Subject: Re: Add a MAP_ALIGNED flag for mmap(2).
To: Matt Thomas <>
From: Jason R Thorpe <>
List: tech-kern
Date: 02/28/2003 20:13:09
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.

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

        -- Jason R. Thorpe <>