Re: mmap not working?

Rik van Riel
2001-11-17T18:39:31Z

On Sat, 17 Nov 2001, Rogier Wolff wrote:

> The SGI manpage says:
>
> All implementations interpret an addr value of
> zero as granting the system complete freedom in selecting pa, subject to
> constraints described below. A non-zero value of addr is taken to be a
> suggestion of a process address near which the mapping should be placed.
^^^^^^^^^^

The key word here is "suggestion". There is absolutely no
requirement that the OS actually uses this address.

> which hints at a possible non-alignment. It also mentions that
> "offset" should be page-aligned, which I disagree with here:
> everything has been set up to "do the right thing" when the mapping is
> possible with an unaligned offset.

I don't know what MMU your machine has, but on most (if not
all) machines an mmap() is only possible when it's page-aligned.

regards,

Rik
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