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Message-ID: <20250817031120.GW1827@brightrain.aerifal.cx>
Date: Sat, 16 Aug 2025 23:11:21 -0400
From: Rich Felker <dalias@...c.org>
To: Alex Rønne Petersen <alex@...xrp.com>
Cc: musl@...ts.openwall.com
Subject: Re: Re: [PATCH] s390x: manually inline __tls_get_addr in
__tls_get_offset
On Sat, Aug 16, 2025 at 07:37:58PM +0200, Alex Rønne Petersen wrote:
> On Fri, Jan 24, 2025, at 06:12, Alex Rønne Petersen wrote:
> > Calling __tls_get_addr with brasl is not valid since it's a global symbol; doing
> > so results in an R_390_PC32DBL relocation error from lld. We could fix this by
> > marking __tls_get_addr hidden since it is not part of the s390x ABI, or by using
> > a different instruction. However, given its simplicity, it makes more sense to
> > just manually inline it into __tls_get_offset for performance.
> >
> > The patch has been tested by applying to Zig's bundled musl copy and running the
> > full Zig test suite under qemu-s390x.
> > ---
> > src/thread/s390x/__tls_get_offset.s | 20 ++++++++++----------
> > 1 file changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/src/thread/s390x/__tls_get_offset.s
> > b/src/thread/s390x/__tls_get_offset.s
> > index 8ee92de8..405f118b 100644
> > --- a/src/thread/s390x/__tls_get_offset.s
> > +++ b/src/thread/s390x/__tls_get_offset.s
> > @@ -1,17 +1,17 @@
> > .global __tls_get_offset
> > .type __tls_get_offset,%function
> > __tls_get_offset:
> > - stmg %r14, %r15, 112(%r15)
> > - aghi %r15, -160
> > + ear %r0, %a0
> > + sllg %r0, %r0, 32
> > + ear %r0, %a1
> >
> > - la %r2, 0(%r2, %r12)
> > - brasl %r14, __tls_get_addr
> > + la %r1, 0(%r2, %r12)
> >
> > - ear %r1, %a0
> > - sllg %r1, %r1, 32
> > - ear %r1, %a1
> > + lg %r3, 0(%r1)
> > + sllg %r4, %r3, 3
> > + lg %r5, 8(%r0)
> > + lg %r2, 0(%r4, %r5)
> > + ag %r2, 8(%r1)
> > + sgr %r2, %r0
> >
> > - sgr %r2, %r1
> > -
> > - lmg %r14, %r15, 272(%r15)
> > br %r14
> > --
> > 2.43.0
>
> Friendly ping.
This was already merged as commit 6af4f25b899e89e4b91f8c197ae5a6ce04bcce7b.
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