Re: [PATCH v4 05/10] signal: Introduce TRAP_PERF si_code and si_perf to siginfo

From: Marco Elver <elver@google.com>
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>,
	Dmitry Vyukov <dvyukov@google.com>, Jann Horn <jannh@google.com>,
	Jens Axboe <axboe@kernel.dk>, Matt Morehouse <mascasa@google.com>,
	Peter Collingbourne <pcc@google.com>,
	Ian Rogers <irogers@google.com>, Oleg Nesterov <oleg@redhat.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-tegra@vger.kernel.org, jonathanh@nvidia.com
Subject: Re: [PATCH v4 05/10] signal: Introduce TRAP_PERF si_code and si_perf to siginfo
Date: Thu, 22 Apr 2021 08:47:13 +0200	[thread overview]
Message-ID: <CANpmjNPbMOUd_Wh5aHGdH8WLrYpyBFUpwx6g3Kj2D6eevvaU8w@mail.gmail.com> (raw)
In-Reply-To: <dd99b921-3d79-a21f-8942-40fa5bf53190@samsung.com>

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