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[135.23.175.80]) by smtp.gmail.com with ESMTPSA id s6sm13221670qko.93.2022.02.02.14.28.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Feb 2022 14:28:56 -0800 (PST) Message-ID: <3081decb-11a5-11bf-4810-7c5ebe5dcc51@redhat.com> Date: Wed, 2 Feb 2022 17:28:55 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: Aligning tcmalloc with glibc 2.35 rseq ABI Content-Language: en-US From: Carlos O'Donell To: Florian Weimer , Mathieu Desnoyers Cc: Chris Kennelly , Peter Oskolkov , Peter Zijlstra , linux-kernel , libc-alpha , Paul Turner References: <432231420.24682.1643727496135.JavaMail.zimbra@efficios.com> <87mtja1fuz.fsf@oldenburg.str.redhat.com> <875ypx1x0d.fsf@oldenburg.str.redhat.com> <1375227765.27051.1643801804042.JavaMail.zimbra@efficios.com> <770517862.27112.1643807335312.JavaMail.zimbra@efficios.com> <87o83pxqh0.fsf@oldenburg.str.redhat.com> Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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 Reviewed-by: Carlos O'Donell -- Cheers, Carlos.