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Mon, 23 Sep 2024 23:56:57 -0700 (PDT) Received: from google.com ([2401:fa00:8f:203:93d1:1107:fd24:adf0]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-7e6b7c4f04esm566711a12.44.2024.09.23.23.56.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Sep 2024 23:56:57 -0700 (PDT) Date: Tue, 24 Sep 2024 15:56:53 +0900 From: Sergey Senozhatsky To: Christoph Hellwig Cc: Sergey Senozhatsky , Andrew Morton , Christophe JAILLET , Andrey Skvortsov , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv2] mm: do not export const kfree and kstrdup variants Message-ID: <20240924065653.GQ38742@google.com> References: <20240924050937.697118-1-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: ssghoga99qa4zghky1xwudun5g636rhy X-Rspamd-Queue-Id: C6057180008 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1727161018-924100 X-HE-Meta: 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 Tat0Nb24 0IZFg819SJ3V8wAAEcptifwwUP3bFkKg0A2Toc6Fh1oqn9wLFaAl6hEkAvUU1/nfLxhM4ru7iKlWYIIp4frWhcSziFM3QkULWocEw20DZxfx1/oEtTugswmpfDx6TI8trah62YYMXiZtewXAPMgebF0GjHioBSDJt2gIxlKeVw++5iZQYMtY965snX2pJMqD+N4nLVuMYF1M+AQS2Rd0ENwAbsNrhZo++W7z6Zwv40HRhbOys5i0/RV0RSPsgSHZgpFCTNAUAg9y+3RulJtgDU8+UGUCbuECr0ZpnOHwFIc8LZCq0Si6lwiNlRmNiSmaplsRS50yp1l8BPP3aRc+WGFvRYeMka21NzNzxmCDj/OYR2JKKU/Rb23EGGQ4vCUF4Nk/pZJz7NQE4FU/CTMNx0jXnL5wmOg/8QCL5G5AyM41yNfQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.004311, 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 (24/09/23 23:43), Christoph Hellwig wrote: > On Tue, Sep 24, 2024 at 02:08:37PM +0900, Sergey Senozhatsky wrote: > > Both kfree_const() and kstrdup_const() use __start_rodata > > and __end_rodata, which do not work for modules. This is > > especially important for kfree_const(). Stop exporting > > these functions, as they cannot be used in the modules. > > Well, they do work when called from modules, they just don't work > on constant data that is in modules. There's also plenty of > existing callers in modules. > > So just unexporting them is going to break. The API is kinda > horrible, but an implementation to check for constants in modules > would also be quite horrible. So I don't have a good answer here, > but simply unexporting them is not going to cut it. Totally agree with all the points, I haven't looked at how popular that API was before sending out the patch. Is there some sort of "built time const" but for strings that we, perhaps, can add to kfree_const() (and make kfree_const() always inline)? So that we can turn this str = "boom"; ... kfree_const(str); into a safe scenario for modules.