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From:   Marco Elver <elver@google.com>
Date:   Thu, 22 Apr 2021 08:47:13 +0200
Message-ID: <CANpmjNPbMOUd_Wh5aHGdH8WLrYpyBFUpwx6g3Kj2D6eevvaU8w@mail.gmail.com>
Subject: Re: [PATCH v4 05/10] signal: Introduce TRAP_PERF si_code and si_perf
 to siginfo
To:     Marek Szyprowski <m.szyprowski@samsung.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Jiri Olsa <jolsa@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Alexander Potapenko <glider@google.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        Christian Brauner <christian@brauner.io>,
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On Thu, 22 Apr 2021 at 08:12, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
[...]
> > So I think we just have to settle on 'unsigned long' here. On many
> > architectures, like 32-bit Arm, the alignment of a structure is that of
> > its largest member. This means that there is no portable way to add
> > 64-bit integers to siginfo_t on 32-bit architectures.
> >
> > In the case of the si_perf field, word size is sufficient since the data
> > it contains is user-defined. On 32-bit architectures, any excess bits of
> > perf_event_attr::sig_data will therefore be truncated when copying into
> > si_perf.
> >
> > Feel free to test the below if you have time, but the below lets me boot
> > 32-bit arm which previously timed out. It also passes all the
> > static_asserts() I added (will send those as separate patches).
> >
> > Once I'm convinced this passes all others tests too, I'll send a patch.
>
> This fixes the issue I've observed on my test systems. Feel free to add:
>
> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

Thank you for testing! It's been sent:
https://lkml.kernel.org/r/20210422064437.3577327-1-elver@google.com

Thanks,
-- Marco