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On Jun 16, 2013, at 3:14 AM, Owen Shepherd wrote:

> Coda Highland wrote:
>> Unless I'm wrong, ASLR isn't restricted to 48 bits. Virtual memory
>> allocation can use whatever addresses it wants.
> The hardware itself is physically limited to 48-bits.  Each page is 4kB, plus there are 4 layers of page tables, bringing the total up to 48 bits.
> The processors throw an exception on a memory access if bits 63-48 don't match bit 47.
> This is all baked into silicon

Amusingly, 64-bit ARM is 49-bit. Twice as good as amd64!

64-bit ARM also has a mode which ignores the high 8 bits of addresses. Sadly, NaNs are still then in the high part of memory.