From:	Roman Suzi <nuser AT rsuzi DOT pgu DOT karelia DOT ru>
Newsgroups:	comp.os.msdos.djgpp
Subject:	General Protection Fault Interception vs. Stack checks
Date:	Mon, 03 Nov 97 17:39:53 +0300
Distribution:	world
Organization:	unknown
Message-ID:	<ADv8UNq4WL@rsuzi.pgu.karelia.ru>
Sender:	news-service AT sampo DOT karelia DOT ru
Reply-To:	nuser AT rsuzi DOT pgu DOT karelia DOT ru
Lines:	48
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hi!

It is now clear how to check free stack space:

Eli Zaretskii wrote:
>Here's one version of `_stackavail' function:
>
>static __inline__ int _stackavail(void)
>{
>  extern unsigned __djgpp_stack_limit;
>  unsigned sp;
>  __asm__ __volatile__ ("movl %%esp,%k0\n" : "=r" (sp) : );
>  return (int)(sp - __djgpp_stack_limit);
>}

Thank you! Its better than nothing.

Meanwhile I contacted a person who reported similar problem
(about mmap() )
as me and have not found solution to it yet.

As he stated, sometimes, stack-availability checks are inacceptable due to
their inefficiency and are trusted to the hardware.

HOWEVER:
My posting about Fighting Gen.Prot.Faults
was addressing the question is there any mechanism
in DJGPP to intercept GPEs, caused by stack overflow ?

It seems, there is not any...
Possibly, existing DPMIs are not permitting to
intercept GPF of stack frame.

I think, this GPF interception question could be important to people,
writing interpreters and stack-greedy real-time applications.
So, if someone can enlighten us on the topic,
you are welcome!


Roman.


--
 --               *                            --
--  Roman A. Suzi * Petrozavodsk Karelia Russia --
 --    http://sampo.karelia.ru/~rnd            --

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