Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1384 insertions, 0 deletions

diff --git a/ipc/sem.c b/ipc/sem.c
new file mode 100644
index 000000000000..5ad7ac0ed60d
--- /dev/null
+++ b/ipc/sem.c
@@ -0,0 +1,1384 @@
+/*
+ * linux/ipc/sem.c
+ * Copyright (C) 1992 Krishna Balasubramanian
+ * Copyright (C) 1995 Eric Schenk, Bruno Haible
+ *
+ * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
+ * This code underwent a massive rewrite in order to solve some problems
+ * with the original code. In particular the original code failed to
+ * wake up processes that were waiting for semval to go to 0 if the
+ * value went to 0 and was then incremented rapidly enough. In solving
+ * this problem I have also modified the implementation so that it
+ * processes pending operations in a FIFO manner, thus give a guarantee
+ * that processes waiting for a lock on the semaphore won't starve
+ * unless another locking process fails to unlock.
+ * In addition the following two changes in behavior have been introduced:
+ * - The original implementation of semop returned the value
+ *   last semaphore element examined on success. This does not
+ *   match the manual page specifications, and effectively
+ *   allows the user to read the semaphore even if they do not
+ *   have read permissions. The implementation now returns 0
+ *   on success as stated in the manual page.
+ * - There is some confusion over whether the set of undo adjustments
+ *   to be performed at exit should be done in an atomic manner.
+ *   That is, if we are attempting to decrement the semval should we queue
+ *   up and wait until we can do so legally?
+ *   The original implementation attempted to do this.
+ *   The current implementation does not do so. This is because I don't
+ *   think it is the right thing (TM) to do, and because I couldn't
+ *   see a clean way to get the old behavior with the new design.
+ *   The POSIX standard and SVID should be consulted to determine
+ *   what behavior is mandated.
+ *
+ * Further notes on refinement (Christoph Rohland, December 1998):
+ * - The POSIX standard says, that the undo adjustments simply should
+ *   redo. So the current implementation is o.K.
+ * - The previous code had two flaws:
+ *   1) It actively gave the semaphore to the next waiting process
+ *      sleeping on the semaphore. Since this process did not have the
+ *      cpu this led to many unnecessary context switches and bad
+ *      performance. Now we only check which process should be able to
+ *      get the semaphore and if this process wants to reduce some
+ *      semaphore value we simply wake it up without doing the
+ *      operation. So it has to try to get it later. Thus e.g. the
+ *      running process may reacquire the semaphore during the current
+ *      time slice. If it only waits for zero or increases the semaphore,
+ *      we do the operation in advance and wake it up.
+ *   2) It did not wake up all zero waiting processes. We try to do
+ *      better but only get the semops right which only wait for zero or
+ *      increase. If there are decrement operations in the operations
+ *      array we do the same as before.
+ *
+ * With the incarnation of O(1) scheduler, it becomes unnecessary to perform
+ * check/retry algorithm for waking up blocked processes as the new scheduler
+ * is better at handling thread switch than the old one.
+ *
+ * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
+ *
+ * SMP-threaded, sysctl's added
+ * (c) 1999 Manfred Spraul <manfreds@colorfullife.com>
+ * Enforced range limit on SEM_UNDO
+ * (c) 2001 Red Hat Inc <alan@redhat.com>
+ * Lockless wakeup
+ * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
+ */
+
+#include <linux/config.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/init.h>
+#include <linux/proc_fs.h>
+#include <linux/time.h>
+#include <linux/smp_lock.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/audit.h>
+#include <asm/uaccess.h>
+#include "util.h"
+
+
+#define sem_lock(id)    ((struct sem_array*)ipc_lock(&sem_ids,id))
+#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
+#define sem_rmid(id)    ((struct sem_array*)ipc_rmid(&sem_ids,id))
+#define sem_checkid(sma, semid) \
+        ipc_checkid(&sem_ids,&sma->sem_perm,semid)
+#define sem_buildid(id, seq) \
+        ipc_buildid(&sem_ids, id, seq)
+static struct ipc_ids sem_ids;
+
+static int newary (key_t, int, int);
+static void freeary (struct sem_array *sma, int id);
+#ifdef CONFIG_PROC_FS
+static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
+#endif
+
+#define SEMMSL_FAST     256 /* 512 bytes on stack */
+#define SEMOPM_FAST     64  /* ~ 372 bytes on stack */
+
+/*
+ * linked list protection:
+ *      sem_undo.id_next,
+ *      sem_array.sem_pending{,last},
+ *      sem_array.sem_undo: sem_lock() for read/write
+ *      sem_undo.proc_next: only "current" is allowed to read/write that field.
+ *      
+ */
+
+int sem_ctls[4] = {SEMMSL, SEMMNS, SEMOPM, SEMMNI};
+#define sc_semmsl       (sem_ctls[0])
+#define sc_semmns       (sem_ctls[1])
+#define sc_semopm       (sem_ctls[2])
+#define sc_semmni       (sem_ctls[3])
+
+static int used_sems;
+
+void __init sem_init (void)
+{
+        used_sems = 0;
+        ipc_init_ids(&sem_ids,sc_semmni);
+
+#ifdef CONFIG_PROC_FS
+        create_proc_read_entry("sysvipc/sem", 0, NULL, sysvipc_sem_read_proc, NULL);
+#endif
+}
+
+/*
+ * Lockless wakeup algorithm:
+ * Without the check/retry algorithm a lockless wakeup is possible:
+ * - queue.status is initialized to -EINTR before blocking.
+ * - wakeup is performed by
+ *      * unlinking the queue entry from sma->sem_pending
+ *      * setting queue.status to IN_WAKEUP
+ *        This is the notification for the blocked thread that a
+ *        result value is imminent.
+ *      * call wake_up_process
+ *      * set queue.status to the final value.
+ * - the previously blocked thread checks queue.status:
+ *      * if it's IN_WAKEUP, then it must wait until the value changes
+ *      * if it's not -EINTR, then the operation was completed by
+ *        update_queue. semtimedop can return queue.status without
+ *        performing any operation on the semaphore array.
+ *      * otherwise it must acquire the spinlock and check what's up.
+ *
+ * The two-stage algorithm is necessary to protect against the following
+ * races:
+ * - if queue.status is set after wake_up_process, then the woken up idle
+ *   thread could race forward and try (and fail) to acquire sma->lock
+ *   before update_queue had a chance to set queue.status
+ * - if queue.status is written before wake_up_process and if the
+ *   blocked process is woken up by a signal between writing
+ *   queue.status and the wake_up_process, then the woken up
+ *   process could return from semtimedop and die by calling
+ *   sys_exit before wake_up_process is called. Then wake_up_process
+ *   will oops, because the task structure is already invalid.
+ *   (yes, this happened on s390 with sysv msg).
+ *
+ */
+#define IN_WAKEUP       1
+
+static int newary (key_t key, int nsems, int semflg)
+{
+        int id;
+        int retval;
+        struct sem_array *sma;
+        int size;
+
+        if (!nsems)
+                return -EINVAL;
+        if (used_sems + nsems > sc_semmns)
+                return -ENOSPC;
+
+        size = sizeof (*sma) + nsems * sizeof (struct sem);
+        sma = ipc_rcu_alloc(size);
+        if (!sma) {
+                return -ENOMEM;
+        }
+        memset (sma, 0, size);
+
+        sma->sem_perm.mode = (semflg & S_IRWXUGO);
+        sma->sem_perm.key = key;
+
+        sma->sem_perm.security = NULL;
+        retval = security_sem_alloc(sma);
+        if (retval) {
+                ipc_rcu_putref(sma);
+                return retval;
+        }
+
+        id = ipc_addid(&sem_ids, &sma->sem_perm, sc_semmni);
+        if(id == -1) {
+                security_sem_free(sma);
+                ipc_rcu_putref(sma);
+                return -ENOSPC;
+        }
+        used_sems += nsems;
+
+        sma->sem_base = (struct sem *) &sma[1];
+        /* sma->sem_pending = NULL; */
+        sma->sem_pending_last = &sma->sem_pending;
+        /* sma->undo = NULL; */
+        sma->sem_nsems = nsems;
+        sma->sem_ctime = get_seconds();
+        sem_unlock(sma);
+
+        return sem_buildid(id, sma->sem_perm.seq);
+}
+
+asmlinkage long sys_semget (key_t key, int nsems, int semflg)
+{
+        int id, err = -EINVAL;
+        struct sem_array *sma;
+
+        if (nsems < 0 || nsems > sc_semmsl)
+                return -EINVAL;
+        down(&sem_ids.sem);
+        
+        if (key == IPC_PRIVATE) {
+                err = newary(key, nsems, semflg);
+        } else if ((id = ipc_findkey(&sem_ids, key)) == -1) {  /* key not used */
+                if (!(semflg & IPC_CREAT))
+                        err = -ENOENT;
+                else
+                        err = newary(key, nsems, semflg);
+        } else if (semflg & IPC_CREAT && semflg & IPC_EXCL) {
+                err = -EEXIST;
+        } else {
+                sma = sem_lock(id);
+                if(sma==NULL)
+                        BUG();
+                if (nsems > sma->sem_nsems)
+                        err = -EINVAL;
+                else if (ipcperms(&sma->sem_perm, semflg))
+                        err = -EACCES;
+                else {
+                        int semid = sem_buildid(id, sma->sem_perm.seq);
+                        err = security_sem_associate(sma, semflg);
+                        if (!err)
+                                err = semid;
+                }
+                sem_unlock(sma);
+        }
+
+        up(&sem_ids.sem);
+        return err;
+}
+
+/* Manage the doubly linked list sma->sem_pending as a FIFO:
+ * insert new queue elements at the tail sma->sem_pending_last.
+ */
+static inline void append_to_queue (struct sem_array * sma,
+                                    struct sem_queue * q)
+{
+        *(q->prev = sma->sem_pending_last) = q;
+        *(sma->sem_pending_last = &q->next) = NULL;
+}
+
+static inline void prepend_to_queue (struct sem_array * sma,
+                                     struct sem_queue * q)
+{
+        q->next = sma->sem_pending;
+        *(q->prev = &sma->sem_pending) = q;
+        if (q->next)
+                q->next->prev = &q->next;
+        else /* sma->sem_pending_last == &sma->sem_pending */
+                sma->sem_pending_last = &q->next;
+}
+
+static inline void remove_from_queue (struct sem_array * sma,
+                                      struct sem_queue * q)
+{
+        *(q->prev) = q->next;
+        if (q->next)
+                q->next->prev = q->prev;
+        else /* sma->sem_pending_last == &q->next */
+                sma->sem_pending_last = q->prev;
+        q->prev = NULL; /* mark as removed */
+}
+
+/*
+ * Determine whether a sequence of semaphore operations would succeed
+ * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
+ */
+
+static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
+                             int nsops, struct sem_undo *un, int pid)
+{
+        int result, sem_op;
+        struct sembuf *sop;
+        struct sem * curr;
+
+        for (sop = sops; sop < sops + nsops; sop++) {
+                curr = sma->sem_base + sop->sem_num;
+                sem_op = sop->sem_op;
+                result = curr->semval;
+  
+                if (!sem_op && result)
+                        goto would_block;
+
+                result += sem_op;
+                if (result < 0)
+                        goto would_block;
+                if (result > SEMVMX)
+                        goto out_of_range;
+                if (sop->sem_flg & SEM_UNDO) {
+                        int undo = un->semadj[sop->sem_num] - sem_op;
+                        /*
+                         *      Exceeding the undo range is an error.
+                         */
+                        if (undo < (-SEMAEM - 1) || undo > SEMAEM)
+                                goto out_of_range;
+                }
+                curr->semval = result;
+        }
+
+        sop--;
+        while (sop >= sops) {
+                sma->sem_base[sop->sem_num].sempid = pid;
+                if (sop->sem_flg & SEM_UNDO)
+                        un->semadj[sop->sem_num] -= sop->sem_op;
+                sop--;
+        }
+        
+        sma->sem_otime = get_seconds();
+        return 0;
+
+out_of_range:
+        result = -ERANGE;
+        goto undo;
+
+would_block:
+        if (sop->sem_flg & IPC_NOWAIT)
+                result = -EAGAIN;
+        else
+                result = 1;
+
+undo:
+        sop--;
+        while (sop >= sops) {
+                sma->sem_base[sop->sem_num].semval -= sop->sem_op;
+                sop--;
+        }
+
+        return result;
+}
+
+/* Go through the pending queue for the indicated semaphore
+ * looking for tasks that can be completed.
+ */
+static void update_queue (struct sem_array * sma)
+{
+        int error;
+        struct sem_queue * q;
+
+        q = sma->sem_pending;
+        while(q) {
+                error = try_atomic_semop(sma, q->sops, q->nsops,
+                                         q->undo, q->pid);
+
+                /* Does q->sleeper still need to sleep? */
+                if (error <= 0) {
+                        struct sem_queue *n;
+                        remove_from_queue(sma,q);
+                        q->status = IN_WAKEUP;
+                        /*
+                         * Continue scanning. The next operation
+                         * that must be checked depends on the type of the
+                         * completed operation:
+                         * - if the operation modified the array, then
+                         *   restart from the head of the queue and
+                         *   check for threads that might be waiting
+                         *   for semaphore values to become 0.
+                         * - if the operation didn't modify the array,
+                         *   then just continue.
+                         */
+                        if (q->alter)
+                                n = sma->sem_pending;
+                        else
+                                n = q->next;
+                        wake_up_process(q->sleeper);
+                        /* hands-off: q will disappear immediately after
+                         * writing q->status.
+                         */
+                        q->status = error;
+                        q = n;
+                } else {
+                        q = q->next;
+                }
+        }
+}
+
+/* The following counts are associated to each semaphore:
+ *   semncnt        number of tasks waiting on semval being nonzero
+ *   semzcnt        number of tasks waiting on semval being zero
+ * This model assumes that a task waits on exactly one semaphore.
+ * Since semaphore operations are to be performed atomically, tasks actually
+ * wait on a whole sequence of semaphores simultaneously.
+ * The counts we return here are a rough approximation, but still
+ * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
+ */
+static int count_semncnt (struct sem_array * sma, ushort semnum)
+{
+        int semncnt;
+        struct sem_queue * q;
+
+        semncnt = 0;
+        for (q = sma->sem_pending; q; q = q->next) {
+                struct sembuf * sops = q->sops;
+                int nsops = q->nsops;
+                int i;
+                for (i = 0; i < nsops; i++)
+                        if (sops[i].sem_num == semnum
+                            && (sops[i].sem_op < 0)
+                            && !(sops[i].sem_flg & IPC_NOWAIT))
+                                semncnt++;
+        }
+        return semncnt;
+}
+static int count_semzcnt (struct sem_array * sma, ushort semnum)
+{
+        int semzcnt;
+        struct sem_queue * q;
+
+        semzcnt = 0;
+        for (q = sma->sem_pending; q; q = q->next) {
+                struct sembuf * sops = q->sops;
+                int nsops = q->nsops;
+                int i;
+                for (i = 0; i < nsops; i++)
+                        if (sops[i].sem_num == semnum
+                            && (sops[i].sem_op == 0)
+                            && !(sops[i].sem_flg & IPC_NOWAIT))
+                                semzcnt++;
+        }
+        return semzcnt;
+}
+
+/* Free a semaphore set. freeary() is called with sem_ids.sem down and
+ * the spinlock for this semaphore set hold. sem_ids.sem remains locked
+ * on exit.
+ */
+static void freeary (struct sem_array *sma, int id)
+{
+        struct sem_undo *un;
+        struct sem_queue *q;
+        int size;
+
+        /* Invalidate the existing undo structures for this semaphore set.
+         * (They will be freed without any further action in exit_sem()
+         * or during the next semop.)
+         */
+        for (un = sma->undo; un; un = un->id_next)
+                un->semid = -1;
+
+        /* Wake up all pending processes and let them fail with EIDRM. */
+        q = sma->sem_pending;
+        while(q) {
+                struct sem_queue *n;
+                /* lazy remove_from_queue: we are killing the whole queue */
+                q->prev = NULL;
+                n = q->next;
+                q->status = IN_WAKEUP;
+                wake_up_process(q->sleeper); /* doesn't sleep */
+                q->status = -EIDRM;     /* hands-off q */
+                q = n;
+        }
+
+        /* Remove the semaphore set from the ID array*/
+        sma = sem_rmid(id);
+        sem_unlock(sma);
+
+        used_sems -= sma->sem_nsems;
+        size = sizeof (*sma) + sma->sem_nsems * sizeof (struct sem);
+        security_sem_free(sma);
+        ipc_rcu_putref(sma);
+}
+
+static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
+{
+        switch(version) {
+        case IPC_64:
+                return copy_to_user(buf, in, sizeof(*in));
+        case IPC_OLD:
+            {
+                struct semid_ds out;
+
+                ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
+
+                out.sem_otime   = in->sem_otime;
+                out.sem_ctime   = in->sem_ctime;
+                out.sem_nsems   = in->sem_nsems;
+
+                return copy_to_user(buf, &out, sizeof(out));
+            }
+        default:
+                return -EINVAL;
+        }
+}
+
+static int semctl_nolock(int semid, int semnum, int cmd, int version, union semun arg)
+{
+        int err = -EINVAL;
+        struct sem_array *sma;
+
+        switch(cmd) {
+        case IPC_INFO:
+        case SEM_INFO:
+        {
+                struct seminfo seminfo;
+                int max_id;
+
+                err = security_sem_semctl(NULL, cmd);
+                if (err)
+                        return err;
+                
+                memset(&seminfo,0,sizeof(seminfo));
+                seminfo.semmni = sc_semmni;
+                seminfo.semmns = sc_semmns;
+                seminfo.semmsl = sc_semmsl;
+                seminfo.semopm = sc_semopm;
+                seminfo.semvmx = SEMVMX;
+                seminfo.semmnu = SEMMNU;
+                seminfo.semmap = SEMMAP;
+                seminfo.semume = SEMUME;
+                down(&sem_ids.sem);
+                if (cmd == SEM_INFO) {
+                        seminfo.semusz = sem_ids.in_use;
+                        seminfo.semaem = used_sems;
+                } else {
+                        seminfo.semusz = SEMUSZ;
+                        seminfo.semaem = SEMAEM;
+                }
+                max_id = sem_ids.max_id;
+                up(&sem_ids.sem);
+                if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo))) 
+                        return -EFAULT;
+                return (max_id < 0) ? 0: max_id;
+        }
+        case SEM_STAT:
+        {
+                struct semid64_ds tbuf;
+                int id;
+
+                if(semid >= sem_ids.entries->size)
+                        return -EINVAL;
+
+                memset(&tbuf,0,sizeof(tbuf));
+
+                sma = sem_lock(semid);
+                if(sma == NULL)
+                        return -EINVAL;
+
+                err = -EACCES;
+                if (ipcperms (&sma->sem_perm, S_IRUGO))
+                        goto out_unlock;
+
+                err = security_sem_semctl(sma, cmd);
+                if (err)
+                        goto out_unlock;
+
+                id = sem_buildid(semid, sma->sem_perm.seq);
+
+                kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
+                tbuf.sem_otime  = sma->sem_otime;
+                tbuf.sem_ctime  = sma->sem_ctime;
+                tbuf.sem_nsems  = sma->sem_nsems;
+                sem_unlock(sma);
+                if (copy_semid_to_user (arg.buf, &tbuf, version))
+                        return -EFAULT;
+                return id;
+        }
+        default:
+                return -EINVAL;
+        }
+        return err;
+out_unlock:
+        sem_unlock(sma);
+        return err;
+}
+
+static int semctl_main(int semid, int semnum, int cmd, int version, union semun arg)
+{
+        struct sem_array *sma;
+        struct sem* curr;
+        int err;
+        ushort fast_sem_io[SEMMSL_FAST];
+        ushort* sem_io = fast_sem_io;
+        int nsems;
+
+        sma = sem_lock(semid);
+        if(sma==NULL)
+                return -EINVAL;
+
+        nsems = sma->sem_nsems;
+
+        err=-EIDRM;
+        if (sem_checkid(sma,semid))
+                goto out_unlock;
+
+        err = -EACCES;
+        if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
+                goto out_unlock;
+
+        err = security_sem_semctl(sma, cmd);
+        if (err)
+                goto out_unlock;
+
+        err = -EACCES;
+        switch (cmd) {
+        case GETALL:
+        {
+                ushort __user *array = arg.array;
+                int i;
+
+                if(nsems > SEMMSL_FAST) {
+                        ipc_rcu_getref(sma);
+                        sem_unlock(sma);                        
+
+                        sem_io = ipc_alloc(sizeof(ushort)*nsems);
+                        if(sem_io == NULL) {
+                                ipc_lock_by_ptr(&sma->sem_perm);
+                                ipc_rcu_putref(sma);
+                                sem_unlock(sma);
+                                return -ENOMEM;
+                        }
+
+                        ipc_lock_by_ptr(&sma->sem_perm);
+                        ipc_rcu_putref(sma);
+                        if (sma->sem_perm.deleted) {
+                                sem_unlock(sma);
+                                err = -EIDRM;
+                                goto out_free;
+                        }
+                }
+
+                for (i = 0; i < sma->sem_nsems; i++)
+                        sem_io[i] = sma->sem_base[i].semval;
+                sem_unlock(sma);
+                err = 0;
+                if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
+                        err = -EFAULT;
+                goto out_free;
+        }
+        case SETALL:
+        {
+                int i;
+                struct sem_undo *un;
+
+                ipc_rcu_getref(sma);
+                sem_unlock(sma);
+
+                if(nsems > SEMMSL_FAST) {
+                        sem_io = ipc_alloc(sizeof(ushort)*nsems);
+                        if(sem_io == NULL) {
+                                ipc_lock_by_ptr(&sma->sem_perm);
+                                ipc_rcu_putref(sma);
+                                sem_unlock(sma);
+                                return -ENOMEM;
+                        }
+                }
+
+                if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
+                        ipc_lock_by_ptr(&sma->sem_perm);
+                        ipc_rcu_putref(sma);
+                        sem_unlock(sma);
+                        err = -EFAULT;
+                        goto out_free;
+                }
+
+                for (i = 0; i < nsems; i++) {
+                        if (sem_io[i] > SEMVMX) {
+                                ipc_lock_by_ptr(&sma->sem_perm);
+                                ipc_rcu_putref(sma);
+                                sem_unlock(sma);
+                                err = -ERANGE;
+                                goto out_free;
+                        }
+                }
+                ipc_lock_by_ptr(&sma->sem_perm);
+                ipc_rcu_putref(sma);
+                if (sma->sem_perm.deleted) {
+                        sem_unlock(sma);
+                        err = -EIDRM;
+                        goto out_free;
+                }
+
+                for (i = 0; i < nsems; i++)
+                        sma->sem_base[i].semval = sem_io[i];
+                for (un = sma->undo; un; un = un->id_next)
+                        for (i = 0; i < nsems; i++)
+                                un->semadj[i] = 0;
+                sma->sem_ctime = get_seconds();
+                /* maybe some queued-up processes were waiting for this */
+                update_queue(sma);
+                err = 0;
+                goto out_unlock;
+        }
+        case IPC_STAT:
+        {
+                struct semid64_ds tbuf;
+                memset(&tbuf,0,sizeof(tbuf));
+                kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
+                tbuf.sem_otime  = sma->sem_otime;
+                tbuf.sem_ctime  = sma->sem_ctime;
+                tbuf.sem_nsems  = sma->sem_nsems;
+                sem_unlock(sma);
+                if (copy_semid_to_user (arg.buf, &tbuf, version))
+                        return -EFAULT;
+                return 0;
+        }
+        /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
+        }
+        err = -EINVAL;
+        if(semnum < 0 || semnum >= nsems)
+                goto out_unlock;
+
+        curr = &sma->sem_base[semnum];
+
+        switch (cmd) {
+        case GETVAL:
+                err = curr->semval;
+                goto out_unlock;
+        case GETPID:
+                err = curr->sempid;
+                goto out_unlock;
+        case GETNCNT:
+                err = count_semncnt(sma,semnum);
+                goto out_unlock;
+        case GETZCNT:
+                err = count_semzcnt(sma,semnum);
+                goto out_unlock;
+        case SETVAL:
+        {
+                int val = arg.val;
+                struct sem_undo *un;
+                err = -ERANGE;
+                if (val > SEMVMX || val < 0)
+                        goto out_unlock;
+
+                for (un = sma->undo; un; un = un->id_next)
+                        un->semadj[semnum] = 0;
+                curr->semval = val;
+                curr->sempid = current->tgid;
+                sma->sem_ctime = get_seconds();
+                /* maybe some queued-up processes were waiting for this */
+                update_queue(sma);
+                err = 0;
+                goto out_unlock;
+        }
+        }
+out_unlock:
+        sem_unlock(sma);
+out_free:
+        if(sem_io != fast_sem_io)
+                ipc_free(sem_io, sizeof(ushort)*nsems);
+        return err;
+}
+
+struct sem_setbuf {
+        uid_t   uid;
+        gid_t   gid;
+        mode_t  mode;
+};
+
+static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __user *buf, int version)
+{
+        switch(version) {
+        case IPC_64:
+            {
+                struct semid64_ds tbuf;
+
+                if(copy_from_user(&tbuf, buf, sizeof(tbuf)))
+                        return -EFAULT;
+
+                out->uid        = tbuf.sem_perm.uid;
+                out->gid        = tbuf.sem_perm.gid;
+                out->mode       = tbuf.sem_perm.mode;
+
+                return 0;
+            }
+        case IPC_OLD:
+            {
+                struct semid_ds tbuf_old;
+
+                if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
+                        return -EFAULT;
+
+                out->uid        = tbuf_old.sem_perm.uid;
+                out->gid        = tbuf_old.sem_perm.gid;
+                out->mode       = tbuf_old.sem_perm.mode;
+
+                return 0;
+            }
+        default:
+                return -EINVAL;
+        }
+}
+
+static int semctl_down(int semid, int semnum, int cmd, int version, union semun arg)
+{
+        struct sem_array *sma;
+        int err;
+        struct sem_setbuf setbuf;
+        struct kern_ipc_perm *ipcp;
+
+        if(cmd == IPC_SET) {
+                if(copy_semid_from_user (&setbuf, arg.buf, version))
+                        return -EFAULT;
+                if ((err = audit_ipc_perms(0, setbuf.uid, setbuf.gid, setbuf.mode)))
+                        return err;
+        }
+        sma = sem_lock(semid);
+        if(sma==NULL)
+                return -EINVAL;
+
+        if (sem_checkid(sma,semid)) {
+                err=-EIDRM;
+                goto out_unlock;
+        }       
+        ipcp = &sma->sem_perm;
+        
+        if (current->euid != ipcp->cuid && 
+            current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) {
+                err=-EPERM;
+                goto out_unlock;
+        }
+
+        err = security_sem_semctl(sma, cmd);
+        if (err)
+                goto out_unlock;
+
+        switch(cmd){
+        case IPC_RMID:
+                freeary(sma, semid);
+                err = 0;
+                break;
+        case IPC_SET:
+                ipcp->uid = setbuf.uid;
+                ipcp->gid = setbuf.gid;
+                ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
+                                | (setbuf.mode & S_IRWXUGO);
+                sma->sem_ctime = get_seconds();
+                sem_unlock(sma);
+                err = 0;
+                break;
+        default:
+                sem_unlock(sma);
+                err = -EINVAL;
+                break;
+        }
+        return err;
+
+out_unlock:
+        sem_unlock(sma);
+        return err;
+}
+
+asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
+{
+        int err = -EINVAL;
+        int version;
+
+        if (semid < 0)
+                return -EINVAL;
+
+        version = ipc_parse_version(&cmd);
+
+        switch(cmd) {
+        case IPC_INFO:
+        case SEM_INFO:
+        case SEM_STAT:
+                err = semctl_nolock(semid,semnum,cmd,version,arg);
+                return err;
+        case GETALL:
+        case GETVAL:
+        case GETPID:
+        case GETNCNT:
+        case GETZCNT:
+        case IPC_STAT:
+        case SETVAL:
+        case SETALL:
+                err = semctl_main(semid,semnum,cmd,version,arg);
+                return err;
+        case IPC_RMID:
+        case IPC_SET:
+                down(&sem_ids.sem);
+                err = semctl_down(semid,semnum,cmd,version,arg);
+                up(&sem_ids.sem);
+                return err;
+        default:
+                return -EINVAL;
+        }
+}
+
+static inline void lock_semundo(void)
+{
+        struct sem_undo_list *undo_list;
+
+        undo_list = current->sysvsem.undo_list;
+        if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1))
+                spin_lock(&undo_list->lock);
+}
+
+/* This code has an interaction with copy_semundo().
+ * Consider; two tasks are sharing the undo_list. task1
+ * acquires the undo_list lock in lock_semundo().  If task2 now
+ * exits before task1 releases the lock (by calling
+ * unlock_semundo()), then task1 will never call spin_unlock().
+ * This leave the sem_undo_list in a locked state.  If task1 now creats task3
+ * and once again shares the sem_undo_list, the sem_undo_list will still be
+ * locked, and future SEM_UNDO operations will deadlock.  This case is
+ * dealt with in copy_semundo() by having it reinitialize the spin lock when 
+ * the refcnt goes from 1 to 2.
+ */
+static inline void unlock_semundo(void)
+{
+        struct sem_undo_list *undo_list;
+
+        undo_list = current->sysvsem.undo_list;
+        if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1))
+                spin_unlock(&undo_list->lock);
+}
+
+
+/* If the task doesn't already have a undo_list, then allocate one
+ * here.  We guarantee there is only one thread using this undo list,
+ * and current is THE ONE
+ *
+ * If this allocation and assignment succeeds, but later
+ * portions of this code fail, there is no need to free the sem_undo_list.
+ * Just let it stay associated with the task, and it'll be freed later
+ * at exit time.
+ *
+ * This can block, so callers must hold no locks.
+ */
+static inline int get_undo_list(struct sem_undo_list **undo_listp)
+{
+        struct sem_undo_list *undo_list;
+        int size;
+
+        undo_list = current->sysvsem.undo_list;
+        if (!undo_list) {
+                size = sizeof(struct sem_undo_list);
+                undo_list = (struct sem_undo_list *) kmalloc(size, GFP_KERNEL);
+                if (undo_list == NULL)
+                        return -ENOMEM;
+                memset(undo_list, 0, size);
+                /* don't initialize unodhd->lock here.  It's done
+                 * in copy_semundo() instead.
+                 */
+                atomic_set(&undo_list->refcnt, 1);
+                current->sysvsem.undo_list = undo_list;
+        }
+        *undo_listp = undo_list;
+        return 0;
+}
+
+static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
+{
+        struct sem_undo **last, *un;
+
+        last = &ulp->proc_list;
+        un = *last;
+        while(un != NULL) {
+                if(un->semid==semid)
+                        break;
+                if(un->semid==-1) {
+                        *last=un->proc_next;
+                        kfree(un);
+                } else {
+                        last=&un->proc_next;
+                }
+                un=*last;
+        }
+        return un;
+}
+
+static struct sem_undo *find_undo(int semid)
+{
+        struct sem_array *sma;
+        struct sem_undo_list *ulp;
+        struct sem_undo *un, *new;
+        int nsems;
+        int error;
+
+        error = get_undo_list(&ulp);
+        if (error)
+                return ERR_PTR(error);
+
+        lock_semundo();
+        un = lookup_undo(ulp, semid);
+        unlock_semundo();
+        if (likely(un!=NULL))
+                goto out;
+
+        /* no undo structure around - allocate one. */
+        sma = sem_lock(semid);
+        un = ERR_PTR(-EINVAL);
+        if(sma==NULL)
+                goto out;
+        un = ERR_PTR(-EIDRM);
+        if (sem_checkid(sma,semid)) {
+                sem_unlock(sma);
+                goto out;
+        }
+        nsems = sma->sem_nsems;
+        ipc_rcu_getref(sma);
+        sem_unlock(sma);
+
+        new = (struct sem_undo *) kmalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
+        if (!new) {
+                ipc_lock_by_ptr(&sma->sem_perm);
+                ipc_rcu_putref(sma);
+                sem_unlock(sma);
+                return ERR_PTR(-ENOMEM);
+        }
+        memset(new, 0, sizeof(struct sem_undo) + sizeof(short)*nsems);
+        new->semadj = (short *) &new[1];
+        new->semid = semid;
+
+        lock_semundo();
+        un = lookup_undo(ulp, semid);
+        if (un) {
+                unlock_semundo();
+                kfree(new);
+                ipc_lock_by_ptr(&sma->sem_perm);
+                ipc_rcu_putref(sma);
+                sem_unlock(sma);
+                goto out;
+        }
+        ipc_lock_by_ptr(&sma->sem_perm);
+        ipc_rcu_putref(sma);
+        if (sma->sem_perm.deleted) {
+                sem_unlock(sma);
+                unlock_semundo();
+                kfree(new);
+                un = ERR_PTR(-EIDRM);
+                goto out;
+        }
+        new->proc_next = ulp->proc_list;
+        ulp->proc_list = new;
+        new->id_next = sma->undo;
+        sma->undo = new;
+        sem_unlock(sma);
+        un = new;
+        unlock_semundo();
+out:
+        return un;
+}
+
+asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
+                        unsigned nsops, const struct timespec __user *timeout)
+{
+        int error = -EINVAL;
+        struct sem_array *sma;
+        struct sembuf fast_sops[SEMOPM_FAST];
+        struct sembuf* sops = fast_sops, *sop;
+        struct sem_undo *un;
+        int undos = 0, decrease = 0, alter = 0, max;
+        struct sem_queue queue;
+        unsigned long jiffies_left = 0;
+
+        if (nsops < 1 || semid < 0)
+                return -EINVAL;
+        if (nsops > sc_semopm)
+                return -E2BIG;
+        if(nsops > SEMOPM_FAST) {
+                sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
+                if(sops==NULL)
+                        return -ENOMEM;
+        }
+        if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
+                error=-EFAULT;
+                goto out_free;
+        }
+        if (timeout) {
+                struct timespec _timeout;
+                if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
+                        error = -EFAULT;
+                        goto out_free;
+                }
+                if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
+                        _timeout.tv_nsec >= 1000000000L) {
+                        error = -EINVAL;
+                        goto out_free;
+                }
+                jiffies_left = timespec_to_jiffies(&_timeout);
+        }
+        max = 0;
+        for (sop = sops; sop < sops + nsops; sop++) {
+                if (sop->sem_num >= max)
+                        max = sop->sem_num;
+                if (sop->sem_flg & SEM_UNDO)
+                        undos++;
+                if (sop->sem_op < 0)
+                        decrease = 1;
+                if (sop->sem_op > 0)
+                        alter = 1;
+        }
+        alter |= decrease;
+
+retry_undos:
+        if (undos) {
+                un = find_undo(semid);
+                if (IS_ERR(un)) {
+                        error = PTR_ERR(un);
+                        goto out_free;
+                }
+        } else
+                un = NULL;
+
+        sma = sem_lock(semid);
+        error=-EINVAL;
+        if(sma==NULL)
+                goto out_free;
+        error = -EIDRM;
+        if (sem_checkid(sma,semid))
+                goto out_unlock_free;
+        /*
+         * semid identifies are not unique - find_undo may have
+         * allocated an undo structure, it was invalidated by an RMID
+         * and now a new array with received the same id. Check and retry.
+         */
+        if (un && un->semid == -1) {
+                sem_unlock(sma);
+                goto retry_undos;
+        }
+        error = -EFBIG;
+        if (max >= sma->sem_nsems)
+                goto out_unlock_free;
+
+        error = -EACCES;
+        if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
+                goto out_unlock_free;
+
+        error = security_sem_semop(sma, sops, nsops, alter);
+        if (error)
+                goto out_unlock_free;
+
+        error = try_atomic_semop (sma, sops, nsops, un, current->tgid);
+        if (error <= 0) {
+                if (alter && error == 0)
+                        update_queue (sma);
+                goto out_unlock_free;
+        }
+
+        /* We need to sleep on this operation, so we put the current
+         * task into the pending queue and go to sleep.
+         */
+                
+        queue.sma = sma;
+        queue.sops = sops;
+        queue.nsops = nsops;
+        queue.undo = un;
+        queue.pid = current->tgid;
+        queue.id = semid;
+        queue.alter = alter;
+        if (alter)
+                append_to_queue(sma ,&queue);
+        else
+                prepend_to_queue(sma ,&queue);
+
+        queue.status = -EINTR;
+        queue.sleeper = current;
+        current->state = TASK_INTERRUPTIBLE;
+        sem_unlock(sma);
+
+        if (timeout)
+                jiffies_left = schedule_timeout(jiffies_left);
+        else
+                schedule();
+
+        error = queue.status;
+        while(unlikely(error == IN_WAKEUP)) {
+                cpu_relax();
+                error = queue.status;
+        }
+
+        if (error != -EINTR) {
+                /* fast path: update_queue already obtained all requested
+                 * resources */
+                goto out_free;
+        }
+
+        sma = sem_lock(semid);
+        if(sma==NULL) {
+                if(queue.prev != NULL)
+                        BUG();
+                error = -EIDRM;
+                goto out_free;
+        }
+
+        /*
+         * If queue.status != -EINTR we are woken up by another process
+         */
+        error = queue.status;
+        if (error != -EINTR) {
+                goto out_unlock_free;
+        }
+
+        /*
+         * If an interrupt occurred we have to clean up the queue
+         */
+        if (timeout && jiffies_left == 0)
+                error = -EAGAIN;
+        remove_from_queue(sma,&queue);
+        goto out_unlock_free;
+
+out_unlock_free:
+        sem_unlock(sma);
+out_free:
+        if(sops != fast_sops)
+                kfree(sops);
+        return error;
+}
+
+asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsops)
+{
+        return sys_semtimedop(semid, tsops, nsops, NULL);
+}
+
+/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
+ * parent and child tasks.
+ *
+ * See the notes above unlock_semundo() regarding the spin_lock_init()
+ * in this code.  Initialize the undo_list->lock here instead of get_undo_list()
+ * because of the reasoning in the comment above unlock_semundo.
+ */
+
+int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
+{
+        struct sem_undo_list *undo_list;
+        int error;
+
+        if (clone_flags & CLONE_SYSVSEM) {
+                error = get_undo_list(&undo_list);
+                if (error)
+                        return error;
+                if (atomic_read(&undo_list->refcnt) == 1)
+                        spin_lock_init(&undo_list->lock);
+                atomic_inc(&undo_list->refcnt);
+                tsk->sysvsem.undo_list = undo_list;
+        } else 
+                tsk->sysvsem.undo_list = NULL;
+
+        return 0;
+}
+
+/*
+ * add semadj values to semaphores, free undo structures.
+ * undo structures are not freed when semaphore arrays are destroyed
+ * so some of them may be out of date.
+ * IMPLEMENTATION NOTE: There is some confusion over whether the
+ * set of adjustments that needs to be done should be done in an atomic
+ * manner or not. That is, if we are attempting to decrement the semval
+ * should we queue up and wait until we can do so legally?
+ * The original implementation attempted to do this (queue and wait).
+ * The current implementation does not do so. The POSIX standard
+ * and SVID should be consulted to determine what behavior is mandated.
+ */
+void exit_sem(struct task_struct *tsk)
+{
+        struct sem_undo_list *undo_list;
+        struct sem_undo *u, **up;
+
+        undo_list = tsk->sysvsem.undo_list;
+        if (!undo_list)
+                return;
+
+        if (!atomic_dec_and_test(&undo_list->refcnt))
+                return;
+
+        /* There's no need to hold the semundo list lock, as current
+         * is the last task exiting for this undo list.
+         */
+        for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
+                struct sem_array *sma;
+                int nsems, i;
+                struct sem_undo *un, **unp;
+                int semid;
+               
+                semid = u->semid;
+
+                if(semid == -1)
+                        continue;
+                sma = sem_lock(semid);
+                if (sma == NULL)
+                        continue;
+
+                if (u->semid == -1)
+                        goto next_entry;
+
+                BUG_ON(sem_checkid(sma,u->semid));
+
+                /* remove u from the sma->undo list */
+                for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
+                        if (u == un)
+                                goto found;
+                }
+                printk ("exit_sem undo list error id=%d\n", u->semid);
+                goto next_entry;
+found:
+                *unp = un->id_next;
+                /* perform adjustments registered in u */
+                nsems = sma->sem_nsems;
+                for (i = 0; i < nsems; i++) {
+                        struct sem * sem = &sma->sem_base[i];
+                        if (u->semadj[i]) {
+                                sem->semval += u->semadj[i];
+                                /*
+                                 * Range checks of the new semaphore value,
+                                 * not defined by sus:
+                                 * - Some unices ignore the undo entirely
+                                 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
+                                 * - some cap the value (e.g. FreeBSD caps
+                                 *   at 0, but doesn't enforce SEMVMX)
+                                 *
+                                 * Linux caps the semaphore value, both at 0
+                                 * and at SEMVMX.
+                                 *
+                                 *      Manfred <manfred@colorfullife.com>
+                                 */
+                                if (sem->semval < 0)
+                                        sem->semval = 0;
+                                if (sem->semval > SEMVMX)
+                                        sem->semval = SEMVMX;
+                                sem->sempid = current->tgid;
+                        }
+                }
+                sma->sem_otime = get_seconds();
+                /* maybe some queued-up processes were waiting for this */
+                update_queue(sma);
+next_entry:
+                sem_unlock(sma);
+        }
+        kfree(undo_list);
+}
+
+#ifdef CONFIG_PROC_FS
+static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data)
+{
+        off_t pos = 0;
+        off_t begin = 0;
+        int i, len = 0;
+
+        len += sprintf(buffer, "       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n");
+        down(&sem_ids.sem);
+
+        for(i = 0; i <= sem_ids.max_id; i++) {
+                struct sem_array *sma;
+                sma = sem_lock(i);
+                if(sma) {
+                        len += sprintf(buffer + len, "%10d %10d  %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
+                                sma->sem_perm.key,
+                                sem_buildid(i,sma->sem_perm.seq),
+                                sma->sem_perm.mode,
+                                sma->sem_nsems,
+                                sma->sem_perm.uid,
+                                sma->sem_perm.gid,
+                                sma->sem_perm.cuid,
+                                sma->sem_perm.cgid,
+                                sma->sem_otime,
+                                sma->sem_ctime);
+                        sem_unlock(sma);
+
+                        pos += len;
+                        if(pos < offset) {
+                                len = 0;
+                                begin = pos;
+                        }
+                        if(pos > offset + length)
+                                goto done;
+                }
+        }
+        *eof = 1;
+done:
+        up(&sem_ids.sem);
+        *start = buffer + (offset - begin);
+        len -= (offset - begin);
+        if(len > length)
+                len = length;
+        if(len < 0)
+                len = 0;
+        return len;
+}
+#endif