IPC之util.h源码解读

Posted 2021-03-23 still-smile

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * linux/ipc/util.h
 * Copyright (C) 1999 Christoph Rohland
 *
 * ipc helper functions (c) 1999 Manfred Spraul <[e-mail]>
 * namespaces support.      2006 OpenVZ, SWsoft Inc.
 *                               Pavel Emelianov <[e-mail]>
 */

#ifndef _IPC_UTIL_H
#define _IPC_UTIL_H

#include <linux/unistd.h>
#include <linux/err.h>
#include <linux/ipc_namespace.h>

/*
 * The IPC ID contains 2 separate numbers - index and sequence number.
 * By default,
 *   bits  0-14: index (32k, 15 bits)
 *   bits 15-30: sequence number (64k, 16 bits)
 *
 * When IPCMNI extension mode is turned on, the composition changes:
 *   bits  0-23: index (16M, 24 bits)
 *   bits 24-30: sequence number (128, 7 bits)
 */
#define IPCMNI_SHIFT		15
#define IPCMNI_EXTEND_SHIFT	24
#define IPCMNI_EXTEND_MIN_CYCLE	(RADIX_TREE_MAP_SIZE * RADIX_TREE_MAP_SIZE)
#define IPCMNI			(1 << IPCMNI_SHIFT)
#define IPCMNI_EXTEND		(1 << IPCMNI_EXTEND_SHIFT)

#ifdef CONFIG_SYSVIPC_SYSCTL
extern int ipc_mni;
extern int ipc_mni_shift;
extern int ipc_min_cycle;

#define ipcmni_seq_shift()	ipc_mni_shift
#define IPCMNI_IDX_MASK		((1 << ipc_mni_shift) - 1)

#else /* CONFIG_SYSVIPC_SYSCTL */

#define ipc_mni			IPCMNI
#define ipc_min_cycle		((int)RADIX_TREE_MAP_SIZE)
#define ipcmni_seq_shift()	IPCMNI_SHIFT
#define IPCMNI_IDX_MASK		((1 << IPCMNI_SHIFT) - 1)
#endif /* CONFIG_SYSVIPC_SYSCTL */

void sem_init(void);
void msg_init(void);
void shm_init(void);

struct ipc_namespace;
struct pid_namespace;

#ifdef CONFIG_POSIX_MQUEUE
extern void mq_clear_sbinfo(struct ipc_namespace *ns);
extern void mq_put_mnt(struct ipc_namespace *ns);
#else
static inline void mq_clear_sbinfo(struct ipc_namespace *ns) { }
static inline void mq_put_mnt(struct ipc_namespace *ns) { }
#endif

#ifdef CONFIG_SYSVIPC
void sem_init_ns(struct ipc_namespace *ns);
void msg_init_ns(struct ipc_namespace *ns);
void shm_init_ns(struct ipc_namespace *ns);

void sem_exit_ns(struct ipc_namespace *ns);
void msg_exit_ns(struct ipc_namespace *ns);
void shm_exit_ns(struct ipc_namespace *ns);
#else
static inline void sem_init_ns(struct ipc_namespace *ns) { }
static inline void msg_init_ns(struct ipc_namespace *ns) { }
static inline void shm_init_ns(struct ipc_namespace *ns) { }

static inline void sem_exit_ns(struct ipc_namespace *ns) { }
static inline void msg_exit_ns(struct ipc_namespace *ns) { }
static inline void shm_exit_ns(struct ipc_namespace *ns) { }
#endif

/*
 * Structure that holds the parameters needed by the ipc operations
 * (see after)
 */
struct ipc_params {
	key_t key;
	int flg;
	union {
		size_t size;	/* for shared memories */
		int nsems;	/* for semaphores */
	} u;			/* holds the getnew() specific param */
};

/*
 * Structure that holds some ipc operations. This structure is used to unify
 * the calls to sys_msgget(), sys_semget(), sys_shmget()
 *      . routine to call to create a new ipc object. Can be one of newque,
 *        newary, newseg
 *      . routine to call to check permissions for a new ipc object.
 *        Can be one of security_msg_associate, security_sem_associate,
 *        security_shm_associate
 *      . routine to call for an extra check if needed
 */
struct ipc_ops {
	int (*getnew)(struct ipc_namespace *, struct ipc_params *);
	int (*associate)(struct kern_ipc_perm *, int);
	int (*more_checks)(struct kern_ipc_perm *, struct ipc_params *);
};

struct seq_file;
struct ipc_ids;

void ipc_init_ids(struct ipc_ids *ids);
#ifdef CONFIG_PROC_FS
void __init ipc_init_proc_interface(const char *path, const char *header,
		int ids, int (*show)(struct seq_file *, void *));
struct pid_namespace *ipc_seq_pid_ns(struct seq_file *);
#else
#define ipc_init_proc_interface(path, header, ids, show) do {} while (0)
#endif

#define IPC_SEM_IDS	0
#define IPC_MSG_IDS	1
#define IPC_SHM_IDS	2

#define ipcid_to_idx(id)  ((id) & IPCMNI_IDX_MASK)
#define ipcid_to_seqx(id) ((id) >> ipcmni_seq_shift())
#define ipcid_seq_max()	  (INT_MAX >> ipcmni_seq_shift())

/* must be called with ids->rwsem acquired for writing */
int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);

/* must be called with both locks acquired. */
void ipc_rmid(struct ipc_ids *, struct kern_ipc_perm *);

/* must be called with both locks acquired. */
void ipc_set_key_private(struct ipc_ids *, struct kern_ipc_perm *);

/* must be called with ipcp locked */
int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flg);

/**
 * ipc_get_maxidx - get the highest assigned index
 * @ids: ipc identifier set
 *
 * Called with ipc_ids.rwsem held for reading.
 */
static inline int ipc_get_maxidx(struct ipc_ids *ids)
{
	if (ids->in_use == 0)
		return -1;

	if (ids->in_use == ipc_mni)
		return ipc_mni - 1;

	return ids->max_idx;
}

/*
 * For allocation that need to be freed by RCU.
 * Objects are reference counted, they start with reference count 1.
 * getref increases the refcount, the putref call that reduces the recount
 * to 0 schedules the rcu destruction. Caller must guarantee locking.
 *
 * refcount is initialized by ipc_addid(), before that point call_rcu()
 * must be used.
 */
bool ipc_rcu_getref(struct kern_ipc_perm *ptr);
void ipc_rcu_putref(struct kern_ipc_perm *ptr,
			void (*func)(struct rcu_head *head));

struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id);

void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out);
void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out);
int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out);
struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
					     struct ipc_ids *ids, int id, int cmd,
					     struct ipc64_perm *perm, int extra_perm);

static inline void ipc_update_pid(struct pid **pos, struct pid *pid)
{
	struct pid *old = *pos;
	if (old != pid) {
		*pos = get_pid(pid);
		put_pid(old);
	}
}

#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
int ipc_parse_version(int *cmd);
#endif

extern void free_msg(struct msg_msg *msg);
extern struct msg_msg *load_msg(const void __user *src, size_t len);
extern struct msg_msg *copy_msg(struct msg_msg *src, struct msg_msg *dst);
extern int store_msg(void __user *dest, struct msg_msg *msg, size_t len);

static inline int ipc_checkid(struct kern_ipc_perm *ipcp, int id)
{
	return ipcid_to_seqx(id) != ipcp->seq;
}

static inline void ipc_lock_object(struct kern_ipc_perm *perm)
{
	spin_lock(&perm->lock);
}

static inline void ipc_unlock_object(struct kern_ipc_perm *perm)
{
	spin_unlock(&perm->lock);
}

static inline void ipc_assert_locked_object(struct kern_ipc_perm *perm)
{
	assert_spin_locked(&perm->lock);
}

static inline void ipc_unlock(struct kern_ipc_perm *perm)
{
	ipc_unlock_object(perm);
	rcu_read_unlock();
}

/*
 * ipc_valid_object() - helper to sort out IPC_RMID races for codepaths
 * where the respective ipc_ids.rwsem is not being held down.
 * Checks whether the ipc object is still around or if it‘s gone already, as
 * ipc_rmid() may have already freed the ID while the ipc lock was spinning.
 * Needs to be called with kern_ipc_perm.lock held -- exception made for one
 * checkpoint case at sys_semtimedop() as noted in code commentary.
 */
static inline bool ipc_valid_object(struct kern_ipc_perm *perm)
{
	return !perm->deleted;
}

struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id);
int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
			const struct ipc_ops *ops, struct ipc_params *params);
void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
		void (*free)(struct ipc_namespace *, struct kern_ipc_perm *));

static inline int sem_check_semmni(struct ipc_namespace *ns) {
	/*
	 * Check semmni range [0, ipc_mni]
	 * semmni is the last element of sem_ctls[4] array
	 */
	return ((ns->sem_ctls[3] < 0) || (ns->sem_ctls[3] > ipc_mni))
		? -ERANGE : 0;
}

#ifdef CONFIG_COMPAT
#include <linux/compat.h>
struct compat_ipc_perm {
	key_t key;
	__compat_uid_t uid;
	__compat_gid_t gid;
	__compat_uid_t cuid;
	__compat_gid_t cgid;
	compat_mode_t mode;
	unsigned short seq;
};

void to_compat_ipc_perm(struct compat_ipc_perm *, struct ipc64_perm *);
void to_compat_ipc64_perm(struct compat_ipc64_perm *, struct ipc64_perm *);
int get_compat_ipc_perm(struct ipc64_perm *, struct compat_ipc_perm __user *);
int get_compat_ipc64_perm(struct ipc64_perm *,
			  struct compat_ipc64_perm __user *);

static inline int compat_ipc_parse_version(int *cmd)
{
	int version = *cmd & IPC_64;
	*cmd &= ~IPC_64;
	return version;
}

long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg);
long compat_ksys_old_msgctl(int msqid, int cmd, void __user *uptr);
long compat_ksys_msgrcv(int msqid, compat_uptr_t msgp, compat_ssize_t msgsz,
			compat_long_t msgtyp, int msgflg);
long compat_ksys_msgsnd(int msqid, compat_uptr_t msgp,
		       compat_ssize_t msgsz, int msgflg);
long compat_ksys_old_shmctl(int shmid, int cmd, void __user *uptr);

#endif

#endif