ipc: provide the protected payload in ipc_kmsg_copyout_header

* ipc/ipc_kmsg.c (ipc_kmsg_copyout_header): If a protected payload is
set for the destination port, provide it in msgh_protected_payload.
* ipc/mach_msg.c (mach_msg_trap): Likewise in the fast paths.
* doc/mach.texi (Message Receive): Document message semantics with
protected payloads.

3 files changed, 104 insertions, 26 deletions

diff --git a/doc/mach.texi b/doc/mach.texi
index b187888..c57e607 100644
--- a/doc/mach.texi
+++ b/doc/mach.texi
@@ -1949,6 +1949,25 @@ loses the receive right after the message was dequeued from it, then
 right still exists, but isn't held by the caller, then
 @code{msgh_local_port} specifies @code{MACH_PORT_NULL}.
 
+Servers usually associate some state with a receive right.  To that
+end, they might use a hash table to look up the state for the port a
+message was sent to.  To optimize this, a task may associate an opaque
+@var{payload} with a receive right using the
+@code{mach_port_set_protected_payload} function.  Once this is done,
+the kernel will set the @code{msgh_protected_payload} field to
+@var{payload} when delivering a message to this right and indicate
+this by setting the local part of @code{msgh_bits} to
+@code{MACH_MSG_TYPE_PROTECTED_PAYLOAD}.
+
+The support for protected payloads was added to GNU Mach.  To preserve
+binary compatibility, the @code{msgh_local_port} and
+@code{msgh_local_port} share the same location.  This makes it
+possible to add the payload information without increasing the size of
+@code{mach_msg_header_t}.  This is an implementation detail.  Which
+field is valid is determined by the local part of the
+@code{msgh_bits}.  Existing software is not affected.  When a receive
+right is transferred to another task, its payload is cleared.
+
 Received messages are stamped with a sequence number, taken from the
 port from which the message was received.  (Messages received from a
 port set are stamped with a sequence number from the appropriate member
diff --git a/ipc/ipc_kmsg.c b/ipc/ipc_kmsg.c
index 06cec72..71a0d74 100644
--- a/ipc/ipc_kmsg.c
+++ b/ipc/ipc_kmsg.c
@@ -1799,9 +1799,17 @@ ipc_kmsg_copyout_header(
 		} else
 			ip_unlock(dest);
 
-		msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
-				  MACH_MSGH_BITS(0, MACH_MSG_TYPE_PORT_SEND));
-		msg->msgh_local_port = dest_name;
+		if (! ipc_port_flag_protected_payload(dest)) {
+			msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				MACH_MSGH_BITS(0, MACH_MSG_TYPE_PORT_SEND));
+			msg->msgh_local_port = dest_name;
+		} else {
+			msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				MACH_MSGH_BITS(
+					0, MACH_MSG_TYPE_PROTECTED_PAYLOAD));
+			msg->msgh_protected_payload =
+				dest->ip_protected_payload;
+		}
 		msg->msgh_remote_port = MACH_PORT_NULL;
 		return MACH_MSG_SUCCESS;
 	    }
@@ -1897,10 +1905,18 @@ ipc_kmsg_copyout_header(
 		} else
 			ip_unlock(dest);
 
-		msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
-				  MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE,
-						 MACH_MSG_TYPE_PORT_SEND));
-		msg->msgh_local_port = dest_name;
+		if (! ipc_port_flag_protected_payload(dest)) {
+			msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE,
+					       MACH_MSG_TYPE_PORT_SEND));
+			msg->msgh_local_port = dest_name;
+		} else {
+			msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE,
+					MACH_MSG_TYPE_PROTECTED_PAYLOAD));
+			msg->msgh_protected_payload =
+				dest->ip_protected_payload;
+		}
 		msg->msgh_remote_port = reply_name;
 		return MACH_MSG_SUCCESS;
 	    }
@@ -1932,9 +1948,18 @@ ipc_kmsg_copyout_header(
 			dest_name = MACH_PORT_NULL;
 		}
 
-		msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
-			MACH_MSGH_BITS(0, MACH_MSG_TYPE_PORT_SEND_ONCE));
-		msg->msgh_local_port = dest_name;
+		if (! ipc_port_flag_protected_payload(dest)) {
+			msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				MACH_MSGH_BITS(0,
+					MACH_MSG_TYPE_PORT_SEND_ONCE));
+			msg->msgh_local_port = dest_name;
+		} else {
+			msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				MACH_MSGH_BITS(0,
+					MACH_MSG_TYPE_PROTECTED_PAYLOAD));
+			msg->msgh_protected_payload =
+				dest->ip_protected_payload;
+		}
 		msg->msgh_remote_port = MACH_PORT_NULL;
 		return MACH_MSG_SUCCESS;
 	    }
@@ -2224,9 +2249,16 @@ ipc_kmsg_copyout_header(
 	if (IP_VALID(reply))
 		ipc_port_release(reply);
 
-	msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
-			  MACH_MSGH_BITS(reply_type, dest_type));
-	msg->msgh_local_port = dest_name;
+	if (! ipc_port_flag_protected_payload(dest)) {
+		msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				  MACH_MSGH_BITS(reply_type, dest_type));
+		msg->msgh_local_port = dest_name;
+	} else {
+		msg->msgh_bits = (MACH_MSGH_BITS_OTHER(mbits) |
+				  MACH_MSGH_BITS(reply_type,
+					MACH_MSG_TYPE_PROTECTED_PAYLOAD));
+		msg->msgh_protected_payload = dest->ip_protected_payload;
+	}
 	msg->msgh_remote_port = reply_name;
     }
 
diff --git a/ipc/mach_msg.c b/ipc/mach_msg.c
index 01d974b..1e122c7 100644
--- a/ipc/mach_msg.c
+++ b/ipc/mach_msg.c
@@ -1132,11 +1132,19 @@ mach_msg_trap(
 			} else
 				ip_unlock(dest_port);
 
-			kmsg->ikm_header.msgh_bits =
-				MACH_MSGH_BITS(MACH_MSG_TYPE_PORT_SEND_ONCE,
-					       MACH_MSG_TYPE_PORT_SEND);
+			if (! ipc_port_flag_protected_payload(dest_port)) {
+				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
+					MACH_MSG_TYPE_PORT_SEND_ONCE,
+					MACH_MSG_TYPE_PORT_SEND);
+				kmsg->ikm_header.msgh_local_port = dest_name;
+			} else {
+				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
+					MACH_MSG_TYPE_PORT_SEND_ONCE,
+					MACH_MSG_TYPE_PROTECTED_PAYLOAD);
+				kmsg->ikm_header.msgh_protected_payload =
+					dest_port->ip_protected_payload;
+			}
 			kmsg->ikm_header.msgh_remote_port = reply_name;
-			kmsg->ikm_header.msgh_local_port = dest_name;
 			goto fast_put;
 
 		    abort_request_copyout:
@@ -1170,11 +1178,19 @@ mach_msg_trap(
 				dest_name = MACH_PORT_NULL;
 			}
 
-			kmsg->ikm_header.msgh_bits =
-				MACH_MSGH_BITS(0,
-					       MACH_MSG_TYPE_PORT_SEND_ONCE);
+			if (! ipc_port_flag_protected_payload(dest_port)) {
+				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
+					0,
+					MACH_MSG_TYPE_PORT_SEND_ONCE);
+				kmsg->ikm_header.msgh_local_port = dest_name;
+			} else {
+				kmsg->ikm_header.msgh_bits = MACH_MSGH_BITS(
+					0,
+					MACH_MSG_TYPE_PROTECTED_PAYLOAD);
+				kmsg->ikm_header.msgh_protected_payload =
+					dest_port->ip_protected_payload;
+			}
 			kmsg->ikm_header.msgh_remote_port = MACH_PORT_NULL;
-			kmsg->ikm_header.msgh_local_port = dest_name;
 			goto fast_put;
 		    }
 
@@ -1204,12 +1220,23 @@ mach_msg_trap(
 				dest_name = MACH_PORT_NULL;
 			}
 
-			kmsg->ikm_header.msgh_bits =
-				MACH_MSGH_BITS_COMPLEX |
-				MACH_MSGH_BITS(0,
-					       MACH_MSG_TYPE_PORT_SEND_ONCE);
+			if (! ipc_port_flag_protected_payload(dest_port)) {
+				kmsg->ikm_header.msgh_bits =
+					MACH_MSGH_BITS_COMPLEX
+					| MACH_MSGH_BITS(
+						0,
+						MACH_MSG_TYPE_PORT_SEND_ONCE);
+				kmsg->ikm_header.msgh_local_port = dest_name;
+			} else {
+				kmsg->ikm_header.msgh_bits =
+					MACH_MSGH_BITS_COMPLEX
+					| MACH_MSGH_BITS(
+					    0,
+					    MACH_MSG_TYPE_PROTECTED_PAYLOAD);
+				kmsg->ikm_header.msgh_protected_payload =
+					dest_port->ip_protected_payload;
+			}
 			kmsg->ikm_header.msgh_remote_port = MACH_PORT_NULL;
-			kmsg->ikm_header.msgh_local_port = dest_name;
 
 			mr = ipc_kmsg_copyout_body(
 				(vm_offset_t) (&kmsg->ikm_header + 1),