Re: Stack bias

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> Anyway, the main purpose of the bias is to have an odd stack pointer,
> so the kernel can very easily know if it's dealing with a 32bit or
> 64bit process in trap handlers, w/o even doing the full curlwp()
> dance to check the process flags.

Except it can't; that test can mistake a 64-bit process that's trashed
its %sp - or is using %o6 as a general-purpose register - for a 32-bit
process, probably leading to lossage like randomly destroying half of
each register.  (Destroying %fp - %i6 - is more serious, but leaf
routines often enough have no particular need for %sp but could use
another general-purpose register.)

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