Subject: Re: Add a MAP_ALIGNED flag for mmap(2).
To: Jason R Thorpe <>
From: Matt Thomas <>
List: tech-kern
Date: 02/28/2003 21:16:46
At 08:13 PM 2/28/2003, Jason R Thorpe wrote:
>On Fri, Feb 28, 2003 at 06:01:47PM -0800, Matt Thomas wrote:
>  > Currently, ld.elf_so doesn't honor the alignment specified in a
>  > ELF file's psections.  This is due to the lack of ability to request
>  > an aligned block of addresses from mmap(2).  I propose we add a
>  > MAP_ALIGNED flag which would mean that the addr argument to mmap(2)
>  > would be the required alignment of the block.  Supplying both
>  > MAP_ALIGNED|MAP_FIXED would cause an error EINVAL to be returned.
>  >
>  > Any thought on this proposal?
>Sounds good.  I'm a little concerned that it means you can't pass a
>"please map it in this general neighborhood of the address space", but
>I definitely want the ability to specify alignment.

Define general area.  1MB? 16MB? 128MB?

>One question -- what happens if mmap can't satisfy the alignment
>contraint?  Is it just a hint or a strict requirement?

I'd say it's a strict requirement like MAP_FIXED it.

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