From cde88d5bbf3f9f9ead196fe7a7a544ccf2becf54 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Sat, 7 Sep 2019 18:52:09 +0200
Subject: [PATCH] signal: Use SA_RESTORER on x86-64.

* lib/linux/signal.c (signal)[x86_64]: Avoid segfault by setting
SA_RESTORER flag.
---
 lib/linux/signal.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/linux/signal.c b/lib/linux/signal.c
index fe18d048..2f17a320 100644
--- a/lib/linux/signal.c
+++ b/lib/linux/signal.c
@@ -60,7 +60,11 @@ signal (int signum, sighandler_t action)
   setup_action.sa_mask.items[bitindex / itembitcount] = 1UL << (bitindex % itembitcount);
   old.sa_handler = SIG_DFL;
   setup_action.sa_flags = SA_RESTART;
-  int r = _sys_call4 (SYS_rt_sigaction, signum, &setup_action, &old, sizeof (sigset_t));
+#if __x86_64__
+  /* Tell kernel that we use a restorer, on penalty of segfault.  */
+  setup_action.sa_flags |= SA_RESTORER;
+#endif
+  int r = _sys_call4 (SYS_rt_sigaction, signum, (long)&setup_action, (long)&old, sizeof (sigset_t));
   if (r)
     return 0;
   return old.sa_handler;