README.armor.kgdb.kdb

• Readme for KGDB and KDB Tools
• Debugging using KGDB

Readme for KGDB and KDB Tools

1. Enable following configurations in the open-estuary kernel defconfig file, if it is not already done.

   CONFIG_HAVE_ARCH_KGDB=y
   CONFIG_KGDB=y
   CONFIG_KGDB_SERIAL_CONSOLE=y
   CONFIG_KGDB_TESTS=y
   CONFIG_KGDB_KDB=y
   CONFIG_KDB_DEFAULT_ENABLE=0x1
   CONFIG_KDB_KEYBOARD=y
   CONFIG_KDB_CONTINUE_CATASTROPHIC=0
   CONFIG_MAGIC_SYSRQ=y

2. Build kernel.

3. Set Kernel Debugger Boot Arguments (kgdboc=ttyS0,115200) in the grub.conf file as given in the following example.

   menuentry "ubuntu64-nfs" --id ubuntu64-nfs {
   set root=(tftp,192.168.0.3)
   linux /ftp-X/Image rdinit=/init console=ttyS0,115200  kgdboc=ttyS0,115200 earlycon=uart8250,mmio32,0x80300000 ...
   devicetree /ftp-X/hip05-d02.dtb
   }

4. Boot the target D02 board with the above grub.conf and kernal image built in step 2.

5. On D02, enter the kernel debugger(kdb) manually or by waiting for an oops or fault.
   There are several ways you can enter the kernel debugger manually; all involve using the sysrq-g. When logged in as root or with a super user session you can run:
   echo g > /proc/sysrq-trigger
   This will enter kdb terminal and then coninue with kernel debugging using kdb commands.

Debugging using KGDB

1. On D02 kdb terminal type ‘kgdb’ command. Then please attach debugger from host machine to remotely debug using gdb.

2. On the host machine install gdb-multiarch
   sudo adb-get install gdb-multiarch

3. run command on the host machine. ‘sudo gdb-multiarch ./vmlinux’
   where vmlinux is the uncompressed kernel image built in step (2).

4. On the gdb terminal, run following commands

   (gdb) set remote interrupt-sequence Ctrl-C BREAK BREAK-g  -> optional 
   (gdb) set serial baud 115200 -> set serial baud rate
   (gdb) set debug remote 1  -> optional for more gdb debug messages
   (gdb) target remote /dev/ttyUSB1 -> connect to the kgdb over serial port /dev/ttyUSB1 on host machine.
   (gdb) target remote `/dev/ttyUSB1`

   Remote debugging using /dev/ttyUSB1
   Sending packet: $qSupported:multiprocess+;xmlRegisters=i386;qRelocInsn+#b5...Ack
   ……….
   Sending packet: $g#67...Ack
   Packet received:

   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

   Sending packet: $mffffffc00015ccbc,4#15...Ack
   Packet received: 208020d4
   arch_kgdb_breakpoint () at ./arch/arm64/include/asm/kgdb.h:32
32 ./arch/arm64/include/asm/kgdb.h: No such file or directory.
   Sending packet: $qSymbol::#5b...Ack
   Packet received:

5. Once the gdb successfully connected to the remote kgdb on D02, kernel can be debugged as user space applications using normal gdb commands.