Re: don't let mmap allocate down to zero

[William Lee Irwin III <wli@holomorphy.com>]

On Wed, Jan 26, 2005 at 11:18:08AM -0500, Rik van Riel wrote:
>> With some programs the 2.6 kernel can end up allocating memory
>> at address zero, for a non-MAP_FIXED mmap call!  This causes
>> problems with some programs and is generally rude to do. This
>> simple patch fixes the problem in my tests.
>> Make sure that we don't allocate memory all the way down to zero,
>> so the NULL pointer never gets covered up with anonymous memory
>> and we don't end up violating the C standard.
>> Signed-off-by: Rik van Riel <riel@redhat.com>

On Wed, Jan 26, 2005 at 09:25:38AM -0800, William Lee Irwin III wrote:
> SHLIB_BASE does not appear to be present in 2.6.9; perhaps something
> else is going on.
> I think we are better off:
> 	(a) checking for hitting zero explicitly as opposed to
> 		enforcing a randomly-chosen lower limit for addresses
> 	(b) enforcing vma allocation above FIRST_USER_PGD_NR*PGDIR_SIZE,
> 		to which SHLIB_BASE bears no relation.

There's a long discussion here, in which no one appears to have noticed
that SHLIB_BASE does not exist in mainline. Is anyone else awake here?


-- wli