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Re: [MiNT] kernel 1.15.10b fragmentation



On Tue, Jan 02, 2001 at 12:18:05PM +0100, Petr Stehlik wrote:
> > The main problem with that call is of course that it would not help at
> > all when the user doesn't run a MiNT kernel that already supports it.
> 
> I haven't read Draco's doc about MP friendly programming but I believe
> it's not that hard to make new applications MP compatible.

If your application only sends pointers to other applications: Not at
all, it's just a matter of using the correct memory allocation flags
(after checking that Mxalloc() accepts memory protection flags, the
recommend method is to check whether Sysconf(-1) returns anything but
ENOSYS).

If your application also receives pointers from other applications and
you want to be sure it doesn't get killed if another app sends a pointer
to private memory, things are a bit more tricky. Currently, you have to
install a signal handler for SIGBUS to catch memory violations and have
it react accordingly. Guido's proposal would allow doing this using a
simple kernel call, but of course that wouldn't help of the kernel in
use doesn't already support it. In the latter case, you'd either have to
implement the SIGBUS method as well, or risk your program crashing when
used with older versions of MiNT and an ill-designed application (like
ST-Guide) uses private memory for protocol communications.

> The main problem is IMHO in those old applications that do not have
> replacements yet and their source code is not available (ST-Guide has
> been recently named as one of those problematic but widely used
> programs). The proposed kernel call doesn't help them, does it?

Nope. But it helps to set the memory protection flags of such offending
programs to `readable' in most cases - sometimes you need `global',
depending on what protocol messages they use.


Ciao

Thomas


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Thomas Binder (Gryf @ IRCNet)  gryf@hrzpub.tu-darmstadt.de
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