RFC 0909
Loader Debugger Protocol
Pages: 135
Experimental
Experimental
Part 4 of 4 – Pages 100 to 135
o the condition list is evaluated in sequence until either a
TRUE and_list is found (condition list <- TRUE), or the end
of the condition list is reached (condition list <- FALSE).
An and_list is TRUE if all its conditions are TRUE.
The distillation of these rules into BNF is:
<condition_list> :== <and_list> [OR <and_list>]*
<and_list> :== <condition> [AND <condition>]*
<condition> :== CHANGED | COMPARE | COUNT | TEST
where: OR is a breakpoint command
AND is implicit for any pair of consecutive conditions
For example, the following condition list, with one command per
line,
COUNT_EQ 1
OR
COUNT_GT 10
COUNT_LT 20
evaluates to:
(COUNT = 1) OR (COUNT > 10 AND COUNT < 20)
and will cause the command list that follows it to be executed if
the counter is equal to one, or is between 10 and 20.
10.1 Condition Command Format
Condition commands start with the standard four-octet
command header. The high-order bit of the command type byte is
used as a negate flag: if this bit is set, the boolean value of
the condition is negated. This flag applies to one condition
only, and not to other conditions in the condition list.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | Command Length |
+---------------+---------------+
1 | CONDITION |N| Type |
+---------------+---------------+
Condition Command Header
Figure 66
10.2 COUNT Conditions
The COUNT conditions (COUNT_EQ, COUNT_GT and COUNT_LT) are
used to compare the breakpoint counter to a specified value. The
counter is set to zero when the breakpoint is STARTed, and is
incremented by the INC_COUNT breakpoint command. The format is
the same for the COUNT_EQ, COUNT_GT and COUNT_LT conditions.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 8 |
+---------------+---------------+
1 | CONDITION |N| Type |
+---------------+---------------+
2 | |
+-- Value --+
3 | |
+---------------+---------------+
COUNT Condition Format
Figure 67
COUNT_* Condition FIELDS:
Type
One of COUNT_EQ, COUNT_LT and COUNT_GT. The condition is
TRUE if the breakpoint counter is [EQ | LT | GT] the
specified value.
Value
A 32-bit value to be compared to the counter.
10.3 CHANGED Condition
The CHANGED condition is TRUE if the contents of the
specified location have changed since the last time this
breakpoint occurred. Only one location may be specified as the
object of CHANGED conditions per breakpoint. The CHANGED
condition is always FALSE the first time the breakpoint occurs.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 14 |
+---------------+---------------+
1 | CONDITION |N| CHANGED |
+---------------+---------------+
2 | |
+-- --+
3 | Address |
+-- --+
4 | |
+-- --+
5 | |
+-- --+
6 | |
+---------------+---------------+
CHANGED Condition
Figure 68
CHANGED FIELDS:
Address
The full 5-word address of the location to be tested by the
CHANGED command.
10.4 COMPARE Condition
The COMPARE condition compares two locations using a mask.
The condition is TRUE if (<loc1> & <mask>) = (<loc2> & <mask>).
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 28 |
+---------------+---------------+
1 | CONDITION |N| COMPARE |
+---------------+---------------+
2 | |
+-- --+
3 | Address 1 |
+-- --+
4 | |
+-- --+
5 | |
+-- --+
6 | |
+---------------+---------------+
7 | |
+-- Mask --+
8 | |
+-------------------------------+
9 | |
+-- --+
10| Address 2 |
+-- --+
11| |
+-- --+
12| |
+-- --+
13| |
+-------------------------------+
COMPARE Condition
Figure 69
COMPARE FIELDS:
Address 1
Address 2
The 5-word addresses of the locations to be compared.
Mask
A 32-bit mask specifying which bits in the locations should
be compared.
10.5 TEST Condition
The TEST condition is used to compare a location to a value,
using a mask. The condition is TRUE if (<loc> & <mask>) =
<value>.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 22 |
+---------------+---------------+
1 | CONDITION |N| TEST |
+---------------+---------------+
2 | |
+-- --+
3 | Address |
+-- --+
4 | |
+-- --+
5 | |
+-- --+
6 | |
+---------------+---------------+
7 | |
+-- Mask --+
8 | |
+-------------------------------+
9 | |
+-- Value --+
10| |
+-------------------------------+
TEST Condition
Figure 70
TEST FIELDS:
Address
The 5-word address of the location to be compared to the
value.
Mask
A 32-bit mask specifying which bits in the location should
be compared.
Value
A 32-bit value to compare to the masked location.
CHAPTER 11
Breakpoint Commands
Breakpoint commands are used to set the value of breakpoint
variables. These commands are only valid within breakpoints and
watchpoints. They are sent from the host to the target as data
in BREAKPOINT_DATA commands. Figure 71 contains a summary of
breakpoint commands:
Command Description
------------------------+-------------------------------------
INCREMENT <location> Increment the specified location
INC_COUNT Increment the breakpoint counter
OR OR two breakpoint condition lists
SET_PTR <n> <location> Set pointer <n> to the contents of
<location>
SET_STATE <n> Set the breakpoint state variable
to <n>
Breakpoint Command Summary
Figure 71
11.1 INCREMENT Command
The INCREMENT command increments the contents of a specified
location. The location may be in any address space writable from
LDP.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 14 |
+---------------+---------------+
1 | BREAKPOINT | INCREMENT |
+---------------+---------------+
2 | |
+-- --+
3 | Address |
+-- --+
4 | |
+-- --+
5 | |
+-- --+
6 | |
+---------------+---------------+
INCREMENT Command Format
Figure 72
INCREMENT FIELDS:
Address
The full address of the location whose contents are to be
incremented.
11.2 INC_COUNT Command
The INC_COUNT command increments the breakpoint counter.
There is one counter variable for each breakpoint. It is
initialized to zero when the breakpoint is created, when it is
armed with the START command, and whenever the breakpoint state
changes. The counter is tested by the COUNT_* conditions.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 4 |
+---------------+---------------+
1 | BREAKPOINT | INC_COUNT |
+---------------+---------------+
INC_COUNT Command Format
Figure 73
11.3 OR Command
The OR command delineates two and_lists in a breakpoint
condition list. A condition list is TRUE if any of the OR
separated and_lists in it are TRUE. A breakpoint condition list
may contain zero, one or, many OR commands. See 'Condition
Commands' for an explanation of condition lists.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 4 |
+---------------+---------------+
1 | BREAKPOINT | OR |
+---------------+---------------+
OR Command Format
Figure 74
11.4 SET_PTR Command
The SET_PTR command loads the specified breakpoint pointer
with the contents of a location. The pointer variables and the
SET_PTR command are intended to provide a primitive but unlimited
indirect addressing capability. Two addressing modes,
BPT_PTR_OFFSET and BPT_PTR_INDIRECT, are used for referencing the
breakpoint pointers. For example, to follow a linked list, use
SET_PTR to load a pointer with the start of the list, then use
successive SET_PTR commands with addressing mode BPT_PTR_OFFSET
to get successive elements.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 16 |
+---------------+---------------+
1 | BREAKPOINT | SET_PTR |
+---------------+---------------+
2 | Pointer |
+---------------+---------------+
3 | |
+-- --+
4 | Address |
+-- --+
5 | |
+-- --+
6 | |
+-- --+
7 | |
+---------------+---------------+
SET_PTR Command Format
Figure 75
SET_PTR FIELDS:
Pointer
The pointer to be changed. Allowable values are 0 and 1.
Address
The full address of the location whose contents are to be
loaded into the given pointer variable.
11.5 SET_STATE Command
The SET_STATE command sets the breakpoint state variable to
the specified value. This is the only method of changing a
breakpoint's state from within a breakpoint. The breakpoint's
state may be also be changed by a START command from the host.
The state variable is initialized to zero when the breakpoint is
created.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 6 |
+---------------+---------------+
1 | BREAKPOINT | SET_STATE |
+---------------+---------------+
2 | State Value |
+-------------------------------+
SET_STATE Command Format
Figure 76
SET_STATE FIELDS:
State Value
The new value for the breakpoint state variable. Must not
be greater than the maximum state value specified in the
CREATE BREAKPOINT command that created this breakpoint.
APPENDIX A
Diagram Conventions
Command and message diagrams are used in this document to
illustrate the format of these entities. Words are listed in
order of transmission down the page. The first word is word
zero. Bits within a word run left to right, most significant to
least. However, following a convention observed in other
protocol documents, bits are numbered in order of transmission;
the most significant bit in a word is transmitted first. The bit
labelled '0' is the most significant bit.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 |M| |L|
+---------------+---------------+
1 | Most Sig Octet| Least S. Octet|
+---------------+---------------+
M = most significant bit in word zero,
transmitted first
L = least significant bit in word zero,
transmitted last
Sample Diagram
Figure 77
APPENDIX B
Command Summary
The following table lists all non-breakpoint LDP commands in
alphabetical order, with a brief description of each.
Sender
Command | Host Target | Function
-------------------+-------------+---------------------------
ABORT X Abort outstanding commands
ABORT_DONE X Acknowledge ABORT
ADDRESS_LIST X Return valid address ranges
BREAKPOINT_DATA X Send breakpoint commands
BREAKPOINT_LIST X Return list of breakpoints
CONTINUE X Resume execution
CREATE X Create target object
CREATE_DONE X Acknowledge CREATE
DELETE X Delete target object
DELETE_DONE X Acknowledge DELETE
EXCEPTION X Report target exception
ERROR X Report error with a host command
ERRACK X Acknowledge ERROR
GET_OBJECT X Get object descriptor from name
GET_PHYS_ADDRESS X Get address in physical form
GOT_OBJECT X Return object descriptor
GOT_PHYS_ADDRESS X Return physical address
HELLO X Initiate LDP session
HELLO_REPLY X Return LDP parameters
LIST_ADDRESSES X Request valid address ranges
LIST_BREAKPOINTS X Request breakpoint list
LIST_NAMES X Request name list
LIST_PROCESSES X Request process list
MOVE X Read data from target
MOVE_DONE X Acknowledge MOVE completion
MOVE_DATA X Send data request by MOVE
NAME_LIST X Return name list
PROCESS_LIST X Return process list
READ X Read data from target
READ_DATA X Return data requested by READ
READ_DONE X Acknowledge READ completion
REPEAT_DATA X Write copies of data
REPORT X Request status of object
START X Start target object
STATUS X Return status of object
STEP X Step execution of target object
STOP X Stop target object
SYNCH X Check sequence number
SYNCH_REPLY X Confirm sequence number
WRITE X Write data
WRITE_MASK X Write data with mask
Command Summary
Figure 78
APPENDIX C
Commands, Responses and Replies
The following table shows the relationship between commands,
responses and replies. Commands are sent from the host to the
target. Some commands elicit responses and/or replies from the
target. Responses and replies are sent from the target to the
host. The distinction between them is that the target sends only
one reply to a command, but may send multiple responses.
Responses always contain data, whereas replies may or may not.
Command | Response | Reply
-------------------+--------------+------------------
ABORT ABORT_DONE
BREAKPOINT_DATA
CONTINUE
CREATE CREATE_DONE
DELETE DELETE_DONE
GET_OBJECT GOT_OBJECT
GET_PHYS_ADDRESS GOT_PHYS_ADDRESS
HELLO HELLO_REPLY
LIST_ADDRESSES ADDRESS_LIST
LIST_BREAKPOINTS BREAKPOINT_LIST
LIST_NAMES NAME_LIST
LIST_PROCESSES PROCESS_LIST
MOVE MOVE_DATA MOVE_DONE
READ READ_DATA READ_DONE
REPEAT_DATA
REPORT STATUS
START
STEP
STOP
SYNCH SYNCH_REPLY
WRITE
WRITE_MASK
Commands, Responses and Replies
Figure 79
APPENDIX D
Glossary
FSM
Finite state machine. Commands of each breakpoint or
watchpoint are implemented as part of a finite state
machine. A list of breakpoint commands is associated with
each state. There are several breakpoint commands to change
from one state to another.
host
The 'host' in an LDP session is the timesharing system on
which the user process runs.
long
A long is a 32-bit quantity.
octet
An octet is an eight-bit quantity.
RDP
The Reliable Data Protocol (RDP) is a transport layer
protocol designed as a low-overhead alternative to TCP. RDP
is a connection oriented protocol that provides reliable,
sequenced message delivery.
server process
The LDP server process is the passive participant in an LDP
session. The server process usually resides on a target
machine such as a PAD, PSN or gateway. The server process
waits for a user process to initiate a session, and responds
to commands from the user process. In response to user
commands, the server may perform services on the target like
reading and writing memory locations or setting breakpoints.
'Server' is sometimes employed as a shorthand for 'server
process'.
target
The 'target' in an LDP session is the PSN, PAD or gateway
that is being loaded, dumped or debugged by the host.
Normally, LDP will be implemented in the target as a server
process. However, in some targets with strange
requirements, notably the Butterfly, the target LDP may be a
user process.
user process
The LDP user process is the active participant in an LDP
session. The user process initiates and terminates the
session and sends commands to the server process which
control the session. The user process usually resides on a
timesharing host and is driven by a higher-level entity
(e.g., an application program like an interactive debugger).
'User' is sometimes employed as a shorthand for 'user
process'.
word
A word is a sixteen-bit quantity.
INDEX
ABORT command............................................ 35
ABORT_DONE reply......................................... 36
address.............................................. 60, 66
address descriptor....................................... 20
address format................................... 19, 25, 31
address ID............................................... 22
address mode......................................... 20, 22
address mode argument.................................... 21
address offset........................................... 20
addressing............................................... 19
ADDRESS_LIST reply................................... 76, 77
BASIC_DEBUGGER....................................... 12, 32
breakpoint... 9, 13, 57, 60, 71, 79, 92, 93, 95, 96, 99, 107
breakpoint commands.......................... 9, 94, 95, 107
breakpoint counter........................ 94, 100, 101, 110
breakpoint data...................................... 97, 99
breakpoint state variable........................... 94, 107
breakpoint variables..................................... 94
BREAKPOINT_DATA command..................... 73, 94, 95, 107
BREAKPOINT_LIST reply................................ 79, 80
CHANGED condition....................................... 102
command class............................................ 16
command length field..................................... 16
COMPARE Condition....................................... 103
condition command header................................ 101
conditional commands................................. 94, 99
CONTINUE command......................................... 62
control commands...................................... 9, 57
COUNT condition.................................... 110, 111
COUNT_EQ condition...................................... 101
COUNT_GT condition...................................... 101
COUNT_LT condition...................................... 101
CREATE command............................... 69, 70, 73, 75
create types............................................. 70
CREATE_DONE reply.................................... 73, 75
data octets...................................... 43, 47, 52
data packing............................................. 10
data transfer commands................................ 9, 41
data transmission........................................ 10
datagrams................................................. 5
debugging.............................................. 1, 3
default breakpoint................................... 71, 92
DELETE command....................................... 73, 75
DELETE_DONE reply........................................ 75
descriptor........... 20, 57, 61, 62, 63, 64, 65, 73, 75, 93
dumping................................................... 3
ERRACK............................................... 10, 39
ERROR codes.............................................. 38
ERROR reply.......................................... 37, 67
EXCEPTION trap........................................... 66
finite state machine................................. 60, 93
FSM breakpoint................................... 71, 92, 94
FULL-DEBUGGER............................................ 12
FULL_DEBUGGER............................................ 32
gateway................................................ 3, 9
GET_OBJECT command................................... 89, 91
GET_PHYS_ADDR command................................ 87, 88
GOT_OBJECT reply..................................... 89, 91
GOT_PHYS_ADDR reply.................................. 87, 88
HELLO command......................................... 9, 29
HELLO_REPLY....................................... 9, 19, 30
host descriptor.......................................... 41
implementation....................................... 12, 31
INC_COUNT command......................... 94, 107, 110, 111
INCREMENT command....................................... 109
internet.................................................. 5
internet protocols........................................ 4
IP........................................................ 5
LDP command formats...................................... 15
LDP header........................................... 15, 16
LDP Version.............................................. 30
LIST commands............................................ 73
LIST_ADDRESSES command............................... 76, 77
LIST_BREAKPOINTS command............................. 79, 80
LIST_NAMES command................................... 84, 85
LIST_PROCESSES command................................... 82
LOADER_DUMPER........................................ 12, 32
loading................................................ 1, 3
long address format...................................... 20
management commands...................................... 67
memory object............................................ 73
MOVE command................................. 22, 41, 47, 49
MOVE sequence number..................................... 52
MOVE_DATA response................................... 22, 51
MOVE_DONE reply.......................................... 52
NAME_LIST reply...................................... 84, 85
offset............................................... 20, 22
OR command.............................................. 111
PAD.................................................... 3, 9
pattern.................................................. 54
PHYS_ADDRESS............................................. 57
PHYS_MACRO............................................... 60
PROCESS.................................................. 57
PROCESS_CODE............................................. 60
PROCESS_LIST reply....................................... 82
protocol commands......................................... 9
PSN.................................................... 3, 9
RDP................................................... 5, 15
READ command..................................... 41, 43, 44
READ sequence number..................................... 47
READ_DATA response................................... 45, 46
READ_DONE reply.......................................... 47
repeat count............................................. 54
REPEAT_DATA command.................................. 41, 53
REPORT command................................... 63, 64, 94
sequence number...................................... 10, 39
session................................................... 9
SET_PTR command................................ 94, 111, 112
SET_STATE command.............................. 94, 107, 113
short address format..................................... 25
START command........................................ 59, 60
STATUS reply..................................... 64, 65, 94
STEP command......................................... 62, 63
STOP command......................................... 60, 61
SYNCH.................................................... 10
SYNCH command............................................ 33
SYNCH_REPLY.............................................. 34
system type.............................................. 30
target start address......................... 43, 44, 46, 54
transport................................................. 9
watchpoint.......... 13, 57, 60, 71, 92, 93, 95, 96, 99, 107
WRITE command........................................ 41, 42
WRITE_MASK command....................................... 56