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freebsd-skq/sys/kern/sysv_msg.c
jkh 808a36ef65 Make the long-awaited change from $Id$ to $FreeBSD$ 
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore.  This update would have been
insane otherwise.
1997-01-14 07:20:47 +00:00

1035 lines
23 KiB
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/* $FreeBSD$ */
/*
* 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.
*/
#include "opt_sysvipc.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/msg.h>
#include <sys/sysent.h>
static void msginit __P((void *));
SYSINIT(sysv_msg, SI_SUB_SYSV_MSG, SI_ORDER_FIRST, msginit, NULL)
#define MSG_DEBUG
#undef MSG_DEBUG_OK
#ifndef _SYS_SYSPROTO_H_
struct msgctl_args;
int msgctl __P((struct proc *p, struct msgctl_args *uap, int *retval));
struct msgget_args;
int msgget __P((struct proc *p, struct msgget_args *uap, int *retval));
struct msgsnd_args;
int msgsnd __P((struct proc *p, struct msgsnd_args *uap, int *retval));
struct msgrcv_args;
int msgrcv __P((struct proc *p, struct msgrcv_args *uap, int *retval));
#endif
static void msg_freehdr __P((struct msg *msghdr));
/* XXX casting to (sy_call_t *) is bogus, as usual. */
static sy_call_t *msgcalls[] = {
(sy_call_t *)msgctl, (sy_call_t *)msgget,
(sy_call_t *)msgsnd, (sy_call_t *)msgrcv
};
static int nfree_msgmaps; /* # of free map entries */
static short free_msgmaps; /* head of linked list of free map entries */
static struct msg *free_msghdrs; /* list of free msg headers */
char *msgpool; /* MSGMAX byte long msg buffer pool */
struct msgmap *msgmaps; /* MSGSEG msgmap structures */
struct msg *msghdrs; /* MSGTQL msg headers */
struct msqid_ds *msqids; /* MSGMNI msqid_ds struct's */
void
msginit(dummy)
void *dummy;
{
register int i;
/*
* 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++) {
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++) {
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++) {
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
*/
int
msgsys(p, uap, retval)
struct proc *p;
/* XXX actually varargs. */
struct msgsys_args /* {
u_int which;
int a2;
int a3;
int a4;
int a5;
int a6;
} */ *uap;
int *retval;
{
if (uap->which >= sizeof(msgcalls)/sizeof(msgcalls[0]))
return (EINVAL);
return ((*msgcalls[uap->which])(p, &uap->a2, 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++;
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;
}
#ifndef _SYS_SYSPROTO_H_
struct msgctl_args {
int msqid;
int cmd;
struct msqid_ds *buf;
};
#endif
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->buf;
struct ucred *cred = p->p_ucred;
int 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:
{
struct msg *msghdr;
if ((eval = ipcperm(cred, &msqptr->msg_perm, IPC_M)))
return(eval);
/* Free the message headers */
msghdr = msqptr->msg_first;
while (msghdr != NULL) {
struct msg *msghdr_tmp;
/* Free the segments of each message */
msqptr->msg_cbytes -= msghdr->msg_ts;
msqptr->msg_qnum--;
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 */
wakeup((caddr_t)msqptr);
}
break;
case IPC_SET:
if ((eval = ipcperm(cred, &msqptr->msg_perm, IPC_M)))
return(eval);
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:
if ((eval = ipcperm(cred, &msqptr->msg_perm, IPC_R))) {
#ifdef MSG_DEBUG_OK
printf("requester doesn't have read access\n");
#endif
return(eval);
}
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);
}
#ifndef _SYS_SYSPROTO_H_
struct msgget_args {
key_t key;
int msgflg;
};
#endif
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 = NULL;
#ifdef MSG_DEBUG_OK
printf("msgget(0x%x, 0%o)\n", key, msgflg);
#endif
if (key != IPC_PRIVATE) {
for (msqid = 0; msqid < msginfo.msgmni; msqid++) {
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 = ipcperm(cred, &msqptr->msg_perm, msgflg & 0700 ))) {
#ifdef MSG_DEBUG_OK
printf("requester doesn't have 0%o access\n",
msgflg & 0700);
#endif
return(eval);
}
goto found;
}
}
#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++) {
/*
* 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);
#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);
/* Make sure that the returned msqid is unique */
msqptr->msg_perm.seq++;
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);
}
found:
/* Construct the unique msqid */
*retval = IXSEQ_TO_IPCID(msqid, msqptr->msg_perm);
return(0);
}
#ifndef _SYS_SYSPROTO_H_
struct msgsnd_args {
int msqid;
void *msgp;
size_t msgsz;
int msgflg;
};
#endif
int
msgsnd(p, uap, retval)
struct proc *p;
register struct msgsnd_args *uap;
int *retval;
{
int msqid = uap->msqid;
void *user_msgp = uap->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 = ipcperm(cred, &msqptr->msg_perm, IPC_W))) {
#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
for (;;) {
int need_more_resources = 0;
/*
* check msgsz
* (inside this loop in case msg_qbytes changes while we sleep)
*/
if (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,
"msgwait", 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");
if (segs_needed > nfree_msgmaps)
panic("segs_needed > nfree_msgmaps");
if (msgsz + msqptr->msg_cbytes > msqptr->msg_qbytes)
panic("msgsz + msg_cbytes > msg_qbytes");
if (free_msghdrs == NULL)
panic("no more msghdrs");
/*
* 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--;
msgmaps[next].next = msghdr->msg_spot;
msghdr->msg_spot = next;
segs_needed--;
}
/*
* 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);
return(eval);
}
user_msgp = (char *)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);
#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);
return(eval);
}
msgsz -= tlen;
user_msgp = (char *)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);
/* 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++;
msqptr->msg_lspid = p->p_pid;
msqptr->msg_stime = time.tv_sec;
wakeup((caddr_t)msqptr);
*retval = 0;
return(0);
}
#ifndef _SYS_SYSPROTO_H_
struct msgrcv_args {
int msqid;
void *msgp;
size_t msgsz;
long msgtyp;
int msgflg;
};
#endif
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 = ipcperm(cred, &msqptr->msg_perm, IPC_R))) {
#ifdef MSG_DEBUG_OK
printf("requester doesn't have read access\n");
#endif
return(eval);
}
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, "msgwait",
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--;
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);
return(eval);
}
user_msgp = (char *)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);
return(eval);
}
user_msgp = (char *)user_msgp + tlen;
next = msgmaps[next].next;
}
/*
* Done, return the actual number of bytes copied out.
*/
msg_freehdr(msghdr);
wakeup((caddr_t)msqptr);
*retval = msgsz;
return(0);
}
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