Changeset 0dc4258 in mainline

Timestamp:

2007-09-29T12:21:39Z (17 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

bb725a9

Parents:

b878df3

Message:

Enable forwarding of IPC_M_AS_AREA_SEND, IPC_M_AS_AREA_RECV, IPC_M_DATA_SEND
calls. In order to prevent the forwarder from cloberring the call data (i.e.
source and destination address, and size) by treating these three methods as
immutable on forward. This feature is experimental, but has huge benefits in
that it can significantly reduce the amount of data sharing (the middle man need
not modify its address space mappings) or the amount of data copying (the middle
man need not receive the data from the sender and then resend them to the next
recipient). As a result, it can reduce N such calls for a communication channel
with N tasks along the way to 1 such call.

File:

• kernel/generic/src/ipc/sysipc.c (modified) (5 diffs)

kernel/generic/src/ipc/sysipc.c

@@ -70 +70 @@
  *                      Otherwise return 0.
  */
-static inline int is_system_method(unative_t method)
+static inline int method_is_system(unative_t method)
 {
         if (method <= IPC_M_LAST_SYSTEM)
@@ -87 +87 @@
  *                      Otherwise return 0.
  */
-static inline int is_forwardable(unative_t method)
+static inline int method_is_forwardable(unative_t method)
 {
         switch (method) {
         case IPC_M_PHONE_HUNGUP:
-        case IPC_M_AS_AREA_SEND:
-        case IPC_M_AS_AREA_RECV:
-        case IPC_M_DATA_SEND:
                 /* This message is meant only for the original recipient. */
                 return 0;
         default:
                 return 1;
+        }
+}
+
+/** Decide if the message with this method is immutable on forward.
+ *
+ * - some system messages may be forwarded, for some of them
+ *   it is useless
+ *
+ * @param method        Method to be decided.
+ *
+ * @return              Return 1 if the method is immutable on forward.
+ *                      Otherwise return 0.
+ */
+static inline int method_is_immutable(unative_t method)
+{
+        switch (method) {
+        case IPC_M_AS_AREA_SEND:
+        case IPC_M_AS_AREA_RECV:
+        case IPC_M_DATA_SEND:
+                return 1;
+                break;
+        default:
+                return 0;
         }
 }
@@ -504 +524 @@
  * in the forwarded message with the new method and the new arg1, respectively.
  * Otherwise the METHOD and ARG1 are rewritten with the new method and arg1,
- * respectively.
+ * respectively. Also note there is a set of immutable methods, for which the
+ * new method and argument is not set and these values are ignored.
  *
  * Warning: If implementing non-fast version, make sure that
@@ -527 +548 @@
         });             
 
-        if (!is_forwardable(IPC_GET_METHOD(call->data))) {
+        if (!method_is_forwardable(IPC_GET_METHOD(call->data))) {
                 IPC_SET_RETVAL(call->data, EFORWARD);
                 ipc_answer(&TASK->answerbox, call);
@@ -533 +554 @@
         }
 
-        /* Userspace is not allowed to change method of system methods
-         * on forward, allow changing ARG1 and ARG2 by means of method and arg1
+        /*
+         * Userspace is not allowed to change method of system methods on
+         * forward, allow changing ARG1 and ARG2 by means of method and arg1.
+         * If the method is immutable, don't change anything.
          */
-        if (is_system_method(IPC_GET_METHOD(call->data))) {
-                if (IPC_GET_METHOD(call->data) == IPC_M_CONNECT_TO_ME)
-                        phone_dealloc(IPC_GET_ARG3(call->data));
-
-                IPC_SET_ARG1(call->data, method);
-                IPC_SET_ARG2(call->data, arg1);
-        } else {
-                IPC_SET_METHOD(call->data, method);
-                IPC_SET_ARG1(call->data, arg1);
+        if (!method_is_immutable(IPC_GET_METHOD(call->data))) {
+                if (method_is_system(IPC_GET_METHOD(call->data))) {
+                        if (IPC_GET_METHOD(call->data) == IPC_M_CONNECT_TO_ME)
+                                phone_dealloc(IPC_GET_ARG3(call->data));
+
+                        IPC_SET_ARG1(call->data, method);
+                        IPC_SET_ARG2(call->data, arg1);
+                } else {
+                        IPC_SET_METHOD(call->data, method);
+                        IPC_SET_ARG1(call->data, arg1);
+                }
         }