Date: Wed, 21 Nov 2018 11:14:00 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Question regarding dynamic loader On Wed, Nov 21, 2018 at 09:25:50AM -0500, Rich Felker wrote: > On Wed, Nov 21, 2018 at 02:55:19PM +0100, Gernot Reisinger wrote: > > I wonder if calling constructor functions from crt code is an intended musl > > libc behavior. My personal - non expert - gut feeling considers glibc > > behavior "more correct". Is there a chance that musl will change this > > behavior? > > The musl behavior here is intentional. For FDPIC targets, it's > impossible to run *any* application code, in the main application or > shared libraries, before the main application's crt1 has executed, > because there are (essentially -- the equivalent of) self-relocations > performed at that stage that the dynamic linker can't see. If any > ctors were invoked directly by the dynamic linker before passing > control the the main application's entry point, they would run without > these relocations in the main application having been performed, > possibly resulting in runaway-wrong execution. For reference, this was initially done in commit c87a52103399135d2f57a91a8bcc749d8cb2ca83. Of course these code paths have changed significantly since then, but it gives some historical context. Rich
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