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Date: Sun, 28 Feb 2021 15:34:38 +0100
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Subject: Re: cygwin + binutils 2.36 + ASLR/dynamicbase defaults
To: ASSI <Stromeko AT nexgo DOT de>
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From: Christoph Reiter via Cygwin <cygwin AT cygwin DOT com>
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On Sun, Feb 28, 2021 at 3:22 PM ASSI <Stromeko AT nexgo DOT de> wrote:
>
> Christoph Reiter via Cygwin writes:
> > MSYS2 builds all packages with ASLR since 6 months, so things look
> > good.
>
> That doesn't tell you all that much since you will have to wait for some
> unfavorable address space layout constellation to appear for the problem
> to announce itself and then you need someone to recognize the reason and
> report it back to you.  I tend to see this only on 32bit on my
> development machine where I have a large amount of dependencies
> installed.  After a reboot the problem will move somewhere else, which
> means that you will need to find another reproducer.

To clarify: I was referring to non-cygwin targets. I had assumed you
meant that by "cross compilation toolchain".

> > We've added a patch that allows reverting the base address if needed:
> > https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-binutils/2001-ld-option-to-move-default-bases-under-4GB.patch
>
> In other words, that should be the default then since you can't know if
> it works otherwise.  Also, I really don't think we should need to change
> all toolchains to use these options just in order to produce working
> executables.  If "safer" means "it doesn't work", then there are clearly
> easier ways to get there.

We've only needed this to to work around linker errors, so it's pretty
clear when it is needed as the build will fail.

Anyway, maybe the linked patches can be helpful to you.

regards
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