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Re: Preventing preemption of 'protected' symbols in GNU ld 2.26
- From: Cary Coutant <ccoutant at gmail dot com>
- To: Alan Modra <amodra at gmail dot com>
- Cc: Jeff Law <law at redhat dot com>, "H.J. Lu" <hjl dot tools at gmail dot com>, Joe Groff <jgroff at apple dot com>, Binutils <binutils at sourceware dot org>
- Date: Wed, 30 Mar 2016 17:45:54 -0700
- Subject: Re: Preventing preemption of 'protected' symbols in GNU ld 2.26
- Authentication-results: sourceware.org; auth=none
- References: <AB592ABD-D6D7-4D2F-A0D6-45738F168DC4 at apple dot com> <BEDD88C6-7F80-45DA-9021-10587244AAE5 at apple dot com> <CAMe9rOq6rmvH458nufzfZnnU_=_n1yysbLzERNy-LWvEmjmN1A at mail dot gmail dot com> <983472E1-A1BC-4970-9CF9-0138A6BAD16D at apple dot com> <CAMe9rOqTTwirymAY6ORp6D_GnCsMc_hYEdy1NbZpG6x5vQc5DQ at mail dot gmail dot com> <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>
> 2) Emit dynamic text relocations for non-PIC executable access to
> protected visibility variables defined in shared libraries. Makes
> executable pages with text relocations non-shared between processes.
> (But can be shared again after relocation if two processes have the
> same layout.)
Note that this is not always possible, depending on the addressing
range of the code emitted. For example, a pc-relative access may have
sufficient range to reach a variable copied into the executable's bss,
but not sufficient range to reach the original definition in a shared
library.
-cary