linux-kernel - Re: [PATCH v7 10/25] arm64: compat: Add vDSO

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Message-ID: <alpine.DEB.2.21.1907100811170.1758@nanos.tec.linutronix.de>
Date:   Wed, 10 Jul 2019 08:12:21 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     John Stultz <john.stultz@...aro.org>
cc:     Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-arch@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>, linux-mips@...r.kernel.org,
        linux-kselftest@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
        Andre Przywara <andre.przywara@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Huw Davies <huw@...eweavers.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Russell King <linux@...linux.org.uk>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Paul Burton <paul.burton@...s.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Shijith Thotton <sthotton@...vell.com>,
        Peter Collingbourne <pcc@...gle.com>
Subject: Re: [PATCH v7 10/25] arm64: compat: Add vDSO

On Tue, 9 Jul 2019, John Stultz wrote:
> Though unfortunately, it seems the arm64 vdso code that just landed is
> breaking AOSP for me.
> 
> I see a lot of the following errors:
> 01-01 01:22:14.097   755   755 F libc    : Fatal signal 11 (SIGSEGV),
> code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 755 (cameraserver),
> pid 755 (cameraserver)
> 01-01 01:22:14.112   759   759 F libc    : Fatal signal 11 (SIGSEGV),
> code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 759
> (android.hardwar), pid 759 (android.hardwar)
> 01-01 01:22:14.120   756   756 F libc    : Fatal signal 11 (SIGSEGV),
> code 1 (SEGV_MAPERR), fault addr 0x3cf2c96c in tid 756 (drmserver),
> pid 756 (drmserver)
> 
> Which go away if I revert the vdso merge that went in via tip/timers.
> 
> I tried to bisect things down a bit, but as some later fixes are
> required (at one point, date was returning the start epoch and never
> increasing), this hasn't worked too well. But I'm guessing since I
> see: "CROSS_COMPILE_COMPAT not defined or empty, the compat vDSO will
> not be built", and the system is half working, I'm guessing this is an
> issue with just the 32bit code failing.  While I can try to sort out
> the proper CROSS_COMPILE_COMPAT in my build environment, I assume
> userland shouldn't be crashing if that value isn't set.

The obvious question is whether the VDSO is mapped to the 32bit process in
that case. It shouldn't...

Thanks,

	tglx