When entering the scheduler from the signal handler, tell

the kernel to (re)use the alternate signal stack.  In this
case, we don't return normally from the signal handler,
so the kernel still thinks we are using the signal stack.
The fixes a nasty bug where the signal handler can start
fiddling with the stack of a thread while the handler is
actually running on the same stack.

MFC candidate

1 files changed, 4 insertions, 1 deletions

diff --git a/lib/libpthread/thread/thr_private.h b/lib/libpthread/thread/thr_private.h
index e8fff12..9d6bc31 100644
--- a/lib/libpthread/thread/thr_private.h
+++ b/lib/libpthread/thread/thr_private.h
@@ -1127,6 +1127,9 @@ SCLASS	volatile int	_sigq_check_reqd
 #endif
 ;
 
+/* The signal stack. */
+SCLASS struct sigaltstack _thread_sigstack;
+
 /* Thread switch hook. */
 SCLASS pthread_switch_routine_t _sched_switch_hook
 #ifdef GLOBAL_PTHREAD_PRIVATE
@@ -1268,7 +1271,7 @@ int     _thread_sys_sigsuspend(const sigset_t *);
 int     _thread_sys_siginterrupt(int, int);
 int     _thread_sys_sigpause(int);
 int     _thread_sys_sigreturn(ucontext_t *);
-int     _thread_sys_sigaltstack(const struct sigaltstack *, struct sigstack *);
+int     _thread_sys_sigaltstack(const struct sigaltstack *, struct sigaltstack *);
 int     _thread_sys_sigstack(const struct sigstack *, struct sigstack *);
 int     _thread_sys_sigvec(int, struct sigvec *, struct sigvec *);
 void    _thread_sys_psignal(unsigned int, const char *);