Md Display Memory Contents, also mdWcN, e.g. Task Addr Pid Parent cpu State Thread Command Kgdb: Waiting for connection from remote gdb.Įntering kdb (current=0xdb81abc0, pid 1) due to Keyboard Entry kdb> psġ7 sleeping system daemon (state M) processes suppressed, Linux version 3.6.11+ (gcc version 4.7.3 (Buildroot 2013.05) ) #13 PREEMPT Thu Jul 4 13:02:ĬPU: ARMv6-compatible processor revision 7 (ARMv7), cr=00c5387dĬPU: PIPT / VIPT nonaliasing data cache, VIPT nonaliasing instruction cacheĬonsole: switching to colour frame buffer device 82x26 You will require a terminal emulator app running on the Linux host system- I’d highly recommend ‘screen’ over ‘minicom’:īoot the R Pi! Uncompressing Linux. Also, the “debug” param is not strictly required.Ģ. Want more details? See Documentation/kernel-parameters. Here’s the kernel command-line am currently using : # cat /boot/cmdline.txtĭwc_otg.lpm_enable=0 dwc_otg.speed=1 debug console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 kgdbwait console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwaitġ. How? Edit the ‘ /boot/cmdline.txt‘ file in the boot partition of the R Pi SD card (usually mounted via the device file /dev/mmcblk0p1 on a Linux box, mount point usually is /boot). To try this, setup the R Pi kernel to boot with the ‘ kgdbwait‘ kernel parameter. Scenario I | Using KDB at early Kernel Boot-time These usually include the following: CONFIG_DEBUG_INFO=y ĬONFIG_MAGIC_SYSRQ=y ĬONFIG_FRAME_POINTER=y ĬONFIG_KGDB=y Īnd, in addition for KDB, under the same menu: CONFIG_KGDB_KDB=y CONFIG_KDB_KEYBOARD=yįor the discussion below, we assume that the kernel has been successfully configured, built (and works) for the R Pi.
#Kernel r4 n5 how to
This blog post is not intended to cover it all in gruesome detail rather, it gives you a flavor of how to setup and use these tools on the R Pi running a custom (yes, that’s right – your very own compiled-from-source) Linux kernel.įirst, configure the R Pi kerne l source tree with the “usual” (described earlier) configuration options for KGDB.
So: when you do have a kernel bug, how does one proceed? A little googling will quickly reveal some powerful Linux kernel debugging tools- often near the top of the list is KDB and KGDB. Yes, it runs Linux (the Raspbian distro for R Pi is particularly popular), and yes, Linux does run into trouble now and then, especially when we geeky types fiddle with kernel-level touch-me-not’s. The R Pi (that’s Raspberry Pi for those of you still not wakey-wakey) is a fun powerful embedded computer to play with.
– A good tutorial on building-from-scratch for the R Pi root filesystem and Linux kernel, using the excellent Buildroot tool,
– Using kgdb, kdb and the kernel debugger internals RXD (GPIO 15) TX-O board (directly opp the USB mini connector)) TXD (GPIO 14) RX-I (RX-I and TX-O pins are at the front of the FTDI My R Pi (Model B) attached to a FTDI FT232R USB-to-TTL breakout boardĪbove pic: My R Pi (Model B) attached to a FTDI FT232R USB-to-TTL breakout board. I’m using FTDI’s FT232R Breakout board it works very well indeed. I find a simple and efficient way to do this is to make use of the GPIO pins 14 (TXD) and 15 (RXD) on the board, connecting them to a simple FTDI
#Kernel r4 n5 serial
– the R Pi does not have a dedicated physical serial port we require one to get (and send) console I/O (so that we can see kernel printk’s and interact via the keyboard). – have a custom Linux kernel running on it (need to be able to modify kernel configuration and rebuild at will) – have an R Pi (I use the Rev B R Pi) with an SD card – have some familiarity with setting up and using KDB and KGDB (a bit of this is covered here, not all) also, see some useful Resources just below. – know something about Linux kernel programming, writing kernel module code, etc – know how to build a Linux kernel from source