Mailinglist Archive: opensuse-buildservice (124 mails)

[Marcus Meissner <meissner@xxxxxxx>]

Hi Werner,

We do not have exec shield, but we might have other methods.

They are however not just enabled on AARCH64, you would see
similar issues on all architectures.

randomize_va_space we have, but it is effective for this issue
only if you build with PIE support enabled.

I think this specific issue is aarch64 architecture specific
and not related to kernel security features.

Ciao, Marcus
On Fri, Nov 11, 2016 at 08:53:11AM +0100, Dr. Werner Fink wrote:
> Hi,
>
> just seen such build messages on aarch64 for GNU Emacs:
>
> [ 1604s] **************************************************
> [ 1604s] Warning: Your system has a gap between BSS and the
> [ 1604s] heap (418602288 bytes).  This usually means that exec-shield[ 
> 1519.794139] pgd = ffff8001f2320000
> [ 1604s]
> [ 1604s] [ 1519.828659] [00949000] *pgd=0000000232181003, 
> *pud=000000022ec05003or something similar is in effect.  The dump may, 
> *pmd=00000002330f4003, *pte=0000000000000000
> [ 1604s]
> [ 1604s] fail because of this.  See the section about
> [ 1604s] exec-shield in etc/PROBLEMS for more information.
>
> and indeed on emacs-25.1/etc/PROBLEMS I read
>
> | Another issue is that in Red Hat Linux kernels, Exec-shield is enabled by
> | default, and this creates a different memory layout.  Emacs should
> | handle this at build time, but if this fails the following
> | instructions may be useful.  Exec-shield is enabled on your system if
> |
> |    cat /proc/sys/kernel/exec-shield
> |
> |prints a nonzero value.  You can temporarily disable it as follows:
> |
> |    echo 0 > /proc/sys/kernel/exec-shield
>
> similar for randomize_va_space:
>
> | To work around the ASLR problem in either an older or a newer kernel,
> | you can temporarily disable the feature while building Emacs.  On
> | GNU/Linux you can do so using the following command (as root).
> | 
> |     echo 0 > /proc/sys/kernel/randomize_va_space
> | 
> | You can re-enable the feature when you are done, by echoing the
> | original value back to the file.
> | 
> | Alternatively, you can try using the 'setarch' command when building
> | temacs like this, where -R disables address space randomization:
> | 
> |     setarch $(uname -m) -R make
>
> That is if we support exec-shield and/or randomize_va_space I'd like to
> be able to disable this in the build environment for GNU emacs as well as
> e.g. for clisp and maybe other packages.
>
> Werner
>
> -- 
>   "Having a smoking section in a restaurant is like having
>           a peeing section in a swimming pool." -- Edward Burr



-- 
Marcus Meissner,SUSE LINUX GmbH; Maxfeldstrasse 5; D-90409 Nuernberg; Zi. 
3.1-33,+49-911-740 53-432,,serv=loki,mail=wotan,type=real <meissner@xxxxxxx>
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