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Null pointers, one month later

Null pointers, one month later

Posted Aug 18, 2009 18:41 UTC (Tue) by drag (subscriber, #31333)
In reply to: Null pointers, one month later by patrick_g
Parent article: Null pointers, one month later

I think that DosBox does also.

Is this something that programmers of emulation machines (yes I know Wine isn't emulation, but in this case it seems want to do emulation-ish things?) typically want to be able to do?

Would it make sense for the kernel to simply lie? Make it so that address zero from the applications VM perspective isn't really address zero from the kernel's or machines's perspective?

(I am struggling to understand everything going on here. It seems like it wouldn't be difficult to do.. I always understood the point to having virtual memory is so that applications can abritrarially get their memory mapped to any section of memory.)

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Null pointers, one month later

Posted Aug 18, 2009 19:56 UTC (Tue) by taviso (subscriber, #34037) [Link]

The reason they want to do this is to use an intel hardware feature called v8086 mode, which maps the segmented real address space onto the first megabyte of the linear address space.

You could fake it, but then you wouldn't be using the "hardware acclerated" emulation that makes things like dosemu very fast despite being a relatively complex feat.

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