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Sun, 22 Aug 2021 23:43:17 -0700 (PDT) Received: from [172.16.11.1] ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id r20sm1359329lff.93.2021.08.22.23.43.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Aug 2021 23:43:17 -0700 (PDT) Subject: Re: [PATCH for-next 13/25] compiler_types.h: Remove __compiletime_object_size() To: Kees Cook , linux-kernel@vger.kernel.org Cc: Nick Desaulniers , Miguel Ojeda , Daniel Micay , Francis Laniel , Bart Van Assche , David Gow , linux-mm@kvack.org, clang-built-linux@googlegroups.com, linux-hardening@vger.kernel.org References: <20210822075122.864511-1-keescook@chromium.org> <20210822075122.864511-14-keescook@chromium.org> From: Rasmus Villemoes Message-ID: <4fff1f46-ab10-317b-8cf0-05871e4a9d71@rasmusvillemoes.dk> Date: Mon, 23 Aug 2021 08:43:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210822075122.864511-14-keescook@chromium.org> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=rasmusvillemoes.dk header.s=google header.b=Ib8+qMiG; dmarc=none; spf=pass (imf25.hostedemail.com: domain of linux@rasmusvillemoes.dk designates 209.85.208.171 as permitted sender) smtp.mailfrom=linux@rasmusvillemoes.dk X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4CE71B000182 X-Stat-Signature: ib6dkxe3h7wqrz5sz8j8q5e3q3667wmg X-HE-Tag: 1629700999-825566 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 22/08/2021 09.51, Kees Cook wrote: > - int sz = __compiletime_object_size(addr); > + int sz = __builtin_object_size(addr, 0); Not directly related to this patch, but seeing this I wonder if there would be some value in introducing names for those magic 0/1/2/3 that are used with __b_o_s. Every time I stumble on code using that I have to go to the gcc docs, and even then it takes me a while to grok what TYPE is an integer constant from 0 to 3. If the least significant bit is clear, objects are whole variables, if it is set, a closest surrounding subobject is considered the object a pointer points to. The second bit determines if maximum or minimum of remaining bytes is computed. means. The names don't need to be too verbose, just having a few #defines in-tree with the above quoted above them makes it a lot easier to figure out what they mean. Rasmus