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Sat, 18 Apr 2026 04:40:01 -0700 (PDT) Received: from localhost ([2a01:4b00:d036:ae00:3ab1:89ce:8d93:ae6c]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-488fb74c789sm39341825e9.5.2026.04.18.04.40.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Apr 2026 04:40:01 -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 v6 3/4] liveupdate: add LIVEUPDATE_SESSION_GET_NAME ioctl Date: Sat, 18 Apr 2026 12:38:40 +0100 Message-ID: <20260418113956.2146648-3-luca.boccassi@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260418113956.2146648-1-luca.boccassi@gmail.com> References: <20260418113956.2146648-1-luca.boccassi@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7878840010 X-Stat-Signature: xs9kqs1tpmk4r9p34qrrpg41jfaebx14 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1776512403-156428 X-HE-Meta: U2FsdGVkX18QVq+e7PjoXRraCGGSXPL8tR14xwpAYuCcHsWcYT8n7Cigpyy9XOlD3vBKRPSrHN/D5HU/Zrsf1RoDah1a2WOlVrOMgoHu53d8mCr67J+UhopWk6bnQolsCxL32mJ6SqadTzYbmG82nJDTk7swSdo2KCAdxXJiExMyKyrjr5QxQnR4W3Fh1Wpzx7w76tbxLsEGZT0VAL8peItMEFHAX7MlEDB5eBb8948B2B7yARqC856yRUL6u4+lXt8XJzEX9ODuPbZnuAzyI4UPuDxPdXFn/GPtIbqV2UxE0qqMOj+2WUnaphPoIFP6pdq24Kg2PmdVVaOqLhkMehFb8L9G50HPP7yF51KKt0d6yLl2kmb3DK0J3h6FgXhqyLbeuSA7kJ/JNCS89clo3Vl4g3uBBgIvW8m48xU0jiT1gKIq4K5ZIj7p/f82N9mIZ2XT9KIMgul65DuNqjjqA/MO9taWYstuy5XDz2YqyHW5yfsYChec51mICQBxscpgVihNwuzJeN6VQSgCJty/ZFd/Ie+P1A1oIXNxtog7HHeypEfo3X0E9CEYtpvWMzjngokWOQ17jAMJBylE4J19krx5z9H4sQJkatBLT7yv0x2+CQCIU1bp2ANSc4KBzFgLbBFqQkdcmm1HKjIJkBUN6D2QGLCglDPBMRWyImNehKYIc9n+xdINOLBW3i4ZwCOhhyef2riNi/zjILZYhaBNobtXTCVJJESMyXPkj0zQPLcsm0YgaLfO0fifHlb4E71jrLTnY/L+YmLkfBPpUnjb0pU4GZkKnshtvXKHHEngCEySZBFPNP+84EOzuScmo3vyndoa9VWwhlethP+WKO3WjN7tDHcv0U3ErRYLjq/Ax8L49PsPHaCmBbnFjAfaJeTsDxUGxA6OLACahtYu/oklTgXKg8leswd3a3pbqAyiIRtRyXWk6X05abqbdnrNrmvQOL4QPsldBwsvrLNW9xp JiHpJRom 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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 v6: fix docstring include/uapi/linux/liveupdate.h | 21 +++++++++++++++++++++ kernel/liveupdate/luo_session.c | 13 +++++++++++++ 2 files changed, 34 insertions(+) diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h index 30bc66ee9436..3a9ff53b02e0 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 +214,24 @@ 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) + * @reserved: Input; Must be zero. Reserved for future use. + * @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 5e315cc0dfd5..f30151c37bd4 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