From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1B2E5F8E498 for ; Fri, 17 Apr 2026 00:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=wonoc5490QuGHhln27veolm76wdYSRsus2wubp5nw+8=; b=YxSbk6zUlUIfBb9jKS2zOcwFpw ts6Skr3MWScTxgwH0I0NENFwqmkTfqGJoJQHeSo1QSUj1ELlxhKREcz7JAkQ/056jCwFJ2ftND9Bf SmbXGLHeHhmaQwD+O2E0xWvojUskWemaXDobKprru7B1Vd3N4LDv9Clfw+2NKhucRl1+NIhFhUEo+ zTWMqQLzHxbViOiKFluGmfmTsrwfStx3IpSCG7bwTDHh974v28Bi0kkSZlAg27mmRrLIU3pqSYXzl 7rm9RQ/BHrWROvOPqXNFaaXfD/MDZVDpCKS6idrGworX7TAx/65zQCmAg3sFfcriuNptgqweZiqrD fRdNJk8Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDXEh-00000003EtF-3vFS; Fri, 17 Apr 2026 00:39:07 +0000 Received: from mail-wm1-x32c.google.com ([2a00:1450:4864:20::32c]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDXEc-00000003EsU-1Y8C for kexec@lists.infradead.org; Fri, 17 Apr 2026 00:39:03 +0000 Received: by mail-wm1-x32c.google.com with SMTP id 5b1f17b1804b1-482f454be5bso12065075e9.0 for ; Thu, 16 Apr 2026 17:39:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1776386340; x=1776991140; darn=lists.infradead.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=wonoc5490QuGHhln27veolm76wdYSRsus2wubp5nw+8=; b=L0JF6GHtNk2DLwaDAwFOJJ5HQi5kynP8jpLpoOczutMsu7x5vBPCftj4fNR98VDq+P O28y5qNk9Ugy/Z0rxChDZgAEMCYyRVmZAaJHlGLRhNjD8/U6g64JX3RY9VBprxqBdyPp GH516lTi2REPvcuxkPz2CmIj3x2xVAHumgqSUBbrYEyaz6JASaje1quP61RQdFKIgnyJ 1904OxPKsk5Ej7pKdQk2/DOM/07P0mlpOq20JZy9kgv/4qwTy8w7uTCoANAp2ri0OETs vaeAi2hJgBe7Q9poGBqCPu1ZDc6dC/Q0WhMtgRxxTPFXlYGffRtJ9iekXCFJXmsbCrgd Nd9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776386340; x=1776991140; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=wonoc5490QuGHhln27veolm76wdYSRsus2wubp5nw+8=; b=godIW1zU7Xn94gmwLapQqsPFDHfMvZ6Bcui6B/JztO/YFvHEHCcrsZhp1t7SYTaXDU ofETJ5a62465WdDF/j0AFlAw6pai0vhSAe7MNnSpxahJ7qfpqKoZypfdEKDLgzXMVCwk cgChnndbLAJylp/tturnCYBOC6gsM7u9RMtDnA7eVmcYAZM1SlQz8dmnksWu3edhRyMg eFgiYXFOme8f5KVdfDH//rJFtAL1YI/dgY1C2suMr6r+pmo3U9nfM0PfG0zXpn+uaYwp JOGKP8lypt8SNVpQYIbc5l8WZzDdNrG5FCvKInlhoAXcnFIDImI2h1IX8T2sVxRPQTuW +HoA== X-Gm-Message-State: AOJu0YyAe/ZReoLfwYApGq+8C8VuuHdGy6Yu/SGZd6UW95p/ANTw52l7 l500trPHxRtp21xDfhIEt0Pa5fsOQwEAkhcH/MNa4U6pw1tqZd+emnHJXSazEpM1 X-Gm-Gg: AeBDiev2675xeRgRb9W3am7NrGF8rs+GBo3UBAFbdzdVnVhJCbkV0y8rmY6+exMFPzk kkuM6GlhP7SUB/yRbqz1/923KgQcZKcnT8U3HnoD5QFRw1wQauVJixKssAQKNXedeSrkPNGrBrU UC5MeF13mJp95KavB7jqRvlS1ok5ldqkwl5UO1UK9PDkV86vr3oB/e+XQYrwybl8GonbaEHUFtw DJsEFyUKwHTswWgrcEpiDLAot2HCTfkeZlLOuAjyD9u8RGW1vLYPDMq/aG2d+rcKfcygiDUxOjI LUe0HubDD+0VsZEdhT8nMlr8/5IXAeq/FvlI1+2tLyNctf4yQGRwGJ0wmQVJ1nSAKoNL6R3AC0k v4m8IizFyYgk0Ltu3gOvEdXoZaOVo9u1FlBXoswQUok0d8XMT+wf5oRx86b61nGhd1GK+LQiZXb LkdQsjES2Gu+jZbcWG8YtrPf+33SAZu7qApXK4/9E= X-Received: by 2002:a05:600c:8884:b0:477:9890:9ab8 with SMTP id 5b1f17b1804b1-488fb88380amr4504715e9.3.1776386339675; Thu, 16 Apr 2026 17:38:59 -0700 (PDT) Received: from localhost ([2a01:4b00:d036:ae00:f478:3ca4:c1b8:70d5]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-488fc189f2esm2442535e9.7.2026.04.16.17.38.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Apr 2026 17:38:59 -0700 (PDT) From: luca.boccassi@gmail.com To: kexec@lists.infradead.org Cc: linux-mm@kvack.org, graf@amazon.com, rppt@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, brauner@kernel.org, Luca Boccassi Subject: [PATCH v2] liveupdate: add LIVEUPDATE_SESSION_GET_NAME ioctl Date: Fri, 17 Apr 2026 01:36:58 +0100 Message-ID: <20260417003856.1525287-1-luca.boccassi@gmail.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260416_173902_497794_14F9E7FA X-CRM114-Status: GOOD ( 20.04 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org From: Luca Boccassi Userspace when requesting a session via the ioctl specifies a name and gets a FD, but then there is no ioctl to go back the other way and get the name given a LUO session FD. This is problematic especially when there is a userspace orchestrator that wants to check what FDs it is handling for clients without having to do manual string scraping of procfs, or without procfs at all. Add a ioctl to simply get the name from an FD. Signed-off-by: Luca Boccassi --- This was requested by Lennart and Christian when discussing integration with systemd for LUO management. v2: apply one fix from bot review about cleanup on error path: https://sashiko.dev/#/patchset/20260415184536.1155220-1-luca.boccassi%40gmail.com the other comments are invalid: luo is not a kmod, and the write hooks are not set up include/uapi/linux/liveupdate.h | 19 +++++ kernel/liveupdate/luo_session.c | 13 ++++ .../testing/selftests/liveupdate/liveupdate.c | 71 +++++++++++++++++++ 3 files changed, 103 insertions(+) diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h index 30bc66ee9436a..41dc44d239dde 100644 --- a/include/uapi/linux/liveupdate.h +++ b/include/uapi/linux/liveupdate.h @@ -59,6 +59,7 @@ enum { LIVEUPDATE_CMD_SESSION_PRESERVE_FD = LIVEUPDATE_CMD_SESSION_BASE, LIVEUPDATE_CMD_SESSION_RETRIEVE_FD = 0x41, LIVEUPDATE_CMD_SESSION_FINISH = 0x42, + LIVEUPDATE_CMD_SESSION_GET_NAME = 0x43, }; /** @@ -213,4 +214,22 @@ struct liveupdate_session_finish { #define LIVEUPDATE_SESSION_FINISH \ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_FINISH) +/** + * struct liveupdate_session_get_name - ioctl(LIVEUPDATE_SESSION_GET_NAME) + * @size: Input; sizeof(struct liveupdate_session_get_name) + * @name: Output; A null-terminated string with the full session name. + * + * Retrieves the full name of the session associated with this file descriptor. + * This is useful because the kernel may truncate the name shown in /proc. + * + * Return: 0 on success, negative error code on failure. + */ +struct liveupdate_session_get_name { + __u32 size; + __u8 name[LIVEUPDATE_SESSION_NAME_LENGTH]; +}; + +#define LIVEUPDATE_SESSION_GET_NAME \ + _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_NAME) + #endif /* _UAPI_LIVEUPDATE_H */ diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c index 25ae704d77873..af9e498206d24 100644 --- a/kernel/liveupdate/luo_session.c +++ b/kernel/liveupdate/luo_session.c @@ -289,10 +289,21 @@ static int luo_session_finish(struct luo_session *session, return luo_ucmd_respond(ucmd, sizeof(*argp)); } +static int luo_session_get_name(struct luo_session *session, + struct luo_ucmd *ucmd) +{ + struct liveupdate_session_get_name *argp = ucmd->cmd; + + strscpy((char *)argp->name, session->name, sizeof(argp->name)); + + return luo_ucmd_respond(ucmd, sizeof(*argp)); +} + union ucmd_buffer { struct liveupdate_session_finish finish; struct liveupdate_session_preserve_fd preserve; struct liveupdate_session_retrieve_fd retrieve; + struct liveupdate_session_get_name get_name; }; struct luo_ioctl_op { @@ -319,6 +330,8 @@ static const struct luo_ioctl_op luo_session_ioctl_ops[] = { struct liveupdate_session_preserve_fd, token), IOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd, struct liveupdate_session_retrieve_fd, token), + IOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name, + struct liveupdate_session_get_name, name), }; static long luo_session_ioctl(struct file *filep, unsigned int cmd, diff --git a/tools/testing/selftests/liveupdate/liveupdate.c b/tools/testing/selftests/liveupdate/liveupdate.c index c2878e3d5ef90..bdc1cedc4f944 100644 --- a/tools/testing/selftests/liveupdate/liveupdate.c +++ b/tools/testing/selftests/liveupdate/liveupdate.c @@ -102,6 +102,22 @@ static int create_session(int lu_fd, const char *name) return args.fd; } +/* Helper function to get a session name via ioctl. */ +static int get_session_name(int session_fd, char *name, size_t name_len) +{ + struct liveupdate_session_get_name args = {}; + + args.size = sizeof(args); + + if (ioctl(session_fd, LIVEUPDATE_SESSION_GET_NAME, &args)) + return -errno; + + strncpy(name, (char *)args.name, name_len - 1); + name[name_len - 1] = '\0'; + + return 0; +} + /* * Test Case: Create Duplicate Session * @@ -345,4 +361,59 @@ TEST_F(liveupdate_device, preserve_unsupported_fd) ASSERT_EQ(close(session_fd), 0); } +/* + * Test Case: Get Session Name + * + * Verifies that the full session name can be retrieved from a session file + * descriptor via ioctl. + */ +TEST_F(liveupdate_device, get_session_name) +{ + char name_buf[LIVEUPDATE_SESSION_NAME_LENGTH] = {}; + const char *session_name = "get-name-test-session"; + int session_fd; + + self->fd1 = open(LIVEUPDATE_DEV, O_RDWR); + if (self->fd1 < 0 && errno == ENOENT) + SKIP(return, "%s does not exist", LIVEUPDATE_DEV); + ASSERT_GE(self->fd1, 0); + + session_fd = create_session(self->fd1, session_name); + ASSERT_GE(session_fd, 0); + + ASSERT_EQ(get_session_name(session_fd, name_buf, sizeof(name_buf)), 0); + ASSERT_STREQ(name_buf, session_name); + + ASSERT_EQ(close(session_fd), 0); +} + +/* + * Test Case: Get Session Name at Maximum Length + * + * Verifies that a session name using the full LIVEUPDATE_SESSION_NAME_LENGTH + * (minus the null terminator) can be correctly retrieved. + */ +TEST_F(liveupdate_device, get_session_name_max_length) +{ + char name_buf[LIVEUPDATE_SESSION_NAME_LENGTH] = {}; + char long_name[LIVEUPDATE_SESSION_NAME_LENGTH]; + int session_fd; + + memset(long_name, 'A', sizeof(long_name) - 1); + long_name[sizeof(long_name) - 1] = '\0'; + + self->fd1 = open(LIVEUPDATE_DEV, O_RDWR); + if (self->fd1 < 0 && errno == ENOENT) + SKIP(return, "%s does not exist", LIVEUPDATE_DEV); + ASSERT_GE(self->fd1, 0); + + session_fd = create_session(self->fd1, long_name); + ASSERT_GE(session_fd, 0); + + ASSERT_EQ(get_session_name(session_fd, name_buf, sizeof(name_buf)), 0); + ASSERT_STREQ(name_buf, long_name); + + ASSERT_EQ(close(session_fd), 0); +} + TEST_HARNESS_MAIN -- 2.47.3