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15df03c879
For a custom microbenchmark on a 3.30GHz Xeon SandyBridge, which calls
IPC_STAT over and over, it was calculated that, on avg the cost of
ipc_get_maxid() for increasing amounts of keys was:
10 keys: ~900 cycles
100 keys: ~15000 cycles
1000 keys: ~150000 cycles
10000 keys: ~2100000 cycles
This is unsurprising as maxid is currently O(n).
By having the max_id available in O(1) we save all those cycles for each
semctl(_STAT) command, the idr_find can be expensive -- which some real
(customer) workloads actually poll on.
Note that this used to be the case, until commit 7ca7e564e0 ("ipc:
store ipcs into IDRs"). The cost is the extra idr_find when doing
RMIDs, but we simply go backwards, and should not take too many
iterations to find the new value.
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20170831172049.14576-5-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
239 lines
7.2 KiB
C
239 lines
7.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* linux/ipc/util.h
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* Copyright (C) 1999 Christoph Rohland
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*
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* ipc helper functions (c) 1999 Manfred Spraul <manfred@colorfullife.com>
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* namespaces support. 2006 OpenVZ, SWsoft Inc.
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* Pavel Emelianov <xemul@openvz.org>
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*/
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#ifndef _IPC_UTIL_H
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#define _IPC_UTIL_H
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#include <linux/unistd.h>
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#include <linux/err.h>
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#include <linux/ipc_namespace.h>
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#define SEQ_MULTIPLIER (IPCMNI)
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int sem_init(void);
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int msg_init(void);
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void shm_init(void);
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struct ipc_namespace;
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#ifdef CONFIG_POSIX_MQUEUE
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extern void mq_clear_sbinfo(struct ipc_namespace *ns);
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extern void mq_put_mnt(struct ipc_namespace *ns);
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#else
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static inline void mq_clear_sbinfo(struct ipc_namespace *ns) { }
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static inline void mq_put_mnt(struct ipc_namespace *ns) { }
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#endif
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#ifdef CONFIG_SYSVIPC
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int sem_init_ns(struct ipc_namespace *ns);
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int msg_init_ns(struct ipc_namespace *ns);
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int shm_init_ns(struct ipc_namespace *ns);
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void sem_exit_ns(struct ipc_namespace *ns);
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void msg_exit_ns(struct ipc_namespace *ns);
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void shm_exit_ns(struct ipc_namespace *ns);
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#else
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static inline int sem_init_ns(struct ipc_namespace *ns) { return 0; }
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static inline int msg_init_ns(struct ipc_namespace *ns) { return 0; }
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static inline int shm_init_ns(struct ipc_namespace *ns) { return 0; }
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static inline void sem_exit_ns(struct ipc_namespace *ns) { }
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static inline void msg_exit_ns(struct ipc_namespace *ns) { }
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static inline void shm_exit_ns(struct ipc_namespace *ns) { }
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#endif
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/*
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* Structure that holds the parameters needed by the ipc operations
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* (see after)
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*/
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struct ipc_params {
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key_t key;
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int flg;
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union {
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size_t size; /* for shared memories */
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int nsems; /* for semaphores */
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} u; /* holds the getnew() specific param */
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};
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/*
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* Structure that holds some ipc operations. This structure is used to unify
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* the calls to sys_msgget(), sys_semget(), sys_shmget()
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* . routine to call to create a new ipc object. Can be one of newque,
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* newary, newseg
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* . routine to call to check permissions for a new ipc object.
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* Can be one of security_msg_associate, security_sem_associate,
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* security_shm_associate
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* . routine to call for an extra check if needed
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*/
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struct ipc_ops {
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int (*getnew)(struct ipc_namespace *, struct ipc_params *);
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int (*associate)(struct kern_ipc_perm *, int);
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int (*more_checks)(struct kern_ipc_perm *, struct ipc_params *);
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};
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struct seq_file;
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struct ipc_ids;
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int ipc_init_ids(struct ipc_ids *);
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#ifdef CONFIG_PROC_FS
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void __init ipc_init_proc_interface(const char *path, const char *header,
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int ids, int (*show)(struct seq_file *, void *));
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#else
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#define ipc_init_proc_interface(path, header, ids, show) do {} while (0)
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#endif
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#define IPC_SEM_IDS 0
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#define IPC_MSG_IDS 1
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#define IPC_SHM_IDS 2
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#define ipcid_to_idx(id) ((id) % SEQ_MULTIPLIER)
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#define ipcid_to_seqx(id) ((id) / SEQ_MULTIPLIER)
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#define IPCID_SEQ_MAX min_t(int, INT_MAX/SEQ_MULTIPLIER, USHRT_MAX)
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/* must be called with ids->rwsem acquired for writing */
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int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);
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/* must be called with both locks acquired. */
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void ipc_rmid(struct ipc_ids *, struct kern_ipc_perm *);
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/* must be called with both locks acquired. */
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void ipc_set_key_private(struct ipc_ids *, struct kern_ipc_perm *);
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/* must be called with ipcp locked */
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int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flg);
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/**
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* ipc_get_maxid - get the last assigned id
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* @ids: ipc identifier set
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*
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* Called with ipc_ids.rwsem held for reading.
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*/
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static inline int ipc_get_maxid(struct ipc_ids *ids)
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{
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if (ids->in_use == 0)
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return -1;
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if (ids->in_use == IPCMNI)
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return IPCMNI - 1;
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return ids->max_id;
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}
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/*
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* For allocation that need to be freed by RCU.
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* Objects are reference counted, they start with reference count 1.
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* getref increases the refcount, the putref call that reduces the recount
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* to 0 schedules the rcu destruction. Caller must guarantee locking.
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*
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* refcount is initialized by ipc_addid(), before that point call_rcu()
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* must be used.
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*/
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int ipc_rcu_getref(struct kern_ipc_perm *ptr);
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void ipc_rcu_putref(struct kern_ipc_perm *ptr,
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void (*func)(struct rcu_head *head));
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struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
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struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id);
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void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out);
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void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out);
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int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out);
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struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
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struct ipc_ids *ids, int id, int cmd,
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struct ipc64_perm *perm, int extra_perm);
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#ifndef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
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/* On IA-64, we always use the "64-bit version" of the IPC structures. */
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# define ipc_parse_version(cmd) IPC_64
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#else
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int ipc_parse_version(int *cmd);
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#endif
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extern void free_msg(struct msg_msg *msg);
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extern struct msg_msg *load_msg(const void __user *src, size_t len);
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extern struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst);
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extern int store_msg(void __user *dest, struct msg_msg *msg, size_t len);
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static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int uid)
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{
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return uid / SEQ_MULTIPLIER != ipcp->seq;
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}
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static inline void ipc_lock_object(struct kern_ipc_perm *perm)
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{
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spin_lock(&perm->lock);
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}
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static inline void ipc_unlock_object(struct kern_ipc_perm *perm)
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{
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spin_unlock(&perm->lock);
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}
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static inline void ipc_assert_locked_object(struct kern_ipc_perm *perm)
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{
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assert_spin_locked(&perm->lock);
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}
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static inline void ipc_unlock(struct kern_ipc_perm *perm)
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{
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ipc_unlock_object(perm);
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rcu_read_unlock();
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}
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/*
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* ipc_valid_object() - helper to sort out IPC_RMID races for codepaths
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* where the respective ipc_ids.rwsem is not being held down.
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* Checks whether the ipc object is still around or if it's gone already, as
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* ipc_rmid() may have already freed the ID while the ipc lock was spinning.
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* Needs to be called with kern_ipc_perm.lock held -- exception made for one
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* checkpoint case at sys_semtimedop() as noted in code commentary.
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*/
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static inline bool ipc_valid_object(struct kern_ipc_perm *perm)
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{
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return !perm->deleted;
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}
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struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id);
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int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
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const struct ipc_ops *ops, struct ipc_params *params);
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void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
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void (*free)(struct ipc_namespace *, struct kern_ipc_perm *));
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#ifdef CONFIG_COMPAT
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#include <linux/compat.h>
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struct compat_ipc_perm {
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key_t key;
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__compat_uid_t uid;
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__compat_gid_t gid;
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__compat_uid_t cuid;
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__compat_gid_t cgid;
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compat_mode_t mode;
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unsigned short seq;
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};
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void to_compat_ipc_perm(struct compat_ipc_perm *, struct ipc64_perm *);
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void to_compat_ipc64_perm(struct compat_ipc64_perm *, struct ipc64_perm *);
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int get_compat_ipc_perm(struct ipc64_perm *, struct compat_ipc_perm __user *);
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int get_compat_ipc64_perm(struct ipc64_perm *,
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struct compat_ipc64_perm __user *);
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static inline int compat_ipc_parse_version(int *cmd)
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{
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#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
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int version = *cmd & IPC_64;
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*cmd &= ~IPC_64;
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return version;
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#else
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return IPC_64;
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#endif
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}
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#endif
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#endif
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