The current Linux implementation of shmat() insists on SHMLBA alignment
even when shmflg & SHM_RND == 0. This is not consistent with the man pages
and the single UNIX spec, which require only a page-aligned address.

man page:

> If shmaddr isn’t NULL and SHM_RND is asserted  in  shmflg,  the  attach
> occurs at the address equal to shmaddr rounded down to the nearest mul-
> tiple of SHMLBA.  Otherwise shmaddr must be a page-aligned  address  at
> which the attach occurs.

This is not a problem for many platforms because SHMLBA == PAGE_SIZE. It's
also not a problem for 64 bit programs running on 64 bit platforms,
because arch_get_unmapped_area() typically guarantees SHMLBA alignment,
even when SHM_RND is not asserted.

However, for 32 bit compatiblity programs, an innocuous sequence such as:

p = shmat(id, 0, shmflg)  /* shmflag & SHM_RND == 0 */
/* p is page-aligned, but may not be SHMLBA aligned */
shmdt(p)
shmat(id, p, shmflg) == -EINVAL ??

can fail. The attached patch fixes the problem for ia64. Can other arch
maintainers confirm that it doesn't break anything for you ?

	-Arun