Arkady V.Belousov wrote:
...
+ cmp word [_OemHook21], -1
+ je no_oemhndlr
+ cmp word [_OemHook21+2], -1
+ je no_oemhndlr
This is "if (FP_OFF (OemHook21) != -1 && FP_SEG (OemHook21) != -1)",
which is not equal to "if (OemHook21 != -1)" _and_ prevents OemHook21 point
to HMA. I suggest, check only for offset is enough. (And in this case you
may restore DS right before JE.)
sounds like a reasonble solution as I doubt anyone really would set this
to XXXX:FFFF for a valid pointer.
+ pop dx
+ pop ds
+ jmp far [ds:_OemHook21] ; invoke OEM handler (no return)
Looks like bug: if before "ds=cs:_DGROUP_" DS doesn't contains segment
of _OemHook21, then it willn't contain it after POP DS (and JMP then tries
to get jump address from wrong point). Else, if DS contains segment of
_OemHook21 before this code, then why MOV DS above?
...
I agree there is a bug here, I originally coded this differently (copied
address to a variable in code segment which I believe a comments still
has remnants of) and then simplified it at some point (which introduced
the bug). I have a fix locally (just need to compile and test).
Jeremy
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