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    SubjectRe: getting false SIGTRAP breakpoints in kernel i.e. kernel hung unless gdb remotely attached on x86 & cont is issued
    Hi Jason,
    The problem I believe is very reproducable.
    I'm doing nothing special with kgdb just using it to help me with
    3g modem driver development & my driver wasn't loaded when the problem occured.
    I have the following command in my /boot/grub/menu.lst kernel parameter to enable gdb.
    kgdboc=/dev/ttyS0,115200 maxcpus=1

    And when I do the steps mentioned when in a console I get a message waiting for gdb to attach
    I'm familiar with kgdb, have been using it for years & know enough to be sure this is undesired behaviour.

    Jason Wessel wrote:
    > Denis Joseph Barrow wrote:
    >> Hi ladies/gentlemen,
    >> The kernel I'm running gdb with is 2.6.27-rc4
    >> The false sigtrap is occuring in ia32_sysenter_target in arch/x86/kernel/entry_32.S:303
    >> when gdb is stepped from the user process as described below
    > Your example does not indicate how or why you setup kgdb. kgdb can be
    > compiled into the kernel, but it should not have any effect what so ever
    > unless it is configured for use because it will not register to receive
    > any of the breakpoint or single stepping traps.
    > Perhaps there is more to the description of your problem?
    > Jason.
    >> To reproduce
    >> compile kernel with kgdb support
    >> compile my randsleep program attached using the .mk script
    >> as root
    >> attach randsleep to an idle serial port e.g. /dev/ttyS0 by typing
    >> randsleep /dev/ttyS0
    >> from another bash shell type
    >> ps -aux | grep randsleep
    >> gdb ./randsleep
    >> attach <pid of randsleep>
    >> You should get messages from gdb like
    >> Attaching to program: /home/djbarrow/devel2/randsleep/randsleep, process 6397
    >> Reading symbols from /lib/tls/i686/cmov/
    >> Loaded symbols for /lib/tls/i686/cmov/
    >> Reading symbols from /lib/
    >> Loaded symbols for /lib/
    >> 0xb7fda430 in __kernel_vsyscall ()
    >> Now type step.
    >> The machine is now hung until gdb attaches remotely.

    best regards,
    D.J. Barrow

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