pmap of amd64

Matthew Dillon dillon at
Sat Oct 13 16:30:36 PDT 2007

:On Fri, Oct 12, 2007 at 07:54:16PM -0700, Matthew Dillon wrote:
:>     (1) We can map a page containing the address of the per-cpu globaldata
:>         structure and use %fs in the trap code:
:>         movq	$SOME_FIXED_CONSTANT_ADDRESS,%fs
:You don't have to play such games on AMD64 -- the swapgs instruction is
:normally used by traps and system calls to load a well-defined address
:base for that. Note that gs is expected to be used for, but that is a
:minor detail.

    I don't think we can use swapgs.  The problem with swapgs is that it's
    a swap, not a load, which means it can only be used at the syscall
    interface and can't be used at the interrupt or exception interface.

					Matthew Dillon 
					<dillon at>

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