6198 Let's EOL cachefs

[illumos-gate.git] / usr / src / uts / common / os / core.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) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2011, Joyent Inc. All rights reserved.
 */

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

#include <sys/param.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/sysmacros.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/cred.h>
#include <sys/user.h>
#include <sys/utsname.h>
#include <sys/errno.h>
#include <sys/signal.h>
#include <sys/siginfo.h>
#include <sys/fault.h>
#include <sys/syscall.h>
#include <sys/ucontext.h>
#include <sys/prsystm.h>
#include <sys/vnode.h>
#include <sys/var.h>
#include <sys/file.h>
#include <sys/pathname.h>
#include <sys/vfs.h>
#include <sys/exec.h>
#include <sys/debug.h>
#include <sys/stack.h>
#include <sys/kmem.h>
#include <sys/schedctl.h>
#include <sys/core.h>
#include <sys/corectl.h>
#include <sys/cmn_err.h>
#include <vm/as.h>
#include <sys/rctl.h>
#include <sys/nbmlock.h>
#include <sys/stat.h>
#include <sys/zone.h>
#include <sys/contract/process_impl.h>
#include <sys/ddi.h>

/*
 * Processes running within a zone potentially dump core in 3 locations,
 * based on the per-process, per-zone, and the global zone's core settings.
 *
 * Per-zone and global zone settings are often referred to as "global"
 * settings since they apply to the system (or zone) as a whole, as
 * opposed to a particular process.
 */
enum core_types {
        CORE_PROC,      /* Use per-process settings */
        CORE_ZONE,      /* Use per-zone settings */
        CORE_GLOBAL     /* Use global zone settings */
};

/*
 * Log information about "global" core dumps to syslog.
 */
static void
core_log(struct core_globals *cg, int error, const char *why, const char *path,
    zoneid_t zoneid)
{
        proc_t *p = curproc;
        pid_t pid = p->p_pid;
        char *fn = PTOU(p)->u_comm;

        if (!(cg->core_options & CC_GLOBAL_LOG))
                return;

        if (path == NULL)
                zcmn_err(zoneid, CE_NOTE, "core_log: %s[%d] %s", fn, pid, why);
        else if (error == 0)
                zcmn_err(zoneid, CE_NOTE, "core_log: %s[%d] %s: %s", fn, pid,
                    why, path);
        else
                zcmn_err(zoneid, CE_NOTE, "core_log: %s[%d] %s, errno=%d: %s",
                    fn, pid, why, error, path);
}

/*
 * Private version of vn_remove().
 * Refuse to unlink a directory or an unwritable file.
 * Also allow the process to access files normally inaccessible due to
 * chroot(2) or Zone limitations.
 */
static int
remove_core_file(char *fp, enum core_types core_type)
{
        vnode_t *vp = NULL;             /* entry vnode */
        vnode_t *dvp;                   /* ptr to parent dir vnode */
        vfs_t *dvfsp;
        int error;
        int in_crit = 0;
        pathname_t pn;                  /* name of entry */
        vnode_t *startvp, *rootvp;

        if ((error = pn_get(fp, UIO_SYSSPACE, &pn)) != 0)
                return (error);
        /*
         * Determine what rootvp to use.
         */
        if (core_type == CORE_PROC) {
                rootvp = (PTOU(curproc)->u_rdir == NULL ?
                    curproc->p_zone->zone_rootvp : PTOU(curproc)->u_rdir);
                startvp = (fp[0] == '/' ? rootvp : PTOU(curproc)->u_cdir);
        } else if (core_type == CORE_ZONE) {
                startvp = curproc->p_zone->zone_rootvp;
                rootvp = curproc->p_zone->zone_rootvp;
        } else {
                ASSERT(core_type == CORE_GLOBAL);
                startvp = rootdir;
                rootvp = rootdir;
        }
        VN_HOLD(startvp);
        if (rootvp != rootdir)
                VN_HOLD(rootvp);
        if ((error = lookuppnvp(&pn, NULL, NO_FOLLOW, &dvp, &vp, rootvp,
            startvp, CRED())) != 0) {
                pn_free(&pn);
                return (error);
        }
        /*
         * Succeed if there is no file.
         * Fail if the file is not a regular file.
         * Fail if the filesystem is mounted read-only.
         * Fail if the file is not writeable.
         * Fail if the file has NBMAND share reservations.
         */
        if (vp == NULL)
                error = 0;
        else if (vp->v_type != VREG)
                error = EACCES;
        else if ((dvfsp = dvp->v_vfsp) != NULL &&
            (dvfsp->vfs_flag & VFS_RDONLY))
                error = EROFS;
        else if ((error = VOP_ACCESS(vp, VWRITE, 0, CRED(), NULL)) == 0) {
                if (nbl_need_check(vp)) {
                        nbl_start_crit(vp, RW_READER);
                        in_crit = 1;
                        if (nbl_share_conflict(vp, NBL_REMOVE, NULL)) {
                                error = EACCES;
                        }
                }
                if (!error) {
                        error = VOP_REMOVE(dvp, pn.pn_path, CRED(), NULL, 0);
                }
        }

        pn_free(&pn);
        if (vp != NULL) {
                if (in_crit)
                        nbl_end_crit(vp);
                VN_RELE(vp);
        }
        VN_RELE(dvp);
        return (error);
}

/*
 * Create the core file in a location that may be normally inaccessible due
 * to chroot(2) or Zone limitations.
 */
static int
create_core_file(char *fp, enum core_types core_type, vnode_t **vpp)
{
        int error;
        mode_t perms = (S_IRUSR | S_IWUSR);
        pathname_t pn;
        char *file;
        vnode_t *vp;
        vnode_t *dvp;
        vattr_t vattr;
        cred_t *credp = CRED();

        if (core_type == CORE_PROC) {
                file = fp;
                dvp = NULL;     /* regular lookup */
        } else {
                vnode_t *startvp, *rootvp;

                ASSERT(core_type == CORE_ZONE || core_type == CORE_GLOBAL);
                /*
                 * This is tricky because we want to dump the core in
                 * a location which may normally be inaccessible
                 * to us (due to chroot(2) limitations, or zone
                 * membership), and hence need to overcome u_rdir
                 * restrictions.  The basic idea is to separate
                 * the path from the filename, lookup the
                 * pathname separately (starting from the global
                 * zone's root directory), and then open the
                 * file starting at the directory vnode.
                 */
                if (error = pn_get(fp, UIO_SYSSPACE, &pn))
                        return (error);

                if (core_type == CORE_ZONE) {
                        startvp = rootvp = curproc->p_zone->zone_rootvp;
                } else {
                        startvp = rootvp = rootdir;
                }
                /*
                 * rootvp and startvp will be VN_RELE()'d by lookuppnvp() if
                 * necessary.
                 */
                VN_HOLD(startvp);
                if (rootvp != rootdir)
                        VN_HOLD(rootvp);
                /*
                 * Do a lookup on the full path, ignoring the actual file, but
                 * finding the vnode for the directory.  It's OK if the file
                 * doesn't exist -- it most likely won't since we just removed
                 * it.
                 */
                error = lookuppnvp(&pn, NULL, FOLLOW, &dvp, NULLVPP,
                    rootvp, startvp, credp);
                pn_free(&pn);
                if (error != 0)
                        return (error);
                ASSERT(dvp != NULL);
                /*
                 * Now find the final component in the path (ie, the name of
                 * the core file).
                 */
                if (error = pn_get(fp, UIO_SYSSPACE, &pn)) {
                        VN_RELE(dvp);
                        return (error);
                }
                pn_setlast(&pn);
                file = pn.pn_path;
        }
        error =  vn_openat(file, UIO_SYSSPACE,
            FWRITE | FTRUNC | FEXCL | FCREAT | FOFFMAX,
            perms, &vp, CRCREAT, PTOU(curproc)->u_cmask, dvp, -1);
        if (core_type != CORE_PROC) {
                VN_RELE(dvp);
                pn_free(&pn);
        }
        /*
         * Don't dump a core file owned by "nobody".
         */
        vattr.va_mask = AT_UID;
        if (error == 0 &&
            (VOP_GETATTR(vp, &vattr, 0, credp, NULL) != 0 ||
            vattr.va_uid != crgetuid(credp))) {
                (void) VOP_CLOSE(vp, FWRITE, 1, (offset_t)0,
                    credp, NULL);
                VN_RELE(vp);
                (void) remove_core_file(fp, core_type);
                error = EACCES;
        }
        *vpp = vp;
        return (error);
}

/*
 * Install the specified held cred into the process, and return a pointer to
 * the held cred which was previously the value of p->p_cred.
 */
static cred_t *
set_cred(proc_t *p, cred_t *newcr)
{
        cred_t *oldcr;
        uid_t olduid, newuid;

        /*
         * Place a hold on the existing cred, and then install the new
         * cred into the proc structure.
         */
        mutex_enter(&p->p_crlock);
        oldcr = p->p_cred;
        crhold(oldcr);
        p->p_cred = newcr;
        mutex_exit(&p->p_crlock);

        ASSERT(crgetzoneid(oldcr) == crgetzoneid(newcr));

        /*
         * If the real uid is changing, keep the per-user process
         * counts accurate.
         */
        olduid = crgetruid(oldcr);
        newuid = crgetruid(newcr);
        if (olduid != newuid) {
                zoneid_t zoneid = crgetzoneid(newcr);

                mutex_enter(&pidlock);
                upcount_dec(olduid, zoneid);
                upcount_inc(newuid, zoneid);
                mutex_exit(&pidlock);
        }

        /*
         * Broadcast the new cred to all the other threads.  The old
         * cred can be safely returned because we have a hold on it.
         */
        crset(p, newcr);
        return (oldcr);
}

static int
do_core(char *fp, int sig, enum core_types core_type, struct core_globals *cg)
{
        proc_t *p = curproc;
        cred_t *credp = CRED();
        rlim64_t rlimit;
        vnode_t *vp;
        int error = 0;
        struct execsw *eswp;
        cred_t *ocredp = NULL;
        int is_setid = 0;
        core_content_t content;
        uid_t uid;
        gid_t gid;

        if (core_type == CORE_GLOBAL || core_type == CORE_ZONE) {
                mutex_enter(&cg->core_lock);
                content = cg->core_content;
                mutex_exit(&cg->core_lock);
                rlimit = cg->core_rlimit;
        } else {
                mutex_enter(&p->p_lock);
                rlimit = rctl_enforced_value(rctlproc_legacy[RLIMIT_CORE],
                    p->p_rctls, p);
                content = corectl_content_value(p->p_content);
                mutex_exit(&p->p_lock);
        }

        if (rlimit == 0)
                return (EFBIG);

        /*
         * If SNOCD is set, or if the effective, real, and saved ids do
         * not match up, no one but a privileged user is allowed to view
         * this core file.  Set the credentials and the owner to root.
         */
        if ((p->p_flag & SNOCD) ||
            (uid = crgetuid(credp)) != crgetruid(credp) ||
            uid != crgetsuid(credp) ||
            (gid = crgetgid(credp)) != crgetrgid(credp) ||
            gid != crgetsgid(credp)) {
                /*
                 * Because this is insecure against certain forms of file
                 * system attack, do it only if set-id core files have been
                 * enabled via corectl(CC_GLOBAL_SETID | CC_PROCESS_SETID).
                 */
                if (((core_type == CORE_GLOBAL || core_type == CORE_ZONE) &&
                    !(cg->core_options & CC_GLOBAL_SETID)) ||
                    (core_type == CORE_PROC &&
                    !(cg->core_options & CC_PROCESS_SETID)))
                        return (ENOTSUP);

                is_setid = 1;
        }

        /*
         * If we are doing a "global" core dump or a set-id core dump,
         * use kcred to do the dumping.
         */
        if (core_type == CORE_GLOBAL || core_type == CORE_ZONE || is_setid) {
                /*
                 * Use the zone's "kcred" to prevent privilege
                 * escalation.
                 */
                credp = zone_get_kcred(getzoneid());
                ASSERT(credp != NULL);
                ocredp = set_cred(p, credp);
        }

        /*
         * First remove any existing core file, then
         * open the new core file with (O_EXCL|O_CREAT).
         *
         * The reasons for doing this are manifold:
         *
         * For security reasons, we don't want root processes
         * to dump core through a symlink because that would
         * allow a malicious user to clobber any file on
         * the system if s/he could convince a root process,
         * perhaps a set-uid root process that s/he started,
         * to dump core in a directory writable by that user.
         * Similar security reasons apply to hard links.
         * For symmetry we do this unconditionally, not
         * just for root processes.
         *
         * If the process has the core file mmap()d into the
         * address space, we would be modifying the address
         * space that we are trying to dump if we did not first
         * remove the core file.  (The command "file core"
         * is the canonical example of this possibility.)
         *
         * Opening the core file with O_EXCL|O_CREAT ensures than
         * two concurrent core dumps don't clobber each other.
         * One is bound to lose; we don't want to make both lose.
         */
        if ((error = remove_core_file(fp, core_type)) == 0) {
                error = create_core_file(fp, core_type, &vp);
        }

        /*
         * Now that vn_open is complete, reset the process's credentials if
         * we changed them, and make 'credp' point to kcred used
         * above.  We use 'credp' to do i/o on the core file below, but leave
         * p->p_cred set to the original credential to allow the core file
         * to record this information.
         */
        if (ocredp != NULL)
                credp = set_cred(p, ocredp);

        if (error == 0) {
                int closerr;
#if defined(__sparc)
                (void) flush_user_windows_to_stack(NULL);
#endif
                if ((eswp = PTOU(curproc)->u_execsw) == NULL ||
                    (eswp = findexec_by_magic(eswp->exec_magic)) == NULL) {
                        error = ENOSYS;
                } else {
                        error = eswp->exec_core(vp, p, credp, rlimit, sig,
                            content);
                        rw_exit(eswp->exec_lock);
                }

                closerr = VOP_CLOSE(vp, FWRITE, 1, (offset_t)0, credp, NULL);
                VN_RELE(vp);
                if (error == 0)
                        error = closerr;
        }

        if (ocredp != NULL)
                crfree(credp);

        return (error);
}

/*
 * Convert a core name pattern to a pathname.
 */
static int
expand_string(const char *pat, char *fp, int size, cred_t *cr)
{
        proc_t *p = curproc;
        char buf[24];
        int len, i;
        char *s;
        char c;

        while ((c = *pat++) != '\0') {
                if (size < 2)
                        return (ENAMETOOLONG);
                if (c != '%') {
                        size--;
                        *fp++ = c;
                        continue;
                }
                if ((c = *pat++) == '\0') {
                        size--;
                        *fp++ = '%';
                        break;
                }
                switch (c) {
                case 'p':       /* pid */
                        (void) sprintf((s = buf), "%d", p->p_pid);
                        break;
                case 'u':       /* effective uid */
                        (void) sprintf((s = buf), "%u", crgetuid(p->p_cred));
                        break;
                case 'g':       /* effective gid */
                        (void) sprintf((s = buf), "%u", crgetgid(p->p_cred));
                        break;
                case 'f':       /* exec'd filename */
                        s = PTOU(p)->u_comm;
                        break;
                case 'd':       /* exec'd dirname */
                        /*
                         * Even if pathname caching is disabled, we should
                         * be able to lookup the pathname for a directory.
                         */
                        if (p->p_execdir != NULL && vnodetopath(NULL,
                            p->p_execdir, fp, size, cr) == 0) {
                                len = (int)strlen(fp);
                                ASSERT(len < size);
                                ASSERT(len >= 1);
                                ASSERT(fp[0] == '/');

                                /*
                                 * Strip off the leading slash.
                                 */
                                for (i = 0; i < len; i++) {
                                        fp[i] = fp[i + 1];
                                }

                                len--;

                                size -= len;
                                fp += len;
                        } else {
                                *fp = '\0';
                        }

                        continue;
                case 'n':       /* system nodename */
                        s = uts_nodename();
                        break;
                case 'm':       /* machine (sun4u, etc) */
                        s = utsname.machine;
                        break;
                case 't':       /* decimal value of time(2) */
                        (void) sprintf((s = buf), "%ld", gethrestime_sec());
                        break;
                case 'z':
                        s = p->p_zone->zone_name;
                        break;
                case 'Z':
                        /* This is zonepath + "/root/", except for GZ */
                        s = p->p_zone->zone_rootpath;
                        break;
                case '%':
                        (void) strcpy((s = buf), "%");
                        break;
                default:
                        s = buf;
                        buf[0] = '%';
                        buf[1] = c;
                        buf[2] = '\0';
                        break;
                }
                len = (int)strlen(s);
                if ((size -= len) <= 0)
                        return (ENAMETOOLONG);
                (void) strcpy(fp, s);
                /* strip trailing "/root/" from non-GZ zonepath string */
                if (c == 'Z' && len > 6) {
                        len -= 6;
                        ASSERT(strncmp(fp + len, "/root/", 6) == 0);
                }
                fp += len;
        }

        *fp = '\0';
        return (0);
}

static int
dump_one_core(int sig, rlim64_t rlimit, enum core_types core_type,
    struct core_globals *cg, char **name)
{
        refstr_t *rp;
        proc_t *p = curproc;
        zoneid_t zoneid;
        int error;
        char *fp;
        cred_t *cr;

        ASSERT(core_type == CORE_ZONE || core_type == CORE_GLOBAL);
        zoneid = (core_type == CORE_ZONE ? getzoneid() : GLOBAL_ZONEID);

        mutex_enter(&cg->core_lock);
        if ((rp = cg->core_file) != NULL)
                refstr_hold(rp);
        mutex_exit(&cg->core_lock);
        if (rp == NULL) {
                core_log(cg, 0, "no global core file pattern exists", NULL,
                    zoneid);
                return (1);     /* core file not generated */
        }
        fp = kmem_alloc(MAXPATHLEN, KM_SLEEP);
        cr = zone_get_kcred(getzoneid());
        error = expand_string(refstr_value(rp), fp, MAXPATHLEN, cr);
        crfree(cr);
        if (error != 0) {
                core_log(cg, 0, "global core file pattern too long",
                    refstr_value(rp), zoneid);
        } else if ((error = do_core(fp, sig, core_type, cg)) == 0) {
                core_log(cg, 0, "core dumped", fp, zoneid);
        } else if (error == ENOTSUP) {
                core_log(cg, 0, "setid process, core not dumped", fp, zoneid);
        } else if (error == ENOSPC) {
                core_log(cg, 0, "no space left on device, core truncated",
                    fp, zoneid);
        } else if (error == EFBIG) {
                if (rlimit == 0)
                        core_log(cg, 0, "core rlimit is zero, core not dumped",
                            fp, zoneid);
                else
                        core_log(cg, 0, "core rlimit exceeded, core truncated",
                            fp, zoneid);
                /*
                 * In addition to the core result logging, we
                 * may also have explicit actions defined on
                 * core file size violations via the resource
                 * control framework.
                 */
                mutex_enter(&p->p_lock);
                (void) rctl_action(rctlproc_legacy[RLIMIT_CORE],
                    p->p_rctls, p, RCA_SAFE);
                mutex_exit(&p->p_lock);
        } else {
                core_log(cg, error, "core dump failed", fp, zoneid);
        }
        refstr_rele(rp);
        if (name != NULL)
                *name = fp;
        else
                kmem_free(fp, MAXPATHLEN);
        return (error);
}

int
core(int sig, int ext)
{
        proc_t *p = curproc;
        klwp_t *lwp = ttolwp(curthread);
        refstr_t *rp;
        char *fp_process = NULL, *fp_global = NULL, *fp_zone = NULL;
        int error1 = 1;
        int error2 = 1;
        int error3 = 1;
        k_sigset_t sigmask;
        k_sigset_t sighold;
        rlim64_t rlimit;
        struct core_globals *my_cg, *global_cg;

        global_cg = zone_getspecific(core_zone_key, global_zone);
        ASSERT(global_cg != NULL);

        my_cg = zone_getspecific(core_zone_key, curproc->p_zone);
        ASSERT(my_cg != NULL);

        /* core files suppressed? */
        if (!(my_cg->core_options & (CC_PROCESS_PATH|CC_GLOBAL_PATH)) &&
            !(global_cg->core_options & CC_GLOBAL_PATH)) {
                if (!ext && p->p_ct_process != NULL)
                        contract_process_core(p->p_ct_process, p, sig,
                            NULL, NULL, NULL);
                return (1);
        }

        /*
         * Block all signals except SIGHUP, SIGINT, SIGKILL, and SIGTERM; no
         * other signal may interrupt a core dump.  For each signal, we
         * explicitly unblock it and set it in p_siginfo to allow for some
         * minimal error reporting.  Additionally, we get the current limit on
         * core file size for handling later error reporting.
         */
        mutex_enter(&p->p_lock);

        p->p_flag |= SDOCORE;
        schedctl_finish_sigblock(curthread);
        sigmask = curthread->t_hold;    /* remember for later */
        sigfillset(&sighold);
        if (!sigismember(&sigmask, SIGHUP))
                sigdelset(&sighold, SIGHUP);
        if (!sigismember(&sigmask, SIGINT))
                sigdelset(&sighold, SIGINT);
        if (!sigismember(&sigmask, SIGKILL))
                sigdelset(&sighold, SIGKILL);
        if (!sigismember(&sigmask, SIGTERM))
                sigdelset(&sighold, SIGTERM);

        sigaddset(&p->p_siginfo, SIGHUP);
        sigaddset(&p->p_siginfo, SIGINT);
        sigaddset(&p->p_siginfo, SIGKILL);
        sigaddset(&p->p_siginfo, SIGTERM);

        curthread->t_hold = sighold;

        rlimit = rctl_enforced_value(rctlproc_legacy[RLIMIT_CORE], p->p_rctls,
            p);

        mutex_exit(&p->p_lock);

        /*
         * Undo any watchpoints.
         */
        pr_free_watched_pages(p);

        /*
         * The presence of a current signal prevents file i/o
         * from succeeding over a network.  We copy the current
         * signal information to the side and cancel the current
         * signal so that the core dump will succeed.
         */
        ASSERT(lwp->lwp_cursig == sig);
        lwp->lwp_cursig = 0;
        lwp->lwp_extsig = 0;
        if (lwp->lwp_curinfo == NULL) {
                bzero(&lwp->lwp_siginfo, sizeof (k_siginfo_t));
                lwp->lwp_siginfo.si_signo = sig;
                lwp->lwp_siginfo.si_code = SI_NOINFO;
        } else {
                bcopy(&lwp->lwp_curinfo->sq_info,
                    &lwp->lwp_siginfo, sizeof (k_siginfo_t));
                siginfofree(lwp->lwp_curinfo);
                lwp->lwp_curinfo = NULL;
        }

        /*
         * Convert the core file name patterns into path names
         * and call do_core() to write the core files.
         */

        if (my_cg->core_options & CC_PROCESS_PATH) {
                mutex_enter(&p->p_lock);
                if (p->p_corefile != NULL)
                        rp = corectl_path_value(p->p_corefile);
                else
                        rp = NULL;
                mutex_exit(&p->p_lock);
                if (rp != NULL) {
                        fp_process = kmem_alloc(MAXPATHLEN, KM_SLEEP);
                        error1 = expand_string(refstr_value(rp),
                            fp_process, MAXPATHLEN, p->p_cred);
                        if (error1 == 0)
                                error1 = do_core(fp_process, sig, CORE_PROC,
                                    my_cg);
                        refstr_rele(rp);
                }
        }

        if (my_cg->core_options & CC_GLOBAL_PATH)
                error2 = dump_one_core(sig, rlimit, CORE_ZONE, my_cg,
                    &fp_global);
        if (global_cg != my_cg && (global_cg->core_options & CC_GLOBAL_PATH))
                error3 = dump_one_core(sig, rlimit, CORE_GLOBAL, global_cg,
                    &fp_zone);

        /*
         * Restore the signal hold mask.
         */
        mutex_enter(&p->p_lock);
        curthread->t_hold = sigmask;
        mutex_exit(&p->p_lock);

        if (!ext && p->p_ct_process != NULL)
                contract_process_core(p->p_ct_process, p, sig,
                    error1 == 0 ? fp_process : NULL,
                    error2 == 0 ? fp_global : NULL,
                    error3 == 0 ? fp_zone : NULL);

        if (fp_process != NULL)
                kmem_free(fp_process, MAXPATHLEN);
        if (fp_global != NULL)
                kmem_free(fp_global, MAXPATHLEN);
        if (fp_zone != NULL)
                kmem_free(fp_zone, MAXPATHLEN);

        /*
         * Return non-zero if no core file was created.
         */
        return (error1 != 0 && error2 != 0 && error3 != 0);
}

/*
 * Maximum chunk size for dumping core files,
 * size in pages, patchable in /etc/system
 */
uint_t  core_chunk = 32;

/*
 * The delay between core_write() calls, in microseconds.  The default
 * matches one "normal" clock tick, or 10 milliseconds.
 */
clock_t core_delay_usec = 10000;

/*
 * Common code to core dump process memory.  The core_seg routine does i/o
 * using core_write() below, and so it has the same failure semantics.
 */
int
core_seg(proc_t *p, vnode_t *vp, offset_t offset, caddr_t addr, size_t size,
    rlim64_t rlimit, cred_t *credp)
{
        caddr_t eaddr;
        caddr_t base;
        size_t len;
        int err = 0;

        eaddr = addr + size;
        for (base = addr; base < eaddr; base += len) {
                len = eaddr - base;
                if (as_memory(p->p_as, &base, &len) != 0)
                        return (0);

                /*
                 * Reduce len to a reasonable value so that we don't
                 * overwhelm the VM system with a monstrously large
                 * single write and cause pageout to stop running.
                 */
                if (len > (size_t)core_chunk * PAGESIZE)
                        len = (size_t)core_chunk * PAGESIZE;

                err = core_write(vp, UIO_USERSPACE,
                    offset + (size_t)(base - addr), base, len, rlimit, credp);

                if (err)
                        return (err);

                /*
                 * If we have taken a signal, return EINTR to allow the dump
                 * to be aborted.
                 */
                if (issig(JUSTLOOKING) && issig(FORREAL))
                        return (EINTR);
        }

        return (0);
}

/*
 * Wrapper around vn_rdwr to perform writes to a core file.  For core files,
 * we always want to write as much as we possibly can, and then make sure to
 * return either 0 to the caller (for success), or the actual errno value.
 * By using this function, the caller can omit additional code for handling
 * retries and errors for partial writes returned by vn_rdwr.  If vn_rdwr
 * unexpectedly returns zero but no progress has been made, we return ENOSPC.
 */
int
core_write(vnode_t *vp, enum uio_seg segflg, offset_t offset,
    const void *buf, size_t len, rlim64_t rlimit, cred_t *credp)
{
        ssize_t resid = len;
        int error = 0;

        while (len != 0) {
                error = vn_rdwr(UIO_WRITE, vp, (caddr_t)buf, len, offset,
                    segflg, 0, rlimit, credp, &resid);

                if (error != 0)
                        break;

                if (resid >= len)
                        return (ENOSPC);

                buf = (const char *)buf + len - resid;
                offset += len - resid;
                len = resid;
        }

        return (error);
}