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Wed, 15 Apr 2026 11:46:51 -0700 (PDT) Received: from localhost ([2a01:4b00:d036:ae00:1648:8c4d:e867:9ebb]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-43ead356616sm7204165f8f.13.2026.04.15.11.46.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2026 11:46:51 -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: Wed, 15 Apr 2026 19:46:14 +0100 Message-ID: <20260415184644.1155360-1-luca.boccassi@gmail.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 8CA271C0006 X-Rspamd-Server: rspam12 X-Stat-Signature: 19k9qr4gocckduq38wugz1apo73kowhd X-Rspam-User: X-HE-Tag: 1776278813-929690 X-HE-Meta: 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 PiDXbb0W 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 --- v2: adjusted the commit message a bit and rebased on liveupdate/next 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