| /* |
| * linux/ipc/msg.c |
| * Copyright (C) 1992 Krishna Balasubramanian |
| * |
| * Removed all the remaining kerneld mess |
| * Catch the -EFAULT stuff properly |
| * Use GFP_KERNEL for messages as in 1.2 |
| * Fixed up the unchecked user space derefs |
| * Copyright (C) 1998 Alan Cox & Andi Kleen |
| * |
| * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com> |
| * |
| * mostly rewritten, threaded and wake-one semantics added |
| * MSGMAX limit removed, sysctl's added |
| * (c) 1999 Manfred Spraul <manfred@colorfullife.com> |
| */ |
| |
| #include <linux/capability.h> |
| #include <linux/config.h> |
| #include <linux/slab.h> |
| #include <linux/msg.h> |
| #include <linux/spinlock.h> |
| #include <linux/init.h> |
| #include <linux/proc_fs.h> |
| #include <linux/list.h> |
| #include <linux/security.h> |
| #include <linux/sched.h> |
| #include <linux/syscalls.h> |
| #include <linux/audit.h> |
| #include <linux/seq_file.h> |
| #include <asm/current.h> |
| #include <asm/uaccess.h> |
| #include "util.h" |
| |
| /* sysctl: */ |
| int msg_ctlmax = MSGMAX; |
| int msg_ctlmnb = MSGMNB; |
| int msg_ctlmni = MSGMNI; |
| |
| /* one msg_receiver structure for each sleeping receiver */ |
| struct msg_receiver { |
| struct list_head r_list; |
| struct task_struct* r_tsk; |
| |
| int r_mode; |
| long r_msgtype; |
| long r_maxsize; |
| |
| struct msg_msg* volatile r_msg; |
| }; |
| |
| /* one msg_sender for each sleeping sender */ |
| struct msg_sender { |
| struct list_head list; |
| struct task_struct* tsk; |
| }; |
| |
| #define SEARCH_ANY 1 |
| #define SEARCH_EQUAL 2 |
| #define SEARCH_NOTEQUAL 3 |
| #define SEARCH_LESSEQUAL 4 |
| |
| static atomic_t msg_bytes = ATOMIC_INIT(0); |
| static atomic_t msg_hdrs = ATOMIC_INIT(0); |
| |
| static struct ipc_ids msg_ids; |
| |
| #define msg_lock(id) ((struct msg_queue*)ipc_lock(&msg_ids,id)) |
| #define msg_unlock(msq) ipc_unlock(&(msq)->q_perm) |
| #define msg_rmid(id) ((struct msg_queue*)ipc_rmid(&msg_ids,id)) |
| #define msg_checkid(msq, msgid) \ |
| ipc_checkid(&msg_ids,&msq->q_perm,msgid) |
| #define msg_buildid(id, seq) \ |
| ipc_buildid(&msg_ids, id, seq) |
| |
| static void freeque (struct msg_queue *msq, int id); |
| static int newque (key_t key, int msgflg); |
| #ifdef CONFIG_PROC_FS |
| static int sysvipc_msg_proc_show(struct seq_file *s, void *it); |
| #endif |
| |
| void __init msg_init (void) |
| { |
| ipc_init_ids(&msg_ids,msg_ctlmni); |
| ipc_init_proc_interface("sysvipc/msg", |
| " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n", |
| &msg_ids, |
| sysvipc_msg_proc_show); |
| } |
| |
| static int newque (key_t key, int msgflg) |
| { |
| int id; |
| int retval; |
| struct msg_queue *msq; |
| |
| msq = ipc_rcu_alloc(sizeof(*msq)); |
| if (!msq) |
| return -ENOMEM; |
| |
| msq->q_perm.mode = (msgflg & S_IRWXUGO); |
| msq->q_perm.key = key; |
| |
| msq->q_perm.security = NULL; |
| retval = security_msg_queue_alloc(msq); |
| if (retval) { |
| ipc_rcu_putref(msq); |
| return retval; |
| } |
| |
| id = ipc_addid(&msg_ids, &msq->q_perm, msg_ctlmni); |
| if(id == -1) { |
| security_msg_queue_free(msq); |
| ipc_rcu_putref(msq); |
| return -ENOSPC; |
| } |
| |
| msq->q_id = msg_buildid(id,msq->q_perm.seq); |
| msq->q_stime = msq->q_rtime = 0; |
| msq->q_ctime = get_seconds(); |
| msq->q_cbytes = msq->q_qnum = 0; |
| msq->q_qbytes = msg_ctlmnb; |
| msq->q_lspid = msq->q_lrpid = 0; |
| INIT_LIST_HEAD(&msq->q_messages); |
| INIT_LIST_HEAD(&msq->q_receivers); |
| INIT_LIST_HEAD(&msq->q_senders); |
| msg_unlock(msq); |
| |
| return msq->q_id; |
| } |
| |
| static inline void ss_add(struct msg_queue* msq, struct msg_sender* mss) |
| { |
| mss->tsk=current; |
| current->state=TASK_INTERRUPTIBLE; |
| list_add_tail(&mss->list,&msq->q_senders); |
| } |
| |
| static inline void ss_del(struct msg_sender* mss) |
| { |
| if(mss->list.next != NULL) |
| list_del(&mss->list); |
| } |
| |
| static void ss_wakeup(struct list_head* h, int kill) |
| { |
| struct list_head *tmp; |
| |
| tmp = h->next; |
| while (tmp != h) { |
| struct msg_sender* mss; |
| |
| mss = list_entry(tmp,struct msg_sender,list); |
| tmp = tmp->next; |
| if(kill) |
| mss->list.next=NULL; |
| wake_up_process(mss->tsk); |
| } |
| } |
| |
| static void expunge_all(struct msg_queue* msq, int res) |
| { |
| struct list_head *tmp; |
| |
| tmp = msq->q_receivers.next; |
| while (tmp != &msq->q_receivers) { |
| struct msg_receiver* msr; |
| |
| msr = list_entry(tmp,struct msg_receiver,r_list); |
| tmp = tmp->next; |
| msr->r_msg = NULL; |
| wake_up_process(msr->r_tsk); |
| smp_mb(); |
| msr->r_msg = ERR_PTR(res); |
| } |
| } |
| /* |
| * freeque() wakes up waiters on the sender and receiver waiting queue, |
| * removes the message queue from message queue ID |
| * array, and cleans up all the messages associated with this queue. |
| * |
| * msg_ids.sem and the spinlock for this message queue is hold |
| * before freeque() is called. msg_ids.sem remains locked on exit. |
| */ |
| static void freeque (struct msg_queue *msq, int id) |
| { |
| struct list_head *tmp; |
| |
| expunge_all(msq,-EIDRM); |
| ss_wakeup(&msq->q_senders,1); |
| msq = msg_rmid(id); |
| msg_unlock(msq); |
| |
| tmp = msq->q_messages.next; |
| while(tmp != &msq->q_messages) { |
| struct msg_msg* msg = list_entry(tmp,struct msg_msg,m_list); |
| tmp = tmp->next; |
| atomic_dec(&msg_hdrs); |
| free_msg(msg); |
| } |
| atomic_sub(msq->q_cbytes, &msg_bytes); |
| security_msg_queue_free(msq); |
| ipc_rcu_putref(msq); |
| } |
| |
| asmlinkage long sys_msgget (key_t key, int msgflg) |
| { |
| int id, ret = -EPERM; |
| struct msg_queue *msq; |
| |
| down(&msg_ids.sem); |
| if (key == IPC_PRIVATE) |
| ret = newque(key, msgflg); |
| else if ((id = ipc_findkey(&msg_ids, key)) == -1) { /* key not used */ |
| if (!(msgflg & IPC_CREAT)) |
| ret = -ENOENT; |
| else |
| ret = newque(key, msgflg); |
| } else if (msgflg & IPC_CREAT && msgflg & IPC_EXCL) { |
| ret = -EEXIST; |
| } else { |
| msq = msg_lock(id); |
| BUG_ON(msq==NULL); |
| if (ipcperms(&msq->q_perm, msgflg)) |
| ret = -EACCES; |
| else { |
| int qid = msg_buildid(id, msq->q_perm.seq); |
| ret = security_msg_queue_associate(msq, msgflg); |
| if (!ret) |
| ret = qid; |
| } |
| msg_unlock(msq); |
| } |
| up(&msg_ids.sem); |
| return ret; |
| } |
| |
| static inline unsigned long copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version) |
| { |
| switch(version) { |
| case IPC_64: |
| return copy_to_user (buf, in, sizeof(*in)); |
| case IPC_OLD: |
| { |
| struct msqid_ds out; |
| |
| memset(&out,0,sizeof(out)); |
| |
| ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm); |
| |
| out.msg_stime = in->msg_stime; |
| out.msg_rtime = in->msg_rtime; |
| out.msg_ctime = in->msg_ctime; |
| |
| if(in->msg_cbytes > USHRT_MAX) |
| out.msg_cbytes = USHRT_MAX; |
| else |
| out.msg_cbytes = in->msg_cbytes; |
| out.msg_lcbytes = in->msg_cbytes; |
| |
| if(in->msg_qnum > USHRT_MAX) |
| out.msg_qnum = USHRT_MAX; |
| else |
| out.msg_qnum = in->msg_qnum; |
| |
| if(in->msg_qbytes > USHRT_MAX) |
| out.msg_qbytes = USHRT_MAX; |
| else |
| out.msg_qbytes = in->msg_qbytes; |
| out.msg_lqbytes = in->msg_qbytes; |
| |
| out.msg_lspid = in->msg_lspid; |
| out.msg_lrpid = in->msg_lrpid; |
| |
| return copy_to_user (buf, &out, sizeof(out)); |
| } |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| struct msq_setbuf { |
| unsigned long qbytes; |
| uid_t uid; |
| gid_t gid; |
| mode_t mode; |
| }; |
| |
| static inline unsigned long copy_msqid_from_user(struct msq_setbuf *out, void __user *buf, int version) |
| { |
| switch(version) { |
| case IPC_64: |
| { |
| struct msqid64_ds tbuf; |
| |
| if (copy_from_user (&tbuf, buf, sizeof (tbuf))) |
| return -EFAULT; |
| |
| out->qbytes = tbuf.msg_qbytes; |
| out->uid = tbuf.msg_perm.uid; |
| out->gid = tbuf.msg_perm.gid; |
| out->mode = tbuf.msg_perm.mode; |
| |
| return 0; |
| } |
| case IPC_OLD: |
| { |
| struct msqid_ds tbuf_old; |
| |
| if (copy_from_user (&tbuf_old, buf, sizeof (tbuf_old))) |
| return -EFAULT; |
| |
| out->uid = tbuf_old.msg_perm.uid; |
| out->gid = tbuf_old.msg_perm.gid; |
| out->mode = tbuf_old.msg_perm.mode; |
| |
| if(tbuf_old.msg_qbytes == 0) |
| out->qbytes = tbuf_old.msg_lqbytes; |
| else |
| out->qbytes = tbuf_old.msg_qbytes; |
| |
| return 0; |
| } |
| default: |
| return -EINVAL; |
| } |
| } |
| |
| asmlinkage long sys_msgctl (int msqid, int cmd, struct msqid_ds __user *buf) |
| { |
| int err, version; |
| struct msg_queue *msq; |
| struct msq_setbuf setbuf; |
| struct kern_ipc_perm *ipcp; |
| |
| if (msqid < 0 || cmd < 0) |
| return -EINVAL; |
| |
| version = ipc_parse_version(&cmd); |
| |
| switch (cmd) { |
| case IPC_INFO: |
| case MSG_INFO: |
| { |
| struct msginfo msginfo; |
| int max_id; |
| if (!buf) |
| return -EFAULT; |
| /* We must not return kernel stack data. |
| * due to padding, it's not enough |
| * to set all member fields. |
| */ |
| |
| err = security_msg_queue_msgctl(NULL, cmd); |
| if (err) |
| return err; |
| |
| memset(&msginfo,0,sizeof(msginfo)); |
| msginfo.msgmni = msg_ctlmni; |
| msginfo.msgmax = msg_ctlmax; |
| msginfo.msgmnb = msg_ctlmnb; |
| msginfo.msgssz = MSGSSZ; |
| msginfo.msgseg = MSGSEG; |
| down(&msg_ids.sem); |
| if (cmd == MSG_INFO) { |
| msginfo.msgpool = msg_ids.in_use; |
| msginfo.msgmap = atomic_read(&msg_hdrs); |
| msginfo.msgtql = atomic_read(&msg_bytes); |
| } else { |
| msginfo.msgmap = MSGMAP; |
| msginfo.msgpool = MSGPOOL; |
| msginfo.msgtql = MSGTQL; |
| } |
| max_id = msg_ids.max_id; |
| up(&msg_ids.sem); |
| if (copy_to_user (buf, &msginfo, sizeof(struct msginfo))) |
| return -EFAULT; |
| return (max_id < 0) ? 0: max_id; |
| } |
| case MSG_STAT: |
| case IPC_STAT: |
| { |
| struct msqid64_ds tbuf; |
| int success_return; |
| if (!buf) |
| return -EFAULT; |
| if(cmd == MSG_STAT && msqid >= msg_ids.entries->size) |
| return -EINVAL; |
| |
| memset(&tbuf,0,sizeof(tbuf)); |
| |
| msq = msg_lock(msqid); |
| if (msq == NULL) |
| return -EINVAL; |
| |
| if(cmd == MSG_STAT) { |
| success_return = msg_buildid(msqid, msq->q_perm.seq); |
| } else { |
| err = -EIDRM; |
| if (msg_checkid(msq,msqid)) |
| goto out_unlock; |
| success_return = 0; |
| } |
| err = -EACCES; |
| if (ipcperms (&msq->q_perm, S_IRUGO)) |
| goto out_unlock; |
| |
| err = security_msg_queue_msgctl(msq, cmd); |
| if (err) |
| goto out_unlock; |
| |
| kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm); |
| tbuf.msg_stime = msq->q_stime; |
| tbuf.msg_rtime = msq->q_rtime; |
| tbuf.msg_ctime = msq->q_ctime; |
| tbuf.msg_cbytes = msq->q_cbytes; |
| tbuf.msg_qnum = msq->q_qnum; |
| tbuf.msg_qbytes = msq->q_qbytes; |
| tbuf.msg_lspid = msq->q_lspid; |
| tbuf.msg_lrpid = msq->q_lrpid; |
| msg_unlock(msq); |
| if (copy_msqid_to_user(buf, &tbuf, version)) |
| return -EFAULT; |
| return success_return; |
| } |
| case IPC_SET: |
| if (!buf) |
| return -EFAULT; |
| if (copy_msqid_from_user (&setbuf, buf, version)) |
| return -EFAULT; |
| break; |
| case IPC_RMID: |
| break; |
| default: |
| return -EINVAL; |
| } |
| |
| down(&msg_ids.sem); |
| msq = msg_lock(msqid); |
| err=-EINVAL; |
| if (msq == NULL) |
| goto out_up; |
| |
| err = -EIDRM; |
| if (msg_checkid(msq,msqid)) |
| goto out_unlock_up; |
| ipcp = &msq->q_perm; |
| err = -EPERM; |
| if (current->euid != ipcp->cuid && |
| current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) |
| /* We _could_ check for CAP_CHOWN above, but we don't */ |
| goto out_unlock_up; |
| |
| err = security_msg_queue_msgctl(msq, cmd); |
| if (err) |
| goto out_unlock_up; |
| |
| switch (cmd) { |
| case IPC_SET: |
| { |
| if ((err = audit_ipc_perms(setbuf.qbytes, setbuf.uid, setbuf.gid, setbuf.mode, ipcp))) |
| goto out_unlock_up; |
| |
| err = -EPERM; |
| if (setbuf.qbytes > msg_ctlmnb && !capable(CAP_SYS_RESOURCE)) |
| goto out_unlock_up; |
| |
| msq->q_qbytes = setbuf.qbytes; |
| |
| ipcp->uid = setbuf.uid; |
| ipcp->gid = setbuf.gid; |
| ipcp->mode = (ipcp->mode & ~S_IRWXUGO) | |
| (S_IRWXUGO & setbuf.mode); |
| msq->q_ctime = get_seconds(); |
| /* sleeping receivers might be excluded by |
| * stricter permissions. |
| */ |
| expunge_all(msq,-EAGAIN); |
| /* sleeping senders might be able to send |
| * due to a larger queue size. |
| */ |
| ss_wakeup(&msq->q_senders,0); |
| msg_unlock(msq); |
| break; |
| } |
| case IPC_RMID: |
| freeque (msq, msqid); |
| break; |
| } |
| err = 0; |
| out_up: |
| up(&msg_ids.sem); |
| return err; |
| out_unlock_up: |
| msg_unlock(msq); |
| goto out_up; |
| out_unlock: |
| msg_unlock(msq); |
| return err; |
| } |
| |
| static int testmsg(struct msg_msg* msg,long type,int mode) |
| { |
| switch(mode) |
| { |
| case SEARCH_ANY: |
| return 1; |
| case SEARCH_LESSEQUAL: |
| if(msg->m_type <=type) |
| return 1; |
| break; |
| case SEARCH_EQUAL: |
| if(msg->m_type == type) |
| return 1; |
| break; |
| case SEARCH_NOTEQUAL: |
| if(msg->m_type != type) |
| return 1; |
| break; |
| } |
| return 0; |
| } |
| |
| static inline int pipelined_send(struct msg_queue* msq, struct msg_msg* msg) |
| { |
| struct list_head* tmp; |
| |
| tmp = msq->q_receivers.next; |
| while (tmp != &msq->q_receivers) { |
| struct msg_receiver* msr; |
| msr = list_entry(tmp,struct msg_receiver,r_list); |
| tmp = tmp->next; |
| if(testmsg(msg,msr->r_msgtype,msr->r_mode) && |
| !security_msg_queue_msgrcv(msq, msg, msr->r_tsk, msr->r_msgtype, msr->r_mode)) { |
| list_del(&msr->r_list); |
| if(msr->r_maxsize < msg->m_ts) { |
| msr->r_msg = NULL; |
| wake_up_process(msr->r_tsk); |
| smp_mb(); |
| msr->r_msg = ERR_PTR(-E2BIG); |
| } else { |
| msr->r_msg = NULL; |
| msq->q_lrpid = msr->r_tsk->pid; |
| msq->q_rtime = get_seconds(); |
| wake_up_process(msr->r_tsk); |
| smp_mb(); |
| msr->r_msg = msg; |
| return 1; |
| } |
| } |
| } |
| return 0; |
| } |
| |
| asmlinkage long sys_msgsnd (int msqid, struct msgbuf __user *msgp, size_t msgsz, int msgflg) |
| { |
| struct msg_queue *msq; |
| struct msg_msg *msg; |
| long mtype; |
| int err; |
| |
| if (msgsz > msg_ctlmax || (long) msgsz < 0 || msqid < 0) |
| return -EINVAL; |
| if (get_user(mtype, &msgp->mtype)) |
| return -EFAULT; |
| if (mtype < 1) |
| return -EINVAL; |
| |
| msg = load_msg(msgp->mtext, msgsz); |
| if(IS_ERR(msg)) |
| return PTR_ERR(msg); |
| |
| msg->m_type = mtype; |
| msg->m_ts = msgsz; |
| |
| msq = msg_lock(msqid); |
| err=-EINVAL; |
| if(msq==NULL) |
| goto out_free; |
| |
| err= -EIDRM; |
| if (msg_checkid(msq,msqid)) |
| goto out_unlock_free; |
| |
| for (;;) { |
| struct msg_sender s; |
| |
| err=-EACCES; |
| if (ipcperms(&msq->q_perm, S_IWUGO)) |
| goto out_unlock_free; |
| |
| err = security_msg_queue_msgsnd(msq, msg, msgflg); |
| if (err) |
| goto out_unlock_free; |
| |
| if(msgsz + msq->q_cbytes <= msq->q_qbytes && |
| 1 + msq->q_qnum <= msq->q_qbytes) { |
| break; |
| } |
| |
| /* queue full, wait: */ |
| if(msgflg&IPC_NOWAIT) { |
| err=-EAGAIN; |
| goto out_unlock_free; |
| } |
| ss_add(msq, &s); |
| ipc_rcu_getref(msq); |
| msg_unlock(msq); |
| schedule(); |
| |
| ipc_lock_by_ptr(&msq->q_perm); |
| ipc_rcu_putref(msq); |
| if (msq->q_perm.deleted) { |
| err = -EIDRM; |
| goto out_unlock_free; |
| } |
| ss_del(&s); |
| |
| if (signal_pending(current)) { |
| err=-ERESTARTNOHAND; |
| goto out_unlock_free; |
| } |
| } |
| |
| msq->q_lspid = current->tgid; |
| msq->q_stime = get_seconds(); |
| |
| if(!pipelined_send(msq,msg)) { |
| /* noone is waiting for this message, enqueue it */ |
| list_add_tail(&msg->m_list,&msq->q_messages); |
| msq->q_cbytes += msgsz; |
| msq->q_qnum++; |
| atomic_add(msgsz,&msg_bytes); |
| atomic_inc(&msg_hdrs); |
| } |
| |
| err = 0; |
| msg = NULL; |
| |
| out_unlock_free: |
| msg_unlock(msq); |
| out_free: |
| if(msg!=NULL) |
| free_msg(msg); |
| return err; |
| } |
| |
| static inline int convert_mode(long* msgtyp, int msgflg) |
| { |
| /* |
| * find message of correct type. |
| * msgtyp = 0 => get first. |
| * msgtyp > 0 => get first message of matching type. |
| * msgtyp < 0 => get message with least type must be < abs(msgtype). |
| */ |
| if(*msgtyp==0) |
| return SEARCH_ANY; |
| if(*msgtyp<0) { |
| *msgtyp=-(*msgtyp); |
| return SEARCH_LESSEQUAL; |
| } |
| if(msgflg & MSG_EXCEPT) |
| return SEARCH_NOTEQUAL; |
| return SEARCH_EQUAL; |
| } |
| |
| asmlinkage long sys_msgrcv (int msqid, struct msgbuf __user *msgp, size_t msgsz, |
| long msgtyp, int msgflg) |
| { |
| struct msg_queue *msq; |
| struct msg_msg *msg; |
| int mode; |
| |
| if (msqid < 0 || (long) msgsz < 0) |
| return -EINVAL; |
| mode = convert_mode(&msgtyp,msgflg); |
| |
| msq = msg_lock(msqid); |
| if(msq==NULL) |
| return -EINVAL; |
| |
| msg = ERR_PTR(-EIDRM); |
| if (msg_checkid(msq,msqid)) |
| goto out_unlock; |
| |
| for (;;) { |
| struct msg_receiver msr_d; |
| struct list_head* tmp; |
| |
| msg = ERR_PTR(-EACCES); |
| if (ipcperms (&msq->q_perm, S_IRUGO)) |
| goto out_unlock; |
| |
| msg = ERR_PTR(-EAGAIN); |
| tmp = msq->q_messages.next; |
| while (tmp != &msq->q_messages) { |
| struct msg_msg *walk_msg; |
| walk_msg = list_entry(tmp,struct msg_msg,m_list); |
| if(testmsg(walk_msg,msgtyp,mode) && |
| !security_msg_queue_msgrcv(msq, walk_msg, current, msgtyp, mode)) { |
| msg = walk_msg; |
| if(mode == SEARCH_LESSEQUAL && walk_msg->m_type != 1) { |
| msg=walk_msg; |
| msgtyp=walk_msg->m_type-1; |
| } else { |
| msg=walk_msg; |
| break; |
| } |
| } |
| tmp = tmp->next; |
| } |
| if(!IS_ERR(msg)) { |
| /* Found a suitable message. Unlink it from the queue. */ |
| if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) { |
| msg = ERR_PTR(-E2BIG); |
| goto out_unlock; |
| } |
| list_del(&msg->m_list); |
| msq->q_qnum--; |
| msq->q_rtime = get_seconds(); |
| msq->q_lrpid = current->tgid; |
| msq->q_cbytes -= msg->m_ts; |
| atomic_sub(msg->m_ts,&msg_bytes); |
| atomic_dec(&msg_hdrs); |
| ss_wakeup(&msq->q_senders,0); |
| msg_unlock(msq); |
| break; |
| } |
| /* No message waiting. Wait for a message */ |
| if (msgflg & IPC_NOWAIT) { |
| msg = ERR_PTR(-ENOMSG); |
| goto out_unlock; |
| } |
| list_add_tail(&msr_d.r_list,&msq->q_receivers); |
| msr_d.r_tsk = current; |
| msr_d.r_msgtype = msgtyp; |
| msr_d.r_mode = mode; |
| if(msgflg & MSG_NOERROR) |
| msr_d.r_maxsize = INT_MAX; |
| else |
| msr_d.r_maxsize = msgsz; |
| msr_d.r_msg = ERR_PTR(-EAGAIN); |
| current->state = TASK_INTERRUPTIBLE; |
| msg_unlock(msq); |
| |
| schedule(); |
| |
| /* Lockless receive, part 1: |
| * Disable preemption. We don't hold a reference to the queue |
| * and getting a reference would defeat the idea of a lockless |
| * operation, thus the code relies on rcu to guarantee the |
| * existance of msq: |
| * Prior to destruction, expunge_all(-EIRDM) changes r_msg. |
| * Thus if r_msg is -EAGAIN, then the queue not yet destroyed. |
| * rcu_read_lock() prevents preemption between reading r_msg |
| * and the spin_lock() inside ipc_lock_by_ptr(). |
| */ |
| rcu_read_lock(); |
| |
| /* Lockless receive, part 2: |
| * Wait until pipelined_send or expunge_all are outside of |
| * wake_up_process(). There is a race with exit(), see |
| * ipc/mqueue.c for the details. |
| */ |
| msg = (struct msg_msg*) msr_d.r_msg; |
| while (msg == NULL) { |
| cpu_relax(); |
| msg = (struct msg_msg*) msr_d.r_msg; |
| } |
| |
| /* Lockless receive, part 3: |
| * If there is a message or an error then accept it without |
| * locking. |
| */ |
| if(msg != ERR_PTR(-EAGAIN)) { |
| rcu_read_unlock(); |
| break; |
| } |
| |
| /* Lockless receive, part 3: |
| * Acquire the queue spinlock. |
| */ |
| ipc_lock_by_ptr(&msq->q_perm); |
| rcu_read_unlock(); |
| |
| /* Lockless receive, part 4: |
| * Repeat test after acquiring the spinlock. |
| */ |
| msg = (struct msg_msg*)msr_d.r_msg; |
| if(msg != ERR_PTR(-EAGAIN)) |
| goto out_unlock; |
| |
| list_del(&msr_d.r_list); |
| if (signal_pending(current)) { |
| msg = ERR_PTR(-ERESTARTNOHAND); |
| out_unlock: |
| msg_unlock(msq); |
| break; |
| } |
| } |
| if (IS_ERR(msg)) |
| return PTR_ERR(msg); |
| |
| msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz; |
| if (put_user (msg->m_type, &msgp->mtype) || |
| store_msg(msgp->mtext, msg, msgsz)) { |
| msgsz = -EFAULT; |
| } |
| free_msg(msg); |
| return msgsz; |
| } |
| |
| #ifdef CONFIG_PROC_FS |
| static int sysvipc_msg_proc_show(struct seq_file *s, void *it) |
| { |
| struct msg_queue *msq = it; |
| |
| return seq_printf(s, |
| "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n", |
| msq->q_perm.key, |
| msq->q_id, |
| msq->q_perm.mode, |
| msq->q_cbytes, |
| msq->q_qnum, |
| msq->q_lspid, |
| msq->q_lrpid, |
| msq->q_perm.uid, |
| msq->q_perm.gid, |
| msq->q_perm.cuid, |
| msq->q_perm.cgid, |
| msq->q_stime, |
| msq->q_rtime, |
| msq->q_ctime); |
| } |
| #endif |