[lldb-dev] gdb-remote to android gdbserver

Wed Aug 28 05:42:05 PDT 2013

Great, thanks for testing/cleaning it!

On Wed, Aug 28, 2013 at 7:37 PM, Abid, Hafiz <Hafiz_Abid at mentor.com> wrote:

>  I committed part of your patch that handles the RLE after cleaning it a
> bit and testing. I noticed though that expanding RLE at this point has a
> little problem. Packet log shows the un-expanded packet. I will fix it
> separately.****
>
> ** **
>
> Regards,****
>
> Abid****
>
> ** **
>
> *From:* Virgile Bello [mailto:virgile.bello at gmail.com]
> *Sent:* 27 August 2013 18:17
>
> *To:* Abid, Hafiz
> *Cc:* Sebastien Metrot; lldb-dev
> *Subject:* Re: [lldb-dev] gdb-remote to android gdbserver****
>
>  ** **
>
> Great, thanks!****
>
> ** **
>
> Hope it will work out, esp. the escaping at encoding time that has never
> been tested (but well, if there is no special characters it should be fine).
> ****
>
> If special characters proves to be useless or causing issues, I have a
> much smaller version just doing the RLE part (basically, encoding part
> disappear and decoding just test for "*").****
>
> ** **
>
> Virgile****
>
> ** **
>
> On Wed, Aug 28, 2013 at 2:08 AM, Abid, Hafiz <Hafiz_Abid at mentor.com>
> wrote:****
>
> Virgile,****
>
> Thanks for the patch. You choose a better place to decode the RLE. I am
> not sure about escape character though as gdbserver does not seem to use
> them for normal packets. The data byte is encoded in as 2-digit asci
> character. For example, this is a response to a g packet request.****
>
>  ****
>
> putpkt ("$2a0*}0*)40e2f*"7f0*S20*hb0b6ddf7ff7f0*"020* 330*"2b0*}0*}0*
> 7f030*(f* 0*}0*}0*}0*}0*}0*c801f0* 3b0*}0*}0*}0*}0*}0*E#c8"); [noack mode]
> ****
>
>  ****
>
> and initial part of how gdb decoded it.****
>
>
> 2a0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040e2
> ****
>
>  ****
>
> I will test the RLE part of your patch. If that is ok then I will merge it.
> ****
>
>  ****
>
> Thanks,****
>
> Abid****
>
>  ****
>
> *From:* Virgile Bello [mailto:virgile.bello at gmail.com]
> *Sent:* 27 August 2013 16:29
> *To:* Abid, Hafiz
> *Cc:* Sebastien Metrot; lldb-dev****
>
>
> *Subject:* Re: [lldb-dev] gdb-remote to android gdbserver****
>
>  ****
>
> Hello,****
>
>  ****
>
> Sorry, since I also had a RLE patch pending, here it is in case it is
> useful (before it's too late).****
>
> Hope we can merge both of them together maybe?****
>
>  ****
>
> This one also tries to handle escaped characters (#, $ and }), when
> receiving and sending.****
>
> Did it from http://sourceware.org/gdb/onlinedocs/gdb/Overview.html****
>
> Also, it converts everything where the packet copy was happening, to avoid
> extra copy and O(n) insertion.****
>
>  ****
>
> Not sure if checksum is supposed to work on the escaped version or not.
> Need to check how GDB is working (spec doesn't say anything).****
>
>  ****
>
> I didn't have a chance to test it again since I added character escaping,
> so I should probably do that again in case there is real interest in it.**
> **
>
> Also couldn't polish it as I intended, but thought it would still be more
> useful as is before the other one get merged than after.****
>
>  ****
>
> Sincerely,****
>
> Virgile****
>
>  ****
>
> On Tue, Aug 27, 2013 at 6:51 PM, Abid, Hafiz <Hafiz_Abid at mentor.com>
> wrote:****
>
> I have been working in the last few weeks on making LLDB working with
> gdbserver on Linux host. Some of the things that I noted missing are.****
>
>  ****
>
> 1.      Run length encoding as already mentioned. I have a patch for it
> that I will submit shortly.****
>
> 2.      I had to hardcode the registers for x86_64 as gdbserver does not
> support qRegisterInfo.****
>
> 3.      Make sure to use g/G packets for registers.****
>
>  ****
>
> After that I had a working connection. But then I noticed the following 2
> problem.****
>
> PC is not decremented by length of breakpoint instruction after target
> stops.****
>
> LLDB failing to recognize a breakpoint is for stepping and stopping before
> a source level step was really complete.****
>
>  ****
>
> I am working on these 2 issues.****
>
>  ****
>
> Regards,****
>
> Abid ****
>
>  ****
>
> *From:* lldb-dev-bounces at cs.uiuc.edu [mailto:lldb-dev-bounces at cs.uiuc.edu]
> *On Behalf Of *Virgile Bello
> *Sent:* 27 August 2013 02:34
> *To:* Sebastien Metrot
> *Cc:* lldb-dev
> *Subject:* Re: [lldb-dev] gdb-remote to android gdbserver****
>
>  ****
>
> Yes, I suppose a lldb-only change would be much more easier for now.****
>
>  ****
>
> From what I remember when I tested, hard-coding the ARM registers
> temporarily + the runtime-length encoding patch (that I will commit soon)
> was enough to to have a simple address breakpoint working.****
>
> Backtrace didn't, but I didn't bother investigate further.****
>
>  ****
>
> On Tue, Aug 27, 2013 at 10:09 AM, Sebastien Metrot <meeloo at gmail.com>
> wrote:****
>
> If I understand correctly 1 and 3 implies modifying the android gdbserver
> while 2 could be done entirely in lldb? Having gdbserver changes accepted
> by the maintainers and integrated in future builds of android and/or the
> NDK looks like a hard path to walk.
> Also I have looked at the gdbserver sources of the current android (found
> here https://android.googlesource.com/toolchain/gdb/ ) and a couple of
> greps seems to indicate that xmlRegisters is only supported on x86 although
> register definition xmls exists for many arm/linux variants.
> In this light 2 seems like a good short term solution to force a register
> mapping on lldb by reading the xml from the gdb sources, until 1 is finally
> implemented in both projects and lldb is able to detect the register
> mapping.
>
> Is that correct?
>
> S.****
>
>
>
> On 26 Aug 2013, at 19:34 , Greg Clayton <gclayton at apple.com> wrote:
>
> > The problem is we don't know the registers. GDB assumes that the GDB
> that is being used knows what registers are on the other side of the remote
> connection. New GDB binaries and GDBSERVER binaries are compiled for each
> target. LLDB has one binary for all systems. So LLDB expects to be able to
> query the GDBSERVER for the register information. LLDB has defined new
> packets to get this information. We have documented the packets we added:
> >
> > svn cat
> http://llvm.org/svn/llvm-project/lldb/trunk/docs/lldb-gdb-remote.txt
> >
> > I believe there is a way defined in the remote protocol to query for
> registers using the "qXfer" command with the "xmlRegisters" gdb feature. We
> haven't added support for this, but the "XML target description" format is
> missing information we need. The details on this are at:
> >
> >
> https://sourceware.org/gdb/onlinedocs/gdb/Target-Description-Format.html#Target-Description-Format
> >
> > It could also be easily extended to support giving us the information
> required.
> >
> > So, in order to get things going you will need to do one of the
> following:
> > 1 - add support for the qRegisterInfo packet (easiest)
> > 2 - add a new "settings set" setting for the "gdb-remote" plug-in that
> contains a path to a register description file. The file format should be
> something parseable like XML and you would need to write a parser for it
> and parse the contents by adding a method to the
>  GDBRemoteDynamicRegisterInfo class (harder)
> > 3 - If the current gdbserver for android does support the "XML target
> description", we would need to modify the GDBRemoteCommunicationClient
> class to be able to retrieve the information and parse the XML. You would
> then need to modify the gdbserver for android to add extra data we need to
> the register info (compiler register numbers for each register if one
> exists, DWARF register numbers, generic register info) (hardest)
> >
> > I think option 1 or 2 would be the easiest.
> >
> > Greg
> >
> > On Aug 25, 2013, at 10:53 AM, Sebastien Metrot <meeloo at gmail.com> wrote:
> >
> >> Hi,
> >>
> >> I have started to investigate connecting lldb to gdbserver running on
> an android device (arm). It connects correctly, I'm able to start the
> remote program and interrupt it but lldb doesn't permit me to access any
> data as it says the current frame is invalid:
> >>
> >> mbp:NativeTest meeloo$ lldb
> ../../../ndk/samples/hello-gl2/libs/armeabi/libgl2jni.so
> >> Current executable set to
> '../../../ndk/samples/hello-gl2/libs/armeabi/libgl2jni.so' (arm).
> >> (lldb) gdb-remote
> >> error: gdb-remote [<hostname>:]<portnum>
> >> (lldb) gdb-remote 127.0.0.1:5039
> >> Process 12260 stopped
> >> * thread #1: tid = 0x2fe4, , stop reason = signal SIGTRAP
> >>    frame #0:
> >> (lldb) frame variable
> >> error: invalid frame
> >> (lldb) continue
> >> Process 12260 resuming
> >> ---- Here I hit Ctrl+C
> >> Process 12260 stopped
> >> * thread #1: tid = 0x2fe4, , stop reason = signal SIGINT
> >>    frame #0:
> >> (lldb) continue
> >> Process 12260 resuming
> >> (lldb) process interrupt
> >> Process 12260 stopped
> >> * thread #1: tid = 0x2fe4, , stop reason = signal SIGINT
> >>    frame #0:
> >> (lldb) register read
> >> error: invalid frame
> >> (lldb) process status
> >> Process 12260 stopped
> >> * thread #1: tid = 0x2fe4, , stop reason = signal SIGINT
> >>    frame #0:
> >>
> >>
> >> Does anyone have already tried to do this kind of things? I'm trying to
> get it to work before moving to implementing android support in my program
> with the C++ API...
> >>
> >> Thanks in advance,
> >>
> >> S.
> >>
> >> _______________________________________________
> >> lldb-dev mailing list
> >> lldb-dev at cs.uiuc.edu
> >> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
> >
>
>
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>  ****
>
>  ****
>
> ** **
>
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