[Bug 1844] Invalid MP packet prefix for message queues

[bugzilla-daemon at rtems.org]

https://www.rtems.org/bugzilla/show_bug.cgi?id=1844

Sebastian Huber <sebastian.huber at embedded-brains.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|MP_PACKET_MINIMUM_PACKET_SI |Invalid MP packet prefix
                   |ZE too small                |for message queues

--- Comment #1 from Sebastian Huber <sebastian.huber at embedded-brains.de> 2011-07-21 02:36:07 CDT ---
It seems that the MP_PACKET_MINIMUM_PACKET_SIZE is not too small.  The
Message_queue_MP_Packet

typedef struct {
  rtems_packet_prefix                Prefix;
  Message_queue_MP_Remote_operations operation;
  rtems_name                         name;
  rtems_option                       option_set;
  Objects_Id                         proxy_id;
  uint32_t                           count;
  size_t                             size;
  uint32_t                           pad0;
  CORE_message_queue_Buffer          Buffer;
}   Message_queue_MP_Packet;

contains a CORE_message_queue_Buffer which is

typedef struct {
  /** This field is the size of this message. */
  size_t      size;
  /** This field contains the actual message. */
  uint32_t    buffer[1];
} CORE_message_queue_Buffer;

Thus the sizeof(CORE_message_queue_Buffer) is actually not that useful.  On the
other hand we have the pad0 field.  What is the use of this field? To put the
buffer begin on a 64 byte alignment?

I think that the packet setup in _Message_queue_MP_Send_request_packet() is
wrong.  Here we have

      the_packet->Prefix.length     = sizeof(Message_queue_MP_Packet);
      if ( size_p )
        the_packet->Prefix.length     += *size_p;
      the_packet->Prefix.to_convert = sizeof(Message_queue_MP_Packet);

and

      the_packet->Prefix.length     = sizeof(Message_queue_MP_Packet);
      the_packet->Prefix.to_convert = sizeof(Message_queue_MP_Packet);

This will convert one 32-bit word of the message, due to the unsuitable usage
of sizeof() in this particular case?

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