Hi!
24-Июл-2005 18:16 [EMAIL PROTECTED] (Eric Auer) wrote to
[email protected]:
>> My question is, does any other software destroy important registers?
EA> A comment in the kernel source code tells that the "bloody fucking" (sic!)
EA> RTSND driver changes SI and DI during the driver strategy call. The
But, unlike RTSND, me may fix fd-emm386.
EA> required workaround eats 4 bytes of precious stack and 4 bytes of low RAM.
:) For stack, each additional byte may be critical. :(
EA> Note that I still recommend to change EXECRHM to preserve ES, as it is not
Why? Note: (most) C language compilers calling conventions assume, that
ES may be changed inside called functions safely, only SI/DI should be
preserved.
EA> clear to me why EXECRHM is assumed to be allowed to change that, which it
EA> does at the moment.
>> I think, this is bad direction: if some external program unexpectedly
>> modifies nondeclared registers/parts (unimportant, syncronously (exoplicit
>> call) or asynchronously (hardware interrupt)), then should be fixed external
>> program, not added extra code into kernel. Especially, saving registers eats
>> prceious stack, whereas fd-emm386 _may_ be fixed without big efforts.
EA> I agree that device drivers should not modify any register when you call
EA> them, but I admit that I do not remember WHERE I have read that device
EA> drivers MUST not modify any registers. In particular, fixing EMM386 would
EA> be pretty easy for those who have SY3PACK and all required compilers.
No. I say, that in servers (drivers, TSR, protected mode provider)
shouldn't be modified undeclared register/s (parts) - notwithstanding, if
this is syncronous call (program call/interrupt to server) or asyncronous
(through hardware interrupt at unpredicatble moments).
EA> Talking about HIMEM: please make the version number BCD as recommended in
EA> RBIL, as some programs do not display "3.0b" (binary) correctly as 3.11 ;-).
:) Agreed.
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