loader: remove devdesc comments and assertions

[unleashed.git] / kernel / os / shm.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1986, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * University Copyright- Copyright (c) 1982, 1986, 1988
 * The Regents of the University of California
 * All Rights Reserved
 *
 * University Acknowledgment- Portions of this document are derived from
 * software developed by the University of California, Berkeley, and its
 * contributors.
 */

/*
 * Inter-Process Communication Shared Memory Facility.
 *
 * See os/ipc.c for a description of common IPC functionality.
 *
 * Resource controls
 * -----------------
 *
 * Control:      zone.max-shm-ids (rc_zone_shmmni)
 * Description:  Maximum number of shared memory ids allowed a zone.
 *
 *   When shmget() is used to allocate a shared memory segment, one id
 *   is allocated.  If the id allocation doesn't succeed, shmget()
 *   fails and errno is set to ENOSPC.  Upon successful shmctl(,
 *   IPC_RMID) the id is deallocated.
 *
 * Control:      project.max-shm-ids (rc_project_shmmni)
 * Description:  Maximum number of shared memory ids allowed a project.
 *
 *   When shmget() is used to allocate a shared memory segment, one id
 *   is allocated.  If the id allocation doesn't succeed, shmget()
 *   fails and errno is set to ENOSPC.  Upon successful shmctl(,
 *   IPC_RMID) the id is deallocated.
 *
 * Control:      zone.max-shm-memory (rc_zone_shmmax)
 * Description:  Total amount of shared memory allowed a zone.
 *
 *   When shmget() is used to allocate a shared memory segment, the
 *   segment's size is allocated against this limit.  If the space
 *   allocation doesn't succeed, shmget() fails and errno is set to
 *   EINVAL.  The size will be deallocated once the last process has
 *   detached the segment and the segment has been successfully
 *   shmctl(, IPC_RMID)ed.
 *
 * Control:      project.max-shm-memory (rc_project_shmmax)
 * Description:  Total amount of shared memory allowed a project.
 *
 *   When shmget() is used to allocate a shared memory segment, the
 *   segment's size is allocated against this limit.  If the space
 *   allocation doesn't succeed, shmget() fails and errno is set to
 *   EINVAL.  The size will be deallocated once the last process has
 *   detached the segment and the segment has been successfully
 *   shmctl(, IPC_RMID)ed.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/cred.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kmem.h>
#include <sys/user.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/prsystm.h>
#include <sys/sysmacros.h>
#include <sys/tuneable.h>
#include <sys/vm.h>
#include <sys/mman.h>
#include <sys/swap.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/lwpchan_impl.h>
#include <sys/avl.h>
#include <sys/modctl.h>
#include <sys/syscall.h>
#include <sys/task.h>
#include <sys/project.h>
#include <sys/policy.h>
#include <sys/zone.h>
#include <sys/rctl.h>

#include <sys/ipc.h>
#include <sys/ipc_impl.h>
#include <sys/shm.h>
#include <sys/shm_impl.h>

#include <vm/hat.h>
#include <vm/seg.h>
#include <vm/as.h>
#include <vm/seg_vn.h>
#include <vm/anon.h>
#include <vm/page.h>
#include <vm/vpage.h>
#include <vm/seg_spt.h>

#include <c2/audit.h>

static int shmem_lock(kshmid_t *sp, struct anon_map *amp);
static void shmem_unlock(kshmid_t *sp, struct anon_map *amp);
static void sa_add(struct proc *pp, caddr_t addr, size_t len, ulong_t flags,
        kshmid_t *id);
static void shm_rm_amp(kshmid_t *sp);
static void shm_dtor(kipc_perm_t *);
static void shm_rmid(kipc_perm_t *);
static void shm_remove_zone(zoneid_t, void *);

/*
 * Semantics for share_page_table and ism_off:
 *
 * These are hooks in /etc/system - only for internal testing purpose.
 *
 * Setting share_page_table automatically turns on the SHM_SHARE_MMU (ISM) flag
 * in a call to shmat(2). In other words, with share_page_table set, you always
 * get ISM, even if say, DISM is specified. It should really be called "ism_on".
 *
 * Setting ism_off turns off the SHM_SHARE_MMU flag from the flags passed to
 * shmat(2).
 *
 * If both share_page_table and ism_off are set, share_page_table prevails.
 *
 * Although these tunables should probably be removed, they do have some
 * external exposure; as long as they exist, they should at least work sensibly.
 */

int share_page_table;
int ism_off;

/*
 * The following tunables are obsolete.  Though for compatibility we
 * still read and interpret shminfo_shmmax and shminfo_shmmni (see
 * os/project.c), the preferred mechanism for administrating the IPC
 * Shared Memory facility is through the resource controls described at
 * the top of this file.
 */
size_t  shminfo_shmmax = 0x800000;      /* (obsolete) */
int     shminfo_shmmni = 100;           /* (obsolete) */
size_t  shminfo_shmmin = 1;             /* (obsolete) */
int     shminfo_shmseg = 6;             /* (obsolete) */

extern rctl_hndl_t rc_zone_shmmax;
extern rctl_hndl_t rc_zone_shmmni;
extern rctl_hndl_t rc_project_shmmax;
extern rctl_hndl_t rc_project_shmmni;
static ipc_service_t *shm_svc;
static zone_key_t shm_zone_key;

/*
 * Module linkage information for the kernel.
 */
static uintptr_t shmsys(int, uintptr_t, uintptr_t, uintptr_t);

static struct sysent ipcshm_sysent = {
        4,
#ifdef  _SYSCALL32_IMPL
        SE_ARGC | SE_NOUNLOAD | SE_64RVAL,
#else   /* _SYSCALL32_IMPL */
        SE_ARGC | SE_NOUNLOAD | SE_32RVAL1,
#endif  /* _SYSCALL32_IMPL */
        (int (*)())shmsys
};

#ifdef  _SYSCALL32_IMPL
static struct sysent ipcshm_sysent32 = {
        4,
        SE_ARGC | SE_NOUNLOAD | SE_32RVAL1,
        (int (*)())shmsys
};
#endif  /* _SYSCALL32_IMPL */

static struct modlsys modlsys = {
        &mod_syscallops, "System V shared memory", &ipcshm_sysent
};

#ifdef  _SYSCALL32_IMPL
static struct modlsys modlsys32 = {
        &mod_syscallops32, "32-bit System V shared memory", &ipcshm_sysent32
};
#endif  /* _SYSCALL32_IMPL */

static struct modlinkage modlinkage = {
        MODREV_1,
        &modlsys,
#ifdef  _SYSCALL32_IMPL
        &modlsys32,
#endif
        NULL
};


int
_init(void)
{
        int result;

        shm_svc = ipcs_create("shmids", rc_project_shmmni, rc_zone_shmmni,
            sizeof (kshmid_t), shm_dtor, shm_rmid, AT_IPC_SHM,
            offsetof(ipc_rqty_t, ipcq_shmmni));
        zone_key_create(&shm_zone_key, NULL, shm_remove_zone, NULL);

        if ((result = mod_install(&modlinkage)) == 0)
                return (0);

        (void) zone_key_delete(shm_zone_key);
        ipcs_destroy(shm_svc);

        return (result);
}

int
_fini(void)
{
        return (EBUSY);
}

int
_info(struct modinfo *modinfop)
{
        return (mod_info(&modlinkage, modinfop));
}

/*
 * Shmat (attach shared segment) system call.
 */
static int
shmat(int shmid, caddr_t uaddr, int uflags, uintptr_t *rvp)
{
        kshmid_t *sp;   /* shared memory header ptr */
        size_t  size;
        int     error = 0;
        proc_t *pp = curproc;
        struct as *as = pp->p_as;
        struct segvn_crargs     crargs; /* segvn create arguments */
        kmutex_t        *lock;
        struct seg      *segspt = NULL;
        caddr_t         addr = uaddr;
        int             flags = (uflags & SHMAT_VALID_FLAGS_MASK);
        int             useISM;
        uchar_t         prot = PROT_ALL;
        int result;

        if ((lock = ipc_lookup(shm_svc, shmid, (kipc_perm_t **)&sp)) == NULL)
                return (EINVAL);
        if (error = ipcperm_access(&sp->shm_perm, SHM_R, CRED()))
                goto errret;
        if ((flags & SHM_RDONLY) == 0 &&
            (error = ipcperm_access(&sp->shm_perm, SHM_W, CRED())))
                goto errret;
        if (spt_invalid(flags)) {
                error = EINVAL;
                goto errret;
        }
        if (ism_off)
                flags = flags & ~SHM_SHARE_MMU;
        if (share_page_table) {
                flags = flags & ~SHM_PAGEABLE;
                flags = flags | SHM_SHARE_MMU;
        }
        useISM = (spt_locked(flags) || spt_pageable(flags));
        if (useISM && (error = ipcperm_access(&sp->shm_perm, SHM_W, CRED())))
                goto errret;
        if (useISM && isspt(sp)) {
                uint_t newsptflags = flags | spt_flags(sp->shm_sptseg);
                /*
                 * If trying to change an existing {D}ISM segment from ISM
                 * to DISM or vice versa, return error. Note that this
                 * validation of flags needs to be done after the effect of
                 * tunables such as ism_off and share_page_table, for
                 * semantics that are consistent with the tunables' settings.
                 */
                if (spt_invalid(newsptflags)) {
                        error = EINVAL;
                        goto errret;
                }
        }
        ANON_LOCK_ENTER(&sp->shm_amp->a_rwlock, RW_WRITER);
        size = sp->shm_amp->size;
        ANON_LOCK_EXIT(&sp->shm_amp->a_rwlock);

        /* somewhere to record spt info for final detach */
        if (sp->shm_sptinfo == NULL)
                sp->shm_sptinfo = kmem_zalloc(sizeof (sptinfo_t), KM_SLEEP);

        as_rangelock(as);

        if (useISM) {
                /*
                 * Handle ISM
                 */
                uint_t  share_szc;
                size_t  share_size;
                struct  shm_data ssd;
                uintptr_t align_hint;

                /*
                 * Pick a share pagesize to use, if (!isspt(sp)).
                 * Otherwise use the already chosen page size.
                 *
                 * For the initial shmat (!isspt(sp)), where sptcreate is
                 * called, map_pgsz is called to recommend a [D]ISM pagesize,
                 * important for systems which offer more than one potential
                 * [D]ISM pagesize.
                 * If the shmat is just to attach to an already created
                 * [D]ISM segment, then use the previously selected page size.
                 */
                if (!isspt(sp)) {
                        share_size = map_pgsz(MAPPGSZ_ISM, pp, addr, size, 0);
                        if (share_size == 0) {
                                as_rangeunlock(as);
                                error = EINVAL;
                                goto errret;
                        }
                        share_szc = page_szc(share_size);
                } else {
                        share_szc = sp->shm_sptseg->s_szc;
                        share_size = page_get_pagesize(share_szc);
                }
                size = P2ROUNDUP(size, share_size);

                align_hint = share_size;
#if defined(__i386) || defined(__amd64)
                /*
                 * For x86, we want to share as much of the page table tree
                 * as possible. We use a large align_hint at first, but
                 * if that fails, then the code below retries with align_hint
                 * set to share_size.
                 *
                 * The explicit extern here is due to the difficulties
                 * of getting to platform dependent includes. When/if the
                 * platform dependent bits of this function are cleaned up,
                 * another way of doing this should found.
                 */
                {
                        extern uint_t ptes_per_table;

                        while (size >= ptes_per_table * (uint64_t)align_hint)
                                align_hint *= ptes_per_table;
                }
#endif /* __i386 || __amd64 */


                if (addr == 0) {
                        for (;;) {
                                addr = (caddr_t)align_hint;
                                map_addr(&addr, size, 0ll, 1, MAP_ALIGN);
                                if (addr != NULL || align_hint == share_size)
                                        break;
                                align_hint = share_size;
                        }
                        if (addr == NULL) {
                                as_rangeunlock(as);
                                error = ENOMEM;
                                goto errret;
                        }
                        ASSERT(((uintptr_t)addr & (align_hint - 1)) == 0);
                } else {
                        /* Use the user-supplied attach address */
                        caddr_t base;
                        size_t len;

                        /*
                         * Check that the address range
                         *  1) is properly aligned
                         *  2) is correct in unix terms
                         *  3) is within an unmapped address segment
                         */
                        base = addr;
                        len = size;             /* use spt aligned size */
                        /* XXX - in SunOS, is sp->shm_segsz */
                        if ((uintptr_t)base & (share_size - 1)) {
                                error = EINVAL;
                                as_rangeunlock(as);
                                goto errret;
                        }
                        result = valid_usr_range(base, len, prot, as,
                            as->a_userlimit);
                        if (result == RANGE_BADPROT) {
                                /*
                                 * We try to accomodate processors which
                                 * may not support execute permissions on
                                 * all ISM segments by trying the check
                                 * again but without PROT_EXEC.
                                 */
                                prot &= ~PROT_EXEC;
                                result = valid_usr_range(base, len, prot, as,
                                    as->a_userlimit);
                        }
                        as_purge(as);
                        if (result != RANGE_OKAY ||
                            as_gap(as, len, &base, &len, AH_LO,
                            NULL) != 0) {
                                error = EINVAL;
                                as_rangeunlock(as);
                                goto errret;
                        }
                }

                if (!isspt(sp)) {
                        error = sptcreate(size, &segspt, sp->shm_amp, prot,
                            flags, share_szc);
                        if (error) {
                                as_rangeunlock(as);
                                goto errret;
                        }
                        sp->shm_sptinfo->sptas = segspt->s_as;
                        sp->shm_sptseg = segspt;
                        sp->shm_sptprot = prot;
                } else if ((prot & sp->shm_sptprot) != sp->shm_sptprot) {
                        /*
                         * Ensure we're attaching to an ISM segment with
                         * fewer or equal permissions than what we're
                         * allowed.  Fail if the segment has more
                         * permissions than what we're allowed.
                         */
                        error = EACCES;
                        as_rangeunlock(as);
                        goto errret;
                }

                ssd.shm_sptseg = sp->shm_sptseg;
                ssd.shm_sptas = sp->shm_sptinfo->sptas;
                ssd.shm_amp = sp->shm_amp;
                error = as_map(as, addr, size, segspt_shmattach, &ssd);
                if (error == 0)
                        sp->shm_ismattch++; /* keep count of ISM attaches */
        } else {

                /*
                 * Normal case.
                 */
                if (flags & SHM_RDONLY)
                        prot &= ~PROT_WRITE;

                if (addr == 0) {
                        /* Let the system pick the attach address */
                        map_addr(&addr, size, 0ll, 1, 0);
                        if (addr == NULL) {
                                as_rangeunlock(as);
                                error = ENOMEM;
                                goto errret;
                        }
                } else {
                        /* Use the user-supplied attach address */
                        caddr_t base;
                        size_t len;

                        if (flags & SHM_RND)
                                addr = (caddr_t)((uintptr_t)addr &
                                    ~(SHMLBA - 1));
                        /*
                         * Check that the address range
                         *  1) is properly aligned
                         *  2) is correct in unix terms
                         *  3) is within an unmapped address segment
                         */
                        base = addr;
                        len = size;             /* use aligned size */
                        /* XXX - in SunOS, is sp->shm_segsz */
                        if ((uintptr_t)base & PAGEOFFSET) {
                                error = EINVAL;
                                as_rangeunlock(as);
                                goto errret;
                        }
                        result = valid_usr_range(base, len, prot, as,
                            as->a_userlimit);
                        if (result == RANGE_BADPROT) {
                                prot &= ~PROT_EXEC;
                                result = valid_usr_range(base, len, prot, as,
                                    as->a_userlimit);
                        }
                        as_purge(as);
                        if (result != RANGE_OKAY ||
                            as_gap(as, len, &base, &len,
                            AH_LO, NULL) != 0) {
                                error = EINVAL;
                                as_rangeunlock(as);
                                goto errret;
                        }
                }

                /* Initialize the create arguments and map the segment */
                crargs = *(struct segvn_crargs *)zfod_argsp;
                crargs.offset = 0;
                crargs.type = MAP_SHARED;
                crargs.amp = sp->shm_amp;
                crargs.prot = prot;
                crargs.maxprot = crargs.prot;
                crargs.flags = 0;

                error = as_map(as, addr, size, segvn_create, &crargs);
        }

        as_rangeunlock(as);
        if (error)
                goto errret;

        /* record shmem range for the detach */
        sa_add(pp, addr, (size_t)size, useISM ? SHMSA_ISM : 0, sp);
        *rvp = (uintptr_t)addr;

        sp->shm_atime = gethrestime_sec();
        sp->shm_lpid = pp->p_pid;
        ipc_hold(shm_svc, (kipc_perm_t *)sp);

        /*
         * Tell machine specific code that lwp has mapped shared memory
         */
        LWP_MMODEL_SHARED_AS(addr, size);

errret:
        mutex_exit(lock);
        return (error);
}

static void
shm_dtor(kipc_perm_t *perm)
{
        kshmid_t *sp = (kshmid_t *)perm;
        uint_t cnt;
        size_t rsize;

        ANON_LOCK_ENTER(&sp->shm_amp->a_rwlock, RW_WRITER);
        anonmap_purge(sp->shm_amp);
        ANON_LOCK_EXIT(&sp->shm_amp->a_rwlock);

        if (sp->shm_sptinfo) {
                if (isspt(sp)) {
                        sptdestroy(sp->shm_sptinfo->sptas, sp->shm_amp);
                        sp->shm_lkcnt = 0;
                }
                kmem_free(sp->shm_sptinfo, sizeof (sptinfo_t));
        }

        if (sp->shm_lkcnt > 0) {
                shmem_unlock(sp, sp->shm_amp);
                sp->shm_lkcnt = 0;
        }

        ANON_LOCK_ENTER(&sp->shm_amp->a_rwlock, RW_WRITER);
        cnt = --sp->shm_amp->refcnt;
        ANON_LOCK_EXIT(&sp->shm_amp->a_rwlock);
        ASSERT(cnt == 0);
        shm_rm_amp(sp);

        if (sp->shm_perm.ipc_id != IPC_ID_INVAL) {
                rsize = ptob(btopr(sp->shm_segsz));
                ipcs_lock(shm_svc);
                sp->shm_perm.ipc_proj->kpj_data.kpd_shmmax -= rsize;
                sp->shm_perm.ipc_zone_ref.zref_zone->zone_shmmax -= rsize;
                ipcs_unlock(shm_svc);
        }
}

/* ARGSUSED */
static void
shm_rmid(kipc_perm_t *perm)
{
        /* nothing to do */
}

/*
 * Shmctl system call.
 */
/* ARGSUSED */
static int
shmctl(int shmid, int cmd, void *arg)
{
        kshmid_t                *sp;    /* shared memory header ptr */
        STRUCT_DECL(shmid_ds, ds);      /* for SVR4 IPC_SET */
        int                     error = 0;
        struct cred             *cr = CRED();
        kmutex_t                *lock;
        model_t                 mdl = get_udatamodel();
        struct shmid_ds64       ds64;
        shmatt_t                nattch;

        STRUCT_INIT(ds, mdl);

        /*
         * Perform pre- or non-lookup actions (e.g. copyins, RMID).
         */
        switch (cmd) {
        case IPC_SET:
                if (copyin(arg, STRUCT_BUF(ds), STRUCT_SIZE(ds)))
                        return (EFAULT);
                break;

        case IPC_SET64:
                if (copyin(arg, &ds64, sizeof (struct shmid_ds64)))
                        return (EFAULT);
                break;

        case IPC_RMID:
                return (ipc_rmid(shm_svc, shmid, cr));
        }

        if ((lock = ipc_lookup(shm_svc, shmid, (kipc_perm_t **)&sp)) == NULL)
                return (EINVAL);

        switch (cmd) {
        /* Set ownership and permissions. */
        case IPC_SET:
                if (error = ipcperm_set(shm_svc, cr, &sp->shm_perm,
                    &STRUCT_BUF(ds)->shm_perm, mdl))
                                break;
                sp->shm_ctime = gethrestime_sec();
                break;

        case IPC_STAT:
                if (error = ipcperm_access(&sp->shm_perm, SHM_R, cr))
                        break;

                nattch = sp->shm_perm.ipc_ref - 1;

                ipcperm_stat(&STRUCT_BUF(ds)->shm_perm, &sp->shm_perm, mdl);
                STRUCT_FSET(ds, shm_segsz, sp->shm_segsz);
                STRUCT_FSETP(ds, shm_amp, NULL);        /* kernel addr */
                STRUCT_FSET(ds, shm_lkcnt, sp->shm_lkcnt);
                STRUCT_FSET(ds, shm_lpid, sp->shm_lpid);
                STRUCT_FSET(ds, shm_cpid, sp->shm_cpid);
                STRUCT_FSET(ds, shm_nattch, nattch);
                STRUCT_FSET(ds, shm_cnattch, sp->shm_ismattch);
                STRUCT_FSET(ds, shm_atime, sp->shm_atime);
                STRUCT_FSET(ds, shm_dtime, sp->shm_dtime);
                STRUCT_FSET(ds, shm_ctime, sp->shm_ctime);

                mutex_exit(lock);
                if (copyout(STRUCT_BUF(ds), arg, STRUCT_SIZE(ds)))
                        return (EFAULT);

                return (0);

        case IPC_SET64:
                if (error = ipcperm_set64(shm_svc, cr,
                    &sp->shm_perm, &ds64.shmx_perm))
                        break;
                sp->shm_ctime = gethrestime_sec();
                break;

        case IPC_STAT64:
                nattch = sp->shm_perm.ipc_ref - 1;

                ipcperm_stat64(&ds64.shmx_perm, &sp->shm_perm);
                ds64.shmx_segsz = sp->shm_segsz;
                ds64.shmx_lkcnt = sp->shm_lkcnt;
                ds64.shmx_lpid = sp->shm_lpid;
                ds64.shmx_cpid = sp->shm_cpid;
                ds64.shmx_nattch = nattch;
                ds64.shmx_cnattch = sp->shm_ismattch;
                ds64.shmx_atime = sp->shm_atime;
                ds64.shmx_dtime = sp->shm_dtime;
                ds64.shmx_ctime = sp->shm_ctime;

                mutex_exit(lock);
                if (copyout(&ds64, arg, sizeof (struct shmid_ds64)))
                        return (EFAULT);

                return (0);

        /* Lock segment in memory */
        case SHM_LOCK:
                if ((error = secpolicy_lock_memory(cr)) != 0)
                        break;

                /* protect against overflow */
                if (sp->shm_lkcnt >= USHRT_MAX) {
                        error = ENOMEM;
                        break;
                }
                if (!isspt(sp) && (sp->shm_lkcnt++ == 0)) {
                        if (error = shmem_lock(sp, sp->shm_amp)) {
                                ANON_LOCK_ENTER(&sp->shm_amp->a_rwlock,
                                    RW_WRITER);
                                cmn_err(CE_NOTE, "shmctl - couldn't lock %ld"
                                    " pages into memory", sp->shm_amp->size);
                                ANON_LOCK_EXIT(&sp->shm_amp->a_rwlock);
                                error = ENOMEM;
                                sp->shm_lkcnt--;
                        }
                }
                break;

        /* Unlock segment */
        case SHM_UNLOCK:
                if ((error = secpolicy_lock_memory(cr)) != 0)
                        break;

                if (sp->shm_lkcnt && (--sp->shm_lkcnt == 0)) {
                        shmem_unlock(sp, sp->shm_amp);
                }
                break;

        default:
                error = EINVAL;
                break;
        }
        mutex_exit(lock);
        return (error);
}

static void
shm_detach(proc_t *pp, segacct_t *sap)
{
        kshmid_t        *sp = sap->sa_id;
        size_t          len = sap->sa_len;
        caddr_t         addr = sap->sa_addr;

        /*
         * Discard lwpchan mappings.
         */
        if (pp->p_lcp != NULL)
                lwpchan_delete_mapping(pp, addr, addr + len);
        (void) as_unmap(pp->p_as, addr, len);

        /*
         * Perform some detach-time accounting.
         */
        (void) ipc_lock(shm_svc, sp->shm_perm.ipc_id);
        if (sap->sa_flags & SHMSA_ISM)
                sp->shm_ismattch--;
        sp->shm_dtime = gethrestime_sec();
        sp->shm_lpid = pp->p_pid;
        ipc_rele(shm_svc, (kipc_perm_t *)sp);   /* Drops lock */

        kmem_free(sap, sizeof (segacct_t));
}

static int
shmdt(caddr_t addr)
{
        proc_t *pp = curproc;
        segacct_t *sap, template;

        mutex_enter(&pp->p_lock);
        prbarrier(pp);                  /* block /proc.  See shmgetid(). */

        template.sa_addr = addr;
        template.sa_len = 0;
        if ((pp->p_segacct == NULL) ||
            ((sap = avl_find(pp->p_segacct, &template, NULL)) == NULL)) {
                mutex_exit(&pp->p_lock);
                return (EINVAL);
        }
        if (sap->sa_addr != addr) {
                mutex_exit(&pp->p_lock);
                return (EINVAL);
        }
        avl_remove(pp->p_segacct, sap);
        mutex_exit(&pp->p_lock);

        shm_detach(pp, sap);

        return (0);
}

/*
 * Remove all shared memory segments associated with a given zone.
 * Called by zone_shutdown when the zone is halted.
 */
/*ARGSUSED1*/
static void
shm_remove_zone(zoneid_t zoneid, void *arg)
{
        ipc_remove_zone(shm_svc, zoneid);
}

/*
 * Shmget (create new shmem) system call.
 */
static int
shmget(key_t key, size_t size, int shmflg, uintptr_t *rvp)
{
        proc_t          *pp = curproc;
        kshmid_t        *sp;
        kmutex_t        *lock;
        int             error;

top:
        if (error = ipc_get(shm_svc, key, shmflg, (kipc_perm_t **)&sp, &lock))
                return (error);

        if (!IPC_FREE(&sp->shm_perm)) {
                /*
                 * A segment with the requested key exists.
                 */
                if (size > sp->shm_segsz) {
                        mutex_exit(lock);
                        return (EINVAL);
                }
        } else {
                /*
                 * A new segment should be created.
                 */
                size_t npages = btopr(size);
                size_t rsize = ptob(npages);

                /*
                 * Check rsize and the per-project and per-zone limit on
                 * shared memory.  Checking rsize handles both the size == 0
                 * case and the size < ULONG_MAX & PAGEMASK case (i.e.
                 * rounding up wraps a size_t).
                 */
                if (rsize == 0 ||
                    (rctl_test(rc_project_shmmax,
                    pp->p_task->tk_proj->kpj_rctls, pp, rsize,
                    RCA_SAFE) & RCT_DENY) ||
                    (rctl_test(rc_zone_shmmax,
                    pp->p_zone->zone_rctls, pp, rsize,
                    RCA_SAFE) & RCT_DENY)) {

                        mutex_exit(&pp->p_lock);
                        mutex_exit(lock);
                        ipc_cleanup(shm_svc, (kipc_perm_t *)sp);
                        return (EINVAL);
                }
                mutex_exit(&pp->p_lock);
                mutex_exit(lock);

                if (anon_resv(rsize) == 0) {
                        ipc_cleanup(shm_svc, (kipc_perm_t *)sp);
                        return (ENOMEM);
                }

                /*
                 * If any new failure points are introduced between the
                 * the above anon_resv() and the below ipc_commit_begin(),
                 * these failure points will need to unreserve the anon
                 * reserved using anon_unresv().
                 *
                 * Once ipc_commit_begin() is called, the anon reserved
                 * above will be automatically unreserved by future calls to
                 * ipcs_cleanup() -> shm_dtor() -> shm_rm_amp().  If
                 * ipc_commit_begin() fails, it internally calls shm_dtor(),
                 * unreserving the above anon, and freeing the below amp.
                 */

                sp->shm_amp = anonmap_alloc(rsize, rsize, ANON_SLEEP);
                sp->shm_amp->a_sp = sp;
                /*
                 * Store the original user's requested size, in bytes,
                 * rather than the page-aligned size.  The former is
                 * used for IPC_STAT and shmget() lookups.  The latter
                 * is saved in the anon_map structure and is used for
                 * calls to the vm layer.
                 */
                sp->shm_segsz = size;
                sp->shm_atime = sp->shm_dtime = 0;
                sp->shm_ctime = gethrestime_sec();
                sp->shm_lpid = (pid_t)0;
                sp->shm_cpid = curproc->p_pid;
                sp->shm_ismattch = 0;
                sp->shm_sptinfo = NULL;
                /*
                 * Check limits one last time, push id into global
                 * visibility, and update resource usage counts.
                 */
                if (error = ipc_commit_begin(shm_svc, key, shmflg,
                    (kipc_perm_t *)sp)) {
                        if (error == EAGAIN)
                                goto top;
                        return (error);
                }

                if ((rctl_test(rc_project_shmmax,
                    sp->shm_perm.ipc_proj->kpj_rctls, pp, rsize,
                    RCA_SAFE) & RCT_DENY) ||
                    (rctl_test(rc_zone_shmmax,
                    sp->shm_perm.ipc_zone_ref.zref_zone->zone_rctls, pp, rsize,
                    RCA_SAFE) & RCT_DENY)) {
                        ipc_cleanup(shm_svc, (kipc_perm_t *)sp);
                        return (EINVAL);
                }
                sp->shm_perm.ipc_proj->kpj_data.kpd_shmmax += rsize;
                sp->shm_perm.ipc_zone_ref.zref_zone->zone_shmmax += rsize;

                lock = ipc_commit_end(shm_svc, &sp->shm_perm);
        }

        if (AU_AUDITING())
                audit_ipcget(AT_IPC_SHM, (void *)sp);

        *rvp = (uintptr_t)(sp->shm_perm.ipc_id);

        mutex_exit(lock);
        return (0);
}

/*
 * shmids system call.
 */
static int
shmids(int *buf, uint_t nids, uint_t *pnids)
{
        return (ipc_ids(shm_svc, buf, nids, pnids));
}

/*
 * System entry point for shmat, shmctl, shmdt, and shmget system calls.
 */
static uintptr_t
shmsys(int opcode, uintptr_t a0, uintptr_t a1, uintptr_t a2)
{
        int     error;
        uintptr_t r_val = 0;

        switch (opcode) {
        case SHMAT:
                error = shmat((int)a0, (caddr_t)a1, (int)a2, &r_val);
                break;
        case SHMCTL:
                error = shmctl((int)a0, (int)a1, (void *)a2);
                break;
        case SHMDT:
                error = shmdt((caddr_t)a0);
                break;
        case SHMGET:
                error = shmget((key_t)a0, (size_t)a1, (int)a2, &r_val);
                break;
        case SHMIDS:
                error = shmids((int *)a0, (uint_t)a1, (uint_t *)a2);
                break;
        default:
                error = EINVAL;
                break;
        }

        if (error)
                return ((uintptr_t)set_errno(error));

        return (r_val);
}

/*
 * segacct_t comparator
 * This works as expected, with one minor change: the first of two real
 * segments with equal addresses is considered to be 'greater than' the
 * second.  We only return equal when searching using a template, in
 * which case we explicitly set the template segment's length to 0
 * (which is invalid for a real segment).
 */
static int
shm_sacompar(const void *x, const void *y)
{
        segacct_t *sa1 = (segacct_t *)x;
        segacct_t *sa2 = (segacct_t *)y;

        if (sa1->sa_addr < sa2->sa_addr) {
                return (-1);
        } else if (sa2->sa_len != 0) {
                if (sa1->sa_addr >= sa2->sa_addr + sa2->sa_len) {
                        return (1);
                } else if (sa1->sa_len != 0) {
                        return (1);
                } else {
                        return (0);
                }
        } else if (sa1->sa_addr > sa2->sa_addr) {
                return (1);
        } else {
                return (0);
        }
}

/*
 * add this record to the segacct list.
 */
static void
sa_add(struct proc *pp, caddr_t addr, size_t len, ulong_t flags, kshmid_t *id)
{
        segacct_t *nsap;
        avl_tree_t *tree = NULL;
        avl_index_t where;

        nsap = kmem_alloc(sizeof (segacct_t), KM_SLEEP);
        nsap->sa_addr = addr;
        nsap->sa_len  = len;
        nsap->sa_flags = flags;
        nsap->sa_id = id;

        if (pp->p_segacct == NULL)
                tree = kmem_alloc(sizeof (avl_tree_t), KM_SLEEP);

        mutex_enter(&pp->p_lock);
        prbarrier(pp);                  /* block /proc.  See shmgetid(). */

        if (pp->p_segacct == NULL) {
                avl_create(tree, shm_sacompar, sizeof (segacct_t),
                    offsetof(segacct_t, sa_tree));
                pp->p_segacct = tree;
        } else if (tree) {
                kmem_free(tree, sizeof (avl_tree_t));
        }

        /*
         * We can ignore the result of avl_find, as the comparator will
         * never return equal for segments with non-zero length.  This
         * is a necessary hack to get around the fact that we do, in
         * fact, have duplicate keys.
         */
        (void) avl_find(pp->p_segacct, nsap, &where);
        avl_insert(pp->p_segacct, nsap, where);

        mutex_exit(&pp->p_lock);
}

/*
 * Duplicate parent's segacct records in child.
 */
void
shmfork(struct proc *ppp, struct proc *cpp)
{
        segacct_t *sap;
        kshmid_t *sp;
        kmutex_t *mp;

        ASSERT(ppp->p_segacct != NULL);

        /*
         * We are the only lwp running in the parent so nobody can
         * mess with our p_segacct list.  Thus it is safe to traverse
         * the list without holding p_lock.  This is essential because
         * we can't hold p_lock during a KM_SLEEP allocation.
         */
        for (sap = (segacct_t *)avl_first(ppp->p_segacct); sap != NULL;
            sap = (segacct_t *)AVL_NEXT(ppp->p_segacct, sap)) {
                sa_add(cpp, sap->sa_addr, sap->sa_len, sap->sa_flags,
                    sap->sa_id);
                sp = sap->sa_id;
                mp = ipc_lock(shm_svc, sp->shm_perm.ipc_id);
                if (sap->sa_flags & SHMSA_ISM)
                        sp->shm_ismattch++;
                ipc_hold(shm_svc, (kipc_perm_t *)sp);
                mutex_exit(mp);
        }
}

/*
 * Detach shared memory segments from exiting process.
 */
void
shmexit(struct proc *pp)
{
        segacct_t *sap;
        avl_tree_t *tree;
        void *cookie = NULL;

        ASSERT(pp->p_segacct != NULL);

        mutex_enter(&pp->p_lock);
        prbarrier(pp);
        tree = pp->p_segacct;
        pp->p_segacct = NULL;
        mutex_exit(&pp->p_lock);

        while ((sap = avl_destroy_nodes(tree, &cookie)) != NULL)
                (void) shm_detach(pp, sap);

        avl_destroy(tree);
        kmem_free(tree, sizeof (avl_tree_t));
}

/*
 * At this time pages should be in memory, so just lock them.
 */
static void
lock_again(size_t npages, kshmid_t *sp, struct anon_map *amp)
{
        struct anon *ap;
        struct page *pp;
        struct vnode *vp;
        uoff_t off;
        ulong_t anon_idx;
        anon_sync_obj_t cookie;

        mutex_enter(&sp->shm_mlock);
        ANON_LOCK_ENTER(&amp->a_rwlock, RW_READER);
        for (anon_idx = 0; npages != 0; anon_idx++, npages--) {

                anon_array_enter(amp, anon_idx, &cookie);
                ap = anon_get_ptr(amp->ahp, anon_idx);
                ASSERT(ap != NULL);
                swap_xlate(ap, &vp, &off);
                anon_array_exit(&cookie);

                pp = page_lookup(&vp->v_object, off, SE_SHARED);
                if (pp == NULL) {
                        panic("lock_again: page not in the system");
                        /*NOTREACHED*/
                }
                /* page should already be locked by caller */
                ASSERT(pp->p_lckcnt > 0);
                (void) page_pp_lock(pp, 0, 0);
                page_unlock(pp);
        }
        ANON_LOCK_EXIT(&amp->a_rwlock);
        mutex_exit(&sp->shm_mlock);
}

/*
 * Attach the shared memory segment to the process
 * address space and lock the pages.
 */
static int
shmem_lock(kshmid_t *sp, struct anon_map *amp)
{
        size_t npages = btopr(amp->size);
        struct as *as;
        struct segvn_crargs crargs;
        uint_t error;

        /*
         * A later ISM/DISM attach may increase the size of the amp, so
         * cache the number of pages locked for the future shmem_unlock()
         */
        sp->shm_lkpages = npages;

        as = as_alloc();
        /* Initialize the create arguments and map the segment */
        crargs = *(struct segvn_crargs *)zfod_argsp;    /* structure copy */
        crargs.offset = 0;
        crargs.type = MAP_SHARED;
        crargs.amp = amp;
        crargs.prot = PROT_ALL;
        crargs.maxprot = crargs.prot;
        crargs.flags = 0;
        error = as_map(as, 0x0, amp->size, segvn_create, &crargs);
        if (!error) {
                if ((error = as_ctl(as, 0x0, amp->size, MC_LOCK, 0, 0,
                    NULL, 0)) == 0) {
                        lock_again(npages, sp, amp);
                }
                (void) as_unmap(as, 0x0, amp->size);
        }
        as_free(as);
        return (error);
}


/*
 * Unlock shared memory
 */
static void
shmem_unlock(kshmid_t *sp, struct anon_map *amp)
{
        struct anon *ap;
        pgcnt_t npages = sp->shm_lkpages;
        struct vnode *vp;
        struct page *pp;
        uoff_t off;
        ulong_t anon_idx;
        size_t unlocked_bytes = 0;
        kproject_t      *proj;
        anon_sync_obj_t cookie;

        proj = sp->shm_perm.ipc_proj;
        mutex_enter(&sp->shm_mlock);
        ANON_LOCK_ENTER(&amp->a_rwlock, RW_READER);
        for (anon_idx = 0; anon_idx < npages; anon_idx++) {

                anon_array_enter(amp, anon_idx, &cookie);
                if ((ap = anon_get_ptr(amp->ahp, anon_idx)) == NULL) {
                        panic("shmem_unlock: null app");
                        /*NOTREACHED*/
                }
                swap_xlate(ap, &vp, &off);
                anon_array_exit(&cookie);
                pp = page_lookup(&vp->v_object, off, SE_SHARED);
                if (pp == NULL) {
                        panic("shmem_unlock: page not in the system");
                        /*NOTREACHED*/
                }
                /*
                 * Page should at least have once lock from previous
                 * shmem_lock
                 */
                ASSERT(pp->p_lckcnt > 0);
                page_pp_unlock(pp, 0, 0);
                if (pp->p_lckcnt == 0)
                        unlocked_bytes += PAGESIZE;

                page_unlock(pp);
        }

        if (unlocked_bytes > 0) {
                rctl_decr_locked_mem(NULL, proj, unlocked_bytes, 0);
        }

        ANON_LOCK_EXIT(&amp->a_rwlock);
        mutex_exit(&sp->shm_mlock);
}

/*
 * We call this routine when we have removed all references to this
 * amp.  This means all shmdt()s and the IPC_RMID have been done.
 */
static void
shm_rm_amp(kshmid_t *sp)
{
        struct anon_map *amp = sp->shm_amp;
        zone_t *zone;

        zone = sp->shm_perm.ipc_zone_ref.zref_zone;
        ASSERT(zone != NULL);
        /*
         * Free up the anon_map.
         */
        lgrp_shm_policy_fini(amp, NULL);
        ANON_LOCK_ENTER(&amp->a_rwlock, RW_WRITER);
        if (amp->a_szc != 0) {
                anon_shmap_free_pages(amp, 0, amp->size);
        } else {
                anon_free(amp->ahp, 0, amp->size);
        }
        ANON_LOCK_EXIT(&amp->a_rwlock);
        anon_unresv_zone(amp->swresv, zone);
        anonmap_free(amp);
}

/*
 * Return the shared memory id for the process's virtual address.
 * Return SHMID_NONE if addr is not within a SysV shared memory segment.
 * Return SHMID_FREE if addr's SysV shared memory segment's id has been freed.
 *
 * shmgetid() is called from code in /proc with the process locked but
 * with pp->p_lock not held.  The address space lock is held, so we
 * cannot grab pp->p_lock here due to lock-ordering constraints.
 * Because of all this, modifications to the p_segacct list must only
 * be made after calling prbarrier() to ensure the process is not locked.
 * See shmdt() and sa_add(), above. shmgetid() may also be called on a
 * thread's own process without the process locked.
 */
int
shmgetid(proc_t *pp, caddr_t addr)
{
        segacct_t *sap, template;

        ASSERT(MUTEX_NOT_HELD(&pp->p_lock));
        ASSERT((pp->p_proc_flag & P_PR_LOCK) || pp == curproc);

        if (pp->p_segacct == NULL)
                return (SHMID_NONE);

        template.sa_addr = addr;
        template.sa_len = 0;
        if ((sap = avl_find(pp->p_segacct, &template, NULL)) == NULL)
                return (SHMID_NONE);

        if (IPC_FREE(&sap->sa_id->shm_perm))
                return (SHMID_FREE);

        return (sap->sa_id->shm_perm.ipc_id);
}