Re: Pure 64 bootloaders

From: Kyle Moffett (mrmacman_g4_at_mac.com)
Date: 09/14/05

  • Next message: Dmitry Torokhov: "Re: [patch] hdaps driver update." 
    Date:	Wed, 14 Sep 2005 13:26:54 -0400
To: Lennart Sorensen <lsorense@csclub.uwaterloo.ca>

    On Sep 14, 2005, at 09:20:45, Lennart Sorensen wrote:
    > On Tue, Sep 13, 2005 at 11:44:55PM -0400, Kyle Moffett wrote:
    >
    >> PowerPC was designed 64-bit from the start too! It's just that the
    >> architecture design group also realized that there would be a demand
    >> for 32-bit CPUs, and so from the _64-bit_ system, they designed a 32-
    >> bit system whose entire instruction set would be forward-compatible
    >> to 64-bit systems when they came out. That's why 32-bit PowerPC
    >> machine code and 64-bit PowerPC machine code are completely identical
    >> except that 64-bit CPUs also have a few opcodes to process 64-bit
    >> data and a few extra kernel-mode registers.
    >
    > Hmm, so how does that fit with needing both 32 and 64bit libraries
    > on a
    > ppc system? It seems apple forgot the 64bit part of a library
    > recently
    > in a security fix, or is that something more to do with their os than
    > the cpu?

    Well, if you want to pass 64-bit pointer values to a library, the
    library needs to have functions that take 64-bit values and use 64-
    bit operations on them, just like all the other archs :-D. It also
    needs 32-bit compatibility functions for the old 32-bit-only
    programs. On the other
    hand, if you don't care about compatibility with 32-bit-pointer
    programs, you can omit functions that deal with 32-bit pointers and
    require everything to use 64-bit pointers. You still need stuff like
    atoi that uses 32-bit values, though, and 64-bit-only does have a
    performance penalty.

    Cheers,
    Kyle Moffett 

    --
There is no way to make Linux robust with unreliable memory  
subsystems, sorry.  It would be like trying to make a human more  
robust with an unreliable O2 supply. Memory just has to work.
   -- Andi Kleen
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