usr/src/sys/kern/sysv_shm.c

/*
 * Copyright (c) 1988 University of Utah.
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department. Originally from University of Wisconsin.
 *
 * %sccs.include.redist.c%
 *
 * from: Utah $Hdr: uipc_shm.c 1.9 89/08/14$
 *
 *      @(#)sysv_shm.c  7.8 (Berkeley) %G%
 */

/*
 * System V shared memory routines.
 * TEMPORARY, until mmap is in place;
 * needed now for HP-UX compatibility and X server (yech!).
 */

#ifdef SYSVSHM

#include "machine/pte.h"

#include "param.h"
#include "systm.h"
#include "syscontext.h"
#include "kernel.h"
#include "proc.h"
#include "vm.h"
#include "shm.h"
#include "mapmem.h"
#include "malloc.h"

#ifdef HPUXCOMPAT
#include "../hpux/hpux.h"
#endif

int     shmat(), shmctl(), shmdt(), shmget();
int     (*shmcalls[])() = { shmat, shmctl, shmdt, shmget };
int     shmtot = 0;

int     shmfork(), shmexit();
struct  mapmemops shmops = { shmfork, (int (*)())0, shmexit, shmexit };

shminit()
{
        register int i;

        if (shminfo.shmmni > SHMMMNI)
                shminfo.shmmni = SHMMMNI;
        for (i = 0; i < shminfo.shmmni; i++) {
                shmsegs[i].shm_perm.mode = 0;
                shmsegs[i].shm_perm.seq = 0;
        }
}

/*
 * Entry point for all SHM calls
 */
shmsys(p, uap, retval)
        struct proc *p;
        struct args {
                u_int which;
        } *uap;
        int *retval;
{

        if (uap->which >= sizeof(shmcalls)/sizeof(shmcalls[0]))
                RETURN (EINVAL);
        RETURN ((*shmcalls[uap->which])(p, &uap[1], retval));
}

/*
 * Get a shared memory segment
 */
shmget(p, uap, retval)
        struct proc *p;
        register struct args {
                key_t key;
                int size;
                int shmflg;
        } *uap;
        int *retval;
{
        register struct shmid_ds *shp;
        register struct ucred *cred = u.u_cred;
        register int i;
        int error, size, rval = 0;
        caddr_t kva;

        /* look up the specified shm_id */
        if (uap->key != IPC_PRIVATE) {
                for (i = 0; i < shminfo.shmmni; i++)
                        if ((shmsegs[i].shm_perm.mode & SHM_ALLOC) &&
                            shmsegs[i].shm_perm.key == uap->key) {
                                rval = i;
                                break;
                        }
        } else
                i = shminfo.shmmni;

        /* create a new shared segment if necessary */
        if (i == shminfo.shmmni) {
                if ((uap->shmflg & IPC_CREAT) == 0)
                        return (ENOENT);
                if (uap->size < shminfo.shmmin || uap->size > shminfo.shmmax)
                        return (EINVAL);
                for (i = 0; i < shminfo.shmmni; i++)
                        if ((shmsegs[i].shm_perm.mode & SHM_ALLOC) == 0) {
                                rval = i;
                                break;
                        }
                if (i == shminfo.shmmni)
                        return (ENOSPC);
                size = clrnd(btoc(uap->size));
                if (shmtot + size > shminfo.shmall)
                        return (ENOMEM);
                shp = &shmsegs[rval];
                /*
                 * We need to do a couple of things to ensure consistency
                 * in case we sleep in malloc().  We mark segment as
                 * allocated so that other shmgets() will not allocate it.
                 * We mark it as "destroyed" to insure that shmvalid() is
                 * false making most operations fail (XXX).  We set the key,
                 * so that other shmget()s will fail.
                 */
                shp->shm_perm.mode = SHM_ALLOC | SHM_DEST;
                shp->shm_perm.key = uap->key;
                kva = (caddr_t) malloc((u_long)ctob(size), M_SHM, M_WAITOK);
                if (kva == NULL) {
                        shp->shm_perm.mode = 0;
                        return (ENOMEM);
                }
                if (!claligned(kva))
                        panic("shmget: non-aligned memory");
                bzero(kva, (u_int)ctob(size));
                shmtot += size;
                shp->shm_perm.cuid = shp->shm_perm.uid = cred->cr_uid;
                shp->shm_perm.cgid = shp->shm_perm.gid = cred->cr_gid;
                shp->shm_perm.mode = SHM_ALLOC | (uap->shmflg&0777);
                shp->shm_handle = (void *) kvtopte(kva);
                shp->shm_segsz = uap->size;
                shp->shm_cpid = p->p_pid;
                shp->shm_lpid = shp->shm_nattch = 0;
                shp->shm_atime = shp->shm_dtime = 0;
                shp->shm_ctime = time.tv_sec;
        } else {
                shp = &shmsegs[rval];
                /* XXX: probably not the right thing to do */
                if (shp->shm_perm.mode & SHM_DEST)
                        return (EBUSY);
                if (error = ipcaccess(&shp->shm_perm, uap->shmflg&0777, cred))
                        return (error);
                if (uap->size && uap->size > shp->shm_segsz)
                        return (EINVAL);
                if ((uap->shmflg&IPC_CREAT) && (uap->shmflg&IPC_EXCL))
                        return (EEXIST);
        }
        *retval = shp->shm_perm.seq * SHMMMNI + rval;
        return (0);
}

/*
 * Shared memory control
 */
/* ARGSUSED */
shmctl(p, uap, retval)
        struct proc *p;
        register struct args {
                int shmid;
                int cmd;
                caddr_t buf;
        } *uap;
        int *retval;
{
        register struct shmid_ds *shp;
        register struct ucred *cred = u.u_cred;
        struct shmid_ds sbuf;
        int error;

        if (error = shmvalid(uap->shmid))
                return (error);
        shp = &shmsegs[uap->shmid % SHMMMNI];
        switch (uap->cmd) {
        case IPC_STAT:
                if (error = ipcaccess(&shp->shm_perm, IPC_R, cred))
                        return (error);
                return (copyout((caddr_t)shp, uap->buf, sizeof(*shp)));

        case IPC_SET:
                if (cred->cr_uid && cred->cr_uid != shp->shm_perm.uid &&
                    cred->cr_uid != shp->shm_perm.cuid)
                        return (EPERM);
                if (error = copyin(uap->buf, (caddr_t)&sbuf, sizeof sbuf))
                        return (error);
                shp->shm_perm.uid = sbuf.shm_perm.uid;
                shp->shm_perm.gid = sbuf.shm_perm.gid;
                shp->shm_perm.mode = (shp->shm_perm.mode & ~0777)
                        | (sbuf.shm_perm.mode & 0777);
                shp->shm_ctime = time.tv_sec;
                break;

        case IPC_RMID:
                if (cred->cr_uid && cred->cr_uid != shp->shm_perm.uid &&
                    cred->cr_uid != shp->shm_perm.cuid)
                        return (EPERM);
                /* set ctime? */
                shp->shm_perm.key = IPC_PRIVATE;
                shp->shm_perm.mode |= SHM_DEST;
                if (shp->shm_nattch <= 0)
                        shmfree(shp);
                break;

#ifdef HPUXCOMPAT
        case SHM_LOCK:
        case SHM_UNLOCK:
                /* don't really do anything, but make them think we did */
                if ((p->p_flag & SHPUX) == 0)
                        return (EINVAL);
                if (cred->cr_uid && cred->cr_uid != shp->shm_perm.uid &&
                    cred->cr_uid != shp->shm_perm.cuid)
                        return (EPERM);
                break;
#endif

        default:
                return (EINVAL);
        }
        return (0);
}

/*
 * Attach to shared memory segment.
 */
shmat(p, uap, retval)
        struct proc *p;
        register struct args {
                int     shmid;
                caddr_t shmaddr;
                int     shmflg;
        } *uap;
        int *retval;
{
        register struct shmid_ds *shp;
        register int size;
        struct mapmem *mp;
        caddr_t uva;
        int error, prot, shmmapin();

        if (error = shmvalid(uap->shmid))
                return (error);
        shp = &shmsegs[uap->shmid % SHMMMNI];
        if (shp->shm_handle == NULL)
                panic("shmat NULL handle");
        if (error = ipcaccess(&shp->shm_perm,
                        (uap->shmflg&SHM_RDONLY) ? IPC_R : IPC_R|IPC_W, u.u_cred))
                return (error);
        uva = uap->shmaddr;
        if (uva && ((int)uva & (SHMLBA-1))) {
                if (uap->shmflg & SHM_RND)
                        uva = (caddr_t) ((int)uva & ~(SHMLBA-1));
                else
                        return (EINVAL);
        }
        /*
         * Make sure user doesn't use more than their fair share
         */
        size = 0;
        for (mp = u.u_mmap; mp; mp = mp->mm_next)
                if (mp->mm_ops == &shmops)
                        size++;
        if (size >= shminfo.shmseg)
                return (EMFILE);
        /*
         * Allocate a mapped memory region descriptor and
         * attempt to expand the user page table to allow for region
         */
        prot = (uap->shmflg & SHM_RDONLY) ? MM_RO : MM_RW;
#if defined(hp300)
        prot |= MM_CI;
#endif
        size = ctob(clrnd(btoc(shp->shm_segsz)));
        error = mmalloc(p, uap->shmid, &uva, (segsz_t)size, prot, &shmops, &mp);
        if (error)
                return (error);
        if (error = mmmapin(p, mp, shmmapin)) {
                (void) mmfree(p, mp);
                return (error);
        }
        /*
         * Fill in the remaining fields
         */
        shp->shm_lpid = p->p_pid;
        shp->shm_atime = time.tv_sec;
        shp->shm_nattch++;
        *retval = (int) uva;
        return (0);
}

/*
 * Detach from shared memory segment.
 */
/* ARGSUSED */
shmdt(p, uap, retval)
        struct proc *p;
        struct args {
                caddr_t shmaddr;
        } *uap;
        int *retval;
{
        register struct mapmem *mp;

        for (mp = u.u_mmap; mp; mp = mp->mm_next)
                if (mp->mm_ops == &shmops && mp->mm_uva == uap->shmaddr)
                        break;
        if (mp == MMNIL)
                return (EINVAL);
        shmsegs[mp->mm_id % SHMMMNI].shm_lpid = p->p_pid;
        return (shmufree(p, mp));
}

shmmapin(mp, off)
        struct mapmem *mp;
{
        register struct shmid_ds *shp;

        shp = &shmsegs[mp->mm_id % SHMMMNI];
        if (off >= ctob(clrnd(btoc(shp->shm_segsz))))
                return(-1);
        return(((struct pte *)shp->shm_handle)[btop(off)].pg_pfnum);
}

/*
 * Increment attach count on fork
 */
/* ARGSUSED */
shmfork(mp, ischild)
        register struct mapmem *mp;
{
        if (!ischild)
                shmsegs[mp->mm_id % SHMMMNI].shm_nattch++;
}

/*
 * Detach from shared memory segment on exit (or exec)
 */
shmexit(mp)
        struct mapmem *mp;
{
        struct proc *p = u.u_procp;             /* XXX */

        return (shmufree(p, mp));
}

shmvalid(id)
        register int id;
{
        register struct shmid_ds *shp;

        if (id < 0 || (id % SHMMMNI) >= shminfo.shmmni)
                return(EINVAL);
        shp = &shmsegs[id % SHMMMNI];
        if (shp->shm_perm.seq == (id / SHMMMNI) &&
            (shp->shm_perm.mode & (SHM_ALLOC|SHM_DEST)) == SHM_ALLOC)
                return(0);
        return(EINVAL);
}

/*
 * Free user resources associated with a shared memory segment
 */
shmufree(p, mp)
        struct proc *p;
        struct mapmem *mp;
{
        register struct shmid_ds *shp;
        int error;

        shp = &shmsegs[mp->mm_id % SHMMMNI];
        mmmapout(p, mp);
        error = mmfree(p, mp);
        shp->shm_dtime = time.tv_sec;
        if (--shp->shm_nattch <= 0 && (shp->shm_perm.mode & SHM_DEST))
                shmfree(shp);
        return (error);
}

/*
 * Deallocate resources associated with a shared memory segment
 */
shmfree(shp)
        register struct shmid_ds *shp;
{
        caddr_t kva;

        if (shp->shm_handle == NULL)
                panic("shmfree");
        kva = (caddr_t) ptetokv(shp->shm_handle);
        free(kva, M_SHM);
        shp->shm_handle = NULL;
        shmtot -= clrnd(btoc(shp->shm_segsz));
        shp->shm_perm.mode = 0;
        /*
         * Increment the sequence number to ensure that outstanding
         * shmids for this segment will be invalid in the event that
         * the segment is reallocated.  Note that shmids must be
         * positive as decreed by SVID.
         */
        shp->shm_perm.seq++;
        if ((int)(shp->shm_perm.seq * SHMMMNI) < 0)
                shp->shm_perm.seq = 0;
}

/*
 * XXX This routine would be common to all sysV style IPC
 *     (if the others were implemented).
 */
ipcaccess(ipc, mode, cred)
        register struct ipc_perm *ipc;
        int mode;
        register struct ucred *cred;
{
        register int m;

        if (cred->cr_uid == 0)
                return(0);
        /*
         * Access check is based on only one of owner, group, public.
         * If not owner, then check group.
         * If not a member of the group, then check public access.
         */
        mode &= 0700;
        m = ipc->mode;
        if (cred->cr_uid != ipc->uid && cred->cr_uid != ipc->cuid) {
                m <<= 3;
                if (!groupmember(ipc->gid, cred) &&
                    !groupmember(ipc->cgid, cred))
                        m <<= 3;
        }
        if ((mode&m) == mode)
                return (0);
        return (EACCES);
}

#endif /* SYSVSHM */