1. 根目录:
2. include
3. linux
4. ipc_namespace.h

#ifndef __IPC_NAMESPACE_H__
#define __IPC_NAMESPACE_H__

#include <linux/err.h>
#include <linux/idr.h>
#include <linux/rwsem.h>
#include <linux/notifier.h>
#include <linux/nsproxy.h>
#include <linux/ns_common.h>

struct user_namespace;

struct ipc_ids {
	int in_use;
	unsigned short seq;
	struct rw_semaphore rwsem;
	struct idr ipcs_idr;
	int next_id;
};

struct ipc_namespace {
	atomic_t	count;
	struct ipc_ids	ids[3];

	int		sem_ctls[4];
	int		used_sems;

	unsigned int	msg_ctlmax;
	unsigned int	msg_ctlmnb;
	unsigned int	msg_ctlmni;
	atomic_t	msg_bytes;
	atomic_t	msg_hdrs;

	size_t		shm_ctlmax;
	size_t		shm_ctlall;
	unsigned long	shm_tot;
	int		shm_ctlmni;
	/*
	 * Defines whether IPC_RMID is forced for _all_ shm segments regardless
	 * of shmctl()
	 */
	int		shm_rmid_forced;

	struct notifier_block ipcns_nb;

	/* The kern_mount of the mqueuefs sb.  We take a ref on it */
	struct vfsmount	*mq_mnt;

	/* # queues in this ns, protected by mq_lock */
	unsigned int    mq_queues_count;

	/* next fields are set through sysctl */
	unsigned int    mq_queues_max;   /* initialized to DFLT_QUEUESMAX */
	unsigned int    mq_msg_max;      /* initialized to DFLT_MSGMAX */
	unsigned int    mq_msgsize_max;  /* initialized to DFLT_MSGSIZEMAX */
	unsigned int    mq_msg_default;
	unsigned int    mq_msgsize_default;

	/* user_ns which owns the ipc ns */
	struct user_namespace *user_ns;

	struct ns_common ns;
};

extern struct ipc_namespace init_ipc_ns;
extern atomic_t nr_ipc_ns;

extern spinlock_t mq_lock;

#ifdef CONFIG_SYSVIPC
extern void shm_destroy_orphaned(struct ipc_namespace *ns);
#else /* CONFIG_SYSVIPC */
static inline void shm_destroy_orphaned(struct ipc_namespace *ns) {}
#endif /* CONFIG_SYSVIPC */

#ifdef CONFIG_POSIX_MQUEUE
extern int mq_init_ns(struct ipc_namespace *ns);
/*
 * POSIX Message Queue default values:
 *
 * MIN_*: Lowest value an admin can set the maximum unprivileged limit to
 * DFLT_*MAX: Default values for the maximum unprivileged limits
 * DFLT_{MSG,MSGSIZE}: Default values used when the user doesn't supply
 *   an attribute to the open call and the queue must be created
 * HARD_*: Highest value the maximums can be set to.  These are enforced
 *   on CAP_SYS_RESOURCE apps as well making them inviolate (so make them
 *   suitably high)
 *
 * POSIX Requirements:
 *   Per app minimum openable message queues - 8.  This does not map well
 *     to the fact that we limit the number of queues on a per namespace
 *     basis instead of a per app basis.  So, make the default high enough
 *     that no given app should have a hard time opening 8 queues.
 *   Minimum maximum for HARD_MSGMAX - 32767.  I bumped this to 65536.
 *   Minimum maximum for HARD_MSGSIZEMAX - POSIX is silent on this.  However,
 *     we have run into a situation where running applications in the wild
 *     require this to be at least 5MB, and preferably 10MB, so I set the
 *     value to 16MB in hopes that this user is the worst of the bunch and
 *     the new maximum will handle anyone else.  I may have to revisit this
 *     in the future.
 */
#define DFLT_QUEUESMAX		      256
#define MIN_MSGMAX			1
#define DFLT_MSG		       10U
#define DFLT_MSGMAX		       10
#define HARD_MSGMAX		    65536
#define MIN_MSGSIZEMAX		      128
#define DFLT_MSGSIZE		     8192U
#define DFLT_MSGSIZEMAX		     8192
#define HARD_MSGSIZEMAX	    (16*1024*1024)
#else
static inline int mq_init_ns(struct ipc_namespace *ns) { return 0; }
#endif

#if defined(CONFIG_IPC_NS)
extern struct ipc_namespace *copy_ipcs(unsigned long flags,
	struct user_namespace *user_ns, struct ipc_namespace *ns);

static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
{
	if (ns)
		atomic_inc(&ns->count);
	return ns;
}

extern void put_ipc_ns(struct ipc_namespace *ns);
#else
static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
	struct user_namespace *user_ns, struct ipc_namespace *ns)
{
	if (flags & CLONE_NEWIPC)
		return ERR_PTR(-EINVAL);

	return ns;
}

static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
{
	return ns;
}

static inline void put_ipc_ns(struct ipc_namespace *ns)
{
}
#endif

#ifdef CONFIG_POSIX_MQUEUE_SYSCTL

struct ctl_table_header;
extern struct ctl_table_header *mq_register_sysctl_table(void);

#else /* CONFIG_POSIX_MQUEUE_SYSCTL */

static inline struct ctl_table_header *mq_register_sysctl_table(void)
{
	return NULL;
}

#endif /* CONFIG_POSIX_MQUEUE_SYSCTL */
#endif