mirror of
https://github.com/checkpoint-restore/criu
synced 2025-08-22 18:07:57 +00:00
0412152fc5
There are cases where a process's file descriptor cannot be restored from the checkpoint images. For example, a pipe file descriptor with one end in the checkpointed process and the other end in a separate process (that was not part of the checkpointed process tree) cannot be restored because after checkpoint the pipe will be broken. There are also cases where the user wants to use a new file during restore instead of the original file at checkpoint time. For example, the user wants to change the log file of a process from /path/to/oldlog to /path/to/newlog. In these cases, criu's caller should set up a new file descriptor to be inherited by the restored process and specify the file descriptor with the --inherit-fd command line option. The argument of --inherit-fd has the format fd[%d]:%s, where %d tells criu which of its own file descriptors to use for restoring the file identified by %s. As a debugging aid, if the argument has the format debug[%d]:%s, it tells criu to write out the string after colon to the file descriptor %d. This can be used, for example, as an easy way to leave a "restore marker" in the output stream of the process. It's important to note that inherit fd support breaks applications that depend on the state of the file descriptor being inherited. So, consider inherit fd only for specific use cases that you know for sure won't break the application. For examples please visit http://criu.org/Category:HOWTO. v2: Added a check in send_fd_to_self() to avoid closing an inherit fd. Also, as an extra measure of caution, added checks in the inherit fd look up functions to make sure that the inherit fd hasn't been reused. The patch also includes minor cosmetic changes. Signed-off-by: Saied Kazemi <saied@google.com> Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
179 lines
4.9 KiB
C
179 lines
4.9 KiB
C
#ifndef __CR_FILES_H__
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#define __CR_FILES_H__
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#include "compiler.h"
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#include "asm/types.h"
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#include "fcntl.h"
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#include "lock.h"
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#include "list.h"
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#include "image.h"
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#include "pid.h"
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#include "rst_info.h"
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#include "protobuf/fdinfo.pb-c.h"
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#include "protobuf/fown.pb-c.h"
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#include "protobuf/vma.pb-c.h"
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struct pstree_item;
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struct file_desc;
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struct cr_imgset;
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struct rst_info;
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struct parasite_ctl;
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struct fd_link {
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union {
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/* Link info for generic file (path) */
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struct {
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char name[PATH_MAX + 1];
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size_t len;
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};
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/* Link info for proc-ns file */
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struct {
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struct ns_desc *ns_d;
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unsigned int ns_kid;
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};
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};
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};
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struct fd_parms {
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int fd;
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off_t pos;
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unsigned int flags;
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char fd_flags;
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struct stat stat;
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pid_t pid;
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FownEntry fown;
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struct fd_link *link;
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long fs_type;
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int mnt_id;
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struct parasite_ctl *ctl;
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};
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#define FD_PARMS_INIT \
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(struct fd_parms) { \
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.fd = FD_DESC_INVALID, \
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.fown = FOWN_ENTRY__INIT, \
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.link = NULL, \
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.mnt_id = -1, \
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}
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extern int fill_fdlink(int lfd, const struct fd_parms *p, struct fd_link *link);
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struct file_desc;
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struct fdinfo_list_entry {
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struct list_head desc_list; /* To chain on @fd_info_head */
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struct file_desc *desc; /* Associated file descriptor */
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struct list_head ps_list; /* To chain per-task files */
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int pid;
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futex_t real_pid;
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FdinfoEntry *fe;
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};
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/* reports whether fd_a takes prio over fd_b */
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static inline int fdinfo_rst_prio(struct fdinfo_list_entry *fd_a, struct fdinfo_list_entry *fd_b)
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{
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return pid_rst_prio(fd_a->pid, fd_b->pid) ||
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((fd_a->pid == fd_b->pid) && (fd_a->fe->fd < fd_b->fe->fd));
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}
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struct file_desc_ops {
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/* fd_types from protobuf/fdinfo.proto */
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unsigned int type;
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/*
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* Opens a file by whatever syscall is required for that.
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* The returned descriptor may be closed (dup2-ed to another)
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* so it shouldn't be saved for any post-actions.
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*/
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int (*open)(struct file_desc *d);
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/*
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* Called on a file when all files of that type are opened
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* and with the fd being the "restored" one.
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*/
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int (*post_open)(struct file_desc *d, int fd);
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/*
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* Report whether the fd in question wants a transport socket
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* in it instead of a real file. See file_master for details.
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*/
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int (*want_transport)(FdinfoEntry *fe, struct file_desc *d);
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/*
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* Called to collect a new fd before adding it on desc. Clients
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* may chose to collect it to some specific rst_info list. See
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* prepare_fds() for details.
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*/
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void (*collect_fd)(struct file_desc *, struct fdinfo_list_entry *,
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struct rst_info *);
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};
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static inline void collect_gen_fd(struct fdinfo_list_entry *fle, struct rst_info *ri)
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{
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list_add_tail(&fle->ps_list, &ri->fds);
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}
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struct file_desc {
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u32 id; /* File id, unique */
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struct hlist_node hash; /* Descriptor hashing and lookup */
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struct list_head fd_info_head; /* Chain of fdinfo_list_entry-s with same ID and type but different pids */
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struct file_desc_ops *ops; /* Associated operations */
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};
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struct fdtype_ops {
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unsigned int type;
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int (*dump)(int lfd, u32 id, const struct fd_parms *p);
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int (*pre_dump)(int pid, int lfd);
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};
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struct cr_img;
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extern int do_dump_gen_file(struct fd_parms *p, int lfd,
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const struct fdtype_ops *ops,
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struct cr_img *);
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struct parasite_drain_fd;
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int dump_task_files_seized(struct parasite_ctl *ctl, struct pstree_item *item,
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struct parasite_drain_fd *dfds);
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int predump_task_files(int pid);
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extern void file_desc_init(struct file_desc *d, u32 id, struct file_desc_ops *ops);
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extern int file_desc_add(struct file_desc *d, u32 id, struct file_desc_ops *ops);
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extern struct fdinfo_list_entry *file_master(struct file_desc *d);
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extern struct file_desc *find_file_desc_raw(int type, u32 id);
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extern int send_fd_to_peer(int fd, struct fdinfo_list_entry *fle, int sock);
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extern int restore_fown(int fd, FownEntry *fown);
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extern int rst_file_params(int fd, FownEntry *fown, int flags);
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extern void show_saved_files(void);
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extern int prepare_fds(struct pstree_item *me);
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extern int prepare_fd_pid(struct pstree_item *me);
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extern int prepare_ctl_tty(int pid, struct rst_info *rst_info, u32 ctl_tty_id);
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extern int prepare_shared_fdinfo(void);
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extern int get_filemap_fd(struct vma_area *);
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extern int restore_fs(struct pstree_item *);
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extern int prepare_fs_pid(struct pstree_item *);
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extern int set_fd_flags(int fd, int flags);
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extern int close_old_fds(struct pstree_item *me);
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#ifndef AT_EMPTY_PATH
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#define AT_EMPTY_PATH 0x1000
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#endif
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#define LREMAP_PARAM "link-remap"
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extern int shared_fdt_prepare(struct pstree_item *item);
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extern struct collect_image_info ext_file_cinfo;
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extern int dump_unsupp_fd(struct fd_parms *p, int lfd,
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struct cr_img *, char *more, char *info);
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extern int inherit_fd_add(char *optarg);
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extern void inherit_fd_log(void);
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extern int inherit_fd_lookup_id(char *id);
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extern struct inherit_fd *inherit_fd_lookup_fd(int fd, const char *caller);
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extern int inherit_fd_resolve_clash(int fd);
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extern int inherit_fd_fini(void);
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#endif /* __CR_FILES_H__ */
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