Xen devel - Aug 2008 - mini-os: sbrk() doesn''t allocate pages?

Hi,

I''m wondering how the mini-os heap allocater work.  The sbrk() function
in mm.c seems to *not* allocate pages for the heap.  Instead it uses the
zero page and maps it into the heap space when a new page is needed ...

I can''t believe is is supposed to work that way.  Is that a bug?  Did I
miss some logic somewhere in the code?

wondering,
  Gerd

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http://kraxel.fedorapeople.org/xenner/

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Gerd Hoffmann wrote:
>   Hi,
> 
> I''m wondering how the mini-os heap allocater work.  The sbrk()
function
> in mm.c seems to *not* allocate pages for the heap.  Instead it uses the
> zero page and maps it into the heap space when a new page is needed ...
> 
> I can''t believe is is supposed to work that way.  Is that a bug? 
Did I
> miss some logic somewhere in the code?
Oh, cow in the pagefault handler, that is the missing bit ...

cheers,
  Gerd


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Gerd Hoffmann, le Thu 14 Aug 2008 10:04:31 +0200, a écrit
:
> I can''t believe is is supposed to work that way.
That''s how it usually works in unix environments :)

Samuel

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