Re: (XFree86) mmap of /proc/XXX/mem

Alexander Viro (viro@math.psu.edu)
Wed, 1 Dec 1999 21:50:53 -0500 (EST)


On Thu, 2 Dec 1999, Egbert Eich wrote:

> Yes, but how? We need a solution otherwise we won't be able to
> use the vm86 mode even on Intel. The emulator makes everything
> even slower.

Check dosemu. The _real_ problem with /proc/<pid>/mem is that it needs
very different behaviour in different parts of process address space. Just
aliasing every page and hoping that extra reference will save your day is
_very_ bad idea - behaviour of pages on swapout, etc. is determined by
vma, not by reference in page table. We _might_ go for /proc/<pid>/object/
a-la Slowlaris, and that might be made mmap'able, but that's a separate
story. And IMO an overkill.

Dosemu does aliasing in very similar situation. Check how it's done.

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