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Message-ID: <20260619001525.GQ27423@brightrain.aerifal.cx>
Date: Thu, 18 Jun 2026 20:15:25 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] or1k: fix local-exec tls with large alignment
On Fri, Jun 19, 2026 at 01:40:49AM +0200, Szabolcs Nagy wrote:
> * Rich Felker <dalias@...c.org> [2026-06-18 17:58:29 -0400]:
> > On Thu, Jun 18, 2026 at 09:12:56PM +0200, Szabolcs Nagy wrote:
> > > or1k uses an unusual variant of the TLS_ABOVE_TP layout:
> > >
> > > powerpc, mips, m68k:
> > > pthread | tls
> > > +----------+-----------------+--
> > > | |< tpoff >|
> > > self a = e = m tp
> > >
> > > arm, aarch64, sh:
> > > pthread < gap >| tls
> > > +----------+-------------+------
> > > | | |
> > > self a = e = tp m
> > >
> > > or1k:
> > > pthread < gap >| tls
> > > +----------+-------------+------
> > > | |< tpoff >|
> > > self a = e m = tp
> >
> > To be sure we understand this correctly, can you draw a diagram like
> > this for the wrong way we have the or1k layout now?
>
> i can resend the patch, but it's just:
No need, I just wanted to see it to make sure I understand what you
meant.
> or1k old:
> pthread | tls
> +----------+--------------------
> | |
> self a = e = m = tp
>
> or1k fixed:
> pthread < gap >| tls
> +----------+-------------+------
> | |< tpoff >|
> self a = e m = tp
OK, so it's essentially the tp being aligned to something nonzero mod
tls_align. That would be an alternate way to implement it (adding
support the the arch to declare the desired residue), though as long
as we can just do it with a GAP_ABOVE_TP, that seems ok.
But are you sure this is correct setting TPOFF_K to cancel the
GAP_ABOVE_TP? TPOFF_K affects all modules not just the main program. I
don't see how changing it doesn't break initial-exec accesses to TLS
in libraries.
Rich
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