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[217.140.110.172]) by mx.google.com with ESMTP id g27si8800045ejc.229.2019.07.24.09.36.49 for ; Wed, 24 Jul 2019 09:36:50 -0700 (PDT) Received-SPF: pass (google.com: domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of steven.price@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=steven.price@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3690E28; Wed, 24 Jul 2019 09:36:49 -0700 (PDT) Received: from [10.1.196.133] (e112269-lin.cambridge.arm.com [10.1.196.133]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C337C3F71F; Wed, 24 Jul 2019 09:36:46 -0700 (PDT) Subject: Re: [PATCH v9 19/21] mm: Add generic ptdump To: Mark Rutland Cc: x86@kernel.org, Arnd Bergmann , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , Dave Hansen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Ingo Molnar , Borislav Petkov , Andy Lutomirski , "H. Peter Anvin" , James Morse , Thomas Gleixner , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, "Liang, Kan" References: <20190722154210.42799-1-steven.price@arm.com> <20190722154210.42799-20-steven.price@arm.com> <20190723095747.GB8085@lakrids.cambridge.arm.com> From: Steven Price Message-ID: Date: Wed, 24 Jul 2019 17:36:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190723095747.GB8085@lakrids.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 23/07/2019 10:57, Mark Rutland wrote: > On Mon, Jul 22, 2019 at 04:42:08PM +0100, Steven Price wrote: >> Add a generic version of page table dumping that architectures can >> opt-in to >> >> Signed-off-by: Steven Price > > [...] > >> +#ifdef CONFIG_KASAN >> +/* >> + * This is an optimization for KASAN=y case. Since all kasan page tables >> + * eventually point to the kasan_early_shadow_page we could call note_page() >> + * right away without walking through lower level page tables. This saves >> + * us dozens of seconds (minutes for 5-level config) while checking for >> + * W+X mapping or reading kernel_page_tables debugfs file. >> + */ >> +static inline bool kasan_page_table(struct ptdump_state *st, void *pt, >> + unsigned long addr) >> +{ >> + if (__pa(pt) == __pa(kasan_early_shadow_pmd) || >> +#ifdef CONFIG_X86 >> + (pgtable_l5_enabled() && >> + __pa(pt) == __pa(kasan_early_shadow_p4d)) || >> +#endif >> + __pa(pt) == __pa(kasan_early_shadow_pud)) { >> + st->note_page(st, addr, 5, pte_val(kasan_early_shadow_pte[0])); >> + return true; >> + } >> + return false; > > Having you tried this with CONFIG_DEBUG_VIRTUAL? > > The kasan_early_shadow_pmd is a kernel object rather than a linear map > object, so you should use __pa_symbol for that. Thanks for pointing that out - it is indeed broken on arm64. This was moved from x86 where CONFIG_DEBUG_VIRTUAL doesn't seem to pick this up. There is actually a problem here that 'pt' might not be in the linear map (so __pa(pt) barfs on arm64 as well as kasan_early_shadow_p?d). It looks like having the comparisons of the form "pt == lm_alias(kasan_early_shadow_p?d)" is probably best. > It's a bit horrid to have to test multiple levels in one function; can't > we check the relevant level inline in each of the test_p?d funcs? > > They're optional anyway, so they only need to be defined for > CONFIG_KASAN. Good point - removing the test_p?d callbacks when !CONFIG_KASAN simplifies the code. Thanks, Steve