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Tue, 3 Mar 2026 15:51:03 -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 21:50:33 +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: <2b1ac7b9-fcc8-4aa3-a0ad-eb37e4bce030@app.fastmail.com> In-Reply-To: <49b7c9f9-198a-49f7-880b-6ae74d7bd985@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> Subject: Re: [PATCH 1/7] x86/vdso: Respect COMPAT_32BIT_TIME Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Tue, Mar 3, 2026, at 19:11, H. Peter Anvin wrote: > On 2026-02-27 01:34, Thomas Wei=C3=9Fschuh wrote: >>>> >>> The thing about gettimeofday() and time() is that they don't have >>> a 64-bit version and libc implementations are expected to call >>> clock_gettime() instead. The result was that there was never a >>> patch to turn the off either. >>=20 >> gettimeofday() is currently the only way to get the timezone of the k= ernel. >> But I guess this is a legacy thing anyways. If you say we should drop= it, >> let's drop it. >>=20 > > The time zone in the kernel has never worked anyway, as it would requi= re the > kernel to contain at least the forward portion of the zoneinfo/tzdata = table in > order to actually work correctly. The only plausible use of it would b= e for > local time-based filesystems like FAT, but I don't think we bother. > > A bigger question is whether or not we should omit these from the vDSO > completely (potentially causing link failures) or replace them with st= ubs > 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. Equally, I see no point in having either version of gettimeofday() or settimeofday() when COMPAT_32BIT_TIME is disabled, as clearly anything calling it would pass incorrect data for times past 2038. Neither glibc nor musl support actually returning the kernel timezone to callers of gettimeofday in modern versions that support time64 syscalls. Arnd