From: "Thomas Weißschuh" <thomas.weissschuh@linutronix.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <chleroy@kernel.org>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-mips@vger.kernel.org
Subject: Re: [PATCH 1/7] x86/vdso: Respect COMPAT_32BIT_TIME
Date: Wed, 4 Mar 2026 08:35:52 +0100 [thread overview]
Message-ID: <20260304081505-a2a3a376-20c9-46cb-8dc9-2c4deec1a55e@linutronix.de> (raw)
In-Reply-To: <49b7c9f9-198a-49f7-880b-6ae74d7bd985@zytor.com>
On Tue, Mar 03, 2026 at 10:11:52AM -0800, H. Peter Anvin wrote:
> On 2026-02-27 01:34, Thomas Weißschuh 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.
> >
> > gettimeofday() is currently the only way to get the timezone of the kernel.
> > But I guess this is a legacy thing anyways. If you say we should drop it,
> > let's drop it.
> >
>
> The time zone in the kernel has never worked anyway, as it would require 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 be for
> local time-based filesystems like FAT, but I don't think we bother.
sys_tz is currently used by a bunch of drivers and filesystems (including FAT).
It is also used when writing to the RTC.
> 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 am a bit confused here. You mention 'link failures' and in another mail
'weak references as fallback'. Both are things that happen during linking
('link failures' could also be interpreted as failures during loading).
Somewhere else someone also mentioned the vDSO to be 'linkable'.
But as far as I understand, only libc interprets the vDSO, it completely
bypasses both the linker and the loader. And libc already does graceful
fallbacks to the regular systemcalls if the vDSO is missing completely or
lacks one of the functions, as both cases may happen on normal systems.
What am I missing?
Thomas
next prev parent reply other threads:[~2026-03-04 7:36 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 6:57 [PATCH 0/7] vDSO: Respect COMPAT_32BIT_TIME Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 1/7] x86/vdso: " Thomas Weißschuh
2026-02-27 8:51 ` Arnd Bergmann
2026-02-27 8:58 ` Arnd Bergmann
2026-02-27 9:34 ` Thomas Weißschuh
2026-03-03 18:11 ` H. Peter Anvin
2026-03-03 20:50 ` Arnd Bergmann
2026-03-03 21:00 ` H. Peter Anvin
2026-03-03 21:27 ` Arnd Bergmann
2026-03-03 21:36 ` H. Peter Anvin
2026-04-10 7:24 ` Thomas Weißschuh
2026-04-13 15:59 ` Arnd Bergmann
2026-04-13 16:13 ` Thomas Weißschuh
2026-04-13 16:57 ` Arnd Bergmann
2026-04-14 10:16 ` Thomas Weißschuh
2026-03-04 7:35 ` Thomas Weißschuh [this message]
2026-03-04 18:30 ` H. Peter Anvin
2026-03-05 9:24 ` Thomas Weißschuh
2026-03-05 23:57 ` H. Peter Anvin
2026-03-06 9:42 ` Thomas Weißschuh
2026-03-06 20:52 ` H. Peter Anvin
2026-02-27 6:57 ` [PATCH 2/7] ARM: VDSO: " Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 3/7] arm64: vdso32: " Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 4/7] powerpc/vdso: " Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 5/7] MIPS: VDSO: Drop kconfig MIPS_CLOCK_VSYSCALL Thomas Weißschuh
2026-02-27 8:46 ` Arnd Bergmann
2026-02-27 9:31 ` Thomas Weißschuh
2026-02-27 10:03 ` Arnd Bergmann
2026-02-27 10:17 ` Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 6/7] MIPS: VDSO: Respect COMPAT_32BIT_TIME Thomas Weißschuh
2026-02-27 6:57 ` [PATCH 7/7] vdso/gettimeofday: Verify COMPAT_32BIT_TIME interactions Thomas Weißschuh
2026-02-27 8:49 ` Arnd Bergmann
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