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References: <20190530141531.43462-1-vincenzo.frascino@arm.com> <20190530141531.43462-2-vincenzo.frascino@arm.com>
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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 31 May 2019 10:16:32 +0200
Message-ID: <CAK8P3a3EnvkLND2RJdZtEY64PhK5g0sbbuytQro=f0cPur2g9g@mail.gmail.com>
Subject: Re: [PATCH v6 01/19] kernel: Standardize vdso_datapage
To:     Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc:     linux-arch <linux-arch@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
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On Thu, May 30, 2019 at 4:15 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:

> + * vdso_data will be accessed by 64 bit and compat code at the same time
> + * so we should be careful before modifying this structure.
> + */
> +struct vdso_data {
> +       u32                     seq;
> +
> +       s32                     clock_mode;
> +       u64                     cycle_last;
> +       u64                     mask;
> +       u32                     mult;
> +       u32                     shift;
> +
> +       struct vdso_timestamp   basetime[VDSO_BASES];
> +
> +       s32                     tz_minuteswest;
> +       s32                     tz_dsttime;
> +       u32                     hrtimer_res;
> +};

The structure contains four padding bytes at the end, which is
something we try to avoid, at least if this ends up being used as
an ABI. Maybe add "u32 __unused" at the end?

     Arnd