Re: don't let mmap allocate down to zero

[William Lee Irwin III <wli@xxxxxxxxxxxxxx>]

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@xxxxxxxxxx>

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.


-- wli
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