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Fri, 9 Feb 2024 09:41:28 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.11.0-alpha0-144-ge5821d614e-fm-20240125.002-ge5821d61 MIME-Version: 1.0 Message-Id: <6eeba3ce-d66c-45e2-8c34-ad0109ec2ef0@app.fastmail.com> In-Reply-To: <20240208225608.11987-1-kernel@valentinobst.de> References: <20240208-alice-mm-v2-2-d821250204a6@google.com> <20240208225608.11987-1-kernel@valentinobst.de> Date: Fri, 09 Feb 2024 15:41:08 +0100 From: "Arnd Bergmann" To: "Valentin Obst" , "Alice Ryhl" Cc: "Andreas Hindborg" , "Andrew Morton" , "Alex Gaynor" , =?UTF-8?Q?Arve_Hj=C3=B8nnev=C3=A5g?= , "Benno Lossin" , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , "Boqun Feng" , "Christian Brauner" , "Carlos Llamas" , "Gary Guo" , "Greg Kroah-Hartman" , "Joel Fernandes" , "Kees Cook" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Martijn Coenen" , "Miguel Ojeda" , rust-for-linux@vger.kernel.org, "Suren Baghdasaryan" , "Todd Kjos" , "Alexander Viro" , "Wedson Almeida Filho" Subject: Re: [PATCH v2 2/4] uaccess: always export _copy_[from|to]_user with CONFIG_RUST Content-Type: text/plain X-Rspam-User: X-Stat-Signature: mhjir94tqpdsnz7aukkmkygixpa6h1y1 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 103051C001A X-HE-Tag: 1707489692-598217 X-HE-Meta: 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 LvcPSwXn ARVAHrdHjJfB/KHS0UzhdaCoSL7e8rDDKtLWVCWYxiqCt7MH1LOo0bhFKL7iVzuGD21eTo6Q6A4c6H0EOk3Rjh+40L2vqxVTGaHamz3WXRaw0OyPze9L/Nk3zPXiQkfVsmC1C2Y4kKgHaPCWZOMSdriuZ0mXgPjOXK5yEzpnM3pI0xWCySSBX2k3glNUMi2ZOKDGh4WfbwUBNQAET64Y2XilfyWBRaQDuSYKcMGms3/+ENnNw371bPKswoG/K93euD0BzhYrxs/Wop95gVWsc08wJ9CkhgbDQkzy0 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 Thu, Feb 8, 2024, at 23:56, Valentin Obst wrote: >> -#else >> extern __must_check unsigned long >> _copy_from_user(void *, const void __user *, unsigned long); >> -#endif > > This function is now unconditionally declared, but only defined if > `!defined(INLINE_COPY_FROM_USER) || defined(CONFIG_RUST)`, i.e., in the > common case where it is inlined and Rust is disabled this can lead to > link-time problems if someone decides to use it. Yes, that is intentional. If someone tries to use it when the declaration is not there, they just get a compile-time error, which is not all that different from a link-time error in practice. It's unlikely to make a difference here, but enclosing declarations in an #ifdef is annoying when you want to reference it from somewhere that is parsed by the compiler but not called without the respective options. The if(IS_ENABLED()) and PTR_IF() constructs in particular only work when the unused functions are still declared. Arnd