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Date:      Fri, 19 Feb 2021 00:00:27 +0000
From:      Jessica Clarke <jrtc27@freebsd.org>
To:        Brandon Bergren <bdragon@FreeBSD.org>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, John Baldwin <jhb@freebsd.org>, src-committers <src-committers@freebsd.org>, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org
Subject:   Re: git: 24fd63e0970f - main - mips: Don't set __NO_TLS to disable some uses of TLS.
Message-ID:  <3045F222-DBAC-463C-B429-075B2CFB115A@freebsd.org>
In-Reply-To: <ce964b75-4a11-4b5e-b47e-43a384da047f@www.fastmail.com>
References:  <202102180035.11I0ZnL3070354@gitrepo.freebsd.org> <9687575c-dd7c-1496-850b-2018f4bca3da@FreeBSD.org> <YC7TcMtrg8r7eAuL@kib.kiev.ua> <DBFAB331-737A-44E0-BBAA-65AF2C870AA9@freebsd.org> <ce964b75-4a11-4b5e-b47e-43a384da047f@www.fastmail.com>

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On 18 Feb 2021, at 23:57, Brandon Bergren <bdragon@FreeBSD.org> wrote:
> On Thu, Feb 18, 2021, at 3:07 PM, Jessica Clarke wrote:
>>> But, I wonder, what does CALL_ELF mean?  Is it for old 64bit PowerPC =
ABI,
>>> that was abandoned with the switch to ELFv2?
>>=20
>> Yes, _CALL_ELF =3D=3D 2 for ELFv2. I highly doubt the defines were =
needed
>> for the ELFv1 ABI, but they're especially redundant now. Presumably
>> David's original fixed commit[1] added powerpc64 to that list because
>> TLS wasn't yet supported in LLVM; that happened later in 2012 and our
>> wiki changed it to being implemented in December 2012[2]. So I =
suspect
>> it should have been deleted 8 years ago.
>=20
> FreeBSD 13 will be the first ELFv2 release. FreeBSD 12 and below are =
ELFv1.
>=20
> The reason for the line was to avoid breaking things during the =
development period for ELFv2. Switching TLS on was one of the things I =
did at the same time as the official ELFv2 transition. See =
2db975b0eb0f3378a39d63eeabe4e3617f4557f0.
>=20
> This is NOT an 8 year old change, but I believe it can go away in HEAD =
as long as the change isn't MFC'd to 12 or earlier.

But TLS isn't broken for ELFv1? Otherwise jemalloc would die in a fire
and nothing would ever work. TLS should have been working for ELFv1 for
many years by this point.

Jess




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