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

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Message-ID: <b2dccce1-8cf2-1330-7ea9-7636e0da3c42@arm.com>
Date:   Wed, 10 Jul 2019 10:48:53 +0100
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>
Cc:     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 10/07/2019 07:12, Thomas Gleixner wrote:
> 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...
>

Agreed. I am investing if/why this is happening and will post a fix accordingly.

> Thanks,
> 
> 	tglx
> 

-- 
Regards,
Vincenzo