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NetBSD/sys/kern/sysv_msg.c

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/*
* Implementation of SVID messages
*
* Author: Daniel Boulet
*
* Copyright 1993 Daniel Boulet and RTMX Inc.
*
* This system call was implemented by Daniel Boulet under contract from RTMX.
*
* Redistribution and use in source forms, with and without modification,
* are permitted provided that this entire comment appears intact.
*
* Redistribution in binary form may occur without any restrictions.
* Obviously, it would be nice if you gave credit where credit is due
* but requiring it would be too onerous.
*
* This software is provided ``AS IS'' without any warranties of any kind.
*/
#ifdef SYSVMSG
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/msg.h>
#include <sys/malloc.h>
#define MSG_DEBUG
#undef MSG_DEBUG_OK
static int msgctl(), msgget(), msgsnd(), msgrcv();
int (*msgcalls[])() = { msgctl, msgget, msgsnd, msgrcv };
int nfree_msgmaps; /* # of free map entries */
short free_msgmaps; /* head of linked list of free map entries */
struct msg *free_msghdrs; /* list of free msg headers */
int
msginit()
{
register int i;
vm_offset_t whocares1, whocares2;
/*
* msginfo.msgssz should be a power of two for efficiency reasons.
* It is also pretty silly if msginfo.msgssz is less than 8
* or greater than about 256 so ...
*/
i = 8;
while ( i < 1024 && i != msginfo.msgssz ) {
i <<= 1;
}
if ( i != msginfo.msgssz ) {
printf("msginfo.msgssz=%d (0x%x)\n",msginfo.msgssz,msginfo.msgssz);
panic("msginfo.msgssz not a small power of 2");
}
if ( msginfo.msgseg > 32767 ) {
printf("msginfo.msgseg=%d\n",msginfo.msgseg);
panic("msginfo.msgseg > 32767");
}
if ( msgmaps == NULL ) {
panic("msgmaps is NULL");
}
for ( i = 0; i < msginfo.msgseg; i += 1 ) {
if ( i > 0 ) {
msgmaps[i-1].next = i;
}
msgmaps[i].next = -1; /* implies entry is available */
}
free_msgmaps = 0;
nfree_msgmaps = msginfo.msgseg;
if ( msghdrs == NULL ) {
panic("msghdrs is NULL");
}
for ( i = 0; i < msginfo.msgtql; i += 1 ) {
msghdrs[i].msg_type = 0;
if ( i > 0 ) {
msghdrs[i-1].msg_next = &msghdrs[i];
}
msghdrs[i].msg_next = NULL;
}
free_msghdrs = &msghdrs[0];
if ( msqids == NULL ) {
panic("msqids is NULL");
}
for ( i = 0; i < msginfo.msgmni; i += 1 ) {
msqids[i].msg_qbytes = 0; /* implies entry is available */
msqids[i].msg_perm.seq = 0; /* reset to a known value */
}
}
/*
* Entry point for all MSG calls
*/
struct msgsys_args {
u_int which;
};
int
msgsys(p, uap, retval)
struct caller *p;
struct msgsys_args *uap;
int *retval;
{
if (uap->which >= sizeof(msgcalls)/sizeof(msgcalls[0]))
return (EINVAL);
return ((*msgcalls[uap->which])(p, &uap[1], retval));
}
static
void
msg_freehdr(msghdr)
struct msg *msghdr;
{
while ( msghdr->msg_ts > 0 ) {
short next;
if ( msghdr->msg_spot < 0 || msghdr->msg_spot >= msginfo.msgseg ) {
panic("msghdr->msg_spot out of range");
}
next = msgmaps[msghdr->msg_spot].next;
msgmaps[msghdr->msg_spot].next = free_msgmaps;
free_msgmaps = msghdr->msg_spot;
nfree_msgmaps += 1;
msghdr->msg_spot = next;
if ( msghdr->msg_ts >= msginfo.msgssz ) {
msghdr->msg_ts -= msginfo.msgssz;
} else {
msghdr->msg_ts = 0;
}
}
if ( msghdr->msg_spot != -1 ) {
panic("msghdr->msg_spot != -1");
}
msghdr->msg_next = free_msghdrs;
free_msghdrs = msghdr;
}
struct msgctl_args {
int msqid;
int cmd;
struct msqid_ds *user_msqptr;
};
int
msgctl(p, uap, retval)
struct proc *p;
register struct msgctl_args *uap;
int *retval;
{
int msqid = uap->msqid;
int cmd = uap->cmd;
struct msqid_ds *user_msqptr = uap->user_msqptr;
struct ucred *cred = p->p_ucred;
int i, rval, eval;
struct msqid_ds msqbuf;
register struct msqid_ds *msqptr;
#ifdef MSG_DEBUG_OK
printf("call to msgctl(%d,%d,0x%x)\n",msqid,cmd,user_msqptr);
#endif
msqid = IPCID_TO_IX(msqid);
if ( msqid < 0 || msqid >= msginfo.msgmni ) {
#ifdef MSG_DEBUG_OK
printf("msqid (%d) out of range (0<=msqid<%d)\n",msqid,msginfo.msgmni);
#endif
return(EINVAL);
}
msqptr = &msqids[msqid];
if ( msqptr->msg_qbytes == 0 ) {
#ifdef MSG_DEBUG_OK
printf("no such msqid\n");
#endif
return(EINVAL);
}
if ( msqptr->msg_perm.seq != IPCID_TO_SEQ(uap->msqid) ) {
#ifdef MSG_DEBUG_OK
printf("wrong sequence number\n");
#endif
return(EINVAL);
}
eval = 0;
rval = 0;
switch (cmd) {
case IPC_RMID:
#ifdef MSG_DEBUG_OK
printf("IPC_RMID\n");
#endif
{
struct msg *msghdr;
if ( cred->cr_uid != 0
&& msqptr->msg_perm.cuid != cred->cr_uid
&& msqptr->msg_perm.uid != cred->cr_uid ) {
return(EPERM);
}
msghdr = msqptr->msg_first;
/* Free the message headers */
while ( msghdr != NULL ) {
struct msg *msghdr_tmp;
/* Free the segments of each message */
msqptr->msg_cbytes -= msghdr->msg_ts;
msqptr->msg_qnum -= 1;
msghdr_tmp = msghdr;
msghdr = msghdr->msg_next;
msg_freehdr(msghdr_tmp);
}
if ( msqptr->msg_cbytes != 0 ) {
panic("msg_cbytes is screwed up");
}
if ( msqptr->msg_qnum != 0 ) {
panic("msg_qnum is screwed up");
}
msqptr->msg_qbytes = 0; /* Mark it as free */
/* Make sure that anybody who is waiting notices the deletion */
wakeup( (caddr_t)msqptr );
}
break;
case IPC_SET:
#ifdef MSG_DEBUG_OK
printf("IPC_SET\n");
#endif
if ( cred->cr_uid != 0
&& msqptr->msg_perm.cuid != cred->cr_uid
&& msqptr->msg_perm.uid != cred->cr_uid ) {
return(EPERM);
}
if ( (eval = copyin(user_msqptr, &msqbuf, sizeof(msqbuf))) != 0 ) {
return(eval);
}
if ( msqbuf.msg_qbytes > msqptr->msg_qbytes
&& cred->cr_uid != 0 ) {
return(EPERM);
}
if ( msqbuf.msg_qbytes > msginfo.msgmnb ) {
#ifdef MSG_DEBUG_OK
printf("can't increase msg_qbytes beyond %d (truncating)\n",msginfo.msgmnb);
#endif
msqbuf.msg_qbytes = msginfo.msgmnb; /* silently restrict qbytes to system limit */
}
if ( msqbuf.msg_qbytes == 0 ) {
#ifdef MSG_DEBUG_OK
printf("can't reduce msg_qbytes to 0\n");
#endif
return(EINVAL); /* non-standard errno! */
}
msqptr->msg_perm.uid = msqbuf.msg_perm.uid; /* change the owner */
msqptr->msg_perm.gid = msqbuf.msg_perm.gid; /* change the owner */
msqptr->msg_perm.mode = (msqptr->msg_perm.mode & ~0777)
| (msqbuf.msg_perm.mode & 0777);
msqptr->msg_qbytes = msqbuf.msg_qbytes;
msqptr->msg_ctime = time.tv_sec;
break;
case IPC_STAT:
#ifdef MSG_DEBUG_OK
printf("IPC_STAT\n");
#endif
if ( (eval = ipcaccess(&msqptr->msg_perm, IPC_R, cred)) ) {
#ifdef MSG_DEBUG_OK
printf("requester doesn't have read access\n");
#endif
return(eval);
}
rval = 0;
eval = copyout((caddr_t)msqptr, user_msqptr, sizeof(struct msqid_ds));
break;
default:
#ifdef MSG_DEBUG_OK
printf("invalid command %d\n",cmd);
#endif
return(EINVAL);
}
if ( eval == 0 ) {
*retval = rval;
}
return(eval);
}
struct msgget_args {
key_t key;
int msgflg;
};
int
msgget(p, uap, retval)
struct proc *p;
register struct msgget_args *uap;
int *retval;
{
int msqid, eval;
int key = uap->key;
int msgflg = uap->msgflg;
struct ucred *cred = p->p_ucred;
register struct msqid_ds *msqptr;
#ifdef MSG_DEBUG_OK
printf("msgget(0x%x,0%o)\n",key,msgflg);
#endif
if ( key == IPC_PRIVATE ) {
#ifdef MSG_DEBUG_OK
printf("private key\n");
#endif
msqid = msginfo.msgmni;
} else {
for ( msqid = 0; msqid < msginfo.msgmni; msqid += 1 ) {
msqptr = &msqids[msqid];
if ( msqptr->msg_qbytes != 0 && msqptr->msg_perm.key == key ) {
break;
}
}
if ( msqid < msginfo.msgmni ) {
#ifdef MSG_DEBUG_OK
printf("found public key\n");
#endif
if ( (msgflg & IPC_CREAT) && (msgflg & IPC_EXCL) ) {
#ifdef MSG_DEBUG_OK
printf("not exclusive\n");
#endif
return(EEXIST);
}
if ( (eval = ipcaccess(&msqptr->msg_perm, msgflg & 0700, cred)) ) {
#ifdef MSG_DEBUG_OK
printf("requester doesn't have 0%o access\n",msgflg & 0700);
#endif
return(eval);
}
} else {
#ifdef MSG_DEBUG_OK
printf("didn't find public key\n");
#endif
}
}
if ( msqid == msginfo.msgmni ) {
#ifdef MSG_DEBUG_OK
printf("need to allocate the msqid_ds\n");
#endif
if ( key == IPC_PRIVATE || (msgflg & IPC_CREAT) ) {
for ( msqid = 0; msqid < msginfo.msgmni; msqid += 1 ) {
/*
* Look for an unallocated and unlocked msqid_ds.
* msqid_ds's can be locked by msgsnd or msgrcv while they
* are copying the message in/out. We can't re-use the
* entry until they release it.
*/
msqptr = &msqids[msqid];
if ( msqptr->msg_qbytes == 0
&& (msqptr->msg_perm.mode & MSG_LOCKED) == 0 ) {
break;
}
}
if ( msqid == msginfo.msgmni ) {
#ifdef MSG_DEBUG_OK
printf("no more msqid_ds's available\n");
#endif
return(ENOSPC);
}
#ifdef MSG_DEBUG_OK
printf("msqid %d is available\n",msqid+1);
#endif
msqptr->msg_perm.key = key;
msqptr->msg_perm.cuid = cred->cr_uid;
msqptr->msg_perm.uid = cred->cr_uid;
msqptr->msg_perm.cgid = cred->cr_gid;
msqptr->msg_perm.gid = cred->cr_gid;
msqptr->msg_perm.mode = (msgflg & 0777);
msqptr->msg_perm.seq += 1; /* Make sure that the returned msqid is unique */
msqptr->msg_first = NULL;
msqptr->msg_last = NULL;
msqptr->msg_cbytes = 0;
msqptr->msg_qnum = 0;
msqptr->msg_qbytes = msginfo.msgmnb;
msqptr->msg_lspid = 0;
msqptr->msg_lrpid = 0;
msqptr->msg_stime = 0;
msqptr->msg_rtime = 0;
msqptr->msg_ctime = time.tv_sec;
} else {
#ifdef MSG_DEBUG_OK
printf("didn't find it and wasn't asked to create it\n");
#endif
return(ENOENT);
}
}
*retval = IXSEQ_TO_IPCID(msqid,msqptr->msg_perm); /* Construct the unique msqid */
return(0);
}
struct msgsnd_args {
int msqid;
void *user_msgp;
size_t msgsz;
int msgflg;
};
int
msgsnd(p, uap, retval)
struct proc *p;
register struct msgsnd_args *uap;
int *retval;
{
int msqid = uap->msqid;
void *user_msgp = uap->user_msgp;
size_t msgsz = uap->msgsz;
int msgflg = uap->msgflg;
int segs_needed, eval;
struct ucred *cred = p->p_ucred;
register struct msqid_ds *msqptr;
register struct msg *msghdr;
short next;
#ifdef MSG_DEBUG_OK
printf("call to msgsnd(%d,0x%x,%d,%d)\n",msqid,user_msgp,msgsz,msgflg);
#endif
msqid = IPCID_TO_IX(msqid);
if ( msqid < 0 || msqid >= msginfo.msgmni ) {
#ifdef MSG_DEBUG_OK
printf("msqid (%d) out of range (0<=msqid<%d)\n",msqid,msginfo.msgmni);
#endif
return(EINVAL);
}
msqptr = &msqids[msqid];
if ( msqptr->msg_qbytes == 0 ) {
#ifdef MSG_DEBUG_OK
printf("no such message queue id\n");
#endif
return(EINVAL);
}
if ( msqptr->msg_perm.seq != IPCID_TO_SEQ(uap->msqid) ) {
#ifdef MSG_DEBUG_OK
printf("wrong sequence number\n");
#endif
return(EINVAL);
}
if ( (eval = ipcaccess(&msqptr->msg_perm, IPC_W, cred)) ) {
#ifdef MSG_DEBUG_OK
printf("requester doesn't have write access\n");
#endif
return(eval);
}
segs_needed = (msgsz + msginfo.msgssz - 1) / msginfo.msgssz;
#ifdef MSG_DEBUG_OK
printf("msgsz=%d, msgssz=%d, segs_needed=%d\n",msgsz,msginfo.msgssz,segs_needed);
#endif
while ( 1 ) {
int need_more_resources = 0;
/*
* check msgsz
* (inside this loop in case msg_qbytes changes while we sleep)
*/
if ( msgsz < 0 || msgsz > msqptr->msg_qbytes ) {
#ifdef MSG_DEBUG_OK
printf("msgsz > msqptr->msg_qbytes\n");
#endif
return(EINVAL);
}
if ( msqptr->msg_perm.mode & MSG_LOCKED ) {
#ifdef MSG_DEBUG_OK
printf("msqid is locked\n");
#endif
need_more_resources = 1;
}
if ( msgsz + msqptr->msg_cbytes > msqptr->msg_qbytes ) {
#ifdef MSG_DEBUG_OK
printf("msgsz + msg_cbytes > msg_qbytes\n");
#endif
need_more_resources = 1;
}
if ( segs_needed > nfree_msgmaps ) {
#ifdef MSG_DEBUG_OK
printf("segs_needed > nfree_msgmaps\n");
#endif
need_more_resources = 1;
}
if ( free_msghdrs == NULL ) {
#ifdef MSG_DEBUG_OK
printf("no more msghdrs\n");
#endif
need_more_resources = 1;
}
if ( need_more_resources ) {
int we_own_it;
if ( (msgflg & IPC_NOWAIT) != 0 ) {
#ifdef MSG_DEBUG_OK
printf("need more resources but caller doesn't want to wait\n");
#endif
return(EAGAIN);
}
if ( (msqptr->msg_perm.mode & MSG_LOCKED) != 0 ) {
#ifdef MSG_DEBUG_OK
printf("we don't own the msqid_ds\n");
#endif
we_own_it = 0;
} else {
/* Force later arrivals to wait for our request */
#ifdef MSG_DEBUG_OK
printf("we own the msqid_ds\n");
#endif
msqptr->msg_perm.mode |= MSG_LOCKED;
we_own_it = 1;
}
#ifdef MSG_DEBUG_OK
printf("goodnight\n");
#endif
eval = tsleep( (caddr_t)msqptr, (PZERO - 4) | PCATCH, "msg wait", 0 );
#ifdef MSG_DEBUG_OK
printf("good morning, eval=%d\n",eval);
#endif
if ( we_own_it ) {
msqptr->msg_perm.mode &= ~MSG_LOCKED;
}
if ( eval != 0 ) {
#ifdef MSG_DEBUG_OK
printf("msgsnd: interrupted system call\n");
#endif
return( EINTR );
}
/*
* Make sure that the msq queue still exists
*/
if ( msqptr->msg_qbytes == 0 ) {
#ifdef MSG_DEBUG_OK
printf("msqid deleted\n");
#endif
/* The SVID says to return EIDRM. */
#ifdef EIDRM
return(EIDRM);
#else
/* Unfortunately, BSD doesn't define that code (yet)! */
return(EINVAL);
#endif
}
} else {
#ifdef MSG_DEBUG_OK
printf("got all the resources that we need\n");
#endif
break;
}
}
/*
* We have the resources that we need.
* Make sure!
*/
if ( msqptr->msg_perm.mode & MSG_LOCKED ) {
panic("msg_perm.mode & MSG_LOCKED"); /* bug somewhere */
}
if ( segs_needed > nfree_msgmaps ) {
panic("segs_needed > nfree_msgmaps"); /* bug somewhere */
}
if ( msgsz + msqptr->msg_cbytes > msqptr->msg_qbytes ) {
panic("msgsz + msg_cbytes > msg_qbytes"); /* bug somewhere */
}
if ( free_msghdrs == NULL ) {
panic("no more msghdrs"); /* bug somewhere */
}
/*
* Re-lock the msqid_ds in case we page-fault when copying in the message
*/
if ( (msqptr->msg_perm.mode & MSG_LOCKED) != 0 ) {
panic("msqid_ds is already locked");
}
msqptr->msg_perm.mode |= MSG_LOCKED;
/*
* Allocate a message header
*/
msghdr = free_msghdrs;
free_msghdrs = msghdr->msg_next;
msghdr->msg_spot = -1;
msghdr->msg_ts = msgsz;
/*
* Allocate space for the message
*/
while ( segs_needed > 0 ) {
if ( nfree_msgmaps <= 0 ) {
panic("not enough msgmaps");
}
if ( free_msgmaps == -1 ) {
panic("nil free_msgmaps");
}
next = free_msgmaps;
if ( next <= -1 ) {
panic("next too low #1");
}
if ( next >= msginfo.msgseg ) {
panic("next out of range #1");
}
#ifdef MSG_DEBUG_OK
printf("allocating segment %d to message\n",next);
#endif
free_msgmaps = msgmaps[next].next;
nfree_msgmaps -= 1;
msgmaps[next].next = msghdr->msg_spot;
msghdr->msg_spot = next;
segs_needed -= 1;
}
/*
* Copy in the message type
*/
if ( (eval = copyin(user_msgp,&msghdr->msg_type,sizeof(msghdr->msg_type))) != 0 ) {
#ifdef MSG_DEBUG_OK
printf("error %d copying the message type\n",eval);
#endif
msg_freehdr(msghdr);
msqptr->msg_perm.mode &= ~MSG_LOCKED;
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
return(eval);
}
user_msgp += sizeof(msghdr->msg_type);
/*
* Validate the message type
*/
if ( msghdr->msg_type < 1 ) {
msg_freehdr(msghdr);
msqptr->msg_perm.mode &= ~MSG_LOCKED;
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
#ifdef MSG_DEBUG_OK
printf("mtype (%d) < 1\n",msghdr->msg_type);
#endif
return(EINVAL);
}
/*
* Copy in the message body
*/
next = msghdr->msg_spot;
while ( msgsz > 0 ) {
size_t tlen;
if ( msgsz > msginfo.msgssz ) {
tlen = msginfo.msgssz;
} else {
tlen = msgsz;
}
if ( next <= -1 ) {
panic("next too low #2");
}
if ( next >= msginfo.msgseg ) {
panic("next out of range #2");
}
if ( (eval = copyin(user_msgp, &msgpool[next * msginfo.msgssz], tlen)) != 0 ) {
#ifdef MSG_DEBUG_OK
printf("error %d copying in message segment\n",eval);
#endif
msg_freehdr(msghdr);
msqptr->msg_perm.mode &= ~MSG_LOCKED;
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
return(eval);
}
msgsz -= tlen;
user_msgp += tlen;
next = msgmaps[next].next;
}
if ( next != -1 ) {
panic("didn't use all the msg segments");
}
/*
* We've got the message. Unlock the msqid_ds.
*/
msqptr->msg_perm.mode &= ~MSG_LOCKED;
/*
* Make sure that the msqid_ds is still allocated.
*/
if ( msqptr->msg_qbytes == 0 ) {
msg_freehdr(msghdr);
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
/* The SVID says to return EIDRM. */
#ifdef EIDRM
return(EIDRM);
#else
/* Unfortunately, BSD doesn't define that code (yet)! */
return(EINVAL);
#endif
}
/*
* Put the message into the queue
*/
if ( msqptr->msg_first == NULL ) {
msqptr->msg_first = msghdr;
msqptr->msg_last = msghdr;
} else {
msqptr->msg_last->msg_next = msghdr;
msqptr->msg_last = msghdr;
}
msqptr->msg_last->msg_next = NULL;
msqptr->msg_cbytes += msghdr->msg_ts;
msqptr->msg_qnum += 1;
msqptr->msg_lspid = p->p_pid;
msqptr->msg_stime = time.tv_sec;
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
*retval = 0;
return(0);
}
struct msgrcv_args {
int msqid;
void *msgp;
size_t msgsz;
long msgtyp;
int msgflg;
};
int
msgrcv(p, uap, retval)
struct proc *p;
register struct msgrcv_args *uap;
int *retval;
{
int msqid = uap->msqid;
void *user_msgp = uap->msgp;
size_t msgsz = uap->msgsz;
long msgtyp = uap->msgtyp;
int msgflg = uap->msgflg;
size_t len;
struct ucred *cred = p->p_ucred;
register struct msqid_ds *msqptr;
register struct msg *msghdr;
int eval;
short next;
#ifdef MSG_DEBUG_OK
printf("call to msgrcv(%d,0x%x,%d,%ld,%d)\n",msqid,user_msgp,msgsz,msgtyp,msgflg);
#endif
msqid = IPCID_TO_IX(msqid);
if ( msqid < 0 || msqid >= msginfo.msgmni ) {
#ifdef MSG_DEBUG_OK
printf("msqid (%d) out of range (0<=msqid<%d)\n",msqid,msginfo.msgmni);
#endif
return(EINVAL);
}
msqptr = &msqids[msqid];
if ( msqptr->msg_qbytes == 0 ) {
#ifdef MSG_DEBUG_OK
printf("no such message queue id\n");
#endif
return(EINVAL);
}
if ( msqptr->msg_perm.seq != IPCID_TO_SEQ(uap->msqid) ) {
#ifdef MSG_DEBUG_OK
printf("wrong sequence number\n");
#endif
return(EINVAL);
}
if ( (eval = ipcaccess(&msqptr->msg_perm, IPC_R, cred)) ) {
#ifdef MSG_DEBUG_OK
printf("requester doesn't have read access\n");
#endif
return(eval);
}
if ( msgsz < 0 ) {
#ifdef MSG_DEBUG_OK
printf("msgsz < 0\n");
#endif
return(EINVAL);
}
msghdr = NULL;
while ( msghdr == NULL ) {
if ( msgtyp == 0 ) {
msghdr = msqptr->msg_first;
if ( msghdr != NULL ) {
if ( msgsz < msghdr->msg_ts && (msgflg & MSG_NOERROR) == 0 ) {
#ifdef MSG_DEBUG_OK
printf("first message on the queue is too big (want %d, got %d)\n",msgsz,msghdr->msg_ts);
#endif
return(E2BIG);
}
if ( msqptr->msg_first == msqptr->msg_last ) {
msqptr->msg_first = NULL;
msqptr->msg_last = NULL;
} else {
msqptr->msg_first = msghdr->msg_next;
if ( msqptr->msg_first == NULL ) {
panic("msg_first/last screwed up #1");
}
}
}
} else {
struct msg *previous;
struct msg **prev;
previous = NULL;
prev = &(msqptr->msg_first);
while ( (msghdr = *prev) != NULL ) {
/*
* Is this message's type an exact match or is this message's
* type less than or equal to the absolute value of a negative msgtyp?
* Note that the second half of this test can NEVER be true
* if msgtyp is positive since msg_type is always positive!
*/
if ( msgtyp == msghdr->msg_type || msghdr->msg_type <= -msgtyp ) {
#ifdef MSG_DEBUG_OK
printf("found message type %d, requested %d\n",msghdr->msg_type,msgtyp);
#endif
if ( msgsz < msghdr->msg_ts && (msgflg & MSG_NOERROR) == 0 ) {
#ifdef MSG_DEBUG_OK
printf("requested message on the queue is too big (want %d, got %d)\n",msgsz,msghdr->msg_ts);
#endif
return(E2BIG);
}
*prev = msghdr->msg_next;
if ( msghdr == msqptr->msg_last ) {
if ( previous == NULL ) {
if ( prev != &msqptr->msg_first ) {
panic("msg_first/last screwed up #2");
}
msqptr->msg_first = NULL;
msqptr->msg_last = NULL;
} else {
if ( prev == &msqptr->msg_first ) {
panic("msg_first/last screwed up #3");
}
msqptr->msg_last = previous;
}
}
break;
}
previous = msghdr;
prev = &(msghdr->msg_next);
}
}
/*
* We've either extracted the msghdr for the appropriate message
* or there isn't one.
* If there is one then bail out of this loop.
*/
if ( msghdr != NULL ) {
break;
}
/*
* Hmph! No message found. Does the user want to wait?
*/
if ( (msgflg & IPC_NOWAIT) != 0 ) {
#ifdef MSG_DEBUG_OK
printf("no appropriate message found (msgtyp=%d)\n",msgtyp);
#endif
/* The SVID says to return ENOMSG. */
#ifdef ENOMSG
return(ENOMSG);
#else
/* Unfortunately, BSD doesn't define that code (yet)! */
return(EAGAIN);
#endif
}
/*
* Wait for something to happen
*/
#ifdef MSG_DEBUG_OK
printf("msgrcv: goodnight\n");
#endif
eval = tsleep( (caddr_t)msqptr, (PZERO - 4) | PCATCH, "msg wait", 0 );
#ifdef MSG_DEBUG_OK
printf("msgrcv: good morning (eval=%d)\n",eval);
#endif
if ( eval != 0 ) {
#ifdef MSG_DEBUG_OK
printf("msgsnd: interrupted system call\n");
#endif
return( EINTR );
}
/*
* Make sure that the msq queue still exists
*/
if ( msqptr->msg_qbytes == 0
|| msqptr->msg_perm.seq != IPCID_TO_SEQ(uap->msqid) ) {
#ifdef MSG_DEBUG_OK
printf("msqid deleted\n");
#endif
/* The SVID says to return EIDRM. */
#ifdef EIDRM
return(EIDRM);
#else
/* Unfortunately, BSD doesn't define that code (yet)! */
return(EINVAL);
#endif
}
}
/*
* Return the message to the user.
*
* First, do the bookkeeping (before we risk being interrupted).
*/
msqptr->msg_cbytes -= msghdr->msg_ts;
msqptr->msg_qnum -= 1;
msqptr->msg_lrpid = p->p_pid;
msqptr->msg_rtime = time.tv_sec;
/*
* Make msgsz the actual amount that we'll be returning.
* Note that this effectively truncates the message if it is too long
* (since msgsz is never increased).
*/
#ifdef MSG_DEBUG_OK
printf("found a message, msgsz=%d, msg_ts=%d\n",msgsz,msghdr->msg_ts);
#endif
if ( msgsz > msghdr->msg_ts ) {
msgsz = msghdr->msg_ts;
}
/*
* Return the type to the user.
*/
eval = copyout((caddr_t)&(msghdr->msg_type), user_msgp, sizeof(msghdr->msg_type));
if ( eval != 0 ) {
#ifdef MSG_DEBUG_OK
printf("error (%d) copying out message type\n",eval);
#endif
msg_freehdr(msghdr);
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
return(eval);
}
user_msgp += sizeof(msghdr->msg_type);
/*
* Return the segments to the user
*/
next = msghdr->msg_spot;
for ( len = 0; len < msgsz; len += msginfo.msgssz ) {
size_t tlen;
if ( msgsz > msginfo.msgssz ) {
tlen = msginfo.msgssz;
} else {
tlen = msgsz;
}
if ( next <= -1 ) {
panic("next too low #3");
}
if ( next >= msginfo.msgseg ) {
panic("next out of range #3");
}
eval = copyout((caddr_t)&msgpool[next * msginfo.msgssz], user_msgp, tlen);
if ( eval != 0 ) {
#ifdef MSG_DEBUG_OK
printf("error (%d) copying out message segment\n",eval);
#endif
msg_freehdr(msghdr);
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
return(eval);
}
user_msgp += tlen;
next = msgmaps[next].next;
}
/*
* Done, return the actual number of bytes copied out.
*/
msg_freehdr(msghdr);
wakeup( (caddr_t)msqptr ); /* Somebody might care - we should check! */
*retval = msgsz;
return(0);
}
#endif
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