linux-kernel - Re: [RFC] mm/pgtable/debug: Add test validating architecture page table helpers

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Message-ID: <066e69dc-6ecc-6aba-0226-ba1d61ca0fa8@arm.com>
Date:   Fri, 26 Jul 2019 09:58:56 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-mm@...ck.org, Mark Rutland <mark.rutland@....com>,
        x86@...nel.org, Kees Cook <keescook@...omium.org>,
        Sri Krishna chowdary <schowdary@...dia.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Dave Hansen <dave.hansen@...el.com>,
        linux-kernel@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Mark Brown <Mark.Brown@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Price <Steven.Price@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC] mm/pgtable/debug: Add test validating architecture page
 table helpers


On 07/25/2019 10:37 PM, Catalin Marinas wrote:
> On Thu, Jul 25, 2019 at 12:25:23PM +0530, Anshuman Khandual wrote:
>> +#if !defined(__PAGETABLE_PMD_FOLDED) && !defined(__ARCH_HAS_4LEVEL_HACK)
>> +static void pud_clear_tests(void)
>> +{
>> +	pud_t pud;
>> +
>> +	pud_clear(&pud);
>> +	WARN_ON(!pud_none(pud));
>> +}
> 
> For the clear tests, I think you should initialise the local variable to
> something non-zero rather than rely on whatever was on the stack. In
> case it fails, you have a more deterministic behaviour.

Sure, it makes sense, will change.