linux-kernel - Re: [PATCH v6 06/18] x86/kasan: Add arch specific kasan functions

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Message-ID: <tide3xvqthah7m7ji6bfzb5i3ofabgwf45bn3qvvzsurnswh6z@wjxzriavwlp5>
Date: Tue, 18 Nov 2025 15:49:28 +0000
From: Maciej Wieczór-Retman <m.wieczorretman@...me>
To: Alexander Potapenko <glider@...gle.com>, xin@...or.com, peterz@...radead.org, kaleshsingh@...gle.com, kbingham@...nel.org, akpm@...ux-foundation.org, nathan@...nel.org, ryabinin.a.a@...il.com, dave.hansen@...ux.intel.com, bp@...en8.de, morbo@...gle.com, jeremy.linton@....com, smostafa@...gle.com, kees@...nel.org, baohua@...nel.org, vbabka@...e.cz, justinstitt@...gle.com, wangkefeng.wang@...wei.com, leitao@...ian.org, jan.kiszka@...mens.com, fujita.tomonori@...il.com, hpa@...or.com, urezki@...il.com, ubizjak@...il.com, ada.coupriediaz@....com, nick.desaulniers+lkml@...il.com, ojeda@...nel.org, brgerst@...il.com, elver@...gle.com, pankaj.gupta@....com, mark.rutland@....com, trintaeoitogc@...il.com, jpoimboe@...nel.org, thuth@...hat.com, pasha.tatashin@...een.com, dvyukov@...gle.com, jhubbard@...dia.com, catalin.marinas@....com, yeoreum.yun@....com, mhocko@...e.com, lorenzo.stoakes@...cle.com, samuel.holland@...ive.com, vincenzo.frascino@....com, bigeasy@...utronix.de,
	surenb@...gle.com, ardb@...nel.org, Liam.Howlett@...cle.com, nicolas.schier@...ux.dev, ziy@...dia.com, kas@...nel.org, tglx@...utronix.de, mingo@...hat.com, broonie@...nel.org, corbet@....net, andreyknvl@...il.com, maciej.wieczor-retman@...el.com, david@...hat.com, maz@...nel.org, rppt@...nel.org, will@...nel.org, luto@...nel.org, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, x86@...nel.org, linux-kbuild@...r.kernel.org, linux-mm@...ck.org, llvm@...ts.linux.dev, linux-doc@...r.kernel.org
Subject: Re: [PATCH v6 06/18] x86/kasan: Add arch specific kasan functions

On 2025-11-17 at 18:41:35 +0000, Maciej Wieczór-Retman wrote:
>On 2025-11-11 at 10:31:13 +0100, Alexander Potapenko wrote:
>>> +#ifdef CONFIG_64BIT
>>> +static inline void *__tag_set(const void *__addr, u8 tag)
>>> +{
>>> +       u64 addr = (u64)__addr;
>>> +
>>> +       addr &= ~__tag_shifted(KASAN_TAG_MASK);
>>
>>KASAN_TAG_MASK is only defined in Patch 07, does this patch compile?
>
>Seems I forgot to remove it from patch 7. It's originally defined
>in the mmzone.h file and looked cleaner there according to Andrey.
>
>Thanks for noticing it's still in patch 7, I'll get rid of it.

You were right before, after removing that define in patch 7 it doesn't
compile. I think I'll just open code this definition here:

>>> +       addr &= ~__tag_shifted((1UL << KASAN_TAG_WIDTH) - 1);

I don't see a nicer solution here if taking things from mmzone.h is out
of the question. I suppose a #ifndef KASAN_TAG_MASK placed here that
would just shadow the one in mmzone.h could work too?