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Tue, 3 Mar 2026 16:27:49 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 X-ThreadId: ARwL1vy566MZ Date: Tue, 03 Mar 2026 22:27:27 +0100 From: "Arnd Bergmann" To: "H. Peter Anvin" , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= Cc: "Andy Lutomirski" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , x86@kernel.org, "Russell King" , "Catalin Marinas" , "Will Deacon" , "Madhavan Srinivasan" , "Michael Ellerman" , "Nicholas Piggin" , "Christophe Leroy" , "Thomas Bogendoerfer" , "Vincenzo Frascino" , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org Message-Id: In-Reply-To: <56591FD5-0DD0-4117-BC7B-4565E3F6512E@zytor.com> References: <20260227-vdso-compat_32bit_time-v1-0-3f0286a7bac3@linutronix.de> <20260227-vdso-compat_32bit_time-v1-1-3f0286a7bac3@linutronix.de> <03cd1e21-a2f2-46a1-a674-cbaef9712016@app.fastmail.com> <20260227103226-cc3bb32c-0107-4c09-b81a-ca33ea03ad5c@linutronix.de> <49b7c9f9-198a-49f7-880b-6ae74d7bd985@zytor.com> <2b1ac7b9-fcc8-4aa3-a0ad-eb37e4bce030@app.fastmail.com> <56591FD5-0DD0-4117-BC7B-4565E3F6512E@zytor.com> Subject: Re: [PATCH 1/7] x86/vdso: Respect COMPAT_32BIT_TIME Content-Type: text/plain Content-Transfer-Encoding: 7bit On Tue, Mar 3, 2026, at 22:00, H. Peter Anvin wrote: > On March 3, 2026 12:50:33 PM PST, Arnd Bergmann wrote: >>On Tue, Mar 3, 2026, at 19:11, H. Peter Anvin wrote: >>> A bigger question is whether or not we should omit these from the vDSO >>> completely (potentially causing link failures) or replace them with stubs >>> returning -ENOSYS. >> >>I see no harm in keeping gettimeofday() in the vdso when >>COMPAT_32BIT_TIME is turned on, as existing code will call it >>no matter whether it's in the vdso or the syscall. > > That wasn't the point. The point was what kind of error behavior we want. I see. I would argue here that a link failure is actually the best case then: the entire point of CONFIG_COMPAT_32BIT_TIME=n is to enforce the fail-early case, as opposed to silent data corruption after (now) 12 years of operation. I don't think there is an actual link failure here, as dl_vdso_vsym() resolves it at runtime by glibc (when using time32), while musl doesn't use __vdso_gettimeofday at all. Arnd