1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2 #ifndef _UAPI_LINUX_MSG_H
3 #define _UAPI_LINUX_MSG_H
4 
5 #include <linux/ipc.h>
6 
7 /* ipcs ctl commands */
8 #define MSG_STAT 11
9 #define MSG_INFO 12
10 #define MSG_STAT_ANY 13
11 
12 /* msgrcv options */
13 #define MSG_NOERROR     010000  /* no error if message is too big */
14 #define MSG_EXCEPT      020000  /* recv any msg except of specified type.*/
15 #define MSG_COPY        040000  /* copy (not remove) all queue messages */
16 
17 /* Obsolete, used only for backwards compatibility and libc5 compiles */
18 struct msqid_ds {
19 	struct ipc_perm msg_perm;
20 	struct msg *msg_first;		/* first message on queue,unused  */
21 	struct msg *msg_last;		/* last message in queue,unused */
22 	__kernel_old_time_t msg_stime;	/* last msgsnd time */
23 	__kernel_old_time_t msg_rtime;	/* last msgrcv time */
24 	__kernel_old_time_t msg_ctime;	/* last change time */
25 	unsigned long  msg_lcbytes;	/* Reuse junk fields for 32 bit */
26 	unsigned long  msg_lqbytes;	/* ditto */
27 	unsigned short msg_cbytes;	/* current number of bytes on queue */
28 	unsigned short msg_qnum;	/* number of messages in queue */
29 	unsigned short msg_qbytes;	/* max number of bytes on queue */
30 	__kernel_ipc_pid_t msg_lspid;	/* pid of last msgsnd */
31 	__kernel_ipc_pid_t msg_lrpid;	/* last receive pid */
32 };
33 
34 /* Include the definition of msqid64_ds */
35 #include <asm/msgbuf.h>
36 
37 /* message buffer for msgsnd and msgrcv calls */
38 struct msgbuf {
39 	__kernel_long_t mtype;          /* type of message */
40 	char mtext[1];                  /* message text */
41 };
42 
43 /* buffer for msgctl calls IPC_INFO, MSG_INFO */
44 struct msginfo {
45 	int msgpool;
46 	int msgmap;
47 	int msgmax;
48 	int msgmnb;
49 	int msgmni;
50 	int msgssz;
51 	int msgtql;
52 	unsigned short  msgseg;
53 };
54 
55 /*
56  * MSGMNI, MSGMAX and MSGMNB are default values which can be
57  * modified by sysctl.
58  *
59  * MSGMNI is the upper limit for the number of messages queues per
60  * namespace.
61  * It has been chosen to be as large possible without facilitating
62  * scenarios where userspace causes overflows when adjusting the limits via
63  * operations of the form retrieve current limit; add X; update limit".
64  *
65  * MSGMNB is the default size of a new message queue. Non-root tasks can
66  * decrease the size with msgctl(IPC_SET), root tasks
67  * (actually: CAP_SYS_RESOURCE) can both increase and decrease the queue
68  * size. The optimal value is application dependent.
69  * 16384 is used because it was always used (since 0.99.10)
70  *
71  * MAXMAX is the maximum size of an individual message, it's a global
72  * (per-namespace) limit that applies for all message queues.
73  * It's set to 1/2 of MSGMNB, to ensure that at least two messages fit into
74  * the queue. This is also an arbitrary choice (since 2.6.0).
75  */
76 
77 #define MSGMNI 32000   /* <= IPCMNI */     /* max # of msg queue identifiers */
78 #define MSGMAX  8192   /* <= INT_MAX */   /* max size of message (bytes) */
79 #define MSGMNB 16384   /* <= INT_MAX */   /* default max size of a message queue */
80 
81 /* unused */
82 #define MSGPOOL (MSGMNI * MSGMNB / 1024) /* size in kbytes of message pool */
83 #define MSGTQL  MSGMNB            /* number of system message headers */
84 #define MSGMAP  MSGMNB            /* number of entries in message map */
85 #define MSGSSZ  16                /* message segment size */
86 #define __MSGSEG ((MSGPOOL * 1024) / MSGSSZ) /* max no. of segments */
87 #define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)
88 
89 
90 #endif /* _UAPI_LINUX_MSG_H */
91