Re: [patch] x86: fix ESP corruption CPU bug

From: Stas Sergeev
Date: Mon Mar 14 2005 - 15:29:14 EST


Brian Gerst wrote:
Can you tell me how the invisible high-word (invisible in VM-86, and
in real mode) could possibly harm something running in VM-86 or
read-mode ??? I don't even think it's a BUG. If the transition
into and out of VM-86 doesn't handle the fact that the high-word
of the stack hasn't been used in VM-86, then that piece of code
is bad (the SP isn't even the same stack, BTW).
Because even in 16-bit mode (real, vm86 or 16-bit protected) you can use 32-bit instructions, with an operand and/or address size override prefix.
And the real problem is when the pure
32bit code is starting to use the 16bit
stack for some strange reasons. Looks like
the common technique for the early dos4gw
-based apps...

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