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GET /api/1.1/patches/2229057/?format=api
{ "id": 2229057, "url": "http://patchwork.ozlabs.org/api/1.1/patches/2229057/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/8780eb2ef80575931a339e5225bc80eb13e9be6c.1777306795.git.chleroy@kernel.org/", "project": { "id": 2, "url": "http://patchwork.ozlabs.org/api/1.1/projects/2/?format=api", "name": "Linux PPC development", "link_name": "linuxppc-dev", "list_id": "linuxppc-dev.lists.ozlabs.org", "list_email": "linuxppc-dev@lists.ozlabs.org", "web_url": "https://github.com/linuxppc/wiki/wiki", "scm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git", "webscm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/" }, "msgid": "<8780eb2ef80575931a339e5225bc80eb13e9be6c.1777306795.git.chleroy@kernel.org>", "date": "2026-04-27T17:13:50", "name": "[RFC,v1,9/9] uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "f38ce621dc214e122a1e5e926e37049e4c6a4559", "submitter": { "id": 92089, "url": "http://patchwork.ozlabs.org/api/1.1/people/92089/?format=api", "name": "Christophe Leroy (CS GROUP)", "email": "chleroy@kernel.org" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/8780eb2ef80575931a339e5225bc80eb13e9be6c.1777306795.git.chleroy@kernel.org/mbox/", "series": [ { "id": 501691, "url": "http://patchwork.ozlabs.org/api/1.1/series/501691/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=501691", "date": "2026-04-27T17:13:41", "name": "uaccess: Convert small fixed size copy_{to/from}_user() to scoped user access", "version": 1, "mbox": "http://patchwork.ozlabs.org/series/501691/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2229057/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2229057/checks/", "tags": {}, "headers": { "Return-Path": "\n <linuxppc-dev+bounces-20184-incoming=patchwork.ozlabs.org@lists.ozlabs.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linuxppc-dev@lists.ozlabs.org" ], "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=k8kV5Zhk;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; 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a=rsa-sha256; c=relaxed/simple; d=kernel.org;\n\ts=k20201202; t=1777310364;\n\tbh=xblTv37x9V4gU3cvmA9ILfz6xXNOv0sNe2zU9C6a5nw=;\n\th=From:To:Cc:Subject:Date:In-Reply-To:References:From;\n\tb=k8kV5Zhk7HZbxy8X7mxqUL5UgTTJPPuuLtSKHKOe5PwbIiNodL9/7ESxRbcOMv4dB\n\t NN/pd897F5mMQZv6MW+RM/3mikWvqmJGQCtupbd6YHiobStaCQu79RRkwt3Bs1rL/A\n\t WmXtcy3vIzgejB2MGSu6MrKJ33itreKKdFlemNypyCUExoUHGXA1bHbqFqaNX4ujdd\n\t iXZiXWTV/w69yfgs2V8e+zdWAilhhtsvDDxzPIT8CbbievjXPmrPwVloE5aoqLKmYP\n\t ca2+sf92YJQm2mLHcpyNlGd6mMQP6QhUed6Hx8vk/CloBjO7tSgz4fayv+CeXka+Fz\n\t NwGM6tvALNVmQ==", "From": "\"Christophe Leroy (CS GROUP)\" <chleroy@kernel.org>", "To": "Yury Norov <ynorov@nvidia.com>,\n\tAndrew Morton <akpm@linux-foundation.org>,\n\tLinus Torvalds <torvalds@linux-foundation.org>,\n\tDavid Laight <david.laight.linux@gmail.com>,\n\tThomas Gleixner <tglx@linutronix.de>", "Cc": "\"Christophe Leroy (CS GROUP)\" <chleroy@kernel.org>,\n\tlinux-alpha@vger.kernel.org,\n\tlinux-kernel@vger.kernel.org,\n\tlinux-snps-arc@lists.infradead.org,\n\tlinux-arm-kernel@lists.infradead.org,\n\tlinux-mips@vger.kernel.org,\n\tlinuxppc-dev@lists.ozlabs.org,\n\tkvm@vger.kernel.org,\n\tlinux-riscv@lists.infradead.org,\n\tlinux-s390@vger.kernel.org,\n\tsparclinux@vger.kernel.org,\n\tlinux-um@lists.infradead.org,\n\tdmaengine@vger.kernel.org,\n\tlinux-efi@vger.kernel.org,\n\tlinux-fsi@lists.ozlabs.org,\n\tamd-gfx@lists.freedesktop.org,\n\tdri-devel@lists.freedesktop.org,\n\tintel-gfx@lists.freedesktop.org,\n\tlinux-wpan@vger.kernel.org,\n\tnetdev@vger.kernel.org,\n\tlinux-wireless@vger.kernel.org,\n\tlinux-spi@vger.kernel.org,\n\tlinux-media@vger.kernel.org,\n\tlinux-staging@lists.linux.dev,\n\tlinux-serial@vger.kernel.org,\n\tlinux-usb@vger.kernel.org,\n\txen-devel@lists.xenproject.org,\n\tlinux-fsdevel@vger.kernel.org,\n\tocfs2-devel@lists.linux.dev,\n\tbpf@vger.kernel.org,\n\tkasan-dev@googlegroups.com,\n\tlinux-mm@kvack.org,\n\tlinux-x25@vger.kernel.org,\n\trust-for-linux@vger.kernel.org,\n\tlinux-sound@vger.kernel.org,\n\tsound-open-firmware@alsa-project.org,\n\tlinux-csky@vger.kernel.org,\n\tlinux-hexagon@vger.kernel.org,\n\tloongarch@lists.linux.dev,\n\tlinux-m68k@lists.linux-m68k.org,\n\tlinux-openrisc@vger.kernel.org,\n\tlinux-parisc@vger.kernel.org,\n\tlinux-sh@vger.kernel.org,\n\tlinux-arch@vger.kernel.org", "Subject": "[RFC PATCH v1 9/9] uaccess: Convert small fixed size\n copy_{to/from}_user() to scoped user access", "Date": "Mon, 27 Apr 2026 19:13:50 +0200", "Message-ID": "\n <8780eb2ef80575931a339e5225bc80eb13e9be6c.1777306795.git.chleroy@kernel.org>", "X-Mailer": "git-send-email 2.49.0", "In-Reply-To": "<cover.1777306795.git.chleroy@kernel.org>", "References": "<cover.1777306795.git.chleroy@kernel.org>", "X-Mailing-List": "linuxppc-dev@lists.ozlabs.org", "List-Id": "<linuxppc-dev.lists.ozlabs.org>", "List-Help": "<mailto:linuxppc-dev+help@lists.ozlabs.org>", "List-Owner": "<mailto:linuxppc-dev+owner@lists.ozlabs.org>", "List-Post": "<mailto:linuxppc-dev@lists.ozlabs.org>", "List-Archive": "<https://lore.kernel.org/linuxppc-dev/>,\n <https://lists.ozlabs.org/pipermail/linuxppc-dev/>", "List-Subscribe": "<mailto:linuxppc-dev+subscribe@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-digest@lists.ozlabs.org>,\n <mailto:linuxppc-dev+subscribe-nomail@lists.ozlabs.org>", "List-Unsubscribe": "<mailto:linuxppc-dev+unsubscribe@lists.ozlabs.org>", "Precedence": "list", "MIME-Version": "1.0", "X-Developer-Signature": "v=1; a=openpgp-sha256; l=3638; i=chleroy@kernel.org;\n h=from:subject:message-id; bh=xblTv37x9V4gU3cvmA9ILfz6xXNOv0sNe2zU9C6a5nw=;\n b=owGbwMvMwCV2d0KB2p7V54MZT6slMWS+nxlr/n9yu2DE7uwkCZGbl0uCp6Y1JLvZTPpz+P/PY\n xNqPMoaOkpZGMS4GGTFFFmO/+feNaPrS2r+1F36MHNYmUCGMHBxCsBE9HwZ/ns82Ho9PV2Q+7Pp\n 5fqvs6O/v3YN+3EgL+Wk4b/co1rlkZ8YGVZxmDl7XFiUcmPSTPW14WGSHT6/1u4pcTY2cjD0U7P\n bzAkA", "X-Developer-Key": "i=chleroy@kernel.org; a=openpgp;\n fpr=10FFE6F8B390DE17ACC2632368A92FEB01B8DD78", "Content-Transfer-Encoding": "8bit", "X-Spam-Status": "No, score=-0.2 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,\n\tDKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS\n\tautolearn=disabled version=4.0.1", "X-Spam-Checker-Version": "SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org" }, "content": "copy_{to/from}_user() is a heavy function optimised for copy of large\nblocs of memory between user and kernel space.\n\nWhen the number of bytes to be copied is known at build time and small,\nusing scoped user access removes the burden of that optimisation.\n\nSigned-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>\n---\n include/linux/uaccess.h | 47 +++++++++++++++++++++++++++++++++++++++++\n 1 file changed, 47 insertions(+)", "diff": "diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h\nindex 33b7d0f5f808..3ac544527af2 100644\n--- a/include/linux/uaccess.h\n+++ b/include/linux/uaccess.h\n@@ -50,6 +50,8 @@\n #define mask_user_address(src) (src)\n #endif\n \n+#define SMALL_COPY_USER\t\t64\n+\n /*\n * Architectures should provide two primitives (raw_copy_{to,from}_user())\n * and get rid of their private instances of copy_{to,from}_user() and\n@@ -191,6 +193,9 @@ _inline_copy_from_user(void *to, const void __user *from, unsigned long n)\n \treturn res;\n }\n \n+static __always_inline __must_check unsigned long\n+_small_copy_from_user(void *to, const void __user *from, unsigned long n);\n+\n extern __must_check unsigned long\n _copy_from_user(void *, const void __user *, unsigned long);\n \n@@ -207,6 +212,9 @@ _inline_copy_to_user(void __user *to, const void *from, unsigned long n)\n \treturn n;\n }\n \n+static __always_inline __must_check unsigned long\n+_small_copy_to_user(void __user *to, const void *from, unsigned long n);\n+\n extern __must_check unsigned long\n _copy_to_user(void __user *, const void *, unsigned long);\n \n@@ -215,6 +223,8 @@ copy_from_user_common(void *to, const void __user *from, unsigned long n, bool p\n {\n \tif (!check_copy_size(to, n, false))\n \t\treturn n;\n+\tif (!partial && __builtin_constant_p(n) && n <= SMALL_COPY_USER)\n+\t\treturn _small_copy_from_user(to, from, n);\n \tif (IS_ENABLED(ARCH_WANTS_NOINLINE_COPY_USER))\n \t\treturn _copy_from_user(to, from, n);\n \telse\n@@ -239,6 +249,8 @@ copy_to_user_common(void __user *to, const void *from, unsigned long n, bool par\n \tif (!check_copy_size(from, n, true))\n \t\treturn n;\n \n+\tif (!partial && __builtin_constant_p(n) && n <= SMALL_COPY_USER)\n+\t\treturn _small_copy_to_user(to, from, n);\n \tif (IS_ENABLED(ARCH_WANTS_NOINLINE_COPY_USER))\n \t\treturn _copy_to_user(to, from, n);\n \telse\n@@ -838,6 +850,41 @@ for (bool done = false; !done; done = true)\t\t\t\t\t\\\n #define scoped_user_rw_access(uptr, elbl)\t\t\t\t\\\n \tscoped_user_rw_access_size(uptr, sizeof(*(uptr)), elbl)\n \n+static __always_inline __must_check unsigned long\n+_small_copy_from_user(void *to, const void __user *from, unsigned long n)\n+{\n+\tmight_fault();\n+\tinstrument_copy_from_user_before(to, from, n);\n+\tscoped_user_read_access_size(from, n, failed) {\n+\t\t/*\n+\t\t * Ensure that bad access_ok() speculation will not lead\n+\t\t * to nasty side effects *after* the copy is finished:\n+\t\t */\n+\t\tif (!can_do_masked_user_access())\n+\t\t\tbarrier_nospec();\n+\t\tunsafe_copy_from_user(to, from, n, failed);\n+\t}\n+\tinstrument_copy_from_user_after(to, from, n, 0);\n+\treturn 0;\n+failed:\n+\tinstrument_copy_from_user_after(to, from, n, n);\n+\treturn n;\n+}\n+\n+static __always_inline __must_check unsigned long\n+_small_copy_to_user(void __user *to, const void *from, unsigned long n)\n+{\n+\tmight_fault();\n+\tif (should_fail_usercopy())\n+\t\treturn n;\n+\tinstrument_copy_to_user(to, from, n);\n+\tscoped_user_write_access_size(to, n, failed)\n+\t\tunsafe_copy_to_user(to, from, n, failed);\n+\treturn 0;\n+failed:\n+\treturn n;\n+}\n+\n /**\n * get_user_inline - Read user data inlined\n * @val:\tThe variable to store the value read from user memory\n", "prefixes": [ "RFC", "v1", "9/9" ] }