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    SubjectRe: [2.6.27] overlapping early reservations [was: early exception - lockdep related?]
    On Sat, Sep 6, 2008 at 4:51 PM, Ingo Molnar <mingo@elte.hu> wrote:
    > * Luca Tettamanti <kronos.it@gmail.com> wrote:
    >
    >> On Fri, Sep 5, 2008 at 10:18 PM, H. Peter Anvin <hpa@kernel.org> wrote:
    >> > Peter Zijlstra wrote:
    >> >>
    >> >> On Fri, 2008-09-05 at 21:17 +0200, Luca Tettamanti wrote:
    >> >>>
    >> >>> On Thu, Sep 4, 2008 at 10:51 PM, Luca Tettamanti <kronos.it@gmail.com>
    >> >>> wrote:
    >> >>>>
    >> >>>> On Thu, Sep 4, 2008 at 4:25 PM, Peter Zijlstra <peterz@infradead.org>
    >> >>>> wrote:
    >> >>>>>
    >> >>>>> Sadly your config just boots, albeit not to userspace due to missing
    >> >>>>> drivers.
    >> >>>>
    >> >>>> Yes, I managed to boot it with qemu... I tried kgdb - without luck -
    >> >>>> kernel dies too early.
    >> >>>> I also managed to get a stack trace :D
    >> >>>>
    >> >>>> http://img151.imageshack.us/my.php?image=tracedm1.jpg
    >> >>>>
    >> >>>> It seems that lockdep is an innocent bystander... the kernel died with
    >> >>>> panic() in __reserve_early, and then took another exception while
    >> >>>> printing the panic (I guess).
    >> >>>> Will add further debug stuff to see wtf is going on.
    >> >>>
    >> >>> Hum, kernel says:
    >> >>>
    >> >>> http://img177.imageshack.us/my.php?image=overlappingus2.jpg
    >> >>>
    >> >>> Overlapping early reservations b98000-eff266 RAMDISK to 200000-d09cf7
    >> >>> TEXT DATA BSS
    >> >>>
    >> >>> It would appear that the initramfs is overlapping the kernel itself,
    >> >>> is the boot loader (LILO) doing something stupid?
    >> >>
    >> >> Suppose it is, lets ask hpa..
    >> >>
    >> >
    >> > It definitely looks like it.
    >>
    >> Is there anything that the kernel could to do confuse lilo? The issue
    >> started appearing with 2.6.27 and the outcome of the boot process
    >> varies between versions and seems sensitive to configuration changes
    >> (though a "bad" kernel consistently fails).
    >
    > good question. Does your successful 2.6.26 bootup actually _depend_ on
    > the initrd? Or does it perhaps have enough built-in drivers that make it
    > boot just fine?

    The image is mostly modular (e.g. ahci drivers + LVM + fs are on the
    ramdisk), see:
    http://marc.info/?l=linux-kernel&m=122046971607455&q=p3

    > or perhaps something made your v2.6.27 bzImage larger so that the
    > overlap happens - while it didnt before.

    The compressed image (bzImage) is roughly the same size as older
    kernels (2MB), the uncompressed vmlinux is slightly bigger, but not
    much (~100k)

    452K ./mm/built-in.o
    100K ./ipc/built-in.o
    8.0K ./security/built-in.o
    3.0M ./drivers/built-in.o
    4.0K ./usr/built-in.o
    216K ./block/built-in.o
    96K ./init/built-in.o
    292K ./lib/built-in.o
    1.3M ./net/built-in.o
    16K ./crypto/built-in.o
    1.1M ./kernel/built-in.o
    1.3M ./fs/built-in.o
    4.0K ./sound/built-in.o

    Luca


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