On Tue, 9 Jan 2001, Szabolcs Szakacsits wrote:
> 3) ask kernel developers to get rid of this "brk hits the fixed start
> address of mmapped areas" or the other way around complaints "mmapped
> area should start at lower address" limitation. E.g. Solaris does
> growing up heap, growing down mmap and fixed size stack at the top.
OK, despite knowing nothing of the kernel internals, I looked at doing
this myself :-)
I notice that TASK_UNMAPPED_BASE is only used in get_unmapped_area() in
mm/mmap.c, which is encouraging. Moreover, get_unmapped_area() is only
called once in mm/mmap.c and once in mm/mremap.c. So I think I would only
have to change get_unmapped_area() to get the desired effect, and this
change should not affect anything else.
If no address is specified, get_unmapped_area() currently chooses the
first (large enough, unused) region above TASK_UNMAPPED_BASE. I guess I
would just have to define something like TASK_UNMAPPED_CEILING and arrange
for get_unmapped_area() to allocate the first region below
TASK_UNMAPPED_CEILING. And I guess TASK_UNMAPPED_CEILING should equal
TASK_SIZE - maximum stack size. What is the maximum stack size? I
couldn't quite figure this out myself.
Am I missing something, or should choosing an appropriate value for
TASK_UNMAPPED_CEILING and changing get_unmapped_area() be sufficient?
Cheers,
Wayne
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This archive was generated by hypermail 2b29 : Mon Jan 15 2001 - 21:00:28 EST