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freebsd-skq/sys/kern/sysv_sem.c
Oleksandr Tymoshenko 23c8064e66 Renew semaphore's pointer after wakeup since during msleep 
sem_base may have been modified by destroying one of semaphores
and semptr would not be valid in this case.

PR: kern/123731
2008-06-19 18:08:42 +00:00

1372 lines
34 KiB
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/*-
* Implementation of SVID semaphores
*
* Author: Daniel Boulet
*
* This software is provided ``AS IS'' without any warranties of any kind.
*/
/*-
* Copyright (c) 2003-2005 McAfee, Inc.
* All rights reserved.
*
* This software was developed for the FreeBSD Project in part by McAfee
* Research, the Security Research Division of McAfee, Inc under DARPA/SPAWAR
* contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS research
* program.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_sysvipc.h"
#include "opt_mac.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/mutex.h>
#include <sys/sem.h>
#include <sys/syscall.h>
#include <sys/syscallsubr.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/uio.h>
#include <sys/malloc.h>
#include <sys/jail.h>
#include <security/mac/mac_framework.h>
static MALLOC_DEFINE(M_SEM, "sem", "SVID compatible semaphores");
#ifdef SEM_DEBUG
#define DPRINTF(a) printf a
#else
#define DPRINTF(a)
#endif
static void seminit(void);
static int sysvsem_modload(struct module *, int, void *);
static int semunload(void);
static void semexit_myhook(void *arg, struct proc *p);
static int sysctl_sema(SYSCTL_HANDLER_ARGS);
static int semvalid(int semid, struct semid_kernel *semakptr);
#ifndef _SYS_SYSPROTO_H_
struct __semctl_args;
int __semctl(struct thread *td, struct __semctl_args *uap);
struct semget_args;
int semget(struct thread *td, struct semget_args *uap);
struct semop_args;
int semop(struct thread *td, struct semop_args *uap);
#endif
static struct sem_undo *semu_alloc(struct thread *td);
static int semundo_adjust(struct thread *td, struct sem_undo **supptr,
int semid, int semnum, int adjval);
static void semundo_clear(int semid, int semnum);
/* XXX casting to (sy_call_t *) is bogus, as usual. */
static sy_call_t *semcalls[] = {
(sy_call_t *)__semctl, (sy_call_t *)semget,
(sy_call_t *)semop
};
static struct mtx sem_mtx; /* semaphore global lock */
static int semtot = 0;
static struct semid_kernel *sema; /* semaphore id pool */
static struct mtx *sema_mtx; /* semaphore id pool mutexes*/
static struct sem *sem; /* semaphore pool */
SLIST_HEAD(, sem_undo) semu_list; /* list of active undo structures */
static int *semu; /* undo structure pool */
static eventhandler_tag semexit_tag;
#define SEMUNDO_MTX sem_mtx
#define SEMUNDO_LOCK() mtx_lock(&SEMUNDO_MTX);
#define SEMUNDO_UNLOCK() mtx_unlock(&SEMUNDO_MTX);
#define SEMUNDO_LOCKASSERT(how) mtx_assert(&SEMUNDO_MTX, (how));
struct sem {
u_short semval; /* semaphore value */
pid_t sempid; /* pid of last operation */
u_short semncnt; /* # awaiting semval > cval */
u_short semzcnt; /* # awaiting semval = 0 */
};
/*
* Undo structure (one per process)
*/
struct sem_undo {
SLIST_ENTRY(sem_undo) un_next; /* ptr to next active undo structure */
struct proc *un_proc; /* owner of this structure */
short un_cnt; /* # of active entries */
struct undo {
short un_adjval; /* adjust on exit values */
short un_num; /* semaphore # */
int un_id; /* semid */
} un_ent[1]; /* undo entries */
};
/*
* Configuration parameters
*/
#ifndef SEMMNI
#define SEMMNI 10 /* # of semaphore identifiers */
#endif
#ifndef SEMMNS
#define SEMMNS 60 /* # of semaphores in system */
#endif
#ifndef SEMUME
#define SEMUME 10 /* max # of undo entries per process */
#endif
#ifndef SEMMNU
#define SEMMNU 30 /* # of undo structures in system */
#endif
/* shouldn't need tuning */
#ifndef SEMMAP
#define SEMMAP 30 /* # of entries in semaphore map */
#endif
#ifndef SEMMSL
#define SEMMSL SEMMNS /* max # of semaphores per id */
#endif
#ifndef SEMOPM
#define SEMOPM 100 /* max # of operations per semop call */
#endif
#define SEMVMX 32767 /* semaphore maximum value */
#define SEMAEM 16384 /* adjust on exit max value */
/*
* Due to the way semaphore memory is allocated, we have to ensure that
* SEMUSZ is properly aligned.
*/
#define SEM_ALIGN(bytes) (((bytes) + (sizeof(long) - 1)) & ~(sizeof(long) - 1))
/* actual size of an undo structure */
#define SEMUSZ SEM_ALIGN(offsetof(struct sem_undo, un_ent[SEMUME]))
/*
* Macro to find a particular sem_undo vector
*/
#define SEMU(ix) \
((struct sem_undo *)(((intptr_t)semu)+ix * seminfo.semusz))
/*
* semaphore info struct
*/
struct seminfo seminfo = {
SEMMAP, /* # of entries in semaphore map */
SEMMNI, /* # of semaphore identifiers */
SEMMNS, /* # of semaphores in system */
SEMMNU, /* # of undo structures in system */
SEMMSL, /* max # of semaphores per id */
SEMOPM, /* max # of operations per semop call */
SEMUME, /* max # of undo entries per process */
SEMUSZ, /* size in bytes of undo structure */
SEMVMX, /* semaphore maximum value */
SEMAEM /* adjust on exit max value */
};
SYSCTL_INT(_kern_ipc, OID_AUTO, semmap, CTLFLAG_RW, &seminfo.semmap, 0,
"Number of entries in the semaphore map");
SYSCTL_INT(_kern_ipc, OID_AUTO, semmni, CTLFLAG_RDTUN, &seminfo.semmni, 0,
"Number of semaphore identifiers");
SYSCTL_INT(_kern_ipc, OID_AUTO, semmns, CTLFLAG_RDTUN, &seminfo.semmns, 0,
"Maximum number of semaphores in the system");
SYSCTL_INT(_kern_ipc, OID_AUTO, semmnu, CTLFLAG_RDTUN, &seminfo.semmnu, 0,
"Maximum number of undo structures in the system");
SYSCTL_INT(_kern_ipc, OID_AUTO, semmsl, CTLFLAG_RW, &seminfo.semmsl, 0,
"Max semaphores per id");
SYSCTL_INT(_kern_ipc, OID_AUTO, semopm, CTLFLAG_RDTUN, &seminfo.semopm, 0,
"Max operations per semop call");
SYSCTL_INT(_kern_ipc, OID_AUTO, semume, CTLFLAG_RDTUN, &seminfo.semume, 0,
"Max undo entries per process");
SYSCTL_INT(_kern_ipc, OID_AUTO, semusz, CTLFLAG_RDTUN, &seminfo.semusz, 0,
"Size in bytes of undo structure");
SYSCTL_INT(_kern_ipc, OID_AUTO, semvmx, CTLFLAG_RW, &seminfo.semvmx, 0,
"Semaphore maximum value");
SYSCTL_INT(_kern_ipc, OID_AUTO, semaem, CTLFLAG_RW, &seminfo.semaem, 0,
"Adjust on exit max value");
SYSCTL_PROC(_kern_ipc, OID_AUTO, sema, CTLFLAG_RD,
NULL, 0, sysctl_sema, "", "");
static void
seminit(void)
{
int i;
TUNABLE_INT_FETCH("kern.ipc.semmap", &seminfo.semmap);
TUNABLE_INT_FETCH("kern.ipc.semmni", &seminfo.semmni);
TUNABLE_INT_FETCH("kern.ipc.semmns", &seminfo.semmns);
TUNABLE_INT_FETCH("kern.ipc.semmnu", &seminfo.semmnu);
TUNABLE_INT_FETCH("kern.ipc.semmsl", &seminfo.semmsl);
TUNABLE_INT_FETCH("kern.ipc.semopm", &seminfo.semopm);
TUNABLE_INT_FETCH("kern.ipc.semume", &seminfo.semume);
TUNABLE_INT_FETCH("kern.ipc.semusz", &seminfo.semusz);
TUNABLE_INT_FETCH("kern.ipc.semvmx", &seminfo.semvmx);
TUNABLE_INT_FETCH("kern.ipc.semaem", &seminfo.semaem);
sem = malloc(sizeof(struct sem) * seminfo.semmns, M_SEM, M_WAITOK);
sema = malloc(sizeof(struct semid_kernel) * seminfo.semmni, M_SEM,
M_WAITOK);
sema_mtx = malloc(sizeof(struct mtx) * seminfo.semmni, M_SEM,
M_WAITOK | M_ZERO);
semu = malloc(seminfo.semmnu * seminfo.semusz, M_SEM, M_WAITOK);
for (i = 0; i < seminfo.semmni; i++) {
sema[i].u.sem_base = 0;
sema[i].u.sem_perm.mode = 0;
sema[i].u.sem_perm.seq = 0;
#ifdef MAC
mac_sysvsem_init(&sema[i]);
#endif
}
for (i = 0; i < seminfo.semmni; i++)
mtx_init(&sema_mtx[i], "semid", NULL, MTX_DEF);
for (i = 0; i < seminfo.semmnu; i++) {
struct sem_undo *suptr = SEMU(i);
suptr->un_proc = NULL;
}
SLIST_INIT(&semu_list);
mtx_init(&sem_mtx, "sem", NULL, MTX_DEF);
semexit_tag = EVENTHANDLER_REGISTER(process_exit, semexit_myhook, NULL,
EVENTHANDLER_PRI_ANY);
}
static int
semunload(void)
{
int i;
if (semtot != 0)
return (EBUSY);
EVENTHANDLER_DEREGISTER(process_exit, semexit_tag);
#ifdef MAC
for (i = 0; i < seminfo.semmni; i++)
mac_sysvsem_destroy(&sema[i]);
#endif
free(sem, M_SEM);
free(sema, M_SEM);
free(semu, M_SEM);
for (i = 0; i < seminfo.semmni; i++)
mtx_destroy(&sema_mtx[i]);
mtx_destroy(&sem_mtx);
return (0);
}
static int
sysvsem_modload(struct module *module, int cmd, void *arg)
{
int error = 0;
switch (cmd) {
case MOD_LOAD:
seminit();
break;
case MOD_UNLOAD:
error = semunload();
break;
case MOD_SHUTDOWN:
break;
default:
error = EINVAL;
break;
}
return (error);
}
static moduledata_t sysvsem_mod = {
"sysvsem",
&sysvsem_modload,
NULL
};
SYSCALL_MODULE_HELPER(semsys);
SYSCALL_MODULE_HELPER(__semctl);
SYSCALL_MODULE_HELPER(semget);
SYSCALL_MODULE_HELPER(semop);
DECLARE_MODULE(sysvsem, sysvsem_mod,
SI_SUB_SYSV_SEM, SI_ORDER_FIRST);
MODULE_VERSION(sysvsem, 1);
/*
* Entry point for all SEM calls.
*/
int
semsys(td, uap)
struct thread *td;
/* XXX actually varargs. */
struct semsys_args /* {
int which;
int a2;
int a3;
int a4;
int a5;
} */ *uap;
{
int error;
if (!jail_sysvipc_allowed && jailed(td->td_ucred))
return (ENOSYS);
if (uap->which < 0 ||
uap->which >= sizeof(semcalls)/sizeof(semcalls[0]))
return (EINVAL);
error = (*semcalls[uap->which])(td, &uap->a2);
return (error);
}
/*
* Allocate a new sem_undo structure for a process
* (returns ptr to structure or NULL if no more room)
*/
static struct sem_undo *
semu_alloc(td)
struct thread *td;
{
int i;
struct sem_undo *suptr;
struct sem_undo **supptr;
int attempt;
SEMUNDO_LOCKASSERT(MA_OWNED);
/*
* Try twice to allocate something.
* (we'll purge an empty structure after the first pass so
* two passes are always enough)
*/
for (attempt = 0; attempt < 2; attempt++) {
/*
* Look for a free structure.
* Fill it in and return it if we find one.
*/
for (i = 0; i < seminfo.semmnu; i++) {
suptr = SEMU(i);
if (suptr->un_proc == NULL) {
SLIST_INSERT_HEAD(&semu_list, suptr, un_next);
suptr->un_cnt = 0;
suptr->un_proc = td->td_proc;
return(suptr);
}
}
/*
* We didn't find a free one, if this is the first attempt
* then try to free a structure.
*/
if (attempt == 0) {
/* All the structures are in use - try to free one */
int did_something = 0;
SLIST_FOREACH_PREVPTR(suptr, supptr, &semu_list,
un_next) {
if (suptr->un_cnt == 0) {
suptr->un_proc = NULL;
did_something = 1;
*supptr = SLIST_NEXT(suptr, un_next);
break;
}
}
/* If we didn't free anything then just give-up */
if (!did_something)
return(NULL);
} else {
/*
* The second pass failed even though we freed
* something after the first pass!
* This is IMPOSSIBLE!
*/
panic("semu_alloc - second attempt failed");
}
}
return (NULL);
}
/*
* Adjust a particular entry for a particular proc
*/
static int
semundo_adjust(td, supptr, semid, semnum, adjval)
struct thread *td;
struct sem_undo **supptr;
int semid, semnum;
int adjval;
{
struct proc *p = td->td_proc;
struct sem_undo *suptr;
struct undo *sunptr;
int i;
SEMUNDO_LOCKASSERT(MA_OWNED);
/* Look for and remember the sem_undo if the caller doesn't provide
it */
suptr = *supptr;
if (suptr == NULL) {
SLIST_FOREACH(suptr, &semu_list, un_next) {
if (suptr->un_proc == p) {
*supptr = suptr;
break;
}
}
if (suptr == NULL) {
if (adjval == 0)
return(0);
suptr = semu_alloc(td);
if (suptr == NULL)
return(ENOSPC);
*supptr = suptr;
}
}
/*
* Look for the requested entry and adjust it (delete if adjval becomes
* 0).
*/
sunptr = &suptr->un_ent[0];
for (i = 0; i < suptr->un_cnt; i++, sunptr++) {
if (sunptr->un_id != semid || sunptr->un_num != semnum)
continue;
if (adjval != 0) {
adjval += sunptr->un_adjval;
if (adjval > seminfo.semaem || adjval < -seminfo.semaem)
return (ERANGE);
}
sunptr->un_adjval = adjval;
if (sunptr->un_adjval == 0) {
suptr->un_cnt--;
if (i < suptr->un_cnt)
suptr->un_ent[i] =
suptr->un_ent[suptr->un_cnt];
}
return(0);
}
/* Didn't find the right entry - create it */
if (adjval == 0)
return(0);
if (adjval > seminfo.semaem || adjval < -seminfo.semaem)
return (ERANGE);
if (suptr->un_cnt != seminfo.semume) {
sunptr = &suptr->un_ent[suptr->un_cnt];
suptr->un_cnt++;
sunptr->un_adjval = adjval;
sunptr->un_id = semid; sunptr->un_num = semnum;
} else
return(EINVAL);
return(0);
}
static void
semundo_clear(semid, semnum)
int semid, semnum;
{
struct sem_undo *suptr;
SEMUNDO_LOCKASSERT(MA_OWNED);
SLIST_FOREACH(suptr, &semu_list, un_next) {
struct undo *sunptr = &suptr->un_ent[0];
int i = 0;
while (i < suptr->un_cnt) {
if (sunptr->un_id == semid) {
if (semnum == -1 || sunptr->un_num == semnum) {
suptr->un_cnt--;
if (i < suptr->un_cnt) {
suptr->un_ent[i] =
suptr->un_ent[suptr->un_cnt];
continue;
}
}
if (semnum != -1)
break;
}
i++, sunptr++;
}
}
}
static int
semvalid(semid, semakptr)
int semid;
struct semid_kernel *semakptr;
{
return ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0 ||
semakptr->u.sem_perm.seq != IPCID_TO_SEQ(semid) ? EINVAL : 0);
}
/*
* Note that the user-mode half of this passes a union, not a pointer.
*/
#ifndef _SYS_SYSPROTO_H_
struct __semctl_args {
int semid;
int semnum;
int cmd;
union semun *arg;
};
#endif
int
__semctl(td, uap)
struct thread *td;
struct __semctl_args *uap;
{
struct semid_ds dsbuf;
union semun arg, semun;
register_t rval;
int error;
switch (uap->cmd) {
case SEM_STAT:
case IPC_SET:
case IPC_STAT:
case GETALL:
case SETVAL:
case SETALL:
error = copyin(uap->arg, &arg, sizeof(arg));
if (error)
return (error);
break;
}
switch (uap->cmd) {
case SEM_STAT:
case IPC_STAT:
semun.buf = &dsbuf;
break;
case IPC_SET:
error = copyin(arg.buf, &dsbuf, sizeof(dsbuf));
if (error)
return (error);
semun.buf = &dsbuf;
break;
case GETALL:
case SETALL:
semun.array = arg.array;
break;
case SETVAL:
semun.val = arg.val;
break;
}
error = kern_semctl(td, uap->semid, uap->semnum, uap->cmd, &semun,
&rval);
if (error)
return (error);
switch (uap->cmd) {
case SEM_STAT:
case IPC_STAT:
error = copyout(&dsbuf, arg.buf, sizeof(dsbuf));
break;
}
if (error == 0)
td->td_retval[0] = rval;
return (error);
}
int
kern_semctl(struct thread *td, int semid, int semnum, int cmd,
union semun *arg, register_t *rval)
{
u_short *array;
struct ucred *cred = td->td_ucred;
int i, error;
struct semid_ds *sbuf;
struct semid_kernel *semakptr;
struct mtx *sema_mtxp;
u_short usval, count;
int semidx;
DPRINTF(("call to semctl(%d, %d, %d, 0x%p)\n",
semid, semnum, cmd, arg));
if (!jail_sysvipc_allowed && jailed(td->td_ucred))
return (ENOSYS);
array = NULL;
switch(cmd) {
case SEM_STAT:
/*
* For this command we assume semid is an array index
* rather than an IPC id.
*/
if (semid < 0 || semid >= seminfo.semmni)
return (EINVAL);
semakptr = &sema[semid];
sema_mtxp = &sema_mtx[semid];
mtx_lock(sema_mtxp);
if ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0) {
error = EINVAL;
goto done2;
}
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_R)))
goto done2;
#ifdef MAC
error = mac_sysvsem_check_semctl(cred, semakptr, cmd);
if (error != 0)
goto done2;
#endif
bcopy(&semakptr->u, arg->buf, sizeof(struct semid_ds));
*rval = IXSEQ_TO_IPCID(semid, semakptr->u.sem_perm);
mtx_unlock(sema_mtxp);
return (0);
}
semidx = IPCID_TO_IX(semid);
if (semidx < 0 || semidx >= seminfo.semmni)
return (EINVAL);
semakptr = &sema[semidx];
sema_mtxp = &sema_mtx[semidx];
mtx_lock(sema_mtxp);
#ifdef MAC
error = mac_sysvsem_check_semctl(cred, semakptr, cmd);
if (error != 0)
goto done2;
#endif
error = 0;
*rval = 0;
switch (cmd) {
case IPC_RMID:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_M)))
goto done2;
semakptr->u.sem_perm.cuid = cred->cr_uid;
semakptr->u.sem_perm.uid = cred->cr_uid;
semtot -= semakptr->u.sem_nsems;
for (i = semakptr->u.sem_base - sem; i < semtot; i++)
sem[i] = sem[i + semakptr->u.sem_nsems];
for (i = 0; i < seminfo.semmni; i++) {
if ((sema[i].u.sem_perm.mode & SEM_ALLOC) &&
sema[i].u.sem_base > semakptr->u.sem_base)
sema[i].u.sem_base -= semakptr->u.sem_nsems;
}
semakptr->u.sem_perm.mode = 0;
#ifdef MAC
mac_sysvsem_cleanup(semakptr);
#endif
SEMUNDO_LOCK();
semundo_clear(semidx, -1);
SEMUNDO_UNLOCK();
wakeup(semakptr);
break;
case IPC_SET:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_M)))
goto done2;
sbuf = arg->buf;
semakptr->u.sem_perm.uid = sbuf->sem_perm.uid;
semakptr->u.sem_perm.gid = sbuf->sem_perm.gid;
semakptr->u.sem_perm.mode = (semakptr->u.sem_perm.mode &
~0777) | (sbuf->sem_perm.mode & 0777);
semakptr->u.sem_ctime = time_second;
break;
case IPC_STAT:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_R)))
goto done2;
bcopy(&semakptr->u, arg->buf, sizeof(struct semid_ds));
break;
case GETNCNT:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_R)))
goto done2;
if (semnum < 0 || semnum >= semakptr->u.sem_nsems) {
error = EINVAL;
goto done2;
}
*rval = semakptr->u.sem_base[semnum].semncnt;
break;
case GETPID:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_R)))
goto done2;
if (semnum < 0 || semnum >= semakptr->u.sem_nsems) {
error = EINVAL;
goto done2;
}
*rval = semakptr->u.sem_base[semnum].sempid;
break;
case GETVAL:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_R)))
goto done2;
if (semnum < 0 || semnum >= semakptr->u.sem_nsems) {
error = EINVAL;
goto done2;
}
*rval = semakptr->u.sem_base[semnum].semval;
break;
case GETALL:
/*
* Unfortunately, callers of this function don't know
* in advance how many semaphores are in this set.
* While we could just allocate the maximum size array
* and pass the actual size back to the caller, that
* won't work for SETALL since we can't copyin() more
* data than the user specified as we may return a
* spurious EFAULT.
*
* Note that the number of semaphores in a set is
* fixed for the life of that set. The only way that
* the 'count' could change while are blocked in
* malloc() is if this semaphore set were destroyed
* and a new one created with the same index.
* However, semvalid() will catch that due to the
* sequence number unless exactly 0x8000 (or a
* multiple thereof) semaphore sets for the same index
* are created and destroyed while we are in malloc!
*
*/
count = semakptr->u.sem_nsems;
mtx_unlock(sema_mtxp);
array = malloc(sizeof(*array) * count, M_TEMP, M_WAITOK);
mtx_lock(sema_mtxp);
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
KASSERT(count == semakptr->u.sem_nsems, ("nsems changed"));
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_R)))
goto done2;
for (i = 0; i < semakptr->u.sem_nsems; i++)
array[i] = semakptr->u.sem_base[i].semval;
mtx_unlock(sema_mtxp);
error = copyout(array, arg->array, count * sizeof(*array));
mtx_lock(sema_mtxp);
break;
case GETZCNT:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_R)))
goto done2;
if (semnum < 0 || semnum >= semakptr->u.sem_nsems) {
error = EINVAL;
goto done2;
}
*rval = semakptr->u.sem_base[semnum].semzcnt;
break;
case SETVAL:
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_W)))
goto done2;
if (semnum < 0 || semnum >= semakptr->u.sem_nsems) {
error = EINVAL;
goto done2;
}
if (arg->val < 0 || arg->val > seminfo.semvmx) {
error = ERANGE;
goto done2;
}
semakptr->u.sem_base[semnum].semval = arg->val;
SEMUNDO_LOCK();
semundo_clear(semidx, semnum);
SEMUNDO_UNLOCK();
wakeup(semakptr);
break;
case SETALL:
/*
* See comment on GETALL for why 'count' shouldn't change
* and why we require a userland buffer.
*/
count = semakptr->u.sem_nsems;
mtx_unlock(sema_mtxp);
array = malloc(sizeof(*array) * count, M_TEMP, M_WAITOK);
error = copyin(arg->array, array, count * sizeof(*array));
mtx_lock(sema_mtxp);
if (error)
break;
if ((error = semvalid(semid, semakptr)) != 0)
goto done2;
KASSERT(count == semakptr->u.sem_nsems, ("nsems changed"));
if ((error = ipcperm(td, &semakptr->u.sem_perm, IPC_W)))
goto done2;
for (i = 0; i < semakptr->u.sem_nsems; i++) {
usval = array[i];
if (usval > seminfo.semvmx) {
error = ERANGE;
break;
}
semakptr->u.sem_base[i].semval = usval;
}
SEMUNDO_LOCK();
semundo_clear(semidx, -1);
SEMUNDO_UNLOCK();
wakeup(semakptr);
break;
default:
error = EINVAL;
break;
}
done2:
mtx_unlock(sema_mtxp);
if (array != NULL)
free(array, M_TEMP);
return(error);
}
#ifndef _SYS_SYSPROTO_H_
struct semget_args {
key_t key;
int nsems;
int semflg;
};
#endif
int
semget(td, uap)
struct thread *td;
struct semget_args *uap;
{
int semid, error = 0;
int key = uap->key;
int nsems = uap->nsems;
int semflg = uap->semflg;
struct ucred *cred = td->td_ucred;
DPRINTF(("semget(0x%x, %d, 0%o)\n", key, nsems, semflg));
if (!jail_sysvipc_allowed && jailed(td->td_ucred))
return (ENOSYS);
mtx_lock(&Giant);
if (key != IPC_PRIVATE) {
for (semid = 0; semid < seminfo.semmni; semid++) {
if ((sema[semid].u.sem_perm.mode & SEM_ALLOC) &&
sema[semid].u.sem_perm.key == key)
break;
}
if (semid < seminfo.semmni) {
DPRINTF(("found public key\n"));
if ((error = ipcperm(td, &sema[semid].u.sem_perm,
semflg & 0700))) {
goto done2;
}
if (nsems > 0 && sema[semid].u.sem_nsems < nsems) {
DPRINTF(("too small\n"));
error = EINVAL;
goto done2;
}
if ((semflg & IPC_CREAT) && (semflg & IPC_EXCL)) {
DPRINTF(("not exclusive\n"));
error = EEXIST;
goto done2;
}
#ifdef MAC
error = mac_sysvsem_check_semget(cred, &sema[semid]);
if (error != 0)
goto done2;
#endif
goto found;
}
}
DPRINTF(("need to allocate the semid_kernel\n"));
if (key == IPC_PRIVATE || (semflg & IPC_CREAT)) {
if (nsems <= 0 || nsems > seminfo.semmsl) {
DPRINTF(("nsems out of range (0<%d<=%d)\n", nsems,
seminfo.semmsl));
error = EINVAL;
goto done2;
}
if (nsems > seminfo.semmns - semtot) {
DPRINTF((
"not enough semaphores left (need %d, got %d)\n",
nsems, seminfo.semmns - semtot));
error = ENOSPC;
goto done2;
}
for (semid = 0; semid < seminfo.semmni; semid++) {
if ((sema[semid].u.sem_perm.mode & SEM_ALLOC) == 0)
break;
}
if (semid == seminfo.semmni) {
DPRINTF(("no more semid_kernel's available\n"));
error = ENOSPC;
goto done2;
}
DPRINTF(("semid %d is available\n", semid));
sema[semid].u.sem_perm.key = key;
sema[semid].u.sem_perm.cuid = cred->cr_uid;
sema[semid].u.sem_perm.uid = cred->cr_uid;
sema[semid].u.sem_perm.cgid = cred->cr_gid;
sema[semid].u.sem_perm.gid = cred->cr_gid;
sema[semid].u.sem_perm.mode = (semflg & 0777) | SEM_ALLOC;
sema[semid].u.sem_perm.seq =
(sema[semid].u.sem_perm.seq + 1) & 0x7fff;
sema[semid].u.sem_nsems = nsems;
sema[semid].u.sem_otime = 0;
sema[semid].u.sem_ctime = time_second;
sema[semid].u.sem_base = &sem[semtot];
semtot += nsems;
bzero(sema[semid].u.sem_base,
sizeof(sema[semid].u.sem_base[0])*nsems);
#ifdef MAC
mac_sysvsem_create(cred, &sema[semid]);
#endif
DPRINTF(("sembase = %p, next = %p\n",
sema[semid].u.sem_base, &sem[semtot]));
} else {
DPRINTF(("didn't find it and wasn't asked to create it\n"));
error = ENOENT;
goto done2;
}
found:
td->td_retval[0] = IXSEQ_TO_IPCID(semid, sema[semid].u.sem_perm);
done2:
mtx_unlock(&Giant);
return (error);
}
#ifndef _SYS_SYSPROTO_H_
struct semop_args {
int semid;
struct sembuf *sops;
size_t nsops;
};
#endif
int
semop(td, uap)
struct thread *td;
struct semop_args *uap;
{
#define SMALL_SOPS 8
struct sembuf small_sops[SMALL_SOPS];
int semid = uap->semid;
size_t nsops = uap->nsops;
struct sembuf *sops;
struct semid_kernel *semakptr;
struct sembuf *sopptr = 0;
struct sem *semptr = 0;
struct sem_undo *suptr;
struct mtx *sema_mtxp;
size_t i, j, k;
int error;
int do_wakeup, do_undos;
#ifdef SEM_DEBUG
sops = NULL;
#endif
DPRINTF(("call to semop(%d, %p, %u)\n", semid, sops, nsops));
if (!jail_sysvipc_allowed && jailed(td->td_ucred))
return (ENOSYS);
semid = IPCID_TO_IX(semid); /* Convert back to zero origin */
if (semid < 0 || semid >= seminfo.semmni)
return (EINVAL);
/* Allocate memory for sem_ops */
if (nsops <= SMALL_SOPS)
sops = small_sops;
else if (nsops <= seminfo.semopm)
sops = malloc(nsops * sizeof(*sops), M_TEMP, M_WAITOK);
else {
DPRINTF(("too many sops (max=%d, nsops=%d)\n", seminfo.semopm,
nsops));
return (E2BIG);
}
if ((error = copyin(uap->sops, sops, nsops * sizeof(sops[0]))) != 0) {
DPRINTF(("error = %d from copyin(%p, %p, %d)\n", error,
uap->sops, sops, nsops * sizeof(sops[0])));
if (sops != small_sops)
free(sops, M_SEM);
return (error);
}
semakptr = &sema[semid];
sema_mtxp = &sema_mtx[semid];
mtx_lock(sema_mtxp);
if ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0) {
error = EINVAL;
goto done2;
}
if (semakptr->u.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
error = EINVAL;
goto done2;
}
/*
* Initial pass thru sops to see what permissions are needed.
* Also perform any checks that don't need repeating on each
* attempt to satisfy the request vector.
*/
j = 0; /* permission needed */
do_undos = 0;
for (i = 0; i < nsops; i++) {
sopptr = &sops[i];
if (sopptr->sem_num >= semakptr->u.sem_nsems) {
error = EFBIG;
goto done2;
}
if (sopptr->sem_flg & SEM_UNDO && sopptr->sem_op != 0)
do_undos = 1;
j |= (sopptr->sem_op == 0) ? SEM_R : SEM_A;
}
if ((error = ipcperm(td, &semakptr->u.sem_perm, j))) {
DPRINTF(("error = %d from ipaccess\n", error));
goto done2;
}
#ifdef MAC
error = mac_sysvsem_check_semop(td->td_ucred, semakptr, j);
if (error != 0)
goto done2;
#endif
/*
* Loop trying to satisfy the vector of requests.
* If we reach a point where we must wait, any requests already
* performed are rolled back and we go to sleep until some other
* process wakes us up. At this point, we start all over again.
*
* This ensures that from the perspective of other tasks, a set
* of requests is atomic (never partially satisfied).
*/
for (;;) {
do_wakeup = 0;
error = 0; /* error return if necessary */
for (i = 0; i < nsops; i++) {
sopptr = &sops[i];
semptr = &semakptr->u.sem_base[sopptr->sem_num];
DPRINTF((
"semop: semakptr=%p, sem_base=%p, "
"semptr=%p, sem[%d]=%d : op=%d, flag=%s\n",
semakptr, semakptr->u.sem_base, semptr,
sopptr->sem_num, semptr->semval, sopptr->sem_op,
(sopptr->sem_flg & IPC_NOWAIT) ?
"nowait" : "wait"));
if (sopptr->sem_op < 0) {
if (semptr->semval + sopptr->sem_op < 0) {
DPRINTF(("semop: can't do it now\n"));
break;
} else {
semptr->semval += sopptr->sem_op;
if (semptr->semval == 0 &&
semptr->semzcnt > 0)
do_wakeup = 1;
}
} else if (sopptr->sem_op == 0) {
if (semptr->semval != 0) {
DPRINTF(("semop: not zero now\n"));
break;
}
} else if (semptr->semval + sopptr->sem_op >
seminfo.semvmx) {
error = ERANGE;
break;
} else {
if (semptr->semncnt > 0)
do_wakeup = 1;
semptr->semval += sopptr->sem_op;
}
}
/*
* Did we get through the entire vector?
*/
if (i >= nsops)
goto done;
/*
* No ... rollback anything that we've already done
*/
DPRINTF(("semop: rollback 0 through %d\n", i-1));
for (j = 0; j < i; j++)
semakptr->u.sem_base[sops[j].sem_num].semval -=
sops[j].sem_op;
/* If we detected an error, return it */
if (error != 0)
goto done2;
/*
* If the request that we couldn't satisfy has the
* NOWAIT flag set then return with EAGAIN.
*/
if (sopptr->sem_flg & IPC_NOWAIT) {
error = EAGAIN;
goto done2;
}
if (sopptr->sem_op == 0)
semptr->semzcnt++;
else
semptr->semncnt++;
DPRINTF(("semop: good night!\n"));
error = msleep(semakptr, sema_mtxp, (PZERO - 4) | PCATCH,
"semwait", 0);
DPRINTF(("semop: good morning (error=%d)!\n", error));
/* return code is checked below, after sem[nz]cnt-- */
/*
* Make sure that the semaphore still exists
*/
if ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0 ||
semakptr->u.sem_perm.seq != IPCID_TO_SEQ(uap->semid)) {
error = EIDRM;
goto done2;
}
/*
* Renew the semaphore's pointer after wakeup since
* during msleep sem_base may have been modified and semptr
* is not valid any more
*/
semptr = &semakptr->u.sem_base[sopptr->sem_num];
/*
* The semaphore is still alive. Readjust the count of
* waiting processes.
*/
if (sopptr->sem_op == 0)
semptr->semzcnt--;
else
semptr->semncnt--;
/*
* Is it really morning, or was our sleep interrupted?
* (Delayed check of msleep() return code because we
* need to decrement sem[nz]cnt either way.)
*/
if (error != 0) {
error = EINTR;
goto done2;
}
DPRINTF(("semop: good morning!\n"));
}
done:
/*
* Process any SEM_UNDO requests.
*/
if (do_undos) {
SEMUNDO_LOCK();
suptr = NULL;
for (i = 0; i < nsops; i++) {
/*
* We only need to deal with SEM_UNDO's for non-zero
* op's.
*/
int adjval;
if ((sops[i].sem_flg & SEM_UNDO) == 0)
continue;
adjval = sops[i].sem_op;
if (adjval == 0)
continue;
error = semundo_adjust(td, &suptr, semid,
sops[i].sem_num, -adjval);
if (error == 0)
continue;
/*
* Oh-Oh! We ran out of either sem_undo's or undo's.
* Rollback the adjustments to this point and then
* rollback the semaphore ups and down so we can return
* with an error with all structures restored. We
* rollback the undo's in the exact reverse order that
* we applied them. This guarantees that we won't run
* out of space as we roll things back out.
*/
for (j = 0; j < i; j++) {
k = i - j - 1;
if ((sops[k].sem_flg & SEM_UNDO) == 0)
continue;
adjval = sops[k].sem_op;
if (adjval == 0)
continue;
if (semundo_adjust(td, &suptr, semid,
sops[k].sem_num, adjval) != 0)
panic("semop - can't undo undos");
}
for (j = 0; j < nsops; j++)
semakptr->u.sem_base[sops[j].sem_num].semval -=
sops[j].sem_op;
DPRINTF(("error = %d from semundo_adjust\n", error));
SEMUNDO_UNLOCK();
goto done2;
} /* loop through the sops */
SEMUNDO_UNLOCK();
} /* if (do_undos) */
/* We're definitely done - set the sempid's and time */
for (i = 0; i < nsops; i++) {
sopptr = &sops[i];
semptr = &semakptr->u.sem_base[sopptr->sem_num];
semptr->sempid = td->td_proc->p_pid;
}
semakptr->u.sem_otime = time_second;
/*
* Do a wakeup if any semaphore was up'd whilst something was
* sleeping on it.
*/
if (do_wakeup) {
DPRINTF(("semop: doing wakeup\n"));
wakeup(semakptr);
DPRINTF(("semop: back from wakeup\n"));
}
DPRINTF(("semop: done\n"));
td->td_retval[0] = 0;
done2:
mtx_unlock(sema_mtxp);
if (sops != small_sops)
free(sops, M_SEM);
return (error);
}
/*
* Go through the undo structures for this process and apply the adjustments to
* semaphores.
*/
static void
semexit_myhook(arg, p)
void *arg;
struct proc *p;
{
struct sem_undo *suptr;
struct sem_undo **supptr;
/*
* Go through the chain of undo vectors looking for one
* associated with this process.
*/
SEMUNDO_LOCK();
SLIST_FOREACH_PREVPTR(suptr, supptr, &semu_list, un_next) {
if (suptr->un_proc == p) {
*supptr = SLIST_NEXT(suptr, un_next);
break;
}
}
SEMUNDO_UNLOCK();
if (suptr == NULL)
return;
DPRINTF(("proc @%p has undo structure with %d entries\n", p,
suptr->un_cnt));
/*
* If there are any active undo elements then process them.
*/
if (suptr->un_cnt > 0) {
int ix;
for (ix = 0; ix < suptr->un_cnt; ix++) {
int semid = suptr->un_ent[ix].un_id;
int semnum = suptr->un_ent[ix].un_num;
int adjval = suptr->un_ent[ix].un_adjval;
struct semid_kernel *semakptr;
struct mtx *sema_mtxp;
semakptr = &sema[semid];
sema_mtxp = &sema_mtx[semid];
mtx_lock(sema_mtxp);
SEMUNDO_LOCK();
if ((semakptr->u.sem_perm.mode & SEM_ALLOC) == 0)
panic("semexit - semid not allocated");
if (semnum >= semakptr->u.sem_nsems)
panic("semexit - semnum out of range");
DPRINTF((
"semexit: %p id=%d num=%d(adj=%d) ; sem=%d\n",
suptr->un_proc, suptr->un_ent[ix].un_id,
suptr->un_ent[ix].un_num,
suptr->un_ent[ix].un_adjval,
semakptr->u.sem_base[semnum].semval));
if (adjval < 0) {
if (semakptr->u.sem_base[semnum].semval <
-adjval)
semakptr->u.sem_base[semnum].semval = 0;
else
semakptr->u.sem_base[semnum].semval +=
adjval;
} else
semakptr->u.sem_base[semnum].semval += adjval;
wakeup(semakptr);
DPRINTF(("semexit: back from wakeup\n"));
mtx_unlock(sema_mtxp);
SEMUNDO_UNLOCK();
}
}
/*
* Deallocate the undo vector.
*/
DPRINTF(("removing vector\n"));
SEMUNDO_LOCK();
suptr->un_proc = NULL;
SEMUNDO_UNLOCK();
}
static int
sysctl_sema(SYSCTL_HANDLER_ARGS)
{
return (SYSCTL_OUT(req, sema,
sizeof(struct semid_kernel) * seminfo.semmni));
}
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