Re: [PATCH] remove sys_security

From: Andi Kleen (akat_private)
Date: Fri Oct 18 2002 - 02:25:02 PDT

  • Next message: David Wagner: "Re: [PATCH] remove sys_security"

    Crispin Cowan <crispinat_private> writes:
    > Could you elaborate on why this is a sign of trouble, design wise?
    David refers to the 32bit emulation issues. Some ports have a 64bit
    kernel, but support 64bit and 32bit userland (e.g. ia64 or x86-64). 
    Some ports even only have 32bit userland but 64bit kernel (like sparc64 or 
    The 32bit and the 64bit worlds have different data types. Structure
    layout are different. To handle this the kernel has an emulation
    layer that converts the arguments of ioctls and system calls between 
    32bit and 64bit.
    This emulation layer sits at the 'edge' of the kernel. For example
    to convert an ioctl it first figures out the ioctl, converts it
    then reissues the same ioctl internally with 64bit arguments. When
    the ioctl returns outgoing arguments are converted too as needed.
    For this to work all data structures need to be transparent.
    The emulation layer needs to have a way to figure out what and
    how to convert without looking at internal state in the kernel.
    Otherwise it cannot do its job. 
    Without working emulation sparc64 won't work and David will be unhappy.
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