From 4a5b56eff5a5122195e1976da00a586c724216f4 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 10 Nov 2022 12:33:21 -0500
Subject: [PATCH 1/2] u3: reposition guard page if needed for new roads

this works around a bug wherein the guard page
could become nonoperable if it happened to coincide
with the padding between inner roads
---
 pkg/urbit/include/noun/events.h |  7 ++++++-
 pkg/urbit/noun/events.c         | 14 ++++++++++++++
 pkg/urbit/noun/manage.c         |  2 ++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/pkg/urbit/include/noun/events.h b/pkg/urbit/include/noun/events.h
index 92d5c2a75e..7edf44a2f9 100644
--- a/pkg/urbit/include/noun/events.h
+++ b/pkg/urbit/include/noun/events.h
@@ -84,9 +84,14 @@
       void
       u3e_foul(void);
 
-    /* u3e_init(): initialize page tracking.
+    /* u3e_init(): initialize guard page tracking.
     */
       void
       u3e_init(void);
 
+    /* u3e_ward(): reposition guard page if needed.
+    */
+      void
+      u3e_ward(u3_post low_p, u3_post hig_p);
+
 #endif /* ifndef U3_EVENTS_H */
diff --git a/pkg/urbit/noun/events.c b/pkg/urbit/noun/events.c
index 6986e91a22..ec2a995d1c 100644
--- a/pkg/urbit/noun/events.c
+++ b/pkg/urbit/noun/events.c
@@ -1097,6 +1097,8 @@ u3e_foul(void)
   memset((void*)u3P.dit_w, 0xff, sizeof(u3P.dit_w));
 }
 
+/* u3e_init(): initialize guard page tracking.
+*/
 void
 u3e_init(void)
 {
@@ -1104,3 +1106,15 @@ u3e_init(void)
   _ce_center_guard_page();
 #endif
 }
+
+/* u3e_ward(): reposition guard page if needed.
+*/
+void
+u3e_ward(u3_post low_p, u3_post hig_p)
+{
+#ifdef U3_GUARD_PAGE
+  if ( (low_p > gar_pag_p) || (hig_p < gar_pag_p) ) {
+    _ce_center_guard_page();
+  }
+#endif
+}
diff --git a/pkg/urbit/noun/manage.c b/pkg/urbit/noun/manage.c
index c0659f42b9..69e5f4b651 100644
--- a/pkg/urbit/noun/manage.c
+++ b/pkg/urbit/noun/manage.c
@@ -803,6 +803,7 @@ u3m_leap(c3_w pad_w)
       u3R->cap_p -= len_w;
 
       rod_u = _pave_south(u3a_into(bot_p), c3_wiseof(u3a_road), len_w);
+      u3e_ward(rod_u->cap_p, rod_u->hat_p);
 #if 0
       fprintf(stderr, "leap: from north %p (cap 0x%x), to south %p\r\n",
               u3R,
@@ -815,6 +816,7 @@ u3m_leap(c3_w pad_w)
       u3R->cap_p += len_w;
 
       rod_u = _pave_north(u3a_into(bot_p), c3_wiseof(u3a_road), len_w);
+      u3e_ward(rod_u->hat_p, rod_u->cap_p);
 #if 0
       fprintf(stderr, "leap: from south %p (cap 0x%x), to north %p\r\n",
               u3R,

From eb7c289ded8f2dc0e9916ce5f2a15aefb677ac34 Mon Sep 17 00:00:00 2001
From: Joe Bryan <joemfb@gmail.com>
Date: Thu, 10 Nov 2022 12:35:00 -0500
Subject: [PATCH 2/2] test: initialize guard page in jam-tests

---
 pkg/urbit/tests/jam_tests.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pkg/urbit/tests/jam_tests.c b/pkg/urbit/tests/jam_tests.c
index eebc27fc1f..55a83009b1 100644
--- a/pkg/urbit/tests/jam_tests.c
+++ b/pkg/urbit/tests/jam_tests.c
@@ -8,6 +8,7 @@ _setup(void)
 {
   u3m_init();
   u3m_pave(c3y);
+  u3e_init();
 }
 
 static void