PE stack trick not working on lowmem machines

[Marcus Meissner]

Hi,

On SuSE 8.2, i586 glibc, loader/wine-* crash due to the 256 MB static array
in main().

The test machine has just 64MB RAM and 200MB swap.

If I start decreasing the array it works, up to 201MB.

$ /lib/ld-linux.so.2 ./wine-kthread
./wine-kthread: error while loading shared libraries: ./wine-kthread: cannot map zero-fill pages: Cannot allocate memory
$

So ld.so really wants to get 20xMB memory but fails.

-> Not good on low memory machines.

(Not sure if we should fix it.)

Btw, why don't we use -Wa,--noexecstack ?

Ciao, Marcus

[Alexandre Julliard]

Marcus Meissner  writes:
> So ld.so really wants to get 20xMB memory but fails.
>
> -> Not good on low memory machines.

Hmmm I would have expected it to overcommit that memory. Do you have
memory limits set?
> Btw, why don't we use -Wa,--noexecstack ?

It doesn't help with prelink AFAICT.

[Mike Hearn]

On Mon, 2003-11-24 at 20:38, Alexandre Julliard wrote:
> > Btw, why don't we use -Wa,--noexecstack ?
>
> It doesn't help with prelink AFAICT.

Is it really too late to get some kind of hook into prelink to stop it
interfering with Wine? It seems daft that we need such a big hack when
surely a flag in the elf headers would work just as well with
co-operation from the rtld.

[Marcus Meissner]

On Mon, Nov 24, 2003 at 12:38:34PM -0800, WINE wrote:
> Marcus Meissner  writes:
> > So ld.so really wants to get 20xMB memory but fails.
> >
> > -> Not good on low memory machines.
>
> Hmmm I would have expected it to overcommit that memory. Do you have
> memory limits set?

No. But the SuSE 8.2 has a "overcommit" sysctl, which is default off.
In this case at least the SuSE kernel uses a heuristic on left over
memory to chek mmap()s. And it limits it at this amount of memory apparently.
If I do
    echo -n 1 >/proc/sys/vm/overcommit_memory
it works again.

Ciao, Marcus