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[209.85.218.43]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b7654cdac18sm1678602966b.11.2025.11.25.14.41.38 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Nov 2025 14:41:38 -0800 (PST) Received: by mail-ej1-f43.google.com with SMTP id a640c23a62f3a-b727f452fffso46456966b.1 for ; Tue, 25 Nov 2025 14:41:38 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCXMc/yUXpAfF6fDzvYM3cUg5L3KfXv5P76XctPcbrleQVL28jJ1IVKusrMVm5X94sZwgW04Na9RrQ==@kvack.org X-Received: by 2002:a17:906:d553:b0:b04:48b5:6ea5 with SMTP id a640c23a62f3a-b766ef1d27emr2056801766b.17.1764110497696; Tue, 25 Nov 2025 14:41:37 -0800 (PST) MIME-Version: 1.0 References: <20251122014258.do.018-kees@kernel.org> <20251122014304.3417954-2-kees@kernel.org> In-Reply-To: From: Linus Torvalds Date: Tue, 25 Nov 2025 14:41:21 -0800 X-Gmail-Original-Message-ID: X-Gm-Features: AWmQ_bnHmATmDGg6MkJpXYuB1__YO7XbeBdtXEi7jxM1H4BelwLZXehOF1vhEBg Message-ID: Subject: Re: [PATCH v5 2/4] slab: Introduce kmalloc_obj() and family To: Vlastimil Babka Cc: Kees Cook , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "Gustavo A . R . Silva" , Bill Wendling , Justin Stitt , Jann Horn , Przemek Kitszel , Marco Elver , Greg Kroah-Hartman , Sasha Levin , linux-mm@kvack.org, Randy Dunlap , Miguel Ojeda , Matthew Wilcox , Vegard Nossum , Harry Yoo , Nathan Chancellor , Peter Zijlstra , Nick Desaulniers , Jonathan Corbet , Jakub Kicinski , Yafang Shao , Tony Ambardar , Alexander Lobakin , Jan Hendrik Farr , Alexander Potapenko , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-doc@vger.kernel.org, llvm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: CE4294000B X-Stat-Signature: jfw1nx41ceqq8xams7kh8nynejce94by X-Rspam-User: X-HE-Tag: 1764110499-199052 X-HE-Meta: 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 lgVY5qmH 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 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: List-Subscribe: List-Unsubscribe: On Tue, 25 Nov 2025 at 10:56, Vlastimil Babka wrote: > > > #define kmalloc_verify(type) \ > > BUILD_BUG_ON_ZERO(__alignof__(type) > ARCH_KMALLOC_MINALIGN) > > So AFAIU this would be too pessimistic. I'm not sure if the alignment rules > can be sensibly encoded in build time checks. Perhaps yes, in a similar way > that we have compile-time size bucket selection via __kmalloc_index(). So I wouldn't worry about it over-much: it's actually pretty unusual that we have any odd alignment rules for anything that we would allocate with kmalloc. And I don't think a 'kmalloc_obj()' case needs to necessarily *handle* such unusual cases, I just want this to be *detected*. IOW, what I worry about would be people who use the simple object allocator mistakenly on auto-pilot. So if it errors out about "you're trying to use the simple model for an object that requires non-simple alignment", that is perfectly fine. Those cases can - and do - use more specialized allocators. Yes, yes, in a perfect world we'd just handle that case automatically, but it really is fairly rare, so forcing people to then use some more involved interface for those cases is maybe not optimal, but it's perfectly ok. Linus