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, 20 insertions, 2 deletions

diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h
index c6651cd..e8edbe1 100644
--- a/lib/libthr/thread/thr_private.h
+++ b/lib/libthr/thread/thr_private.h
@@ -763,7 +763,7 @@ void	_thr_cancel_leave(struct pthread *, int) __hidden;
 void	_thr_testcancel(struct pthread *) __hidden;
 void	_thr_signal_block(struct pthread *) __hidden;
 void	_thr_signal_unblock(struct pthread *) __hidden;
-void	_thr_signal_init(void) __hidden;
+void	_thr_signal_init(int) __hidden;
 void	_thr_signal_deinit(void) __hidden;
 int	_thr_send_sig(struct pthread *, int sig) __hidden;
 void	_thr_list_init(void) __hidden;
@@ -839,7 +839,6 @@ int     __sys_close(int);
 int	__sys_fork(void);
 pid_t	__sys_getpid(void);
 ssize_t __sys_read(int, void *, size_t);
-ssize_t __sys_write(int, const void *, size_t);
 void	__sys_exit(int);
 #endif
 
@@ -906,12 +905,31 @@ int	_sleepq_remove(struct sleepqueue *, struct pthread *) __hidden;
 void	_sleepq_drop(struct sleepqueue *,
 		void (*cb)(struct pthread *, void *arg), void *) __hidden;
 
+int	_pthread_mutex_init_calloc_cb(pthread_mutex_t *mutex,
+	    void *(calloc_cb)(size_t, size_t));
+
 struct dl_phdr_info;
 void __pthread_cxa_finalize(struct dl_phdr_info *phdr_info);
 void _thr_tsd_unload(struct dl_phdr_info *phdr_info) __hidden;
 void _thr_sigact_unload(struct dl_phdr_info *phdr_info) __hidden;
 void _thr_stack_fix_protection(struct pthread *thrd);
 
+int *__error_threaded(void);
+void __thr_interpose_libc(void) __hidden;
+pid_t __thr_fork(void);
+int __thr_pause(void) __hidden;
+int __thr_raise(int sig);
+int __thr_setcontext(const ucontext_t *ucp);
+int __thr_sigaction(int sig, const struct sigaction *act,
+    struct sigaction *oact) __hidden;
+int __thr_sigprocmask(int how, const sigset_t *set, sigset_t *oset);
+int __thr_sigsuspend(const sigset_t * set);
+int __thr_sigtimedwait(const sigset_t *set, siginfo_t *info,
+    const struct timespec * timeout);
+int __thr_sigwait(const sigset_t *set, int *sig);
+int __thr_sigwaitinfo(const sigset_t *set, siginfo_t *info);
+int __thr_swapcontext(ucontext_t *oucp, const ucontext_t *ucp);
+
 __END_DECLS
 
 #endif  /* !_THR_PRIVATE_H */