From: Catalin Marinas <catalin.marinas@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
clang-built-linux@googlegroups.com, x86@kernel.org,
Will Deacon <will.deacon@arm.com>, Arnd Bergmann <arnd@arndb.de>,
Russell King <linux@armlinux.org.uk>,
Paul Burton <paul.burton@mips.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>, Stephen Boyd <sboyd@kernel.org>,
Mark Salyzyn <salyzyn@android.com>,
Kees Cook <keescook@chromium.org>,
Peter Collingbourne <pcc@google.com>,
Dmitry Safonov <0x7f454c46@gmail.com>,
Andrei Vagin <avagin@openvz.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Marc Zyngier <maz@kernel.org>,
Mark Rutland <Mark.Rutland@arm.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h
Date: Mon, 16 Mar 2020 11:22:06 +0000 [thread overview]
Message-ID: <20200316112205.GE3005@mbp> (raw)
In-Reply-To: <77a2e91a-58f4-3ba3-9eef-42d6a8faf859@arm.com>
On Mon, Mar 16, 2020 at 10:55:00AM +0000, Vincenzo Frascino wrote:
> On 3/16/20 10:34 AM, Catalin Marinas wrote:
> >> I tried to fine grain the headers as much as I could in order to avoid
> >> unneeded/unwanted inclusions:
> >> * TASK_SIZE_32 is used to verify ABI consistency on vdso32 (please refer to
> >> arch/arm64/kernel/vdso32/vgettimeofday.c).
> >
> > I see. But the test is probably useless. With 4K pages, TASK_SIZE_32 is
> > 1UL << 32, so you can't have a u32 greater than this. So I'd argue that
> > the ABI compatibility here doesn't matter.
> >
> > With 16K or 64K pages, TASK_SIZE_32 is slightly smaller but arm32 never
> > supported it.
> >
> > What's the side-effect of dropping this check altogether?
>
> The main side-effect is that arm32 and arm64 compat have a different behavior,
> that it is what we want to avoid.
>
> The vdsotest [1] I am using, verifies all the side conditions with respect to
> the ABI, which we are now compatible with. Removing those checks would break
> this condition.
As I said above, I don't see how removing 'if ((u32)ts >= (1UL << 32))'
makes any difference. This check was likely removed by the compiler
already.
Also, userspace doesn't have a trivial way to figure out TASK_SIZE and I
can't see anything that tests this in the vdsotest (though I haven't
spent that much time looking). If it's hard-coded, note that arm32
TASK_SIZE is different from TASK_SIZE_32 on arm64.
Can you tell what actually is failing in vdsotest if you remove the
TASK_SIZE_32 checks in the arm64 compat vdso?
--
Catalin
next prev parent reply other threads:[~2020-03-16 11:22 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-13 15:43 [PATCH v3 00/26] Introduce common headers for vDSO Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 01/26] linux/const.h: Extract common header " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 02/26] linux/bits.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 03/26] linux/limits.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 04/26] x86:Introduce asm/vdso/clocksource.h Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 05/26] arm: Introduce asm/vdso/clocksource.h Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 06/26] arm64: " Vincenzo Frascino
2020-03-15 18:29 ` Catalin Marinas
2020-03-13 15:43 ` [PATCH v3 07/26] mips: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 08/26] linux/clocksource.h: Extract common header for vDSO Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 09/26] linux/math64.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 10/26] linux/time.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 11/26] linux/time32.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 12/26] linux/time64.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 13/26] linux/jiffies.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 14/26] linux/ktime.h: " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 15/26] common: Introduce processor.h Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 16/26] scripts: Fix the inclusion order in modpost Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 17/26] linux/elfnote.h: Replace elf.h with UAPI equivalent Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h Vincenzo Frascino
2020-03-15 18:30 ` Catalin Marinas
2020-03-16 9:42 ` Vincenzo Frascino
2020-03-16 10:22 ` Mark Rutland
2020-03-16 10:26 ` Catalin Marinas
2020-03-16 10:29 ` Mark Rutland
2020-03-16 10:30 ` Vincenzo Frascino
2020-03-16 10:29 ` Vincenzo Frascino
2020-03-16 10:34 ` Catalin Marinas
2020-03-16 10:55 ` Vincenzo Frascino
2020-03-16 11:22 ` Catalin Marinas [this message]
2020-03-16 13:35 ` Vincenzo Frascino
2020-03-16 14:43 ` Catalin Marinas
2020-03-16 15:33 ` Vincenzo Frascino
2020-03-16 15:49 ` Catalin Marinas
2020-03-16 16:05 ` Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 19/26] arm64: vdso: Include common headers in the vdso library Vincenzo Frascino
2020-03-15 18:30 ` Catalin Marinas
2020-03-13 15:43 ` [PATCH v3 20/26] arm64: vdso32: " Vincenzo Frascino
2020-03-15 18:30 ` Catalin Marinas
2020-03-13 15:43 ` [PATCH v3 21/26] arm64: Introduce asm/vdso/arch_timer.h Vincenzo Frascino
2020-03-15 18:32 ` Catalin Marinas
2020-03-16 15:37 ` Vincenzo Frascino
2020-04-09 13:26 ` Will Deacon
2020-04-09 13:36 ` Vincenzo Frascino
2020-03-16 10:28 ` Mark Rutland
2020-03-13 15:43 ` [PATCH v3 22/26] mips: vdso: Enable mips to use common headers Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 23/26] x86: vdso: Enable x86 " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 24/26] arm: vdso: Enable arm " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 25/26] lib: vdso: Enable " Vincenzo Frascino
2020-03-13 15:43 ` [PATCH v3 26/26] arm64: vdso32: Enable Clang Compilation Vincenzo Frascino
2020-03-16 9:17 ` Catalin Marinas
2020-03-13 16:19 ` [PATCH v3 00/26] Introduce common headers for vDSO Dmitry Safonov
2020-03-15 10:02 ` Thomas Gleixner
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