact = *act;
+	ret = 0;
+	err = 0;
+	usa = __libc_sigaction_slot(sig);
 
 	__sys_sigprocmask(SIG_SETMASK, &_thr_maskset, &oldset);
-	_thr_rwl_wrlock(&_thr_sigact[sig-1].lock);
+	_thr_rwl_wrlock(&usa->lock);
  
 	if (act != NULL) {
-		oldact2 = _thr_sigact[sig-1].sigact;
+		oldact2 = usa->sigact;
+		newact = *act;
 
  		/*
 		 * if a new sig handler is SIG_DFL or SIG_IGN,
-		 * don't remove old handler from _thr_sigact[],
+		 * don't remove old handler from __libc_sigact[],
 		 * so deferred signals still can use the handlers,
 		 * multiple threads invoking sigaction itself is
 		 * a race condition, so it is not a problem.
 		 */
 		if (newact.sa_handler != SIG_DFL &&
 		    newact.sa_handler != SIG_IGN) {
-			_thr_sigact[sig-1].sigact = newact;
-			remove_thr_signals(
-				&_thr_sigact[sig-1].sigact.sa_mask);
+			usa->sigact = newact;
+			remove_thr_signals(&usa->sigact.sa_mask);
 			newact.sa_flags &= ~SA_NODEFER;
 			newact.sa_flags |= SA_SIGINFO;
 			newact.sa_sigaction = thr_sighandler;
 			newact.sa_mask = _thr_maskset; /* mask all signals */
 		}
-		if ((ret = __sys_sigaction(sig, &newact, &oldact))) {
+		ret = __sys_sigaction(sig, &newact, &oldact);
+		if (ret == -1) {
 			err = errno;
-			_thr_sigact[sig-1].sigact = oldact2;
+			usa->sigact = oldact2;
 		}
 	} else if (oact != NULL) {
 		ret = __sys_sigaction(sig, NULL, &oldact);
 		err = errno;
 	}
 
-	if (oldact.sa_handler != SIG_DFL &&
-	    oldact.sa_handler != SIG_IGN) {
+	if (oldact.sa_handler != SIG_DFL && oldact.sa_handler != SIG_IGN) {
 		if (act != NULL)
 			oldact = oldact2;
 		else if (oact != NULL)
-			oldact = _thr_sigact[sig-1].sigact;
+			oldact = usa->sigact;
 	}
 
-	_thr_rwl_unlock(&_thr_sigact[sig-1].lock);
+	_thr_rwl_unlock(&usa->lock);
 	__sys_sigprocmask(SIG_SETMASK, &oldset, NULL);
 
 	if (ret == 0) {
@@ -570,10 +600,8 @@ _sigaction(int sig, const struct sigaction * act, struct sigaction * oact)
 	return (ret);
 }
 
-__weak_reference(_sigprocmask, sigprocmask);
-
 int
-_sigprocmask(int how, const sigset_t *set, sigset_t *oset)
+__thr_sigprocmask(int how, const sigset_t *set, sigset_t *oset)
 {
 	const sigset_t *p = set;
 	sigset_t newset;
@@ -598,8 +626,6 @@ _pthread_sigmask(int how, const sigset_t *set, sigset_t *oset)
 	return (0);
 }
 
-__weak_reference(__sigsuspend, sigsuspend);
-
 int
 _sigsuspend(const sigset_t * set)
 {
@@ -609,7 +635,7 @@ _sigsuspend(const sigset_t * set)
 }
 
 int
-__sigsuspend(const sigset_t * set)
+__thr_sigsuspend(const sigset_t * set)
 {
 	struct pthread *curthread;
 	sigset_t newset;
@@ -633,10 +659,6 @@ __sigsuspend(const sigset_t * set)
 	return (ret);
 }
 
-__weak_reference(___sigwait, sigwait);
-__weak_reference(__sigtimedwait, sigtimedwait);
-__weak_reference(__sigwaitinfo, sigwaitinfo);
-
 int
 _sigtimedwait(const sigset_t *set, siginfo_t *info,
 	const struct timespec * timeout)
@@ -653,8 +675,8 @@ _sigtimedwait(const sigset_t *set, siginfo_t *info,
  *   it is not canceled.
  */
 int
-__sigtimedwait(const sigset_t *set, siginfo_t *info,
-	const struct timespec * timeout)
+__thr_sigtimedwait(const sigset_t *set, siginfo_t *info,
+    const struct timespec * timeout)
 {
 	struct pthread	*curthread = _get_curthread();
 	sigset_t newset;
@@ -681,7 +703,7 @@ _sigwaitinfo(const sigset_t *set, siginfo_t *info)
  *   it is not canceled.
  */ 
 int
-__sigwaitinfo(const sigset_t *set, siginfo_t *info)
+__thr_sigwaitinfo(const sigset_t *set, siginfo_t *info)
 {
 	struct pthread	*curthread = _get_curthread();
 	sigset_t newset;
@@ -707,7 +729,7 @@ _sigwait(const sigset_t *set, int *sig)
  *   it is not canceled.
  */ 
 int
-___sigwait(const sigset_t *set, int *sig)
+__thr_sigwait(const sigset_t *set, int *sig)
 {
 	struct pthread	*curthread = _get_curthread();
 	sigset_t newset;
@@ -721,9 +743,8 @@ ___sigwait(const sigset_t *set, int *sig)
 	return (ret);
 }
 
-__weak_reference(_setcontext, setcontext);
 int
-_setcontext(const ucontext_t *ucp)
+__thr_setcontext(const ucontext_t *ucp)
 {
 	ucontext_t uc;
 
@@ -735,12 +756,11 @@ _setcontext(const ucontext_t *ucp)
 		return __sys_setcontext(ucp);
 	(void) memcpy(&uc, ucp, sizeof(uc));
 	SIGDELSET(uc.uc_sigmask, SIGCANCEL);
-	return __sys_setcontext(&uc);
+	return (__sys_setcontext(&uc));
 }
 
-__weak_reference(_swapcontext, swapcontext);
 int
-_swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
+__thr_swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
 {
 	ucontext_t uc;
 
@@ -753,5 +773,5 @@ _swapcontext(ucontext_t *oucp, const ucontext_t *ucp)
 		SIGDELSET(uc.uc_sigmask, SIGCANCEL);
 		ucp = &uc;
 	}
-	return __sys_swapcontext(oucp, ucp);
+	return (__sys_swapcontext(oucp, ucp));
 }