Re: [RFA/RFC Prec] Add process record skip 6/6 (doc)

Hui Zhu
2009-08-31T13:26:35Z

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On Thu, Aug 27, 2009 at 01:50, Eli Zaretskii<eliz@gnu.org> wrote:
>> From: Hui Zhu <teawater@gmail.com>
>> Date: Tue, 25 Aug 2009 11:47:09 +0800
>> Cc: gdb-patches@sourceware.org, msnyder@vmware.com, green@moxielogic.com
>>
>> >> i386_linux_process_record_simple_function is for printf.
>> >> i386_linux_process_record_memset is for memset and memcpy.
>> >
>> > So we currently support record skip of only 3 functions, the ones
>> > mentioned above, is that right?  In that case, we should document
>> > those functions in the manual, I think.
>>
>> Yes, I think after this feature in, we can add more and more functions
>> to support skip.
>
> But then the proposed code is IMHO awfully limited, isn't it?  Why
> not add some more general mechanism, for several broad classes of
> functions (like the `simple_function' class you used for `printf'),
> and let the user specify which functions she wants to skip, instead of
> hard-coding the functions in GDB?
>
> By contrast, the suggested code will cause us to have gobs of library
> functions intimately known to GDB, and will bloat the executable, for
> starters.
>
> Also, why is this code being make Linux-specific?  Surely, most, if
> not all, other implementations of `printf', `memset' and `memcpy' have
> the exact same API and the same external effects as those you have in
> glibc, no?

The api is same, but the ABI for each arch and os is not same, each
printf, memset or memcpy of each arch-os will get the argument from
different memory and different register. And they will change
different memory and reg.

So it be designed to arch-os special.

>
>> What do you think about the doc like this:
>> The record skip support following functions:
>> I386-Linux printf, memcpy, memset.
>
> If we want to hard-code the functions, then we need something like
> this in the manual:
>
>  Only some standard functions are currently supported by the
>  @code{record skip} command; type the command without arguments to
>  see the full list.

OK.

>
>> > Do we lose any information because of skip?  If not, why don't we do
>> > that always, why do we need an option to enable and disable that?
>> >
>>
>> This is a very good question.
>> It will not lose any information.
>> I add a disable function because if customer want reverse debug inside
>> the function,  he will need setp by step without skip like in before.
>> For example, debug the libc.
>
> Okay, but then at least let's have it on by default.
>

Yes, all of them will set to on by default.

I make a new patch. Please help me with it.

Thanks,
Hui

2008-08-31 Hui Zhu <teawater@gmail.com>

* gdb.texinfo (Process Record and Replay): Document
'record skip', 'record skip enable' and 'record skip disable'.

---
doc/gdb.texinfo | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

--- a/doc/gdb.texinfo
+++ b/doc/gdb.texinfo
@@ -5214,6 +5214,31 @@ When record target runs in replay mode (
subsequent execution log and begin to record a new execution log starting
from the current address. This means you will abandon the previously
recorded ``future'' and begin recording a new ``future''.
+
+@kindex record skip
+@kindex rec skip
+@item record skip
+The record skip entry is a special breakpoint. When the process
+record and replay target start, it will be inserted to the
+begin of a function. When this breakpoint break the inferior and
+@value{GDBN} is in record mode, @value{GDBN} will skip record all
+the execution log of this function's instructions and record the
+change of memory and registers of this function as one instruction.
+Show the status of record skip.
+
+Only some standard functions are currently supported by the
+@code{record skip} command; type the command without arguments to
+see the full list.
+
+@kindex record skip disable
+@kindex rec skip disable
+@item record skip disable @r{[}id@r{]}
+Disable the specified record skip entry (or all record skip entries).
+
+@kindex record skip enable
+@kindex rec skip enable
+@item record skip enable @r{[}id@r{]}
+Enable the specified record skip entry (or all record skip entries).
@end table

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---
doc/gdb.texinfo | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

--- a/doc/gdb.texinfo
+++ b/doc/gdb.texinfo
@@ -5214,6 +5214,31 @@ When record target runs in replay mode (
subsequent execution log and begin to record a new execution log starting
from the current address. This means you will abandon the previously
recorded ``future'' and begin recording a new ``future''.
+
+@kindex record skip
+@kindex rec skip
+@item record skip
+The record skip entry is a special breakpoint. When the process
+record and replay target start, it will be inserted to the
+begin of a function. When this breakpoint break the inferior and
+@value{GDBN} is in record mode, @value{GDBN} will skip record all
+the execution log of this function's instructions and record the
+change of memory and registers of this function as one instruction.
+Show the status of record skip.
+
+Only some standard functions are currently supported by the
+@code{record skip} command; type the command without arguments to
+see the full list.
+
+@kindex record skip disable
+@kindex rec skip disable
+@item record skip disable @r{[}id@r{]}
+Disable the specified record skip entry (or all record skip entries).
+
+@kindex record skip enable
+@kindex rec skip enable
+@item record skip enable @r{[}id@r{]}
+Enable the specified record skip entry (or all record skip entries).
@end table