# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1702318645 -3600
# Node ID 5283243773745a6c3556b0bd3a413b30f119322d
# Parent  b84b29de21ea4160f4ebe36e9eaa64df1e9958fd
Permit the sending of deliberately invalid capabilities.

diff -r b84b29de21ea -r 528324377374 libipc/lib/src/message.c
--- a/libipc/lib/src/message.c	Mon Dec 11 17:26:53 2023 +0100
+++ b/libipc/lib/src/message.c	Mon Dec 11 19:17:25 2023 +0100
@@ -1,7 +1,7 @@
 /*
  * Interprocess communication message abstraction.
  *
- * Copyright (C) 2018, 2019, 2021, 2022 Paul Boddie <paul@boddie.org.uk>
+ * Copyright (C) 2018, 2019, 2021, 2022, 2023 Paul Boddie <paul@boddie.org.uk>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -444,8 +444,16 @@
 
 void ipc_message_export_capability(ipc_message_t *msg, int item, l4_cap_idx_t ref)
 {
-  msg->mregs.mr[msg->words + item * 2] = 0 | L4_ITEM_MAP;
-  msg->mregs.mr[msg->words + item * 2 + 1] = l4_obj_fpage(ref, 0, L4_FPAGE_RWX).raw;
+  if (l4_is_valid_cap(ref))
+  {
+    msg->mregs.mr[msg->words + item * 2] = 0 | L4_ITEM_MAP;
+    msg->mregs.mr[msg->words + item * 2 + 1] = l4_obj_fpage(ref, 0, L4_FPAGE_RWX).raw;
+  }
+  else
+  {
+    msg->mregs.mr[msg->words + item * 2] = 0;
+    msg->mregs.mr[msg->words + item * 2 + 1] = 0;
+  }
 }
 
 /* Export a flexpage at the given position in the message. Here, the snd_base
diff -r b84b29de21ea -r 528324377374 libipc/lib/src/util_ipc.c
--- a/libipc/lib/src/util_ipc.c	Mon Dec 11 17:26:53 2023 +0100
+++ b/libipc/lib/src/util_ipc.c	Mon Dec 11 19:17:25 2023 +0100
@@ -1,7 +1,7 @@
 /*
  * Interprocess communication abstractions.
  *
- * Copyright (C) 2018, 2019, 2021, 2022 Paul Boddie <paul@boddie.org.uk>
+ * Copyright (C) 2018, 2019, 2021, 2022, 2023 Paul Boddie <paul@boddie.org.uk>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -154,10 +154,10 @@
     *local = 1;
   }
 
-  /* Unsupported item. */
+  /* Unsupported item which may legitimately be an invalid capability. */
 
   else
-    return -L4_EIO;
+    *ref = L4_INVALID_CAP;
 
   return L4_EOK;
 }