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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id 19-20020a170902c11300b001b9d7c8f44dsm175831pli.182.2023.09.13.16.54.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 Sep 2023 16:54:16 -0700 (PDT) From: Kees Cook To: Luis Chamberlain Cc: Kees Cook , Johan Hovold , Jessica Yu , Sagi Grimberg , Nick Desaulniers , Miguel Ojeda , Joe Perches , linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2] module: Clarify documentation of module_param_call() Date: Wed, 13 Sep 2023 16:54:14 -0700 Message-Id: <20230913235407.gonna.817-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2680; i=keescook@chromium.org; h=from:subject:message-id; bh=pNcngmHYrvDvUxoczJLnyZVd+nVJiePsfxEYP+mQ0xQ=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlAkuma27fQb+IVRynpM5+rd9HXGa5bQURQdPIS Wt4kC4XqSeJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZQJLpgAKCRCJcvTf3G3A JqnbD/42vpNafZEmP4ggRIZjSYnTNljv/5iB7eQ3O5HsbD5EckktJlskTx4nh5U8W6Aq19QK2ud cpUdzg+pXwtgB6Cc8dE/tSxo48uWZInMrTT2ImA75OAgvHUoTukoDigzVuGNfNSrj8wwOCRNOgp 5Z9CVTPYynY4j4HAk0gix5Vb7hKvTofXGIvDZxeKISf6PHd9GQaF+u90y3eC5GXv7jbXG2nUWMd 4NXLlFB0iZ5C+DHn4YK8I3agbJcRGR8AQlUunhBMMCJxeU3HUju5BiP3kEbx4DBIYjBrSA/QU1O 8/tjv6OGGs3fYvAQ3xMFWvy2TbCupCo1lfgi3O6BiRNEv50X+1mcQkXNI54EXvhubFgNuxReHZH 2fm2UDFT/B5IPWfve0GeE0NEa0xOIb917g8ValpzTBbn1wwa4Cb37YnEqKyRG22SBqa0NqTjB0S iHnXFAqAXLpyx//pUD7Ks9PGgleLZaU8eJRa/nFsbK56NHu5jc7aUphIaQMXjJqqPskKe0Nh2cp a9nfclOGfgol2VuYRRce2AEQ7ntXiAMeFWHx2QThOLBUaiUJmwsZgGsG00gYWZtg80rEv3BEcAB Wn7nkaHEBmeBdG64VcXqh1BpeLkTj3RmG8xmxghATmcI4X+1ERuTGdwGWV+cPvnJFVQAOrI4S6w a+qnLUI SM27XxvQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Commit 9bbb9e5a3310 ("param: use ops in struct kernel_param, rather than get and set fns directly") added the comment that module_param_call() was deprecated, during a large scale refactoring to bring sanity to type casting back then. In 2017 following more cleanups, it became useful again as it wraps a common pattern of creating an ops struct for a given get/set pair: b2f270e87473 ("module: Prepare to convert all module_param_call() prototypes") ece1996a21ee ("module: Do not paper over type mismatches in module_param_call()") static const struct kernel_param_ops __param_ops_##name = \ { .flags = 0, .set = _set, .get = _get }; \ __module_param_call(MODULE_PARAM_PREFIX, \ name, &__param_ops_##name, arg, perm, -1, 0) __module_param_call(MODULE_PARAM_PREFIX, name, ops, arg, perm, -1, 0) Many users of module_param_cb() appear to be almost universally open-coding the same thing that module_param_call() does now. Don't discourage[1] people from using module_param_call(): clarify the comment to show that module_param_cb() is useful if you repeatedly use the same pair of get/set functions. [1] https://lore.kernel.org/lkml/202308301546.5C789E5EC@keescook/ Cc: Luis Chamberlain Cc: Johan Hovold Cc: Jessica Yu Cc: Sagi Grimberg Cc: Nick Desaulniers Cc: Miguel Ojeda Cc: Joe Perches Cc: linux-modules@vger.kernel.org Reviewed-by: Miguel Ojeda Signed-off-by: Kees Cook --- Luis, I note that include/linux/moduleparam.h isn't in the MAINTAINERS file pattern. Perhaps you want to use include/linux/module*.h? --- include/linux/moduleparam.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h index 962cd41a2cb5..d4452f93d060 100644 --- a/include/linux/moduleparam.h +++ b/include/linux/moduleparam.h @@ -293,7 +293,11 @@ struct kparam_array = { __param_str_##name, THIS_MODULE, ops, \ VERIFY_OCTAL_PERMISSIONS(perm), level, flags, { arg } } -/* Obsolete - use module_param_cb() */ +/* + * Useful for describing a set/get pair used only once (i.e. for this + * parameter). For repeated set/get pairs (i.e. the same struct + * kernel_param_ops), use module_param_cb() instead. + */ #define module_param_call(name, _set, _get, arg, perm) \ static const struct kernel_param_ops __param_ops_##name = \ { .flags = 0, .set = _set, .get = _get }; \