diff options
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 1384 |
1 files changed, 1384 insertions, 0 deletions
diff --git a/ipc/sem.c b/ipc/sem.c new file mode 100644 index 0000000..5ad7ac0 --- /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 |
