rfc909.txt

RFC 相关的技术文档

                                    |       2       | CREATE_DONE
                                    |       3       | DELETE
                                    |       4       | DELETE_DONE
                                    |       5       | LIST_ADDRESSES
                                    |       6       | ADDRESS_LIST
                                    |       7       | GET_PHYS_ADDRESS
                                    |       8       | GOT_PHYS_ADDRESS
                                    |       9       | GET_OBJECT
                                    |       10      | GOT_OBJECT
                                    |       11      | LIST_BREAKPOINTS
                                    |       12      | BREAKPOINT_LIST



     Page 18



     LDP Specification                            Commands and Formats



                                    |       13      | LIST_NAMES
                                    |       14      | NAME_LIST
                                    |       15      | LIST_PROCESSES
                                    |       16      | PROCESS_LIST
                                    |       17 - 63 | <reserved>
                                    |               |
                      BREAKPOINT    |       1       | INCREMENT
                                    |       2       | INC_COUNT
                                    |       3       | OR
                                    |       4       | SET_PTR
                                    |       5       | SET_STATE
                                    |       6 - 63  | <reserved>
                                    |               |
                      CONDITION     |       1       | CHANGED
                                    |       2       | COMPARE
                                    |       3       | COUNT_EQ
                                    |       4       | COUNT_GT
                                    |       5       | COUNT_LT
                                    |       6       | TEST
                                    |       7 - 63  | <reserved>


                               Command Types
                                 Figure 8





     4.3  Addressing

          Addresses are used  in  LDP  commands  to  refer  to  memory
     locations,  processes,  buffers,  breakpoints and other entities.
     Many of these entities are machine-dependent; some machines  have
     named  objects,  some  machines have multiple address spaces, the
     size of address spaces varies, etc.  The  format  for  specifying
     addresses  needs  to  be  general  enough  to handle all of these
     cases.   This  speaks  for  a  large,  hierarchically  structured
     address  format.   However, the disadvantage of a large format is
     that it imposes extra overhead on communication with targets that
     have simpler address schemes.

          LDP resolves this conflict by employing two address formats:
     a  short  three-word format for addressing simpler targets, and a
     long five-word format for others.  Each target LDP is required to
     implement  at least one of these formats.  At the start of an LDP
     session, the target specifies the address format(s)  it  uses  in



                                                               Page 19



     RFC-909                                                 July 1984



     the  Flag field of the HELLO_REPLY message.  In each address, the
     first bit of the mode octet is a format flag:  0  indicates  LONG
     address format, and 1 indicates SHORT format.




     4.3.1  Long Address Format

          The long address format is five words long and consists of a
     three-word  address  descriptor and a two-word offset (see Figure
     9). The descriptor specifies an address space to which the offset
     is applied.  The descriptor is subdivided into several fields, as
     described below.  The structuring of the descriptor  is  designed
     to  support  complex  addressing  modes.  For example, on targets
     with  multiple  processes,  descriptors  may  reference   virtual
     addresses,  registers,  and  other  entities  within a particular
     process.

          The addressing modes defined below are intended as a base to
     which  target-specific  modes  may be added.  Modes up to 63. are
     reserved by the protocol.  The range 64. to 127. may be used  for
     target-specific address modes.


               Long Format - Format bit is LONG=0

                0             0 0   1         1
                0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
               +-------------------------------+  +-+
               |0|       Mode  |  Mode Arg     |   |
               +-------------------------------+   |
               |                    (31-16)    |   | Descriptor
               +----          ID            ---+   |
               |                    (15-0)     |   |
               +-------------------------------+  +-+
               |                    (31-16)    |   |
               +----        Offset          ---+   | Offset
               |                    (15-0)     |   |
               +-------------------------------+  +-+


                            Long Address Format
                                 Figure 9


     LONG ADDRESS FIELDS:



     Page 20



     LDP Specification                            Commands and Formats



     Mode

          The address mode identifies the type of address space  being
          referenced.   The mode is qualified by the mode argument and
          the ID field.  Implementation of modes other  than  physical
          and  host is machine-dependent.  Currently defined modes and
          the address space they reference are shown in Figure 10.


          Mode | Symbol               | Address space
          -----+----------------------+---------------------------

            0    HOST                   Host
            1    PHYS_MACRO             Macromemory
            2    PHYS_MICRO             Micromemory
            3    PHYS_I/O               I/O space
            4    PHYS_MACRO_PTR         Macro contains a pointer
            5    PHYS_REG               Register
            6    PHYS_REG_OFFSET        Register plus offset
            7    PHYS_REG_INDIRECT      Register contains address
                                        of a pointer

            8    PROCESS_CODE           Process code space
            9    PROCESS_DATA           Process data space
           10    PROCESS_DATA_PTR       Process data contains a ptr
           11    PROCESS_REG            Process virtual register
           12    PROCESS_REG_OFFSET     Process register plus offset
           13    PROCESS_REG_INDIRECT   Process register contains
                                        address of a pointer

           14    OBJECT_OFFSET          Memory object (queue, pool)
           15    OBJECT_HEADER          System header for an object
           16    BREAKPOINT             Breakpoint
           17    WATCHPOINT             Watchpoint
           18    BPT_PTR_OFFSET         Breakpoint ptr plus offset
           19    BPT_PTR_INDIRECT       Breakpoint ptr plus offset
                                        gives address of a pointer
           20 -  <reserved>
           63


                            Long Address Modes
                                 Figure 10



     Mode Argument



                                                               Page 21



     RFC-909                                                 July 1984



          Provides a numeric argument to the  mode  field.   Specifies
          the  register  in  physical  and  process REG and REG_OFFSET
          modes.

     ID Field

          Identifies a particular process, buffer or object.

     Offset

          The offset into the linear  address  space  defined  by  the
          mode.  The size of the machine word determines the number of
          significant bits in the offset.   Likewise,  the  addressing
          units of the target are the units of the offset.

     The interpretation of the mode argument, ID field and offset  for
     each address mode is given below:

     HOST

          The ID and offset fields are numbers assigned arbitrarily by
          the  host  side  of the debugger.  These numbers are used in
          MOVE and MOVE_DATA messages.  MOVE_DATA responses containing
          this  mode  as the destination are sent by the target to the
          host.  This may occur in debugging when data is sent to  the
          host from the target breakpoint.

     PHYS_MACRO

          The  offset  contains  the  32-bit  physical  address  of  a
          location in macromemory.  The mode argument and ID field are
          not used.   For  example,  mode=PHYS_MACRO  and  offset=1000
          specifies location 1000 in physical memory.

     PHYS_MICRO

          Like PHYS_MACRO, but the location is in micromemory.

     PHYS_I/O

          Like PHYS_MACRO, but the location is in I/O space.

     PHYS_MACRO_PTR

          The offset contains the address of a pointer in macromemory.
          The  location  pointed to (the effective address) is also in
          macromemory.  The mode argument and ID field are unused.



     Page 22



     LDP Specification                            Commands and Formats



     PHYS_REG

          The mode argument  gives  the  physical  register.   If  the
          register  is  used by the LDP target process, then the saved
          copy from  the  previous  context  is  used.   This  comment
          applies  to  PHYS_REG_OFFSET  mode as well.  The ID field is
          not used.

     PHYS_REG_OFFSET

          The offset is added to the contents of a register  given  as
          the mode argument.  The result is used as a physical address
          in macromemory.  ID is unused.

     PHYS_REG_INDIRECT

          The register specified in the mode arg contains the  address
          of  a  pointer in macromemory.  The effective address is the
          macromemory location specified  in  the  pointer,  plus  the
          offset.  The ID field is unused.

     PROCESS_CODE

          The ID is a process ID, the offset is into  the  code  space
          for this process.  Mode argument is not used.

     PROCESS_DATA

          The ID is a process ID, the offset is into  the  data  space
          for  this  process.   Mode argument is not used.  On systems
          that do not distinguish between code and data  space,  these
          two  modes are equivalent, and reference the virtual address
          space of the process.

     PROCESS_DATA_PTR

          The offset contains the address of a  pointer  in  the  data
          space  of  the  process  specified  by the ID.  The location
          pointed to (the effective  address)  is  also  in  the  data
          space.  The mode argument is not used.

     PROCESS_REG

          Accesses the  registers  (and  other  system  data)  of  the
          process  given  by the ID field.  Mode argument 0 starts the
          registers.  After the registers, the  mode  argument  is  an
          offset into the system area for the process.



                                                               Page 23



     RFC-909                                                 July 1984



     PROCESS_REG_OFFSET

          The offset plus the contents of the register  given  in  the
          mode  argument specifies a location in the data space of the
          process specified by the ID.

     PROCESS_REG_INDIRECT

          The register specified in the mode arg contains the  address
          of  a  pointer in the data space of the process given by the
          ID.  The effective address is the location in  process  data
          space specified in the pointer, plus the offset.

     OBJECT_OFFSET (optional)

          The offset is into the memory space defined by the object ID
          in   ID.    Recommended  for  remote  control  of  parameter
          segments.

     OBJECT_HEADER (optional)

          The  offset  is  into  the  system  header  for  the  object
          specified by the ID.  Intended for use with the Butterfly.

     BREAKPOINT

          The descriptor specifies a breakpoint.  The offset is  never
          used,  this  type  is  only used in descriptors referring to
          breakpoints.  (See Breakpoints and Watchpoints,  below,  for
          an explanation of breakpoint descriptors.)

     WATCHPOINT

          The descriptor specifies a watchpoint.  The offset is  never
          used,  this  type  is  only used in descriptors referring to
          watchpoints.  (See Breakpoints and Watchpoints,  below,  for
          an explanation of watchpoint descriptors).

     BPT_PTR_OFFSET

          For  this  mode  and  BPT_PTR_INDIRECT,  the  mode  argument
          specifies  one  of two breakpoint pointer variables local to
          the breakpoint in which this address occurs.  These pointers
          and  the  SET_PTR command which manipulates them provide for
          an  arbitrary  amount  of  address  indirection.   They  are
          intended for use in traversing data structures: for example,
          chasing queues.  In BPT_PTR_OFFSET, the offset is  added  to



     Page 24



     LDP Specification                            Commands and Formats



          the  pointer  variable  to  give  the effective address.  In
          targets which support multiple processes, the location is in
          the  data  space of the process given by the ID.  Otherwise,
          the  location  is  a  physical  address   in   macro-memory.
          BPT_PTR.*   modes   are   valid   only  in  breakpoints  and
          watchpoints.

     BPT_PTR_INDIRECT

          Like BPT_PTR_OFFSET, except that it uses one more  level  of
          indirection.    The  pointer  variable  given  by  the  mode
          argument plus the offset specify an address which points  to
          the    effective    address.    See   the   description   of
          BPT_PTR_OFFSET for a discussion of  usage,  limitations  and
          address space.




     4.3.2  Short Address Format

          The  short  address  format   is   intended   for   use   in
     implementations  where protocol overhead must be minimized.  This
     format is a subset of the long address format:  it  contains  the
     same  fields  except  for  the  ID  field.   Therefore, the short
     addressing format supports only HOST and  PHYS_*  address  modes.
     Only  the LOADER_DUMPER implementation level commands may be used
     with the short addressing format.  The short  address  format  is
     three  words  long,  consisting  of  a 16-bit word describing the
     address space, and a 32-bit offset.




















                                                               Page 25



     RFC-909                                                 July 1984





                    Short Format - Format bit is SHORT=1

                     0             0 0   1         1
                     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
                    +-------------------------------+
                    |1|       Mode  | Mode Argument |
                    +-------------------------------+  +-+
                    |                    (31-16)    |   |
                    +----        Offset          ---+   | Offset
                    |                    (15-0)     |   |
                    +-------------------------------+  +-+


                           Short Address Format
                                 Figure 11


     SHORT ADDRESS FIELDS:
     Mode

          The high-order  bit  is  1,  indicating  the  short  address
          format.   A  list  of  the  address modes supported is given
          below.  The interpretation of the  remaining  fields  is  as
          described above for the long addressing format.