On Mon, Apr 23, 2012 at 05:58:23PM +0200, Corinna Vinschen wrote: >On Apr 23 11:44, Christopher Faylor wrote: >> On Mon, Apr 23, 2012 at 04:51:06PM +0200, Corinna Vinschen wrote: >> >On Apr 23 14:23, James Johnston wrote: >> >> Perhaps I did not make it clear enough, but these issues still exist as >> >> far >> >> as I can tell. I have clean Windows 7 and Windows XP virtual machines, >> >> and >> >> a clean install of Cygwin that was updated at the time I sent my original >> >> message. Both issues I described still exist. This is why I wrote the >> >> message. If the issues weren't existing on an up-to-date Cygwin >> >> installation, I would not write to this mailing list and waste anyone's >> >> time >> >> - I am usually not that dumb! >> >> >> >> Just this morning, I turned on my Cygwin installation in the Windows 7 VM. >> >> This time, cygreadline7.dll decided to relocate to 0x70030000 - different >> >> from the original location I mentioned in my original e-mail. This DLL is >> >> not locating itself in a stable location. And there are still system DLLs >> >> located very close to the Cygwin DLLs. >> >> >> >> If having Windows randomly rebase cygreadline7.dll in a child process via >> >> ASLR is not a problem, I'd simply be interested to know why. I thought >> >> *any* Cygwin DLL relocating itself would cause fork to fail. >> > >> >Yes, it is a problem in the first place if DLLs have the dynamicbase >> >flag set, because, obviously, it undermines what rebaseall is doing. >> >It's not a problem if the new address it gets rebased to doesn't collide >> >with any other used DLL since ASLR on Windows only shuffles ASLR-enabled >> >DLL addresses when a DLL is loaded by an application for the first time. >> >Afterwards, it will use the new address for that DLL until reboot. >> >So, yes, we should make sure that the ASLR flag is not used for Cygwin >> >DLLs. >> >> Is this something that rebase could turn off when it touches a DLL? > >In theory that's the job of peflags, not of rebase.
Sure, peflags should be able to unset/set it but it doesn't seem to ever make sense for a dll that rebase has touched so... >But probably we can safely assume that the Cygwin distro DLLs should >not have set the dynamicbase flag and the rebaseall script could call >rebase with an extra flag which automatically removes the dynamicbase >flag from all rebased DLLs. I don't see a real need for an extra rebase flag, unless it is turn off the "remove dynamicbase behavior" but it's no big deal. cgf -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple