Eric Lee / smarc-fsl-linux-kernel

03 Oct, 2009

1 commit

  • 211a64177   ieee1394: update URLs in debugging-via-ohci1394.txt ... Browse Code »

    Update URLs of the userspace tools to use ohci1394_dma=early for
    debugging.

    Seems the address ftp://ftp.suse.de/private/bk/firewire/tools/* is not
    very helpful. After a quick search, seems this was talked about:
    http://www.mail-archive.com/kgdb-bugreport@lists.sourceforge.net/msg02761.html
    (can't find the original thread).

    Signed-off-by: Justin P. Mattock
    Signed-off-by: Stefan Richter

    Justin P. Mattock
     

18 Apr, 2008

1 commit

20 Feb, 2008

1 commit

30 Jan, 2008

1 commit

  • f212ec4b7   x86: early boot debugging via FireWire (ohci1394_dma=early) ... Browse Code »

    This patch adds a new configuration option, which adds support for a new
    early_param which gets checked in arch/x86/kernel/setup_{32,64}.c:setup_arch()
    to decide wether OHCI-1394 FireWire controllers should be initialized and
    enabled for physical DMA access to allow remote debugging of early problems
    like issues ACPI or other subsystems which are executed very early.

    If the config option is not enabled, no code is changed, and if the boot
    paramenter is not given, no new code is executed, and independent of that,
    all new code is freed after boot, so the config option can be even enabled
    in standard, non-debug kernels.

    With specialized tools, it is then possible to get debugging information
    from machines which have no serial ports (notebooks) such as the printk
    buffer contents, or any data which can be referenced from global pointers,
    if it is stored below the 4GB limit and even memory dumps of of the physical
    RAM region below the 4GB limit can be taken without any cooperation from the
    CPU of the host, so the machine can be crashed early, it does not matter.

    In the extreme, even kernel debuggers can be accessed in this way. I wrote
    a small kgdb module and an accompanying gdb stub for FireWire which allows
    to gdb to talk to kgdb using remote remory reads and writes over FireWire.

    An version of the gdb stub fore FireWire is able to read all global data
    from a system which is running a a normal kernel without any kernel debugger,
    without any interruption or support of the system's CPU. That way, e.g. the
    task struct and so on can be read and even manipulated when the physical DMA
    access is granted.

    A HOWTO is included in this patch, in Documentation/debugging-via-ohci1394.txt
    and I've put a copy online at
    ftp://ftp.suse.de/private/bk/firewire/docs/debugging-via-ohci1394.txt

    It also has links to all the tools which are available to make use of it
    another copy of it is online at:
    ftp://ftp.suse.de/private/bk/firewire/kernel/ohci1394_dma_early-v2.diff

    Signed-Off-By: Bernhard Kaindl
    Tested-By: Thomas Renninger
    Signed-off-by: Ingo Molnar
    Signed-off-by: Thomas Gleixner

    Bernhard Kaindl