Date: Fri, 10 Jan 2020 11:22:14 +0100 From: Szabolcs Nagy <nsz@...t70.net> To: musl@...ts.openwall.com Cc: Patrick Oppenlander <patrick.oppenlander@...il.com> Subject: Re: another armv7-m exception handling problem * Rich Felker <dalias@...c.org> [2019-10-21 15:29:37 -0400]: > On Mon, Oct 21, 2019 at 09:08:57PM +0200, Szabolcs Nagy wrote: > > * 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. > > In 2.33.1, the offending code (creating the bad relative relocation) > is at line 11637. It's possible some earlier code path leading to it > is wrong, around line 11515 or so, but I think there just needs to be > an extra else path before this one that covers undefined/undefweak. fyi i have a patch now, hopefully will be included into binutils 2.34 https://sourceware.org/ml/binutils/2020-01/msg00096.html
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