[lldb-dev] Launching the program through 'gdb-remote' process plugin

Greg Clayton gclayton at apple.com
Wed Aug 21 10:01:04 PDT 2013

The "process launch" command should send the 'A' packet, and it is waiting for a stop reply response from the 'A' packet. Try enabling the packet logging in LLDB:

(lldb) log enable gdb-remote packets
(lldb) process connect ...
(lldb) run

My guess is that the 'A' packet isn't responding with a stop reply packet.

On Aug 21, 2013, at 7:47 AM, chansarav <chansarav at gmail.com> wrote:

> Hi,
> I am connecting lldb with my simulator through 'gdb-remote' process plugin. After extablishing the connection, I want to issue the 'process launch' command in lldb which should send the arguments packet 'A' to simulator asking it to launch the program.
> I am facing the problem while issuing the 'process launch' command in lldb. When I give the 'process launch' command, lldb hangs and there is no communication with simulator. When I debugged with gdb, I got the backtrace as follows:
> #2  0xb6703a6f in lldb_private::Condition::Wait (this=0x8077dac, mutex=..., abstime=0x0, timed_out=0xbfffaa9f) at /home/chandra/llvm-3.1/tools/lldb/source/Host/common/Condition.cpp:92
> #3  0xb662768d in lldb_private::Predicate<bool>::WaitForValueEqualTo (this=0x8077d90, value=true, abstime=0x0, timed_out=0xbfffaa9f) at /home/chandra/llvm-3.1/tools/lldb/source/Core/../../include/lldb/Host/Predicate.h:317
> #4  0xb662b03f in lldb_private::Listener::WaitForEventsInternal (this=0x8077d3c, timeout=0x0, broadcaster=0xadb0179c, broadcaster_names=0x0, num_broadcaster_names=0, event_type_mask=3, event_sp=...) at /home/chandra/llvm-3.1/tools/lldb/source/Core/Listener.cpp:409
> #5  0xb662b1f7 in lldb_private::Listener::WaitForEventForBroadcasterWithType (this=0x8077d3c, timeout=0x0, broadcaster=0xadb0179c, event_type_mask=3, event_sp=...) at /home/chandra/llvm-3.1/tools/lldb/source/Core/Listener.cpp:440
> #6  0xb69421ec in lldb_private::Process::WaitForStateChangedEvents (this=0xadb01788, timeout=0x0, event_sp=...) at /home/chandra/llvm-3.1/tools/lldb/source/Target/Process.cpp:1069
> #7  0xb6941f2c in lldb_private::Process::WaitForProcessToStop (this=0xadb01788, timeout=0x0) at /home/chandra/llvm-3.1/tools/lldb/source/Target/Process.cpp:977
> #8  0xb6587d98 in CommandObjectProcessLaunch::DoExecute (this=0x80813d0, launch_args=..., result=...) at /home/chandra/llvm-3.1/tools/lldb/source/Commands/CommandObjectProcess.cpp:220
> #9  0xb672c999 in lldb_private::CommandObjectParsed::Execute (this=0x80813d0, args_string=0xb4d667bc "", result=...) at /home/chandra/llvm-3.1/tools/lldb/source/Interpreter/CommandObject.cpp:856
> #10 0xb67215d3 in lldb_private::CommandInterpreter::HandleCommand (this=0x8077fc8, command_line=0x883a614 "process launch", lazy_add_to_history=lldb_private::eLazyBoolYes, result=..., 
>     override_context=0x0, repeat_on_empty_command=true, no_context_switching=false) at /home/chandra/llvm-3.1/tools/lldb/source/Interpreter/CommandInterpreter.cpp:1571
> #11 0xb64e0ced in lldb::SBCommandInterpreter::HandleCommand (this=0xbfffc2cc, command_line=0x883a614 "process launch", result=..., add_to_history=true) at /home/chandra/llvm-3.1/tools/lldb/source/API/SBCommandInterpreter.cpp:97
> #12 0x0805a103 in Driver::HandleIOEvent (this=0xbfffec7c, event=...) at /home/chandra/llvm-3.1/tools/lldb/tools/driver/Driver.cpp:996
> #13 0x0805b516 in Driver::MainLoop (this=0xbfffec7c) at /home/chandra/llvm-3.1/tools/lldb/tools/driver/Driver.cpp:1430
> #14 0x0805bbf2 in main (argc=4, argv=0xbfffede4, envp=0xbfffedf8) at /home/chandra/llvm-3.1/tools/lldb/tools/driver/Driver.cpp:1562
> Though I am analyzing on this, Can someone help me in finding out what goes wrong while trying to launch a program in simulator through 'gdb-remote' process plugin?
> Following is the communication between lldb and simulator for the "process connect --plugin gdb-remote connect://localhost:51000" command.
> Send Packet: QStartNoAckMode: 15 chars
> Read Packet:
> Send Packet: QThreadSuffixSupported: 22 chars
> Read Packet:
> Send Packet: QListThreadsInStopReply: 23 chars
> Read Packet: E01
> Send Packet: qHostInfo: 9 chars
> Read Packet: cputype:201;cpusubtype:-2;ostype:unknown;vendor:unknown;endian:little;ptrsize:4;
> Send Packet: vCont?: 6 chars
> Read Packet: vCont[;c;s]
> Send Packet: qVAttachOrWaitSupported: 23 chars
> Read Packet: 
> Send Packet: qC: 2 chars
> Read Packet: QC0
> LLDB sets the status as connected after this communication.
> (snip start)
>     if (pid == LLDB_INVALID_PROCESS_ID)
>     {
>         // We don't have a valid process ID, so note that we are connected
>         // and could now request to launch or attach, or get remote process 
>         // listings...
>         SetPrivateState (eStateConnected);
>     }
> (snip end)
> function: ProcessGDBRemote::DoConnectRemote ()
> Thanks, 
> Chandra Kumar R.
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