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-rw-r--r--ipc/sem.c1384
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

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