From: Carlos O'Donell <carlos@redhat.com>
To: Florian Weimer <fweimer@redhat.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Chris Kennelly <ckennelly@google.com>,
Peter Oskolkov <posk@posk.io>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
libc-alpha <libc-alpha@sourceware.org>,
Paul Turner <pjt@google.com>
Subject: Re: Aligning tcmalloc with glibc 2.35 rseq ABI
Date: Wed, 2 Feb 2022 17:28:55 -0500 [thread overview]
Message-ID: <3081decb-11a5-11bf-4810-7c5ebe5dcc51@redhat.com> (raw)
In-Reply-To: <ab2fabcf-b84d-6850-f25e-edc80a80662a@redhat.com>
On 2/2/22 12:31, Carlos O'Donell wrote:
> On 2/2/22 10:01, Florian Weimer via Libc-alpha wrote:
>> * Mathieu Desnoyers:
>>
>>> More to the point: is ptrdiff_t the correct type here ? I think so.
>>> Do we want to revert the ABI and wait another 6 months before we
>>> bring back rseq into glibc just for this ? I'm not sure this limitation
>>> justifies it.
>>>
>>> So if there is a quick way to fix that before the official 2.35 release,
>>> I'm all for it, otherwise I cannot say that __rseq_offset being an "int"
>>> rather than a "ptrdiff_t" will make much real-life difference (unless
>>> I'm proven wrong). But we will be stuck with this quirk forever.
>>
>> I'm going to post a patch. It's fairly small.
>
> I'll review this as glibc release manager for glibc 2.35.
>
> We'll get this right before I cut the release.
I've reviewed the static linker relocation designs, and aside from the odd-duck
for ia64, we've used ptrdiff_t sized relocations, nominally 64-bits for the
64-bit targets (though on AArch64 -mtls-size admits at most 48-bits).
The ptrdiff_t change will be a part of the glibc 2.35 release:
commit 6c33b018438ee799c29486f21d43d8100bdbd597
Author: Florian Weimer <fweimer@redhat.com>
Date: Wed Feb 2 22:37:20 2022 +0100
Linux: Use ptrdiff_t for __rseq_offset
This matches the data size initial-exec relocations use on most
targets.
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
--
Cheers,
Carlos.
prev parent reply other threads:[~2022-02-02 22:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-01 14:58 Mathieu Desnoyers
2022-02-01 20:33 ` Chris Kennelly
2022-02-01 20:39 ` Florian Weimer
2022-02-02 8:41 ` Florian Weimer
2022-02-02 11:36 ` Mathieu Desnoyers
2022-02-02 13:08 ` Mathieu Desnoyers
2022-02-02 15:01 ` Florian Weimer
2022-02-02 17:31 ` Carlos O'Donell
2022-02-02 22:28 ` Carlos O'Donell [this message]
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