published October 20, 2026
A memory-protected ThreadX module's queue request reaches the Module Manager's dispatch layer, which decides how much of the module's buffer the privileged queue copy may touch and hands that extent to the module port's range check. A queue's `tx_queue_message_size` is a count of `ULONG`s and the copy moves that many words, so the extent is `message_size * sizeof(ULONG)` bytes.
The front-send dispatcher passed the word count itself. `tx_queue_send` and `tx_queue_receive`, either side of it in the same header, have always multiplied.
A source buffer ending `message_size` bytes into memory the module may read was therefore accepted, and `_txe_queue_front_send` then read `message_size * sizeof(ULONG)` bytes from it in privileged mode — `3 * message_size` bytes past the end of what the module is allowed to read. The words are written into the queue's message area, so a module that can receive from that queue reads them back.