Fork issue on W10 WOW

Marco Atzeri
Mon Jul 9 11:37:00 GMT 2018

Am 7/9/2018 um 11:03 AM schrieb Corinna Vinschen:
> On Jul  8 18:03, Marco Atzeri wrote:
>> Am 30.06.2018 um 22:47 schrieb Ken Brown:
>>> On 6/30/2018 11:52 AM, Marco Atzeri wrote:
>>> I've never had this problem with my own 32bit installation on W10, but I
>>> just reproduced it by doing a new installation with your list of
>>> packages.  Have you tried just installing a minimal list of packages
>>> that you need for building the packages you maintain?
>> On a fresh minimal installation the problem can arise again
>> $ cygcheck -cd |wc -l
>> 245
>> as the first system shared libs are lower than the rebase
>> DefaultBaseAddress=0x070000000
>> 6F810000-6F811000 r--p  /cygdrive/c/Windows/System32/wow64.dll
>> 6F811000-6F844000 r-xp  /cygdrive/c/Windows/System32/wow64.dll
>> I think that rebase should consider different rebase
>> base address for W10.
>> Using DefaultBaseAddress=0x06F000000 seems fine
>> for the time being
> I can do that in the rebaseall script (I have a matching patch locally),
> but it looks like a race we can't win in the long run.  240 Megs less
> space is a lot given the number of DLLs in the distro.

I know, but until we try to support the 32bit version, we need a
way to handle it.

> To make matters worse, I just checked my local 32 bit W10 and it turns
> out that various Windows DLLs loaded by default (even in a simple tcsh)
> are at even lower addresses, e.g.
>    6B690000-6B6A3000 /mnt/c/Windows/System32/netapi32.dll

I suspect it is due the their 64bit base address

  $ objdump -x /cygdrive/c/Windows/System32/wow64.dll|grep ImageBase
ImageBase               000000006b000000

  $ objdump -x /cygdrive/c/Windows/System32/wow64win.dll |grep ImageBase
ImageBase               000000006b180000

It is like they put the 64bit System 32 over 0x6b000000 (maybe)
and the WoW64 over 0x70000000

But I guess that ALSR can play around that numbers.
There is still a way to disable ALSR?

> Corinna

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