minix3/servers/ipc/sem.c

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2020-02-21 00:59:27 +05:30
#define __USE_MISC
#include <minix/vm.h>
#include "inc.h"
struct waiting {
endpoint_t who; /* who is waiting */
int val; /* value he/she is waiting for */
};
struct semaphore {
unsigned short semval; /* semaphore value */
unsigned short semzcnt; /* # waiting for zero */
unsigned short semncnt; /* # waiting for increase */
struct waiting *zlist; /* process waiting for zero */
struct waiting *nlist; /* process waiting for increase */
pid_t sempid; /* process that did last op */
};
struct sem_struct {
key_t key;
int id;
struct semid_ds semid_ds;
struct semaphore sems[SEMMSL];
};
static struct sem_struct sem_list[SEMMNI];
static int sem_list_nr = 0;
static struct sem_struct *sem_find_key(key_t key)
{
int i;
if (key == IPC_PRIVATE)
return NULL;
for (i = 0; i < sem_list_nr; i++)
if (sem_list[i].key == key)
return sem_list+i;
return NULL;
}
static struct sem_struct *sem_find_id(int id)
{
int i;
for (i = 0; i < sem_list_nr; i++)
if (sem_list[i].id == id)
return sem_list+i;
return NULL;
}
/*===========================================================================*
* do_semget *
*===========================================================================*/
int do_semget(message *m)
{
key_t key;
int nsems, flag, id;
struct sem_struct *sem;
key = m->m_lc_ipc_semget.key;
nsems = m->m_lc_ipc_semget.nr;
flag = m->m_lc_ipc_semget.flag;
if ((sem = sem_find_key(key))) {
if ((flag & IPC_CREAT) && (flag & IPC_EXCL))
return EEXIST;
if (!check_perm(&sem->semid_ds.sem_perm, who_e, flag))
return EACCES;
if (nsems > sem->semid_ds.sem_nsems)
return EINVAL;
id = sem->id;
} else {
if (!(flag & IPC_CREAT))
return ENOENT;
if (nsems < 0 || nsems >= SEMMSL)
return EINVAL;
if (sem_list_nr == SEMMNI)
return ENOSPC;
/* create a new semaphore set */
sem = &sem_list[sem_list_nr];
memset(sem, 0, sizeof(struct sem_struct));
sem->semid_ds.sem_perm.cuid =
sem->semid_ds.sem_perm.uid = getnuid(who_e);
sem->semid_ds.sem_perm.cgid =
sem->semid_ds.sem_perm.gid = getngid(who_e);
sem->semid_ds.sem_perm.mode = flag & 0777;
sem->semid_ds.sem_nsems = nsems;
sem->semid_ds.sem_otime = 0;
sem->semid_ds.sem_ctime = time(NULL);
sem->id = id = identifier++;
sem->key = key;
sem_list_nr++;
}
m->m_lc_ipc_semget.retid = id;
return OK;
}
static void send_message_to_process(endpoint_t who, int ret, int ignore)
{
message m;
m.m_type = ret;
ipc_sendnb(who, &m);
}
static void remove_semaphore(struct sem_struct *sem)
{
int i, nr;
nr = sem->semid_ds.sem_nsems;
for (i = 0; i < nr; i++) {
if (sem->sems[i].zlist)
free(sem->sems[i].zlist);
if (sem->sems[i].nlist)
free(sem->sems[i].nlist);
}
for (i = 0; i < sem_list_nr; i++) {
if (&sem_list[i] == sem)
break;
}
if (i < sem_list_nr && --sem_list_nr != i)
sem_list[i] = sem_list[sem_list_nr];
}
#if 0
static void show_semaphore(void)
{
int i, j, k;
for (i = 0; i < sem_list_nr; i++) {
int nr = sem_list[i].semid_ds.sem_nsems;
printf("===== [%d] =====\n", i);
for (j = 0; j < nr; j++) {
struct semaphore *semaphore = &sem_list[i].sems[j];
if (!semaphore->semzcnt && !semaphore->semncnt)
continue;
printf(" (%d): ", semaphore->semval);
if (semaphore->semzcnt) {
printf("zero(");
for (k = 0; k < semaphore->semzcnt; k++)
printf("%d,", semaphore->zlist[k].who);
printf(") ");
}
if (semaphore->semncnt) {
printf("incr(");
for (k = 0; k < semaphore->semncnt; k++)
printf("%d-%d,",
semaphore->nlist[k].who, semaphore->nlist[k].val);
printf(")");
}
printf("\n");
}
}
printf("\n");
}
#endif
static void remove_process(endpoint_t pt)
{
int i;
for (i = 0; i < sem_list_nr; i++) {
struct sem_struct *sem = &sem_list[i];
int nr = sem->semid_ds.sem_nsems;
int j;
for (j = 0; j < nr; j++) {
struct semaphore *semaphore = &sem->sems[j];
int k;
for (k = 0; k < semaphore->semzcnt; k++) {
endpoint_t who_waiting = semaphore->zlist[k].who;
if (who_waiting == pt) {
/* remove this slot first */
memmove(semaphore->zlist+k, semaphore->zlist+k+1,
sizeof(struct waiting) * (semaphore->semzcnt-k-1));
--semaphore->semzcnt;
/* then send message to the process */
send_message_to_process(who_waiting, EINTR, 1);
break;
}
}
for (k = 0; k < semaphore->semncnt; k++) {
endpoint_t who_waiting = semaphore->nlist[k].who;
if (who_waiting == pt) {
/* remove it first */
memmove(semaphore->nlist+k, semaphore->nlist+k+1,
sizeof(struct waiting) * (semaphore->semncnt-k-1));
--semaphore->semncnt;
/* send the message to the process */
send_message_to_process(who_waiting, EINTR, 1);
break;
}
}
}
}
}
static void update_one_semaphore(struct sem_struct *sem, int is_remove)
{
int i, j, nr;
struct semaphore *semaphore;
endpoint_t who;
nr = sem->semid_ds.sem_nsems;
if (is_remove) {
for (i = 0; i < nr; i++) {
semaphore = &sem->sems[i];
for (j = 0; j < semaphore->semzcnt; j++)
send_message_to_process(semaphore->zlist[j].who, EIDRM, 0);
for (j = 0; j < semaphore->semncnt; j++)
send_message_to_process(semaphore->nlist[j].who, EIDRM, 0);
}
remove_semaphore(sem);
return;
}
for (i = 0; i < nr; i++) {
semaphore = &sem->sems[i];
if (semaphore->zlist && !semaphore->semval) {
/* choose one process, policy: FIFO. */
who = semaphore->zlist[0].who;
memmove(semaphore->zlist, semaphore->zlist+1,
sizeof(struct waiting) * (semaphore->semzcnt-1));
--semaphore->semzcnt;
send_message_to_process(who, OK, 0);
}
if (semaphore->nlist) {
for (j = 0; j < semaphore->semncnt; j++) {
if (semaphore->nlist[j].val <= semaphore->semval) {
semaphore->semval -= semaphore->nlist[j].val;
who = semaphore->nlist[j].who;
memmove(semaphore->nlist+j, semaphore->nlist+j+1,
sizeof(struct waiting) * (semaphore->semncnt-j-1));
--semaphore->semncnt;
send_message_to_process(who, OK, 0);
/* choose only one process */
break;
}
}
}
}
}
static void update_semaphores(void)
{
int i;
for (i = 0; i < sem_list_nr; i++)
update_one_semaphore(sem_list+i, 0 /* not remove */);
}
/*===========================================================================*
* do_semctl *
*===========================================================================*/
int do_semctl(message *m)
{
int r, i;
long opt = 0;
uid_t uid;
int id, num, cmd, val;
unsigned short *buf;
struct semid_ds *ds, tmp_ds;
struct sem_struct *sem;
id = m->m_lc_ipc_semctl.id;
num = m->m_lc_ipc_semctl.num;
cmd = m->m_lc_ipc_semctl.cmd;
if (cmd == IPC_STAT || cmd == IPC_SET || cmd == IPC_INFO ||
cmd == SEM_INFO || cmd == SEM_STAT || cmd == GETALL ||
cmd == SETALL || cmd == SETVAL)
opt = m->m_lc_ipc_semctl.opt;
if (!(sem = sem_find_id(id))) {
return EINVAL;
}
/* IPC_SET and IPC_RMID as its own permission check */
if (cmd != IPC_SET && cmd != IPC_RMID) {
/* check read permission */
if (!check_perm(&sem->semid_ds.sem_perm, who_e, 0444))
return EACCES;
}
switch (cmd) {
case IPC_STAT:
ds = (struct semid_ds *) opt;
if (!ds)
return EFAULT;
r = sys_datacopy(SELF, (vir_bytes) &sem->semid_ds,
who_e, (vir_bytes) ds, sizeof(struct semid_ds));
if (r != OK)
return EINVAL;
break;
case IPC_SET:
uid = getnuid(who_e);
if (uid != sem->semid_ds.sem_perm.cuid &&
uid != sem->semid_ds.sem_perm.uid &&
uid != 0)
return EPERM;
ds = (struct semid_ds *) opt;
r = sys_datacopy(who_e, (vir_bytes) ds,
SELF, (vir_bytes) &tmp_ds, sizeof(struct semid_ds));
if (r != OK)
return EINVAL;
sem->semid_ds.sem_perm.uid = tmp_ds.sem_perm.uid;
sem->semid_ds.sem_perm.gid = tmp_ds.sem_perm.gid;
sem->semid_ds.sem_perm.mode &= ~0777;
sem->semid_ds.sem_perm.mode |= tmp_ds.sem_perm.mode & 0666;
sem->semid_ds.sem_ctime = time(NULL);
break;
case IPC_RMID:
uid = getnuid(who_e);
if (uid != sem->semid_ds.sem_perm.cuid &&
uid != sem->semid_ds.sem_perm.uid &&
uid != 0)
return EPERM;
/* awaken all processes block in semop
* and remove the semaphore set.
*/
update_one_semaphore(sem, 1);
break;
case IPC_INFO:
break;
case SEM_INFO:
break;
case SEM_STAT:
break;
case GETALL:
buf = malloc(sizeof(unsigned short) * sem->semid_ds.sem_nsems);
if (!buf)
return ENOMEM;
for (i = 0; i < sem->semid_ds.sem_nsems; i++)
buf[i] = sem->sems[i].semval;
r = sys_datacopy(SELF, (vir_bytes) buf,
who_e, (vir_bytes) opt,
sizeof(unsigned short) * sem->semid_ds.sem_nsems);
if (r != OK)
return EINVAL;
free(buf);
break;
case GETNCNT:
if (num < 0 || num >= sem->semid_ds.sem_nsems)
return EINVAL;
m->m_lc_ipc_semctl.ret = sem->sems[num].semncnt;
break;
case GETPID:
if (num < 0 || num >= sem->semid_ds.sem_nsems)
return EINVAL;
m->m_lc_ipc_semctl.ret = sem->sems[num].sempid;
break;
case GETVAL:
if (num < 0 || num >= sem->semid_ds.sem_nsems)
return EINVAL;
m->m_lc_ipc_semctl.ret = sem->sems[num].semval;
break;
case GETZCNT:
if (num < 0 || num >= sem->semid_ds.sem_nsems)
return EINVAL;
m->m_lc_ipc_semctl.ret = sem->sems[num].semzcnt;
break;
case SETALL:
buf = malloc(sizeof(unsigned short) * sem->semid_ds.sem_nsems);
if (!buf)
return ENOMEM;
r = sys_datacopy(who_e, (vir_bytes) opt,
SELF, (vir_bytes) buf,
sizeof(unsigned short) * sem->semid_ds.sem_nsems);
if (r != OK)
return EINVAL;
#ifdef DEBUG_SEM
printf("SEMCTL: SETALL: opt: %lu\n", (vir_bytes) opt);
for (i = 0; i < sem->semid_ds.sem_nsems; i++)
printf("SEMCTL: SETALL val: [%d] %d\n", i, buf[i]);
#endif
for (i = 0; i < sem->semid_ds.sem_nsems; i++) {
if (buf[i] > SEMVMX) {
free(buf);
update_semaphores();
return ERANGE;
}
sem->sems[i].semval = buf[i];
}
free(buf);
/* awaken if possible */
update_semaphores();
break;
case SETVAL:
val = (int) opt;
/* check write permission */
if (!check_perm(&sem->semid_ds.sem_perm, who_e, 0222))
return EACCES;
if (num < 0 || num >= sem->semid_ds.sem_nsems)
return EINVAL;
if (val < 0 || val > SEMVMX)
return ERANGE;
sem->sems[num].semval = val;
#ifdef DEBUG_SEM
printf("SEMCTL: SETVAL: %d %d\n", num, val);
#endif
sem->semid_ds.sem_ctime = time(NULL);
/* awaken if possible */
update_semaphores();
break;
default:
return EINVAL;
}
return OK;
}
/*===========================================================================*
* do_semop *
*===========================================================================*/
int do_semop(message *m)
{
int id, i, j, r;
struct sembuf *sops;
unsigned int nsops;
struct sem_struct *sem;
int no_reply = 0;
id = m->m_lc_ipc_semop.id;
nsops = m->m_lc_ipc_semop.size;
r = EINVAL;
if (!(sem = sem_find_id(id)))
goto out;
if (nsops <= 0)
goto out;
r = E2BIG;
if (nsops > SEMOPM)
goto out;
/* check for read permission */
r = EACCES;
if (!check_perm(&sem->semid_ds.sem_perm, who_e, 0444))
goto out;
/* get the array from user application */
r = ENOMEM;
sops = malloc(sizeof(struct sembuf) * nsops);
if (!sops)
goto out_free;
r = sys_datacopy(who_e, (vir_bytes) m->m_lc_ipc_semop.ops,
SELF, (vir_bytes) sops,
sizeof(struct sembuf) * nsops);
if (r != OK) {
r = EINVAL;
goto out_free;
}
#ifdef DEBUG_SEM
for (i = 0; i < nsops; i++)
printf("SEMOP: num:%d op:%d flg:%d\n",
sops[i].sem_num, sops[i].sem_op, sops[i].sem_flg);
#endif
/* check for value range */
r = EFBIG;
for (i = 0; i < nsops; i++)
if (sops[i].sem_num >= sem->semid_ds.sem_nsems)
goto out_free;
/* check for duplicate number */
r = EINVAL;
for (i = 0; i < nsops; i++)
for (j = i + 1; j < nsops; j++)
if (sops[i].sem_num == sops[j].sem_num)
goto out_free;
/* check for EAGAIN error */
r = EAGAIN;
for (i = 0; i < nsops; i++) {
int op_n, val;
op_n = sops[i].sem_op;
val = sem->sems[sops[i].sem_num].semval;
if ((sops[i].sem_flg & IPC_NOWAIT) &&
((!op_n && val) ||
(op_n < 0 &&
-op_n > val)))
goto out_free;
}
/* there will be no errors left, so we can go ahead */
for (i = 0; i < nsops; i++) {
struct semaphore *s;
int op_n;
s = &sem->sems[sops[i].sem_num];
op_n = sops[i].sem_op;
s->sempid = getnpid(who_e);
if (op_n > 0) {
/* check for alter permission */
r = EACCES;
if (!check_perm(&sem->semid_ds.sem_perm, who_e, 0222))
goto out_free;
s->semval += sops[i].sem_op;
} else if (!op_n) {
if (s->semval) {
/* put the process asleep */
s->semzcnt++;
s->zlist = realloc(s->zlist, sizeof(struct waiting) * s->semzcnt);
if (!s->zlist) {
printf("IPC: zero waiting list lost...\n");
break;
}
s->zlist[s->semzcnt-1].who = who_e;
s->zlist[s->semzcnt-1].val = op_n;
#ifdef DEBUG_SEM
printf("SEMOP: Put into sleep... %d\n", who_e);
#endif
no_reply++;
}
} else {
/* check for alter permission */
r = EACCES;
if (!check_perm(&sem->semid_ds.sem_perm, who_e, 0222))
goto out_free;
if (s->semval >= -op_n)
s->semval += op_n;
else {
/* put the process asleep */
s->semncnt++;
s->nlist = realloc(s->nlist, sizeof(struct waiting) * s->semncnt);
if (!s->nlist) {
printf("IPC: increase waiting list lost...\n");
break;
}
s->nlist[s->semncnt-1].who = who_e;
s->nlist[s->semncnt-1].val = -op_n;
no_reply++;
}
}
}
r = OK;
out_free:
free(sops);
out:
/* if we reach here by errors
* or with no errors but we should reply back.
*/
if (r != OK || !no_reply) {
m->m_type = r;
ipc_sendnb(who_e, m);
}
/* awaken process if possible */
update_semaphores();
return 0;
}
/*===========================================================================*
* is_sem_nil *
*===========================================================================*/
int is_sem_nil(void)
{
return (sem_list_nr == 0);
}
/*===========================================================================*
* sem_process_vm_notify *
*===========================================================================*/
void sem_process_vm_notify(void)
{
endpoint_t pt;
int r;
while ((r = vm_query_exit(&pt)) >= 0) {
/* for each enpoint 'pt', check whether it's waiting... */
remove_process(pt);
if (r == 0)
break;
}
if (r < 0)
printf("IPC: query exit error!\n");
}