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    SubjectRe: how to detect a 32 bit process on 64 bit kernel
    Michael S. Tsirkin wrote:

    > Hello!
    > Quoting r. Christoph Hellwig (hch@infradead.org) "Re: how to detect a 32 bit process on 64 bit kernel":
    >
    >>>If no - would not it make a sence to add e.g. a flag in the
    >>>task struct, to make it possible?
    >>
    >>The kernel code shouldn't know. If your driver needs this information
    >>something is seriously wrong with it.
    >
    >
    > A character driver I am working on gets passed a structure
    > from user space by implementing a write file operation.
    > The structure includes a pointer and so the format varies
    > between a 32 and 64 bit processes.

    The most portable way to do this is to have the first member of the
    structure be a 32-bit value containing the size of the structure. This
    can then be used to identify what the structure format is. This also
    has the advantage of future-proofing the interface (add a field? no
    problem, the new size can be checked for). Just be very careful that
    the size from userspace is not trusted (ie. only allow known sizes).

    --
    Brian Gerst
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