Messages in this thread | | | Date | Sat, 01 May 1999 03:05:51 -0700 | From | "H. Peter Anvin" <> | Subject | Re: 64bit port |
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David Miller wrote: > > All UltraSparc chips (to my knowledge) are effected by the second hw > bug, which can only be triggered if the user can execute code in the > top of low 2GB of the 64-bit address space (it involves doing a PC > relative call which over/under-flows the program counter across the > 64-bit top/bottom addresses, while doing an access into the VA space > hole in the delay slot, or something like this, I don't know the exact > trigger sequence yet). This is why Solaris-7 does not allow 64-bit > userspace to map anything in these areas in 64-bit mode, which as a > side-effect makes the medium-low code model close to useless. > > When Jakub and I get the 64-bit userland bootstrapped, I'll start > running crashme to learn what the exact instruction sequences are so > we have a chance at coding a more suitable workaround than what > Solaris has chosen. >
I don't know what you mean with "medium-low code model"; I guess if it was up to me I'd say to heck with it, and waste 1/4294967296 of the address space as a 4 GB "null pointer check region"...
I presume the only reason you want that is to run 32-bit code/64-bit data or something like that (shades of DOS.)
-hpa
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