Subject: Re: Add a MAP_ALIGNED flag for mmap(2).
To: Andrew Brown <>
From: Matt Thomas <>
List: tech-kern
Date: 03/02/2003 21:33:09
At 08:22 PM 3/2/2003, Andrew Brown wrote:
> >+              if (flags & MAP_FIXED) {
> >+                      if ((*addr & (align-1)) != 0)
> >+                              return(EINVAL);
> >+                      align = 0;
>at some point today, something clicked in my head that said "this
>should not be arbitrarily disallowed.

It isn't disallowed.  It's just make sure that the bits you want
to be zero, are zero.

>right now, if you specify MAP_FIXED, all you have to do is make sure
>that specify a hint that's page aligned.  in the case of MAP_ALIGN,
>all you should have to do it make sure specify a hint that's aligned
>to the alignment you want.

Uh.  And why do you think the above code doesn't do that?

>0x60010000 should be fine as an aligned, fixed address, as long as
>don't specify an alignment that's greater than 64k.

Correct.  And that's what the above enfornces.

Matt Thomas               Internet:
3am Software Foundry      WWW URL:
Cupertino, CA             Disclaimer: I avow all knowledge of this message