This is the mail archive of the
binutils@sourceware.org
mailing list for the binutils project.
Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Michael Matz <matz at suse dot de>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, Alan Modra <amodra at gmail dot com>, Jeff Law <law at redhat dot com>, Cary Coutant <ccoutant at gmail dot com>, Joe Groff <jgroff at apple dot com>, Binutils <binutils at sourceware dot org>, GCC <gcc at gcc dot gnu dot org>
- Date: Tue, 19 Apr 2016 12:10:58 -0700
- Subject: Re: Preventing preemption of 'protected' symbols in GNU ld 2.26 [aka should we revert the fix for 65248]
- Authentication-results: sourceware.org; auth=none
- References: <6AAD87D2-90F9-4AD7-A195-AC91B76EA6AE at apple dot com> <CAMe9rOqNcYnm1YocG-m7XNDE0g68YQAGe=ULP-G98gaatpxSeA at mail dot gmail dot com> <CAJimCsHfT=cfb4kZysB2W_1HFfOq==TpP=wa47XPGB41MHmGyQ at mail dot gmail dot com> <56FB5061 dot 9010303 at redhat dot com> <20160330143421 dot GM15812 at bubble dot grove dot modra dot org> <571161D0 dot 10601 at redhat dot com> <CAMe9rOpt2Fd6RLtjr10wCHz9PVsXxtO9a0yvMR_DeHt1OK0ieg at mail dot gmail dot com> <CAFiYyc2PFQdiUj=UPY8HLv+PjwVaNpcvDW6Skp8JC4DR56MkBg at mail dot gmail dot com> <20160418144911 dot GG15088 at bubble dot grove dot modra dot org> <CAMe9rOog=FJ2Si-mUqHYoOsHVwVFcZavT4X7wQdRjRhbDDWRvQ at mail dot gmail dot com> <20160419050805 dot GI15088 at bubble dot grove dot modra dot org> <CAFiYyc1NJD0LAW2Mxe+xdgizTd3j7A9gwHEzHJA3A+hWpDO+Ew at mail dot gmail dot com> <alpine dot LSU dot 2 dot 20 dot 1604191603210 dot 20277 at wotan dot suse dot de>
On Tue, Apr 19, 2016 at 7:06 AM, Michael Matz <matz@suse.de> wrote:
> Hi,
>
> On Tue, 19 Apr 2016, Richard Biener wrote:
>
>> So with all this it sounds that current protected visibility is just
>> broken and we should forgo with it, making it equal to default
>> visibility?
>
> Like how? You mean in GCC regarding protected as default visibility? No,
> that's just throwing out the baby with the water. We should make
> protected do what it was intended to do and accept that not all invariants
> that are true for default visible symbols are also true for protected
> symbols, possibly by ...
>
>> At least I couldn't decipher a solution that solves all of the issues
>> with protected visibility apart from trying to error at link-time (or
>> runtime?) for the cases that are tricky (impossible?) to solve.
>
Protected visibility is a useful feature. But as it stands today,
it is pretty much useless on x86 as seen in ld and ld.so. We
have known this defect for a long time, almost from day 1. To
make it truly useful, we need to clearly spell out how and when
it can be used. We should enforce its limitation in compiler,
ld and ld.so so that there is no surprise, either for correctness or
performance, at run-time.
--
H.J.