linux-kernel - RE: [PATCH] divide by 3*sizeof(u32) when computing array

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Message-ID: <012ccfea2a564274bd9d2e1cfc130873@AcuMS.aculab.com>
Date:   Tue, 13 Jul 2021 11:07:00 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Russell King' <linux@...linux.org.uk>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
CC:     Salah Triki <salah.triki@...il.com>,
        "fabrice.gasnier@...s.st.com" <fabrice.gasnier@...s.st.com>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] divide by 3*sizeof(u32) when computing array_size

From: Russell King
> Sent: 13 July 2021 10:20
....
> I would also note that the code relies on there being no padding in
> struct stm32_breakinput - it should be noted that a strict
> interpretation of the C standard allows padding to be added anywhere
> to a structure - at the start, end or between members.

I'm pretty certain I remember that padding before the first member
isn't allowed.

In any case the kernel generally assumes there is no extra padding.
(eg for structures that map hardware registers.)

For big structures it is worth adding a compile-time check of
the structure size - but not really for three u32.

	David

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