Implement continuations to correctly handle [sig|_]longjmp() inside of a

signal handler.  Explicitly check for jumps to anywhere other than the
current stack, since such jumps are undefined according to POSIX.

While we're at it, convert thread cancellation to use continuations, since
it's cleaner than the original cancellation code.

Avoid delivering a signal to a thread twice.  This was a pre-existing bug,
but was likely unexposed until these other changes were made.

Defer signals generated by pthread_kill() so that they can be delivered on
the appropriate stack.  deischen claims that this is unnecessary, which is
likely true, but without this change, pthread_kill() can cause undefined
priority queue states and/or PANICs in [sig|_]longjmp(), so I'm leaving
this in for now.  To compile this code out and exercise the bug, define
the _NO_UNDISPATCH cpp macro.  Defining _PTHREADS_INVARIANTS as well will
cause earlier crashes.

PR:			kern/14685
Collaboration with:	deischen

1 files changed, 52 insertions, 1 deletions

diff --git a/lib/libpthread/thread/thr_private.h b/lib/libpthread/thread/thr_private.h
index 8a126f4..8bc2d3f 100644
--- a/lib/libpthread/thread/thr_private.h
+++ b/lib/libpthread/thread/thr_private.h
@@ -85,7 +85,11 @@
 #define PTHREAD_WAITQ_CLEARACTIVE()	_waitq_clearactive()
 #define PTHREAD_WAITQ_SETACTIVE()	_waitq_setactive()
 #else
-#define PTHREAD_WAITQ_REMOVE(thrd)	TAILQ_REMOVE(&_waitingq,thrd,pqe)
+#define PTHREAD_WAITQ_REMOVE(thrd) do {					\
+	TAILQ_REMOVE(&_waitingq,thrd,pqe);				\
+	(thrd)->flags &= ~PTHREAD_FLAGS_IN_WAITQ;			\
+} while (0)
+
 #define PTHREAD_WAITQ_INSERT(thrd) do {					\
 	if ((thrd)->wakeup_time.tv_sec == -1)				\
 		TAILQ_INSERT_TAIL(&_waitingq,thrd,pqe);			\
@@ -101,6 +105,7 @@
 		else							\
 			TAILQ_INSERT_BEFORE(tid,thrd,pqe);		\
 	}								\
+	(thrd)->flags | PTHREAD_FLAGS_IN_WAITQ;				\
 } while (0)
 #define PTHREAD_WAITQ_CLEARACTIVE()
 #define PTHREAD_WAITQ_SETACTIVE()
@@ -463,6 +468,12 @@ union pthread_wait_data {
 };
 
 /*
+ * Define a continuation routine that can be used to perform a
+ * transfer of control:
+ */
+typedef void	(*thread_continuation_t) (void *);
+
+/*
  * Thread structure.
  */
 struct pthread {
@@ -514,6 +525,24 @@ struct pthread {
 	 * if sig_saved is FALSE.
 	 */
 	jmp_buf	saved_jmp_buf;
+	jmp_buf	*sighandler_jmp_buf;
+
+	/*
+	 * Saved jump buffers for use when doing nested [sig|_]longjmp()s, as
+	 * when doing signal delivery.
+	 */
+	union {
+		jmp_buf		jmp;
+		sigjmp_buf	sigjmp;
+	}	nested_jmp;
+	int	longjmp_val;
+
+#define	JMPFLAGS_NONE		0x00
+#define	JMPFLAGS_LONGJMP	0x01
+#define	JMPFLAGS__LONGJMP	0x02
+#define	JMPFLAGS_SIGLONGJMP	0x04
+#define	JMPFLAGS_DEFERRED	0x08
+	int	jmpflags;
 
 	/*
 	 * TRUE if the last state saved was a signal context. FALSE if the
@@ -521,6 +550,11 @@ struct pthread {
 	 */
 	int	sig_saved;
 
+	/*
+	 * Used for tracking delivery of nested signal handlers.
+	 */
+	int	signal_nest_level;
+
  	/*
 	 * Cancelability flags - the lower 2 bits are used by cancel
 	 * definitions in pthread.h
@@ -530,14 +564,22 @@ struct pthread {
 #define PTHREAD_CANCEL_NEEDED		0x0010
 	int	cancelflags;
 
+	thread_continuation_t	continuation;
+
 	/*
 	 * Current signal mask and pending signals.
 	 */
 	sigset_t	sigmask;
 	sigset_t	sigpend;
 
+#ifndef _NO_UNDISPATCH
+	/* Non-zero if there are undispatched signals for this thread. */
+	int	undispatched_signals;
+#endif
+	
 	/* Thread state: */
 	enum pthread_state	state;
+	enum pthread_state	oldstate;
 
 	/* Time that this thread was last made active. */
 	struct  timeval		last_active;
@@ -1188,8 +1230,17 @@ pid_t   _thread_sys_wait4(pid_t, int *, int, struct rusage *);
 #ifdef _SYS_POLL_H_
 int 	_thread_sys_poll(struct pollfd *, unsigned, int);
 #endif
+
 /* #include <sys/mman.h> */
+#ifdef _SYS_MMAN_H_
 int	_thread_sys_msync(void *, size_t, int);
+#endif
+
+/* #include <setjmp.h> */
+#ifdef _SETJMP_H_
+extern void	__longjmp(jmp_buf, int);
+extern void	__siglongjmp(sigjmp_buf, int);
+#endif
 __END_DECLS
 
 #endif  /* !_PTHREAD_PRIVATE_H */