diff options
| -rw-r--r-- | include/uapi/linux/liveupdate.h | 64 | ||||
| -rw-r--r-- | kernel/liveupdate/luo_core.c | 178 | ||||
| -rw-r--r-- | kernel/liveupdate/luo_internal.h | 21 |
3 files changed, 263 insertions, 0 deletions
diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h index 40578ae19668..1183cf984b5f 100644 --- a/include/uapi/linux/liveupdate.h +++ b/include/uapi/linux/liveupdate.h @@ -46,4 +46,68 @@ /* The maximum length of session name including null termination */ #define LIVEUPDATE_SESSION_NAME_LENGTH 64 +/* The /dev/liveupdate ioctl commands */ +enum { + LIVEUPDATE_CMD_BASE = 0x00, + LIVEUPDATE_CMD_CREATE_SESSION = LIVEUPDATE_CMD_BASE, + LIVEUPDATE_CMD_RETRIEVE_SESSION = 0x01, +}; + +/** + * struct liveupdate_ioctl_create_session - ioctl(LIVEUPDATE_IOCTL_CREATE_SESSION) + * @size: Input; sizeof(struct liveupdate_ioctl_create_session) + * @fd: Output; The new file descriptor for the created session. + * @name: Input; A null-terminated string for the session name, max + * length %LIVEUPDATE_SESSION_NAME_LENGTH including termination + * character. + * + * Creates a new live update session for managing preserved resources. + * This ioctl can only be called on the main /dev/liveupdate device. + * + * Return: 0 on success, negative error code on failure. + */ +struct liveupdate_ioctl_create_session { + __u32 size; + __s32 fd; + __u8 name[LIVEUPDATE_SESSION_NAME_LENGTH]; +}; + +#define LIVEUPDATE_IOCTL_CREATE_SESSION \ + _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_CREATE_SESSION) + +/** + * struct liveupdate_ioctl_retrieve_session - ioctl(LIVEUPDATE_IOCTL_RETRIEVE_SESSION) + * @size: Input; sizeof(struct liveupdate_ioctl_retrieve_session) + * @fd: Output; The new file descriptor for the retrieved session. + * @name: Input; A null-terminated string identifying the session to retrieve. + * The name must exactly match the name used when the session was + * created in the previous kernel. + * + * Retrieves a handle (a new file descriptor) for a preserved session by its + * name. This is the primary mechanism for a userspace agent to regain control + * of its preserved resources after a live update. + * + * The userspace application provides the null-terminated `name` of a session + * it created before the live update. If a preserved session with a matching + * name is found, the kernel instantiates it and returns a new file descriptor + * in the `fd` field. This new session FD can then be used for all file-specific + * operations, such as restoring individual file descriptors with + * LIVEUPDATE_SESSION_RETRIEVE_FD. + * + * It is the responsibility of the userspace application to know the names of + * the sessions it needs to retrieve. If no session with the given name is + * found, the ioctl will fail with -ENOENT. + * + * This ioctl can only be called on the main /dev/liveupdate device when the + * system is in the LIVEUPDATE_STATE_UPDATED state. + */ +struct liveupdate_ioctl_retrieve_session { + __u32 size; + __s32 fd; + __u8 name[LIVEUPDATE_SESSION_NAME_LENGTH]; +}; + +#define LIVEUPDATE_IOCTL_RETRIEVE_SESSION \ + _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_RETRIEVE_SESSION) + #endif /* _UAPI_LIVEUPDATE_H */ diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c index a0f7788cd003..f7ecaf7740d1 100644 --- a/kernel/liveupdate/luo_core.c +++ b/kernel/liveupdate/luo_core.c @@ -41,7 +41,13 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/atomic.h> +#include <linux/errno.h> +#include <linux/file.h> +#include <linux/fs.h> +#include <linux/init.h> #include <linux/io.h> +#include <linux/kernel.h> #include <linux/kexec_handover.h> #include <linux/kho/abi/luo.h> #include <linux/kobject.h> @@ -246,12 +252,183 @@ bool liveupdate_enabled(void) return luo_global.enabled; } +/** + * DOC: LUO ioctl Interface + * + * The IOCTL user-space control interface for the LUO subsystem. + * It registers a character device, typically found at ``/dev/liveupdate``, + * which allows a userspace agent to manage the LUO state machine and its + * associated resources, such as preservable file descriptors. + * + * To ensure that the state machine is controlled by a single entity, access + * to this device is exclusive: only one process is permitted to have + * ``/dev/liveupdate`` open at any given time. Subsequent open attempts will + * fail with -EBUSY until the first process closes its file descriptor. + * This singleton model simplifies state management by preventing conflicting + * commands from multiple userspace agents. + */ + struct luo_device_state { struct miscdevice miscdev; + atomic_t in_use; }; +static int luo_ioctl_create_session(struct luo_ucmd *ucmd) +{ + struct liveupdate_ioctl_create_session *argp = ucmd->cmd; + struct file *file; + int err; + + argp->fd = get_unused_fd_flags(O_CLOEXEC); + if (argp->fd < 0) + return argp->fd; + + err = luo_session_create(argp->name, &file); + if (err) + goto err_put_fd; + + err = luo_ucmd_respond(ucmd, sizeof(*argp)); + if (err) + goto err_put_file; + + fd_install(argp->fd, file); + + return 0; + +err_put_file: + fput(file); +err_put_fd: + put_unused_fd(argp->fd); + + return err; +} + +static int luo_ioctl_retrieve_session(struct luo_ucmd *ucmd) +{ + struct liveupdate_ioctl_retrieve_session *argp = ucmd->cmd; + struct file *file; + int err; + + argp->fd = get_unused_fd_flags(O_CLOEXEC); + if (argp->fd < 0) + return argp->fd; + + err = luo_session_retrieve(argp->name, &file); + if (err < 0) + goto err_put_fd; + + err = luo_ucmd_respond(ucmd, sizeof(*argp)); + if (err) + goto err_put_file; + + fd_install(argp->fd, file); + + return 0; + +err_put_file: + fput(file); +err_put_fd: + put_unused_fd(argp->fd); + + return err; +} + +static int luo_open(struct inode *inodep, struct file *filep) +{ + struct luo_device_state *ldev = container_of(filep->private_data, + struct luo_device_state, + miscdev); + + if (atomic_cmpxchg(&ldev->in_use, 0, 1)) + return -EBUSY; + + /* Always return -EIO to user if deserialization fail */ + if (luo_session_deserialize()) { + atomic_set(&ldev->in_use, 0); + return -EIO; + } + + return 0; +} + +static int luo_release(struct inode *inodep, struct file *filep) +{ + struct luo_device_state *ldev = container_of(filep->private_data, + struct luo_device_state, + miscdev); + atomic_set(&ldev->in_use, 0); + + return 0; +} + +union ucmd_buffer { + struct liveupdate_ioctl_create_session create; + struct liveupdate_ioctl_retrieve_session retrieve; +}; + +struct luo_ioctl_op { + unsigned int size; + unsigned int min_size; + unsigned int ioctl_num; + int (*execute)(struct luo_ucmd *ucmd); +}; + +#define IOCTL_OP(_ioctl, _fn, _struct, _last) \ + [_IOC_NR(_ioctl) - LIVEUPDATE_CMD_BASE] = { \ + .size = sizeof(_struct) + \ + BUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) < \ + sizeof(_struct)), \ + .min_size = offsetofend(_struct, _last), \ + .ioctl_num = _ioctl, \ + .execute = _fn, \ + } + +static const struct luo_ioctl_op luo_ioctl_ops[] = { + IOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session, + struct liveupdate_ioctl_create_session, name), + IOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session, + struct liveupdate_ioctl_retrieve_session, name), +}; + +static long luo_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) +{ + const struct luo_ioctl_op *op; + struct luo_ucmd ucmd = {}; + union ucmd_buffer buf; + unsigned int nr; + int err; + + nr = _IOC_NR(cmd); + if (nr < LIVEUPDATE_CMD_BASE || + (nr - LIVEUPDATE_CMD_BASE) >= ARRAY_SIZE(luo_ioctl_ops)) { + return -EINVAL; + } + + ucmd.ubuffer = (void __user *)arg; + err = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer); + if (err) + return err; + + op = &luo_ioctl_ops[nr - LIVEUPDATE_CMD_BASE]; + if (op->ioctl_num != cmd) + return -ENOIOCTLCMD; + if (ucmd.user_size < op->min_size) + return -EINVAL; + + ucmd.cmd = &buf; + err = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer, + ucmd.user_size); + if (err) + return err; + + return op->execute(&ucmd); +} + static const struct file_operations luo_fops = { .owner = THIS_MODULE, + .open = luo_open, + .release = luo_release, + .unlocked_ioctl = luo_ioctl, }; static struct luo_device_state luo_dev = { @@ -260,6 +437,7 @@ static struct luo_device_state luo_dev = { .name = "liveupdate", .fops = &luo_fops, }, + .in_use = ATOMIC_INIT(0), }; static int __init liveupdate_ioctl_init(void) diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h index 05ae91695ec6..1292ac47eef8 100644 --- a/kernel/liveupdate/luo_internal.h +++ b/kernel/liveupdate/luo_internal.h @@ -9,6 +9,27 @@ #define _LINUX_LUO_INTERNAL_H #include <linux/liveupdate.h> +#include <linux/uaccess.h> + +struct luo_ucmd { + void __user *ubuffer; + u32 user_size; + void *cmd; +}; + +static inline int luo_ucmd_respond(struct luo_ucmd *ucmd, + size_t kernel_cmd_size) +{ + /* + * Copy the minimum of what the user provided and what we actually + * have. + */ + if (copy_to_user(ucmd->ubuffer, ucmd->cmd, + min_t(size_t, ucmd->user_size, kernel_cmd_size))) { + return -EFAULT; + } + return 0; +} /* * Handles a deserialization failure: devices and memory is in unpredictable |