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Subject: Re: memory protection

Author: Scott Gasch

Date: 11:49:57 01/10/02

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Hi David,

[snip]
>Windows now usually catches pointer-out-of-bounds errors, but in windows, you do
>get writable access to small shared areas with the kernel.  In linux, you don't.

I can't comment on linux.  I also can't comment on win 9x/ME.  But this
statement about usermode applications being able to write in kernel memory is
absolutely untrue.

> Also, in windows, you can leak references to DLL's which then get held in RAM.

I don't fully understand this statement.  Are you saying that a usermode
application can load a DLL, forget to free it, and thus "lock" the DLL in memory
somehow?  That's true within the lifetime of that process.  But when the process
that forgot to unload the DLL terminates the OS reclaims its virtual address
space and thus "unloads" the DLL for it at that point.

>You can also screw up shared in-process DLL's.  Generally, those sorts of things
>are much harder in linux, or not possible.

I don't know what this means.

>I dual-boot NT and linux, and linux has crashed once on me, but i have to
>restart windows every few days or else it will crash for sure ( it does crash if>i forget to reboot ).

If you are running 2k or XP and you are seeing crashes once a week I would be
willing to bet that the cause is a bad device driver.  Bugs in the NT kernel at
this point do exist but they are very few and far between.  In my experience the
only difference between linux and windows in terms of stability now is the
quality of the driver code running on each.  It seems like the calibre of the
driver writer on linux is higher than the calibre of the driver writer on
windows for whatever reason.  But put a bad driver on either one and there goes
the system.  I try to stay with "signed" drivers (though this is hard to do
sometimes).

Scott

>
>dave



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