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Fri, 17 Apr 2026 15:08:40 -0700 (PDT) Received: from localhost ([2a01:4b00:d036:ae00:9586:30a1:a0a6:f076]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-488fb75c695sm25728145e9.14.2026.04.17.15.08.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Apr 2026 15:08:39 -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, linux-kernel@vger.kernel.org, Luca Boccassi Subject: [PATCH v5 3/4] liveupdate: add LIVEUPDATE_SESSION_GET_NAME ioctl Date: Fri, 17 Apr 2026 23:05:44 +0100 Message-ID: <20260417220831.1934945-3-luca.boccassi@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260417220831.1934945-1-luca.boccassi@gmail.com> References: <20260417220831.1934945-1-luca.boccassi@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: D340120006 X-Rspamd-Server: rspam07 X-Stat-Signature: hhc9eue6k3khfb853t4pf6eqj9k77rq6 X-Rspam-User: X-HE-Tag: 1776463721-644399 X-HE-Meta: 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 6f0Vm3oX 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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 --- v5: merge with LUO_SESSION_MAGIC series as they both change the same unit test file, to avoid merge conflicts add '__u32 reserved' to the UAPI struct include/uapi/linux/liveupdate.h | 20 ++++++++++++++++++++ kernel/liveupdate/luo_session.c | 13 +++++++++++++ 2 files changed, 33 insertions(+) diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h index 30bc66ee9436a..079ee6afb15a7 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 +214,23 @@ 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; + __u32 reserved; + __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 5e315cc0dfd52..f30151c37bd43 100644 --- a/kernel/liveupdate/luo_session.c +++ b/kernel/liveupdate/luo_session.c @@ -291,10 +291,21 @@ 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 { @@ -321,6 +332,8 @@ 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, -- 2.47.3