[lldb-dev] LLDB use of G/g packets

[Greg Clayton]

On Feb 10, 2013, at 6:58 AM, Benjamin Kemper <kemperbenny at gmail.com> wrote:

> I noticed something that I've missed when sending the previous Email. Looking at the logs, I see LLDB sending "kill" command for no reason:
> <lldb.driver.main-thread> <  18> send packet: $m1039ede00,200#86
>   1 <lldb.driver.main-thread> <   1> read packet: +
>   0 <lldb.driver.main-thread> <1028> read packet: $4b4c5752000000000000000000000000c04e0000014e0000004e000000000000000000000000000010de9e030100000014de9e030100000018de9e030100000020
>   1 <lldb.driver.main-thread> <   1> send packet: +
>   2 <lldb.driver.main-thread> <  18> send packet: $m1038d4200,200#21
>   3 <lldb.driver.main-thread> <   1> read packet: +
>   4 <lldb.driver.main-thread> <1028> read packet: $e97bf4ffff6666666666662e0f1f8400000000009090909090909090909090909090909090909090909090909090909090909090909090909090909090909090e9
>   5 <lldb.driver.main-thread> <   1> send packet: +
>   6 <lldb.driver.main-thread> <  21> send packet: $Z0,7fff5fc0d6e5,1#de
>   7 <lldb.driver.main-thread> <   1> read packet: +
>   8 <lldb.driver.main-thread> <   6> read packet: $OK#9a
>   9 <lldb.driver.main-thread> <   1> send packet: +
>  10 <lldb.driver.main-thread> <  16> send packet: $qfThreadInfo#bb
>  11 <lldb.driver.main-thread> <   1> read packet: +
>  12 <lldb.driver.main-thread> <   8> read packet: $m707#0b
>  13 <lldb.driver.main-thread> <   1> send packet: +
>  14 <lldb.driver.main-thread> <  16> send packet: $qsThreadInfo#c8
>  15 <lldb.driver.main-thread> <   1> read packet: +
>  16 <lldb.driver.main-thread> <   5> read packet: $l#6c
>  17 <lldb.driver.main-thread> <   1> send packet: +
>  18 <lldb.driver.main-thread> <  18> send packet: $z0,1005f00d7,1#5a
>  19 <lldb.driver.main-thread> <   1> read packet: +
>  20 <lldb.driver.main-thread> <   6> read packet: $OK#9a
>  21 <lldb.driver.main-thread> <   1> send packet: +
>  22 <lldb.driver.main-thread> <  21> send packet: $z0,7fff5fc0d6e5,1#fe
>  23 <lldb.driver.main-thread> <   1> read packet: +
>  24 <lldb.driver.main-thread> <   6> read packet: $OK#9a
>  25 <lldb.driver.main-thread> <   1> send packet: +
>  26 <lldb.driver.main-thread> <   5> send packet: $k#6b
>  27 <lldb.driver.main-thread> <   1> read packet: +
>  28 <lldb.driver.main-thread> <   6> read packet: $OK#9a
>  29 <lldb.driver.main-thread> <   1> send packet: +
>  30    6> send packet: $p2#a2
>  31 <lldb.driver.main-thread> <   1> read packet: +
>  32 <lldb.driver.main-thread> <   4> read packet: $#00
>  33 <lldb.driver.main-thread> <   1> send packet: +
>  34 <lldb.driver.main-thread> <   6> send packet: $p3#a3
> 
> Here are my commands in the lldb console:
> ➜  build  lldb /bin/ls                                             
> Current executable set to '/bin/ls' (x86_64).
> (lldb) log enable -f /tmp/packets.txt  gdb-remote packets
> (lldb) process connect -p gdb-remote connect://localhost:58985
> Process 1799 stopped
> * thread #1: tid = 0x0707, , stop reason = signal SIGINT
>     frame #0: 
> (lldb) 
> 
> Why might LLDB send the 'kill' command without "permission"? 

You will need to debug the LLDB sources to see why this isn't being sent. I know of no reason why this should be happening, so this is probably a bug.

> 
> The weird thing is that after it sends the kill command, it then start requesting for register values using the '$p' commands...
> 
> Any ideas why this is happening?
> 

No, none at all. You will need to debug this. The only place the "k" packet is sent is from inside:

ProcessGDBRemote::DoDestroy ()

There is logging that can be enabled. Add the "process" category to the "gdb-remote" logging and use the "--stack" option to print out a backtrace:

(lldb) log enable --stack -f /tmp/process.txt gdb-remote process

You should then see a stack backtrace to see who is calling DoDestroy()...

> 
> 
> On Sun, Feb 10, 2013 at 3:19 PM, Benjamin Kemper <kemperbenny at gmail.com> wrote:
> Hi,
> 
> I'm implementing a debugger backend that implements the gdb remote protocol and adding extensions to support LLDB also.
> 
> I've added support for the qRegisterInfo packet and I've noticed in the logs that LLDB uses the p/P packets instead of the G/g packets.
> 
> Is there a special reason why it uses multiple packets instead of one?
> 
> Maybe I didn't implement enough "information" packets and LLDB doesn't know how to read g/G packets? If so, what packets are missing?
> 
> Thanks,
> Benjamin.
> 
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