[x264-devel] x86: eliminate text relocation in asm

[Henrik Gramner]

On Wed, Mar 16, 2016 at 6:18 PM, Jean-Baptiste Kempf <jb at videolan.org> wrote:
> On 16 Mar, Henrik Gramner wrote :
>> The fact that some Google engineer on a whim decided to arbitrarily
>> break user space for no good reason by forbidding relocations is
>
> There are good reasons to do that, notably for security.
>
> See:
> https://blog.flameeyes.eu/2016/01/textrels-text-relocations-and-their-impact-on-hardening-techniques
> and
> https://wiki.gentoo.org/wiki/Hardened/Textrels_Guide
>
> Whether that is needed for Android is a different question though :)
>
> With my kindest regards,
>
> --
> Jean-Baptiste Kempf

I don't see why textrels would prevent W^X, what stops the OS from
flagging the memory as non-writable after performing relocations?

Also according to Google, "the VM needs the execmem SELinux capability
anyway", so that's a moot point since W^X isn't even used.