Allow the fetching of current stack info from threaded apps.

This is necessary for alpha setjmp.   The alpha setjmp/longjmp
regression tests pass with -pthread with this change

1 files changed, 36 insertions, 4 deletions

diff --git a/lib/libpthread/uthread/uthread_sigaltstack.c b/lib/libpthread/uthread/uthread_sigaltstack.c
index fff62da3be2..93cfc1f0865 100644
--- a/lib/libpthread/uthread/uthread_sigaltstack.c
+++ b/lib/libpthread/uthread/uthread_sigaltstack.c
@@ -1,4 +1,5 @@
-/*	$OpenBSD: uthread_sigaltstack.c,v 1.2 1999/11/25 07:01:44 d Exp $	*/
+/* $OpenBSD: uthread_sigaltstack.c,v 1.3 2003/01/20 19:24:24 marc Exp $ */
+/* PUBLIC DOMAIN <marc@snafu.org */
 
 #include <signal.h>
 #include <errno.h>
@@ -7,13 +8,44 @@
 #include "pthread_private.h"
 
 /*
- * placeholder for sigaltstack XXX impl to be done
+ * IEEE Std 1003.1-2001 says:
+ *
+ * "Use of this function by library threads that are not bound to
+ * kernel-scheduled entities results in undefined behavior."
+ *
+ * There exists code (e.g. alpha setjmp) that uses this function
+ * to get information about the current stack.
+ *
+ * The "undefined behaviour" in this implementation is thus:
+ * o if ss is *not* null return -1 with errno set to EINVAL
+ * o if oss is *not* null fill it in with information about the
+ *   current stack and return 0.
+ *
+ * This lets things like alpha setjmp work in threaded applications.
  */
 
 int
 sigaltstack(const struct sigaltstack *ss, struct sigaltstack *oss)
 {
-	errno = EINVAL;
-	return (-1);
+	struct pthread *curthread = _get_curthread();
+
+	int ret = 0;
+	if (ss != NULL) {
+		errno = EINVAL;
+		ret = -1;
+	} else if (oss != NULL) {
+		/*
+		 * get the requested info from the kernel if there is no
+		 * thread or if the main thread (no thread stack).
+		 */
+		if (curthread == NULL || curthread->stack == NULL)
+			_thread_sys_sigaltstack(ss, oss);
+		else {
+			oss->ss_sp = curthread->stack->base;
+			oss->ss_size = curthread->stack->size;
+			oss->ss_flags = SS_DISABLE;
+		}
+	}
+	return (ret);
 }
 #endif /* _THREAD_SAFE */