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Message-ID: <CAH9TF6MPzKVCDmctD1-Tugwjr--y3M9D4FrRTsQDbM+Dmd-v-w@mail.gmail.com>
Date: Sat, 23 Nov 2024 13:57:16 +0100
From: Alex Rønne Petersen <alex@...xrp.com>
To: Alexander Monakov <amonakov@...ras.ru>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] s390x: Mark __tls_get_addr hidden before invoking it.
On Sat, Nov 23, 2024 at 1:36 PM Alexander Monakov <amonakov@...ras.ru> wrote:
>
> On Sat, 23 Nov 2024, Alex Rønne Petersen wrote:
>
> > On Sat, Nov 23, 2024 at 9:30 AM Alexander Monakov <amonakov@...ras.ru> wrote:
> > >
> > > On Sat, 23 Nov 2024, Alex Rønne Petersen wrote:
> > >
> > > > Similar to what's done for __syscall_ret, __sigsetjmp_tail, etc. This fixes a
> > > > linker error when building musl libc.so with zig cc.
> > >
> > > Hm, on s390 __tls_get_addr is not used for TLS ABI, so it's fine that it ends up
> > > hidden in libc.so. Unusual.
> > >
> > > (linkers must take the most restrictive visibility from all mentions of a symbol)
> > >
> > > I'm curious, what kind of error with zig cc were you seeing?
> >
> > This:
> >
> > ld.lld: error: relocation R_390_PC32DBL cannot be used against symbol
> > '__tls_get_addr'; recompile with -fPIC
> > >>> defined in obj/src/thread/__tls_get_addr.lo
> > >>> referenced by __tls_get_offset.s:8 (src/thread/s390x/__tls_get_offset.s:8)
> > >>> obj/src/thread/s390x/__tls_get_offset.lo:(.text+0x10)
> >
> > (-fPIC is actually in use.)
> >
> > Presumably this could be fixed in lld, considering GNU ld seems fine
> > with it. But I figured that, since glibc also marks __tls_get_addr
> > hidden for s390x, musl should probably just do the same anyway.
>
> I see, thanks. Your commit message was confusing to me, because unlike
> __syscall_ret and the like, __tls_get_addr is not an internal helper,
> it may not have hidden visibility anywhere except s390. So it felt like
> the commit message was drawing a false parallel.
>
> I would love this to land with a clearer commit message, but that's up
> to Rich and yourself to sort out.
Yeah, I think that's fair. I wrote the commit message before I
actually investigated in detail how __tls_get_addr is supposed to be
handled for s390x.
Should I re-send the patch with an updated commit message, or how is
this usually handled?
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