[uae] Bye bye stack magic
- From: Richard Drummond <evilrich@xxxxxxxxxxxxxx>
- To: uae@xxxxxxxxxxxxx
- Date: Fri, 30 Sep 2005 14:23:43 -0400
Hi All
Been busy the last few days working on the replacement for UAE's stack magic
code (this stuff is currently used in E-UAE's 'new' bsdsocket emulation, for
instance). For those that don't know, the 'stack magic' code is a bunch of
evilness that lets UAE call 68k code by creating a new stack frame and
swapping between that and the main stack to allow the execution of 68k code
to resume.
The problem with this 'stack magic' scheme is that on most operating systems
it's generally not a good idea to manually create your own stack frame: you
have to make lots of assumptions which will may not always be valid (for
instance, the 32-bit OS X version won't currently work on a G5 machine);
also, it's totally non-portable, requiring some ABI and compiler-specific
assembly language voodoo as glue.
Anyway, I've cooked up a new scheme which is functionally similar but uses
threads instead of the manual creation and swapping of stacks - in essence,
the new stack is created by a new thread; a swap is effected by pausing one
thread and allowing the other to run.
I think I've finally sussed all the thread synchronization problems that this
solution creates, and I should have something for testing in a day or two.
The result of all this nonsense is that there will be a fully working
bsdsocket (network) emulation on all platforms - not just a select few whose
ABI we support with the stack magic stuff.
Cheers,
Rich
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