Re: [reverse RFC] Add documentation for process record and replay

teawater
2008-10-22T02:39:28Z

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Hi Eli,

I make a patch for doc.

2008-10-22 Hui Zhu <teawater@gmail.com>

* gdb.texinfo: Add documentation for process record and replay.

Thanks,
Hui

On Sat, Oct 18, 2008 at 03:47, Eli Zaretskii <eliz@gnu.org> wrote:
>> From: "Jakob Engblom" <jakob@virtutech.com>
>> Cc: <msnyder@vmware.com>,
>> <gdb-patches@sourceware.org>
>> Date: Fri, 17 Oct 2008 21:31:36 +0200
>>
>> > > > signals? crashes? etc. Are there things that simply cannot be
>> > > > reproduced exactly, due to fundamental limitations of the replay
>> > > > target?
>> >
>> > Do you have an opinion about these concerns?
>>
>> I would like to jump in here and point out that this will depend on the nature
>> of the target. Simics, and presumably other full-system simulation solutions,
>> can replay the entire IO of a machine. This includes any external IO that is
>> asynch to the simulator execution (such as network packets and user input).
>> Between machines in a simulated network of machines, replay is obviously
>> perfect.
>>
>> If you try to do this on a live machine, it is a bit more tricky.
>>
>> So this is best left to the underlying mechanism, in my experience.
>
> We should at least describe a couple of possibilities and tell the
> reader to consult the documentation of the particular target for the
> full details.
>

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--- a/gdb.texinfo
+++ b/gdb.texinfo
@@ -144,6 +144,7 @@ software in general. We will miss him.
* Running:: Running programs under @value{GDBN}
* Stopping:: Stopping and continuing
* Reverse Execution:: Running programs backward
+* Process record and replay:: Recording programs running message and replay it
* Stack:: Examining the stack
* Source:: Examining source files
* Data:: Examining data
@@ -4963,6 +4964,102 @@ This is the default.
@end table

+@node Process record and replay
+@chapter Recording programs running message and replay it
+@cindex process record and replay
+@cindex recording programs running message and replay it
+
+In a architecture environment that supports process record and replay,
+process record and replay target can record a log of the process execution,
+and replay it with both forward and reverse execute commands.
+
+When this target is in use, if the execution log includes the record for
+the next instruction, @value{GDBN} will debug in replay mode. So inferior
+will not really execute and all the execution events are taken from the
+execution log. Just the values of registers (include pc register) and
+memory of the inferior will be changed.
+
+Otherwise, @value{GDBN} will debug in record mode. So inferior will
+execute normally and @value{GDBN} will record the execution log.
+
+If you are debugging in a architecture environment that supports
+process record and replay, @value{GDBN} provides the following commands.
+
+@table @code
+@kindex target record
+@kindex record
+@kindex rec
+@item target record
+This a standard command to start process record and replay target.
+Process record and replay target can only debug a process that already
+running. Therefore you need to first start the process @code{run},
+and then start the recording @code{record}.
+
+@kindex stoprecord
+@kindex sr
+@item stoprecord
+Stop process record and replay target at once. When Process record and
+replay target stops, all the execution log will be deleted and the inferior
+will either be terminated, or remain in its final state.
+
+When you stop the process record and replay target in record mode (at the
+end of the execution log), the inferior will be stopped at the next
+instruction that would have been recorded. In other words, if you record
+for a while and then stop recording, the inferior process will be left in
+the same state as if recording never happened.
+
+On the other hand, if the process record and replay target is stopped while
+in replay mode (that is, not at the end of the execution log but at some
+earlier point), the inferior process will become ``live'' at that earlier state,
+and it will then be possible to continue debugging the process ``live'' from
+that state.
+
+When the inferior process exits, or @value{GDBN} detaches from it, process
+record and replay target will automatically stop itself.
+
+@kindex set record-insn-number-max
+@item set record-insn-number-max @var{limit}
+Set the limit of instructions to be recorded. Default value is 200000.
+
+In this case, if record instructions number is bigger than @var{limit},
+@value{GDBN} will auto delete the earliest recorded instruction execute
+log.
+
+If set to 0, @value{GDBN} will not delete the earliest recorded instruction
+execute log. Record instructions number limit function will disable.
+
+@kindex show record-insn-number-max
+@item show record-insn-number-max
+Show the value of recorded instructions limit.
+
+@kindex set record-stop-at-limit
+@item set record-stop-at-limit on
+Set the behavior when record instructions limit is reached.
+This is the default mode. Meaning that @value{GDBN} will stop ask user
+want close @code{record-stop-at-limit} or stop inferior.
+
+@item set record-stop-at-limit off
+This mean that @value{GDBN} will auto delete the oldest record to make
+room for each new one.
+
+@kindex show record-stop-at-limit
+@item show record-stop-at-limit
+Show the value of record-stop-at-limit.
+
+@kindex info record-insn-number
+@item info record-insn-number
+Show the current number of recorded instructions.
+
+@kindex delrecord
+@kindex dr
+@item delrecord
+When record target running in replay mode (``in the past''), delete the
+subsequent execution log and begin to record a new execution log starting
+from the current address. It means you will abandon the previously
+recorded ``future'' and begin recording a new ``future''.
+@end table
+
+
@node Stack
@chapter Examining the Stack