[PATCH mig] Check that msgt_name is always smaller than 255.

[Flavio Cruz]

For the x86_64 ABI we want this to always fit into 1 byte. Even for
regular i686, msgt_name is always smaller than 25 (MACH_MSG_TYPE_LAST)
and we don't have plans to have more names.

Also throw an error if we deemed an RPC to be "TooLong" as that won't
work or work badly.

Tested by cross-compiling a basic Hurd system.
---
 type.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/type.c b/type.c
index 6158c14..253a194 100644
--- a/type.c
+++ b/type.c
@@ -323,19 +323,21 @@ itUseLong(const ipc_type_t *it)
     if ((it->itVarArray && !it->itInLine) || it->itIndefinite)
        uselong = ShouldBeLong;
 
+    /* Check that msgt_name fits into 1 byte as the x86_64 ABI requires it.
+       Note that MACH_MSG_TYPE_POLYMORPHIC is -1 hence it is ignored. */
     if (((it->itInName != MACH_MSG_TYPE_POLYMORPHIC) &&
         (it->itInName >= (1<<8))) ||
        ((it->itOutName != MACH_MSG_TYPE_POLYMORPHIC) &&
-        (it->itOutName >= (1<<8))) ||
-       (it->itSize >= (1<<8)) ||
+        (it->itOutName >= (1<<8)))) {
+        error("Cannot have msgt_name greater than 255");
+        uselong = TooLong;
+    }
+
+       if ((it->itSize >= (1<<8)) ||
        (it->itNumber >= (1<<12)))
        uselong = MustBeLong;
 
-    if (((it->itInName != MACH_MSG_TYPE_POLYMORPHIC) &&
-        (it->itInName >= (1<<16))) ||
-       ((it->itOutName != MACH_MSG_TYPE_POLYMORPHIC) &&
-        (it->itOutName >= (1<<16))) ||
-       (it->itSize >= (1<<16)))
+    if (it->itSize >= (1<<16))
        uselong = TooLong;
 
     return uselong;
@@ -416,7 +418,7 @@ itCheckDecl(identifier_t name, ipc_type_t *it)
 
     uselong = itUseLong(it);
     if (uselong == TooLong)
-       warn("%s: too big for mach_msg_type_long_t", name);
+       error("%s: too big for mach_msg_type_long_t", name);
     it->itLongForm = itCheckIsLong(it, it->itFlags,
                                   (int)uselong >= (int)ShouldBeLong, name);
 }
-- 
2.39.2