The gdb server protocol is used in a debug setup between gdb and the gdbserver. The gdbserver is the driver/software interface of the JATG/SWD probe. This allows the user to use an(optional) IDE with gdb to debug firmware running on a MCU.

+------------------+
|        User      |
+------------------+
          |
+------------------+
|        IDE       |
+------------------+
          |
+------------------+
|        gdb       |
+------------------+
          |
          |     <-- gdb server protocol is used here
          |
+------------------+
|     gdb server   |
+------------------+
          |
+------------------+
| JTAG / SWD probe |
+------------------+
          |
+------------------+
|        MCU       |
+------------------+

The remote protocol is specified in Appendix E of the gdb documentation. Wherever appropriate large parts of that documentation have been copied here.

The protocol is used over a serial byte data stream. Examples are a serial port (UART/COM Port) or a TCP port. The data is exchanged over this channel in packets. In this communication the gdb sends commands and the gdb server sends replies.

• '!' Enable extended mode
• '?' question mark
• 'A' A
• 'b' set baur rate don't use
• 'B' set or clear breakpoint don't use
• 'bc' backward continue
• 'bs' backward single step
• 'c' continue
• 'C' continue with signal
• 'd' toggle debug flag don't use
• 'D' detach
• 'F' file i/o
• 'g' read general register
• 'G' write general register
• 'H' select thread
• 'i' single clock step
• 'I' signal cycle step
• 'k' kill
• 'm' read memory
• 'M' write memory
• 'p' read register
• 'P' write register
• 'QAgent' agent on/off
• 'QAllow' allow operations
• 'qC' read current tread id
• 'qCRC' CRC of memory region
• 'QDisableRandomization' disable randomization of virtual addresses
• 'QStartupWithShell' use shell
• 'QEnvironmentHexEncoded' environment variables
• 'QEnvironmentUnset' unset environment variable
• 'QEnvironmentReset' reset environment
• 'QSetWorkingDir' set working directory
• 'qfThreadInfo' get active theads
• 'qsThreadInfo' get active theads
• 'qGetTLSAddr' get address of thread local storage
• 'qGetTIBAddr' get the Windows OS specific thread information block
• 'qL' get thread infromation from RTOS
• 'qMemTags' get memory tags
• 'qIsAddressTagged' check if address is tagged
• 'QMemTags' store memory tags
• 'qOffsets' get section offsets
• 'qP' read thread id don't use
• 'QNonStop' switch non stop mode
• 'QCatchSyscalls' switch catching syscalls
• 'QPassSignals' which signals to pass
• 'QProgramSignals' signals to target
• 'QThreadEvents' switch reporting of thread events
• 'QThreadOptions' apply options
• 'qRcmd' run command
• 'qSearch' search memory
• 'QStartNoAckMode' stop sending acks
• 'qSupported' tell gdbserver which features gdb supports
• 'qSymbol' tell gdb server that gdb can answere symbol requests
• 'qTBuffer' trace
• 'QTBuffer' trace
• 'QTDisconnected' trace
• 'QTDP' trace
• 'QTDPsrc' trace
• 'QTDV' trace
• 'qTfP' trace
• 'qTfV' trace
• 'QTFrame' trace
• 'qTMinFTPILen' trace
• 'qThreadExtraInfo' os decription for thread
• ‘QTNotes’ trace
• 'qTP' trace
• 'QTSave' trace
• 'qTsP' trace
• 'qTsV' trace
• 'QTStart' trace
• 'QTStop' trace
• 'QTEnable' trace
• 'QTDisable' trace
• 'QTinit' trace
• 'QTro' trace
• 'qTStatus' trace
• 'qTV' trace
• 'qTfSTM' trace
• 'qTsSTM' trace
• 'qTSTMat' trace
• 'qXfer' read special area
• 'qAttached' is attached?
• 'Qbtrace' enable branch tracing
• 'Qbtrace-conf' configure branch trace
• 'r' reset don't use
• 'R' restart program being debugged
• 's' single step
• 'S' signal single step
• 't' search backwards
• 'T' is thread alive
• 'vAttach' attach to a new process
• 'vCont' continue trhead
• 'vCont?' request supported actions of 'vCont'
• 'vCtrlC' interrupt remote target
• 'vFile' file operation on target file system
• 'vFlashErase' erase flash
• 'vFlashWrite' write flash
• 'vFlashDone' flash operations done
• 'vKill' kill process
• 'vMustReplyEmpty' test unknown command reply
• 'vRun' run program
• 'vStopped' stopped
• 'x' read memory
• 'X' write data to memory
• 'z' remove breakpoint
• 'Z' insert breakpoint

• empty
• Error Hex
• Error text
• stopped because of Signal
• stopped because of Signal + infos
• thread exited
• process exited
• process terminated
• no more threads
• console output
• host function call
• notification stop