linux-kernel - Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h

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Date:   Mon, 16 Mar 2020 13:35:17 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        clang-built-linux@...glegroups.com, x86@...nel.org,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Paul Burton <paul.burton@...s.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...nvz.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <Mark.Rutland@....com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h

Hi Catalin,

On 3/16/20 11:22 AM, Catalin Marinas wrote:
> On Mon, Mar 16, 2020 at 10:55:00AM +0000, Vincenzo Frascino wrote:
>> On 3/16/20 10:34 AM, Catalin Marinas wrote:
[...]


> 
> 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?
> 

To me does not seem optimized out. Which version of the compiler are you using?

Please find below the list of errors for clock_gettime (similar for the other):

passing UINTPTR_MAX to clock_gettime (VDSO): terminated by unexpected signal 7
clock-gettime-monotonic/abi: 1 failures/inconsistencies encountered

passing UINTPTR_MAX to clock_gettime (VDSO): terminated by unexpected signal 7
clock-gettime-monotonic-coarse/abi: 1 failures/inconsistencies encountered

passing UINTPTR_MAX to clock_gettime (VDSO): terminated by unexpected signal 7
clock-gettime-realtime/abi: 1 failures/inconsistencies encountered

passing UINTPTR_MAX to clock_gettime (VDSO): terminated by unexpected signal 7
clock-gettime-realtime-coarse/abi: 1 failures/inconsistencies encountered

Please refer to [1] for more details on the test.

[1]
https://github.com/nlynch-mentor/vdsotest/blob/master/src/clock_gettime_template.c

-- 
Regards,
Vincenzo