Re: difference between 32 bit and 64 bit .so

[Mike Frysinger <vapier at gentoo dot org>]

On Friday, July 23, 2010 06:33:10 Jakub Jelinek wrote:
> On Fri, Jul 23, 2010 at 06:26:19AM -0400, Mike Frysinger wrote:
> > On Friday, July 23, 2010 01:59:04 Alan Modra wrote:
> > > It would be better to wonder why we still support non-PIC libraries on
> > > 32-bit x86.
> > 
> > because the performance penalty is larger than many people are willing to
> > accept.  there certainly are real world applications where larger memory
> > footprint (due to textrels) are completely worth the speed gain.
> 
> It isn't just larger memory footprint though (and longer startup), it is
> also bad for security reasons, because you need to allow execution of code
> from pages that have been writable by the process.  And, that is, IMNSHO,
> never worth the speed gain.

for many people, the security aspect is irrelevant.  if the process has the 
ability to change the protection on its pages, the fact that the ldso made 
them writable long enough to process textrels isnt terribly relevant.  that 
vector is always available for exploitation.

> Just use x86-64 instead of x86 if speed is a problem.

sure, i'll let the people running proven hardware know that they need to 
"upgrade" all of it to address issues they could care less about
-mike

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