Re: [ITA] _autorebase

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Dec 15 18:20, Achim Gratz wrote:
> Corinna Vinschen writes:
> > The change is required.  The base address 0x4:00000000 is a convention
> > which has been introduced to get reliable memory layout on x86_64.  All
> > of Cygwin's memory allocations, be it thread stack, executable and DLL
> > base addresses, heap address, or mmap's with NULL addresses, are chosen
> > so as not to collide with memory allocations chosen by the OS.  The OS
> > utilizes the lower 2GB 32 bit address space and the upper 0xff0:00000000
> > address space pretty much exclusively, and leaves everything in between
> > for the application.  Thus we developed the following convention, which
> > should be followed by every tool in the distro:
> >
> >   0x000:00000000 - 0x000:7fffffff    Reserved for OS
> >   0x000:80000000 - 0x000:ffffffff    POSIX threads
> >   0x001:00000000 - 0x001:7fffffff    Process image
> >   0x001:80000000 - 0x001:ffffffff    Cygwin DLL w/ all shared data
> >   0x002:00000000 - 0x003:ffffffff    8 Gigs for rebased DLLs
> >   0x004:00000000 - 0x005:ffffffff    8 Gigs for non-rebased DLLs
> >   0x006:00000000 - 0x6ff:ffffffff    Heap bottom-up, mmaps top-down
> >   0x700:00000000 - 0x7ff:ffffffff    Reserved for OS
> >
> > This was discussed and documented multiple times during the development
> > of the 64 bit version.  Please let's stick to that.
> 
> I've missed it at the time or didn't remember any of it.  In any case
> it's implemented exactly like that in rebaselst anyway.
> 
> >> I'll have to see if I can dig out my notes from that time, but I think
> >> it was both the ASLR and the TSAware flag that were creating problems
> >> with some libraries
> >
> > TS aware?  To the contrary.  Don't remove it!
> 
> We're not talking about executables here, see my other reply.

Sorry, missed that.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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