Re: ASLR sometimes stops working on Vista with 1.7? [was: Re: Cygwin 1.7 release (was ...)]

["Yaakov (Cygwin/X)" <yselkowitz at users dot sourceforge dot net>]

On 05/06/2009 11:35, Corinna Vinschen wrote:
> Here's another thought:
>
> I examined the address layout of the perl process again, and it struck
> me as weird that the base addresses of all the DLLs which get dynamically
> loaded by perl are so near together.  It looks like the problem is
> actually tightened by the order in which the DLLs are rebased by rebaseall,
> and the order in which the DLLs are loaded into the running process.
> Some perl DLL (Dumper.dll?) allocates additional memory and that's right
> after it's own image.  That's where Cwd.dll is based to.  Cwd.dll gets
> rebased and ... poof.
>
> What I did then was to change the offset to rebaseall:
>
> ash$ rebaseall -o 0x20000   (default is 0x10000)
>
> Then I reinstalled /bin/cyggmp-3.dll and reran cygport.  This time
> it ran fine.  This is still w/o ASLR flags.
>
> In this configuration, I can reproduce running cygport successfully
> every time.

Alright, I tried a few combinations; finally "-b 0x61000000 -d -o 
0x20000" (IOW descending from cygwin1's base) got autotools (and KDE4, 
which was also suffering heavily from this) working again.  Mind you, 
that leaves my last dll at 0x189f0000, and I'm still not finished with 
KDE yet.

I'm sure more work is needed on this, but in the meantime this 
workaround seems to do the job.  Thanks!


Yaakov

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