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    SubjectRe: TCP LAST-ACK state broken in 2.4.17-pre2 [NEW DATA]
    At 12:28 PM 12/18/2001 -0800, David S. Miller wrote:
    >Unaligned kernel loads and stores must be properly handled by the
    >platform code, and on ARM chips where that is possible it is.

    I don't know what arch you're using, but I work with ARM7TDMI, which has a
    behavior I believe can be found documented in some obscure .pdf from arm.com:

    Unaligned accesses wrap.

    If you have this:

    [mem.] 00 01 02 03 04 05 06 07
    [data] 00 11 22 33 44 55 66 77

    in little-endian mode,

    *(int*)0x00 == 0x33221100
    *(int*)0x01 == 0x00332211
    *(int*)0x02 == 0x11003322
    *(int*)0x03 == 0x22110033
    *(int*)0x04 == 0x77665544

    At least, that's how ARM's docs seem to describe it. I work with this cpu
    embedded in a microcontroller (AT91M40800), and these values result:

    *(int*)0x00 == 0x33221100
    *(int*)0x01 == 0x33221100
    *(int*)0x02 == 0x33221100
    *(int*)0x03 == 0x33221100
    *(int*)0x04 == 0x77665544

    An unaligned access to an assembly-declared variable caused me much grief
    once, overwriting the task scheduler's ready-to-run list under certain
    conditions...

    The moral of the story:
    RISC cpus abhor unaligned accesses.


    --
    Stevie-O

    Real programmers use COPY CON PROGRAM.EXE

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