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.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *      from: Utah $Hdr: uipc_shm.c 1.9 89/08/14$
 *      from: @(#)sysv_shm.c    7.15 (Berkeley) 5/13/91
 *      $Id$
 */

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

#ifdef SYSVSHM

#include "param.h"
#include "systm.h"
#include "kernel.h"
#include "proc.h"
#include "shm.h"
#include "malloc.h"
#include "mman.h"
#include "vm/vm.h"
#include "vm/vm_kern.h"
#include "vm/vm_inherit.h"
#include "vm/vm_pager.h"

#ifdef HPUXCOMPAT
#include "hp300/hpux/hpux.h"
#endif

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

/*
 * Per process internal structure for managing segments.
 * Each process using shm will have an array of ``shmseg'' of these.
 */
struct  shmdesc {
        vm_offset_t     shmd_uva;
        int             shmd_id;
};

/*
 * Per segment internal structure (shm_handle).
 */
struct  shmhandle {
        vm_offset_t     shmh_kva;
        caddr_t         shmh_id;
};

vm_map_t shm_map;       /* address space for shared memory segments */

shminit()
{
        register int i;
        vm_offset_t whocares1, whocares2;

        shm_map = kmem_suballoc(kernel_map, &whocares1, &whocares2,
                                shminfo.shmall * NBPG, FALSE);
        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
 */

struct shmsys_args {
        u_int which;
};

shmsys(p, uap, retval)
        struct proc *p;
        struct shmsys_args *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
 */

struct shmget_args {
        key_t key;
        int size;
        int shmflg;
};

shmget(p, uap, retval)
        struct proc *p;
        register struct shmget_args *uap;
        int *retval;
{
        register struct shmid_ds *shp;
        register struct ucred *cred = p->p_ucred;
        register int i;
        int error, size, rval = 0;
        register struct shmhandle *shmh;

        /* 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;
                shmh = (struct shmhandle *)
                        malloc(sizeof(struct shmhandle), M_SHM, M_WAITOK);
                shmh->shmh_kva = 0;
                shmh->shmh_id = (caddr_t)(0xc0000000|rval);     /* XXX */
                error = vm_mmap(shm_map, &shmh->shmh_kva, ctob(size),
                                VM_PROT_ALL, VM_PROT_DEFAULT, MAP_ANON, shmh->shmh_id, 0);
                if (error) {
                        free((caddr_t)shmh, M_SHM);
                        shp->shm_perm.mode = 0;
                        return(ENOMEM);
                }
                shp->shm_handle = (void *) shmh;
                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_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
 */

struct shmctl_args {
        int shmid;
        int cmd;
        caddr_t buf;
};

/* ARGSUSED */
shmctl(p, uap, retval)
        struct proc *p;
        register struct shmctl_args *uap;
        int *retval;
{
        register struct shmid_ds *shp;
        register struct ucred *cred = p->p_ucred;
        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.
 */

struct shmat_args {
        int     shmid;
        caddr_t shmaddr;
        int     shmflg;
};

shmat(p, uap, retval)
        struct proc *p;
        register struct shmat_args *uap;
        int *retval;
{
        register struct shmid_ds *shp;
        register int size;
        caddr_t uva;
        int error;
        int flags;
        vm_prot_t prot;
        struct shmdesc *shmd;

        /*
         * Allocate descriptors now (before validity check)
         * in case malloc() blocks.
         */
        shmd = (struct shmdesc *)p->p_vmspace->vm_shm;
        size = shminfo.shmseg * sizeof(struct shmdesc);
        if (shmd == NULL) {
                shmd = (struct shmdesc *)malloc(size, M_SHM, M_WAITOK);
                bzero((caddr_t)shmd, size);
                p->p_vmspace->vm_shm = (caddr_t)shmd;
        }
        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, p->p_ucred))
                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
         */
        for (size = 0; size < shminfo.shmseg; size++) {
                if (shmd->shmd_uva == 0)
                        break;
                shmd++;
        }
        if (size >= shminfo.shmseg)
                return (EMFILE);
        size = ctob(clrnd(btoc(shp->shm_segsz)));
        prot = VM_PROT_READ;
        if ((uap->shmflg & SHM_RDONLY) == 0)
                prot |= VM_PROT_WRITE;
        flags = MAP_ANON|MAP_SHARED;
        if (uva)
                flags |= MAP_FIXED;
        else
                uva = (caddr_t)0x1000000;       /* XXX */
        error = vm_mmap(&p->p_vmspace->vm_map, &uva, (vm_size_t)size, prot, VM_PROT_DEFAULT,
            flags, ((struct shmhandle *)shp->shm_handle)->shmh_id, 0);
        if (error)
                return(error);
        shmd->shmd_uva = (vm_offset_t)uva;
        shmd->shmd_id = uap->shmid;
        /*
         * 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.
 */

struct shmdt_args {
        caddr_t shmaddr;
};

/* ARGSUSED */
shmdt(p, uap, retval)
        struct proc *p;
        struct shmdt_args *uap;
        int *retval;
{
        register struct shmdesc *shmd;
        register int i;

        shmd = (struct shmdesc *)p->p_vmspace->vm_shm;
        for (i = 0; i < shminfo.shmseg; i++, shmd++)
                if (shmd->shmd_uva &&
                    shmd->shmd_uva == (vm_offset_t)uap->shmaddr)
                        break;
        if (i == shminfo.shmseg)
                return(EINVAL);
        shmufree(p, shmd);
        shmsegs[shmd->shmd_id % SHMMMNI].shm_lpid = p->p_pid;
}

shmfork(p1, p2, isvfork)
        struct proc *p1, *p2;
        int isvfork;
{
        register struct shmdesc *shmd;
        register int size;

        /*
         * Copy parents descriptive information
         */
        size = shminfo.shmseg * sizeof(struct shmdesc);
        shmd = (struct shmdesc *)malloc(size, M_SHM, M_WAITOK);
        bcopy((caddr_t)p1->p_vmspace->vm_shm, (caddr_t)shmd, size);
        p2->p_vmspace->vm_shm = (caddr_t)shmd;
        /*
         * Increment reference counts
         */
        for (size = 0; size < shminfo.shmseg; size++, shmd++)
                if (shmd->shmd_uva)
                        shmsegs[shmd->shmd_id % SHMMMNI].shm_nattch++;
}

shmexit(p)
        struct proc *p;
{
        register struct shmdesc *shmd;
        register int i;

        shmd = (struct shmdesc *)p->p_vmspace->vm_shm;
        for (i = 0; i < shminfo.shmseg; i++, shmd++)
                if (shmd->shmd_uva)
                        shmufree(p, shmd);
        free((caddr_t)p->p_vmspace->vm_shm, M_SHM);
        p->p_vmspace->vm_shm = NULL;
}

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, shmd)
        struct proc *p;
        struct shmdesc *shmd;
{
        register struct shmid_ds *shp;

        shp = &shmsegs[shmd->shmd_id % SHMMMNI];
        (void) vm_deallocate(&p->p_vmspace->vm_map, shmd->shmd_uva,
                             ctob(clrnd(btoc(shp->shm_segsz))));
        shmd->shmd_id = 0;
        shmd->shmd_uva = 0;
        shp->shm_dtime = time.tv_sec;
        if (--shp->shm_nattch <= 0 && (shp->shm_perm.mode & SHM_DEST))
                shmfree(shp);
}

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

        if (shp->shm_handle == NULL)
                panic("shmfree");
        /*
         * Lose our lingering object reference by deallocating space
         * in kernel.  Pager will also be deallocated as a side-effect.
         */
        vm_deallocate(shm_map,
                      ((struct shmhandle *)shp->shm_handle)->shmh_kva,
                      ctob(clrnd(btoc(shp->shm_segsz))));
        free((caddr_t)shp->shm_handle, 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 */