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Date: Mon, 21 Oct 2019 21:08:57 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: another armv7-m exception handling problem

* Rich Felker <dalias@...c.org> [2019-10-21 15:03:18 -0400]:
> On Mon, Oct 21, 2019 at 08:09:56PM +0200, Szabolcs Nagy wrote:
> > * Patrick Oppenlander <patrick.oppenlander@...il.com> [2019-10-21 15:43:40 +1100]:
> > > Not sure if this is a musl, gcc or ld bug.
> > > 
> > > Running gcc-8.3.0 musl 1.1.24 static pie.
> > 
> > providing binutils version number is useful if there is
> > a chance that it's an ld bug.
> > 
> > this seems to be
> > https://sourceware.org/bugzilla/show_bug.cgi?id=22269
> > 
> > which was supposed to be fixed by
> > https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=95b03e4ad68e7a90f5096b47df595636344b783a
> > 
> > but apperently there are still missing cases.
> > (it does not help that the ld test for this bug
> > greps for R_*_NONE dynrelocs but not R_*_RELATIVE
> > which i is just as bad for undef weak syms in pie)
> > i added a note to the bug.
> > 
> > if you add __attribute__((visibility("hidden")))
> > to the example given by Rich then it works, the
> > bug only affects static pie linking.
> 
> That's really weird. How does it end up having an outstanding
> *relative* relocation when it's not defined locally? I could
> understand having a bogus outstanding symbolic one, but relative makes
> no sense and suggests ld is doing something very wrong...

i'd guess it creates a relative reloc for every
got entry that stores some symbol's address
which is known to be local, which makes sense,
except for undefined weak symbols which should
have fixed 0 address.

and i'd guess there is some logic that special
cases local undef weak in pic so hidden works,
and that check should be extended to cover the
static pie case.

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