From: "David O'Shea" <dcoshea@gmail.com>
To: linux-8086@vger.kernel.org
Subject: Re: Memory issues and USB support? (and OpenWatcom)
Date: Sun, 11 Jun 2017 23:39:02 +0930 [thread overview]
Message-ID: <CAN0DjM1brGUSys-e+gn3e2UKj2vhb=-CF1a5oMJMmLB+KS=2nw@mail.gmail.com> (raw)
Hi Alan, all,
On Tue, Jun 6, 2017 at 12:11 AM, Alan Cox <alan@llwyncelyn.cymru> wrote:
> The bigger limit is that
> for small mode you've only got 64K offsets from each segment register.
That kind of leads me to something else I wanted to ask about: I take
it the requirement to use small mode is because of the bcc compiler?
I saw various mentions of looking at using OpenWatcom in the past
(e.g. http://www.spinics.net/lists/linux-8086/msg00417.html), and I
didn't see these reach any showstoppers or anyone saying it was a
terrible idea, nor success. Is moving to OpenWatcom something that
would be welcome, so long as it was truly an improvement (and didn't
require performing compiles on DOS :) )?
> In the Linux 8086 case the big problem is the kernel stack for each
> process comes from that 64K.
On entry to the kernel, couldn't one change SS:SP to point to some
other memory area? It looks like the parameters to system calls are
in registers rather than on the stack. Is it just a case of not
having done this extra work of managing more bits of memory yet, or is
there an architectural limitation here?
Apologies if any of the above are FAQs!
>> As it is, with LIM EMS
>> 3.2, even if you can only map in a single 64KB page at a time, you
>> could at least do that for some of their memory. I guess you also get
>> some memory protection from this, right?
>
> Not a lot no. Most of this comes in with later processors.
I was kind of thinking that a process whose pages are in EMS are
unlikely to get corrupted by a process running off the end of an
array. I realise that I shouldn't have used the term "memory
protection" though!
Thanks,
David
next reply other threads:[~2017-06-11 14:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-11 14:09 David O'Shea [this message]
2017-06-11 14:54 ` Memory issues and USB support? (and OpenWatcom) Alan Cox
2017-06-12 4:05 ` David O'Shea
2017-06-14 1:23 ` Alan Cox
2017-06-15 10:18 ` David O'Shea
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