dmake: do not set MAKEFLAGS=k

[unleashed/tickless.git] / usr / src / lib / libproc / common / Pcontrol.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 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 *
 * Portions Copyright 2007 Chad Mynhier
 * Copyright 2012 DEY Storage Systems, Inc.  All rights reserved.
 * Copyright (c) 2013 by Delphix. All rights reserved.
 * Copyright 2015, Joyent, Inc.
 */

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#include <fcntl.h>
#include <string.h>
#include <strings.h>
#include <memory.h>
#include <errno.h>
#include <dirent.h>
#include <limits.h>
#include <signal.h>
#include <atomic.h>
#include <zone.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/stat.h>
#include <sys/resource.h>
#include <sys/param.h>
#include <sys/stack.h>
#include <sys/fault.h>
#include <sys/syscall.h>
#include <sys/sysmacros.h>
#include <sys/systeminfo.h>
#include <sys/secflags.h>

#include "libproc.h"
#include "Pcontrol.h"
#include "Putil.h"
#include "P32ton.h"

int     _libproc_debug;         /* set non-zero to enable debugging printfs */
int     _libproc_no_qsort;      /* set non-zero to inhibit sorting */
                                /* of symbol tables */
int     _libproc_incore_elf;    /* only use in-core elf data */

sigset_t blockable_sigs;        /* signals to block when we need to be safe */
static  int     minfd;  /* minimum file descriptor returned by dupfd(fd, 0) */
char    procfs_path[PATH_MAX] = "/proc";

/*
 * Function prototypes for static routines in this module.
 */
static  void    deadcheck(struct ps_prochandle *);
static  void    restore_tracing_flags(struct ps_prochandle *);
static  void    Lfree_internal(struct ps_prochandle *, struct ps_lwphandle *);
static  prheader_t *read_lfile(struct ps_prochandle *, const char *);

/*
 * Ops vector functions for live processes.
 */

/*ARGSUSED*/
static ssize_t
Pread_live(struct ps_prochandle *P, void *buf, size_t n, uintptr_t addr,
    void *data)
{
        return (pread(P->asfd, buf, n, (off_t)addr));
}

/*ARGSUSED*/
static ssize_t
Pwrite_live(struct ps_prochandle *P, const void *buf, size_t n, uintptr_t addr,
    void *data)
{
        return (pwrite(P->asfd, buf, n, (off_t)addr));
}

/*ARGSUSED*/
static int
Pread_maps_live(struct ps_prochandle *P, prmap_t **Pmapp, ssize_t *nmapp,
    void *data)
{
        char mapfile[PATH_MAX];
        int mapfd;
        struct stat statb;
        ssize_t nmap;
        prmap_t *Pmap = NULL;

        (void) snprintf(mapfile, sizeof (mapfile), "%s/%d/map",
            procfs_path, (int)P->pid);
        if ((mapfd = open(mapfile, O_RDONLY)) < 0 ||
            fstat(mapfd, &statb) != 0 ||
            statb.st_size < sizeof (prmap_t) ||
            (Pmap = malloc(statb.st_size)) == NULL ||
            (nmap = pread(mapfd, Pmap, statb.st_size, 0L)) <= 0 ||
            (nmap /= sizeof (prmap_t)) == 0) {
                free(Pmap);
                if (mapfd >= 0)
                        (void) close(mapfd);
                Preset_maps(P); /* utter failure; destroy tables */
                return (-1);
        }
        (void) close(mapfd);

        *Pmapp = Pmap;
        *nmapp = nmap;

        return (0);
}

/*ARGSUSED*/
static void
Pread_aux_live(struct ps_prochandle *P, auxv_t **auxvp, int *nauxp, void *data)
{
        char auxfile[64];
        int fd;
        struct stat statb;
        auxv_t *auxv;
        ssize_t naux;

        (void) snprintf(auxfile, sizeof (auxfile), "%s/%d/auxv",
            procfs_path, (int)P->pid);
        if ((fd = open(auxfile, O_RDONLY)) < 0) {
                dprintf("%s: failed to open %s: %s\n",
                    __func__, auxfile, strerror(errno));
                return;
        }

        if (fstat(fd, &statb) == 0 &&
            statb.st_size >= sizeof (auxv_t) &&
            (auxv = malloc(statb.st_size + sizeof (auxv_t))) != NULL) {
                if ((naux = read(fd, auxv, statb.st_size)) < 0 ||
                    (naux /= sizeof (auxv_t)) < 1) {
                        dprintf("%s: read failed: %s\n",
                            __func__, strerror(errno));
                        free(auxv);
                } else {
                        auxv[naux].a_type = AT_NULL;
                        auxv[naux].a_un.a_val = 0L;

                        *auxvp = auxv;
                        *nauxp = (int)naux;
                }
        }

        (void) close(fd);
}

/*ARGSUSED*/
static int
Pcred_live(struct ps_prochandle *P, prcred_t *pcrp, int ngroups, void *data)
{
        return (proc_get_cred(P->pid, pcrp, ngroups));
}

/* ARGSUSED */
static int
Psecflags_live(struct ps_prochandle *P, prsecflags_t **psf, void *data)
{
        return (proc_get_secflags(P->pid, psf));
}

/*ARGSUSED*/
static int
Ppriv_live(struct ps_prochandle *P, prpriv_t **pprv, void *data)
{
        prpriv_t *pp;

        pp = proc_get_priv(P->pid);
        if (pp == NULL) {
                return (-1);
        }

        *pprv = pp;
        return (0);
}

/*ARGSUSED*/
static const psinfo_t *
Ppsinfo_live(struct ps_prochandle *P, psinfo_t *psinfo, void *data)
{
        if (proc_get_psinfo(P->pid, psinfo) == -1)
                return (NULL);

        return (psinfo);
}

/*ARGSUSED*/
static prheader_t *
Plstatus_live(struct ps_prochandle *P, void *data)
{
        return (read_lfile(P, "lstatus"));
}

/*ARGSUSED*/
static prheader_t *
Plpsinfo_live(struct ps_prochandle *P, void *data)
{
        return (read_lfile(P, "lpsinfo"));
}

/*ARGSUSED*/
static char *
Pplatform_live(struct ps_prochandle *P, char *s, size_t n, void *data)
{
        if (sysinfo(SI_PLATFORM, s, n) == -1)
                return (NULL);
        return (s);
}

/*ARGSUSED*/
static int
Puname_live(struct ps_prochandle *P, struct utsname *u, void *data)
{
        return (uname(u));
}

/*ARGSUSED*/
static char *
Pzonename_live(struct ps_prochandle *P, char *s, size_t n, void *data)
{
        if (getzonenamebyid(P->status.pr_zoneid, s, n) < 0)
                return (NULL);
        s[n - 1] = '\0';
        return (s);
}

/*
 * Callback function for Pfindexec().  We return a match if we can stat the
 * suggested pathname and confirm its device and inode number match our
 * previous information about the /proc/<pid>/object/a.out file.
 */
static int
stat_exec(const char *path, void *arg)
{
        struct stat64 *stp = arg;
        struct stat64 st;

        return (stat64(path, &st) == 0 && S_ISREG(st.st_mode) &&
            stp->st_dev == st.st_dev && stp->st_ino == st.st_ino);
}

/*ARGSUSED*/
static char *
Pexecname_live(struct ps_prochandle *P, char *buf, size_t buflen, void *data)
{
        char exec_name[PATH_MAX];
        char cwd[PATH_MAX];
        char proc_cwd[64];
        struct stat64 st;
        int ret;

        /*
         * Try to get the path information first.
         */
        (void) snprintf(exec_name, sizeof (exec_name),
            "%s/%d/path/a.out", procfs_path, (int)P->pid);
        if ((ret = readlink(exec_name, buf, buflen - 1)) > 0) {
                buf[ret] = '\0';
                (void) Pfindobj(P, buf, buf, buflen);
                return (buf);
        }

        /*
         * Stat the executable file so we can compare Pfindexec's
         * suggestions to the actual device and inode number.
         */
        (void) snprintf(exec_name, sizeof (exec_name),
            "%s/%d/object/a.out", procfs_path, (int)P->pid);

        if (stat64(exec_name, &st) != 0 || !S_ISREG(st.st_mode))
                return (NULL);

        /*
         * Attempt to figure out the current working directory of the
         * target process.  This only works if the target process has
         * not changed its current directory since it was exec'd.
         */
        (void) snprintf(proc_cwd, sizeof (proc_cwd),
            "%s/%d/path/cwd", procfs_path, (int)P->pid);

        if ((ret = readlink(proc_cwd, cwd, PATH_MAX - 1)) > 0)
                cwd[ret] = '\0';

        (void) Pfindexec(P, ret > 0 ? cwd : NULL, stat_exec, &st);

        return (NULL);
}

#if defined(__i386) || defined(__amd64)
/*ARGSUSED*/
static int
Pldt_live(struct ps_prochandle *P, struct ssd *pldt, int nldt, void *data)
{
        return (proc_get_ldt(P->pid, pldt, nldt));
}
#endif

static const ps_ops_t P_live_ops = {
        .pop_pread      = Pread_live,
        .pop_pwrite     = Pwrite_live,
        .pop_read_maps  = Pread_maps_live,
        .pop_read_aux   = Pread_aux_live,
        .pop_cred       = Pcred_live,
        .pop_priv       = Ppriv_live,
        .pop_psinfo     = Ppsinfo_live,
        .pop_lstatus    = Plstatus_live,
        .pop_lpsinfo    = Plpsinfo_live,
        .pop_platform   = Pplatform_live,
        .pop_uname      = Puname_live,
        .pop_zonename   = Pzonename_live,
        .pop_execname   = Pexecname_live,
        .pop_secflags   = Psecflags_live,
#if defined(__i386) || defined(__amd64)
        .pop_ldt        = Pldt_live
#endif
};

/*
 * This is the library's .init handler.
 */
#pragma init(_libproc_init)
void
_libproc_init(void)
{
        _libproc_debug = getenv("LIBPROC_DEBUG") != NULL;
        _libproc_no_qsort = getenv("LIBPROC_NO_QSORT") != NULL;
        _libproc_incore_elf = getenv("LIBPROC_INCORE_ELF") != NULL;

        (void) sigfillset(&blockable_sigs);
        (void) sigdelset(&blockable_sigs, SIGKILL);
        (void) sigdelset(&blockable_sigs, SIGSTOP);
}

void
Pset_procfs_path(const char *path)
{
        (void) snprintf(procfs_path, sizeof (procfs_path), "%s", path);
}

/*
 * Call set_minfd() once before calling dupfd() several times.
 * We assume that the application will not reduce its current file
 * descriptor limit lower than 512 once it has set at least that value.
 */
int
set_minfd(void)
{
        static mutex_t minfd_lock = DEFAULTMUTEX;
        struct rlimit rlim;
        int fd;

        if ((fd = minfd) < 256) {
                (void) mutex_lock(&minfd_lock);
                if ((fd = minfd) < 256) {
                        if (getrlimit(RLIMIT_NOFILE, &rlim) != 0)
                                rlim.rlim_cur = rlim.rlim_max = 0;
                        if (rlim.rlim_cur >= 512)
                                fd = 256;
                        else if ((fd = rlim.rlim_cur / 2) < 3)
                                fd = 3;
                        membar_producer();
                        minfd = fd;
                }
                (void) mutex_unlock(&minfd_lock);
        }
        return (fd);
}

int
dupfd(int fd, int dfd)
{
        int mfd;

        /*
         * Make fd be greater than 255 (the 32-bit stdio limit),
         * or at least make it greater than 2 so that the
         * program will work when spawned by init(1m).
         * Also, if dfd is non-zero, dup the fd to be dfd.
         */
        if ((mfd = minfd) == 0)
                mfd = set_minfd();
        if (dfd > 0 || (0 <= fd && fd < mfd)) {
                if (dfd <= 0)
                        dfd = mfd;
                dfd = fcntl(fd, F_DUPFD, dfd);
                (void) close(fd);
                fd = dfd;
        }
        /*
         * Mark it close-on-exec so any created process doesn't inherit it.
         */
        if (fd >= 0)
                (void) fcntl(fd, F_SETFD, FD_CLOEXEC);
        return (fd);
}

/*
 * Create a new controlled process.
 * Leave it stopped on successful exit from exec() or execve().
 * Return an opaque pointer to its process control structure.
 * Return NULL if process cannot be created (fork()/exec() not successful).
 */
struct ps_prochandle *
Pxcreate(const char *file,      /* executable file name */
    char *const *argv,          /* argument vector */
    char *const *envp,          /* environment */
    int *perr,                  /* pointer to error return code */
    char *path,         /* if non-null, holds exec path name on return */
    size_t len)                 /* size of the path buffer */
{
        char execpath[PATH_MAX];
        char procname[PATH_MAX];
        struct ps_prochandle *P;
        pid_t pid;
        int fd;
        char *fname;
        int rc;
        int lasterrno = 0;

        if (len == 0)   /* zero length, no path */
                path = NULL;
        if (path != NULL)
                *path = '\0';

        if ((P = malloc(sizeof (struct ps_prochandle))) == NULL) {
                *perr = C_STRANGE;
                return (NULL);
        }

        if ((pid = fork1()) == -1) {
                free(P);
                *perr = C_FORK;
                return (NULL);
        }

        if (pid == 0) {                 /* child process */
                id_t id;
                extern char **environ;

                /*
                 * If running setuid or setgid, reset credentials to normal.
                 */
                if ((id = getgid()) != getegid())
                        (void) setgid(id);
                if ((id = getuid()) != geteuid())
                        (void) setuid(id);

                Pcreate_callback(P);    /* execute callback (see below) */
                (void) pause();         /* wait for PRSABORT from parent */

                /*
                 * This is ugly.  There is no execvep() function that takes a
                 * path and an environment.  We cheat here by replacing the
                 * global 'environ' variable right before we call this.
                 */
                if (envp)
                        environ = (char **)envp;

                (void) execvp(file, argv);  /* execute the program */
                _exit(127);
        }

        /*
         * Initialize the process structure.
         */
        (void) memset(P, 0, sizeof (*P));
        (void) mutex_init(&P->proc_lock, USYNC_THREAD, NULL);
        P->flags |= CREATED;
        P->state = PS_RUN;
        P->pid = pid;
        P->asfd = -1;
        P->ctlfd = -1;
        P->statfd = -1;
        P->agentctlfd = -1;
        P->agentstatfd = -1;
        Pinit_ops(&P->ops, &P_live_ops);
        Pinitsym(P);

        /*
         * Open the /proc/pid files.
         */
        (void) snprintf(procname, sizeof (procname), "%s/%d/",
            procfs_path, (int)pid);
        fname = procname + strlen(procname);
        (void) set_minfd();

        /*
         * Exclusive write open advises others not to interfere.
         * There is no reason for any of these open()s to fail.
         */
        (void) strcpy(fname, "as");
        if ((fd = open(procname, (O_RDWR|O_EXCL))) < 0 ||
            (fd = dupfd(fd, 0)) < 0) {
                dprintf("Pcreate: failed to open %s: %s\n",
                    procname, strerror(errno));
                rc = C_STRANGE;
                goto bad;
        }
        P->asfd = fd;

        (void) strcpy(fname, "status");
        if ((fd = open(procname, O_RDONLY)) < 0 ||
            (fd = dupfd(fd, 0)) < 0) {
                dprintf("Pcreate: failed to open %s: %s\n",
                    procname, strerror(errno));
                rc = C_STRANGE;
                goto bad;
        }
        P->statfd = fd;

        (void) strcpy(fname, "ctl");
        if ((fd = open(procname, O_WRONLY)) < 0 ||
            (fd = dupfd(fd, 0)) < 0) {
                dprintf("Pcreate: failed to open %s: %s\n",
                    procname, strerror(errno));
                rc = C_STRANGE;
                goto bad;
        }
        P->ctlfd = fd;

        (void) Pstop(P, 0);     /* stop the controlled process */

        /*
         * Wait for process to sleep in pause().
         * If the process has already called pause(), then it should be
         * stopped (PR_REQUESTED) while asleep in pause and we are done.
         * Else we set up to catch entry/exit to pause() and set the process
         * running again, expecting it to stop when it reaches pause().
         * There is no reason for this to fail other than an interrupt.
         */
        (void) Psysentry(P, SYS_pause, 1);
        (void) Psysexit(P, SYS_pause, 1);
        for (;;) {
                if (P->state == PS_STOP &&
                    P->status.pr_lwp.pr_syscall == SYS_pause &&
                    (P->status.pr_lwp.pr_why == PR_REQUESTED ||
                    P->status.pr_lwp.pr_why == PR_SYSENTRY ||
                    P->status.pr_lwp.pr_why == PR_SYSEXIT))
                        break;

                if (P->state != PS_STOP ||      /* interrupt or process died */
                    Psetrun(P, 0, 0) != 0) {    /* can't restart */
                        if (errno == EINTR || errno == ERESTART)
                                rc = C_INTR;
                        else {
                                dprintf("Pcreate: Psetrun failed: %s\n",
                                    strerror(errno));
                                rc = C_STRANGE;
                        }
                        goto bad;
                }

                (void) Pwait(P, 0);
        }
        (void) Psysentry(P, SYS_pause, 0);
        (void) Psysexit(P, SYS_pause, 0);

        /*
         * Kick the process off the pause() and catch
         * it again on entry to exec() or exit().
         */
        (void) Psysentry(P, SYS_exit, 1);
        (void) Psysentry(P, SYS_execve, 1);
        if (Psetrun(P, 0, PRSABORT) == -1) {
                dprintf("Pcreate: Psetrun failed: %s\n", strerror(errno));
                rc = C_STRANGE;
                goto bad;
        }
        (void) Pwait(P, 0);
        if (P->state != PS_STOP) {
                dprintf("Pcreate: Pwait failed: %s\n", strerror(errno));
                rc = C_STRANGE;
                goto bad;
        }

        /*
         * Move the process through instances of failed exec()s
         * to reach the point of stopped on successful exec().
         */
        (void) Psysexit(P, SYS_execve, TRUE);

        while (P->state == PS_STOP &&
            P->status.pr_lwp.pr_why == PR_SYSENTRY &&
            P->status.pr_lwp.pr_what == SYS_execve) {
                /*
                 * Fetch the exec path name now, before we complete
                 * the exec().  We may lose the process and be unable
                 * to get the information later.
                 */
                (void) Pread_string(P, execpath, sizeof (execpath),
                    (off_t)P->status.pr_lwp.pr_sysarg[0]);
                if (path != NULL)
                        (void) strncpy(path, execpath, len);
                /*
                 * Set the process running and wait for
                 * it to stop on exit from the exec().
                 */
                (void) Psetrun(P, 0, 0);
                (void) Pwait(P, 0);

                if (P->state == PS_LOST &&              /* we lost control */
                    Preopen(P) != 0) {          /* and we can't get it back */
                        rc = C_PERM;
                        goto bad;
                }

                /*
                 * If the exec() failed, continue the loop, expecting
                 * there to be more attempts to exec(), based on PATH.
                 */
                if (P->state == PS_STOP &&
                    P->status.pr_lwp.pr_why == PR_SYSEXIT &&
                    P->status.pr_lwp.pr_what == SYS_execve &&
                    (lasterrno = P->status.pr_lwp.pr_errno) != 0) {
                        /*
                         * The exec() failed.  Set the process running and
                         * wait for it to stop on entry to the next exec().
                         */
                        (void) Psetrun(P, 0, 0);
                        (void) Pwait(P, 0);

                        continue;
                }
                break;
        }

        if (P->state == PS_STOP &&
            P->status.pr_lwp.pr_why == PR_SYSEXIT &&
            P->status.pr_lwp.pr_what == SYS_execve &&
            P->status.pr_lwp.pr_errno == 0) {
                /*
                 * The process is stopped on successful exec() or execve().
                 * Turn off all tracing flags and return success.
                 */
                restore_tracing_flags(P);
#ifndef _LP64
                /* We must be a 64-bit process to deal with a 64-bit process */
                if (P->status.pr_dmodel == PR_MODEL_LP64) {
                        rc = C_LP64;
                        goto bad;
                }
#endif
                /*
                 * Set run-on-last-close so the controlled process
                 * runs even if we die on a signal.
                 */
                (void) Psetflags(P, PR_RLC);
                *perr = 0;
                return (P);
        }

        rc = lasterrno == ENOENT ? C_NOENT : C_NOEXEC;

bad:
        (void) kill(pid, SIGKILL);
        if (path != NULL && rc != C_PERM && rc != C_LP64)
                *path = '\0';
        Pfree(P);
        *perr = rc;
        return (NULL);
}

struct ps_prochandle *
Pcreate(
        const char *file,       /* executable file name */
        char *const *argv,      /* argument vector */
        int *perr,      /* pointer to error return code */
        char *path,     /* if non-null, holds exec path name on return */
        size_t len)     /* size of the path buffer */
{
        return (Pxcreate(file, argv, NULL, perr, path, len));
}

/*
 * Return a printable string corresponding to a Pcreate() error return.
 */
const char *
Pcreate_error(int error)
{
        const char *str;

        switch (error) {
        case C_FORK:
                str = "cannot fork";
                break;
        case C_PERM:
                str = "file is set-id or unreadable";
                break;
        case C_NOEXEC:
                str = "cannot execute file";
                break;
        case C_INTR:
                str = "operation interrupted";
                break;
        case C_LP64:
                str = "program is _LP64, self is not";
                break;
        case C_STRANGE:
                str = "unanticipated system error";
                break;
        case C_NOENT:
                str = "cannot find executable file";
                break;
        default:
                str = "unknown error";
                break;
        }

        return (str);
}

/*
 * Callback to execute in each child process created with Pcreate() after fork
 * but before it execs the new process image.  By default, we do nothing, but
 * by calling this function we allow the client program to define its own
 * version of the function which will interpose on our empty default.  This
 * may be useful for clients that need to modify signal dispositions, terminal
 * attributes, or process group and session properties for each new victim.
 */
/*ARGSUSED*/
void
Pcreate_callback(struct ps_prochandle *P)
{
        /* nothing to do here */
}

/*
 * Grab an existing process.
 * Return an opaque pointer to its process control structure.
 *
 * pid:         UNIX process ID.
 * flags:
 *      PGRAB_RETAIN    Retain tracing flags (default clears all tracing flags).
 *      PGRAB_FORCE     Grab regardless of whether process is already traced.
 *      PGRAB_RDONLY    Open the address space file O_RDONLY instead of O_RDWR,
 *                      and do not open the process control file.
 *      PGRAB_NOSTOP    Open the process but do not force it to stop.
 * perr:        pointer to error return code.
 */
struct ps_prochandle *
Pgrab(pid_t pid, int flags, int *perr)
{
        struct ps_prochandle *P;
        int fd, omode;
        char procname[PATH_MAX];
        char *fname;
        int rc = 0;

        /*
         * PGRAB_RDONLY means that we do not open the /proc/<pid>/control file,
         * and so it implies RETAIN and NOSTOP since both require control.
         */
        if (flags & PGRAB_RDONLY)
                flags |= PGRAB_RETAIN | PGRAB_NOSTOP;

        if ((P = malloc(sizeof (struct ps_prochandle))) == NULL) {
                *perr = G_STRANGE;
                return (NULL);
        }

        P->asfd = -1;
        P->ctlfd = -1;
        P->statfd = -1;

again:  /* Come back here if we lose it in the Window of Vulnerability */
        if (P->ctlfd >= 0)
                (void) close(P->ctlfd);
        if (P->asfd >= 0)
                (void) close(P->asfd);
        if (P->statfd >= 0)
                (void) close(P->statfd);
        (void) memset(P, 0, sizeof (*P));
        (void) mutex_init(&P->proc_lock, USYNC_THREAD, NULL);
        P->ctlfd = -1;
        P->asfd = -1;
        P->statfd = -1;
        P->agentctlfd = -1;
        P->agentstatfd = -1;
        Pinit_ops(&P->ops, &P_live_ops);
        Pinitsym(P);

        /*
         * Open the /proc/pid files
         */
        (void) snprintf(procname, sizeof (procname), "%s/%d/",
            procfs_path, (int)pid);
        fname = procname + strlen(procname);
        (void) set_minfd();

        /*
         * Request exclusive open to avoid grabbing someone else's
         * process and to prevent others from interfering afterwards.
         * If this fails and the 'PGRAB_FORCE' flag is set, attempt to
         * open non-exclusively.
         */
        (void) strcpy(fname, "as");
        omode = (flags & PGRAB_RDONLY) ? O_RDONLY : O_RDWR;

        if (((fd = open(procname, omode | O_EXCL)) < 0 &&
            (fd = ((flags & PGRAB_FORCE)? open(procname, omode) : -1)) < 0) ||
            (fd = dupfd(fd, 0)) < 0) {
                switch (errno) {
                case ENOENT:
                        rc = G_NOPROC;
                        break;
                case EACCES:
                case EPERM:
                        rc = G_PERM;
                        break;
                case EMFILE:
                        rc = G_NOFD;
                        break;
                case EBUSY:
                        if (!(flags & PGRAB_FORCE) || geteuid() != 0) {
                                rc = G_BUSY;
                                break;
                        }
                        /* FALLTHROUGH */
                default:
                        dprintf("Pgrab: failed to open %s: %s\n",
                            procname, strerror(errno));
                        rc = G_STRANGE;
                        break;
                }
                goto err;
        }
        P->asfd = fd;

        (void) strcpy(fname, "status");
        if ((fd = open(procname, O_RDONLY)) < 0 ||
            (fd = dupfd(fd, 0)) < 0) {
                switch (errno) {
                case ENOENT:
                        rc = G_NOPROC;
                        break;
                case EMFILE:
                        rc = G_NOFD;
                        break;
                default:
                        dprintf("Pgrab: failed to open %s: %s\n",
                            procname, strerror(errno));
                        rc = G_STRANGE;
                        break;
                }
                goto err;
        }
        P->statfd = fd;

        if (!(flags & PGRAB_RDONLY)) {
                (void) strcpy(fname, "ctl");
                if ((fd = open(procname, O_WRONLY)) < 0 ||
                    (fd = dupfd(fd, 0)) < 0) {
                        switch (errno) {
                        case ENOENT:
                                rc = G_NOPROC;
                                break;
                        case EMFILE:
                                rc = G_NOFD;
                                break;
                        default:
                                dprintf("Pgrab: failed to open %s: %s\n",
                                    procname, strerror(errno));
                                rc = G_STRANGE;
                                break;
                        }
                        goto err;
                }
                P->ctlfd = fd;
        }

        P->state = PS_RUN;
        P->pid = pid;

        /*
         * We are now in the Window of Vulnerability (WoV).  The process may
         * exec() a setuid/setgid or unreadable object file between the open()
         * and the PCSTOP.  We will get EAGAIN in this case and must start over.
         * As Pstopstatus will trigger the first read() from a /proc file,
         * we also need to handle EOVERFLOW here when 32-bit as an indicator
         * that this process is 64-bit.  Finally, if the process has become
         * a zombie (PS_UNDEAD) while we were trying to grab it, just remain
         * silent about this and pretend there was no process.
         */
        if (Pstopstatus(P, PCNULL, 0) != 0) {
#ifndef _LP64
                if (errno == EOVERFLOW) {
                        rc = G_LP64;
                        goto err;
                }
#endif
                if (P->state == PS_LOST) {      /* WoV */
                        (void) mutex_destroy(&P->proc_lock);
                        goto again;
                }

                if (P->state == PS_UNDEAD)
                        rc = G_NOPROC;
                else
                        rc = G_STRANGE;

                goto err;
        }

        /*
         * If the process is a system process, we can't control it even as root
         */
        if (P->status.pr_flags & PR_ISSYS) {
                rc = G_SYS;
                goto err;
        }
#ifndef _LP64
        /*
         * We must be a 64-bit process to deal with a 64-bit process
         */
        if (P->status.pr_dmodel == PR_MODEL_LP64) {
                rc = G_LP64;
                goto err;
        }
#endif

        /*
         * Remember the status for use by Prelease().
         */
        P->orig_status = P->status;     /* structure copy */

        /*
         * Before stopping the process, make sure we are not grabbing ourselves.
         * If we are, make sure we are doing it PGRAB_RDONLY.
         */
        if (pid == getpid()) {
                /*
                 * Verify that the process is really ourself:
                 * Set a magic number, read it through the
                 * /proc file and see if the results match.
                 */
                uint32_t magic1 = 0;
                uint32_t magic2 = 2;

                errno = 0;

                if (Pread(P, &magic2, sizeof (magic2), (uintptr_t)&magic1)
                    == sizeof (magic2) &&
                    magic2 == 0 &&
                    (magic1 = 0xfeedbeef) &&
                    Pread(P, &magic2, sizeof (magic2), (uintptr_t)&magic1)
                    == sizeof (magic2) &&
                    magic2 == 0xfeedbeef &&
                    !(flags & PGRAB_RDONLY)) {
                        rc = G_SELF;
                        goto err;
                }
        }

        /*
         * If the process is already stopped or has been directed
         * to stop via /proc, do not set run-on-last-close.
         */
        if (!(P->status.pr_lwp.pr_flags & (PR_ISTOP|PR_DSTOP)) &&
            !(flags & PGRAB_RDONLY)) {
                /*
                 * Mark the process run-on-last-close so
                 * it runs even if we die from SIGKILL.
                 */
                if (Psetflags(P, PR_RLC) != 0) {
                        if (errno == EAGAIN) {  /* WoV */
                                (void) mutex_destroy(&P->proc_lock);
                                goto again;
                        }
                        if (errno == ENOENT)    /* No complaint about zombies */
                                rc = G_ZOMB;
                        else {
                                dprintf("Pgrab: failed to set RLC\n");
                                rc = G_STRANGE;
                        }
                        goto err;
                }
        }

        /*
         * If a stop directive is pending and the process has not yet stopped,
         * then synchronously wait for the stop directive to take effect.
         * Limit the time spent waiting for the process to stop by iterating
         * at most 10 times. The time-out of 20 ms corresponds to the time
         * between sending the stop directive and the process actually stopped
         * as measured by DTrace on a slow, busy system. If the process doesn't
         * stop voluntarily, clear the PR_DSTOP flag so that the code below
         * forces the process to stop.
         */
        if (!(flags & PGRAB_RDONLY)) {
                int niter = 0;
                while ((P->status.pr_lwp.pr_flags & (PR_STOPPED|PR_DSTOP)) ==
                    PR_DSTOP && niter < 10 &&
                    Pstopstatus(P, PCTWSTOP, 20) != 0) {
                        niter++;
                        if (flags & PGRAB_NOSTOP)
                                break;
                }
                if (niter == 10 && !(flags & PGRAB_NOSTOP)) {
                        /* Try it harder down below */
                        P->status.pr_lwp.pr_flags &= ~PR_DSTOP;
                }
        }

        /*
         * If the process is not already stopped or directed to stop
         * and PGRAB_NOSTOP was not specified, stop the process now.
         */
        if (!(P->status.pr_lwp.pr_flags & (PR_ISTOP|PR_DSTOP)) &&
            !(flags & PGRAB_NOSTOP)) {
                /*
                 * Stop the process, get its status and signal/syscall masks.
                 */
                if (((P->status.pr_lwp.pr_flags & PR_STOPPED) &&
                    Pstopstatus(P, PCDSTOP, 0) != 0) ||
                    Pstopstatus(P, PCSTOP, 2000) != 0) {
#ifndef _LP64
                        if (errno == EOVERFLOW) {
                                rc = G_LP64;
                                goto err;
                        }
#endif
                        if (P->state == PS_LOST) {      /* WoV */
                                (void) mutex_destroy(&P->proc_lock);
                                goto again;
                        }
                        if ((errno != EINTR && errno != ERESTART) ||
                            (P->state != PS_STOP &&
                            !(P->status.pr_flags & PR_DSTOP))) {
                                if (P->state != PS_RUN && errno != ENOENT) {
                                        dprintf("Pgrab: failed to PCSTOP\n");
                                        rc = G_STRANGE;
                                } else {
                                        rc = G_ZOMB;
                                }
                                goto err;
                        }
                }

                /*
                 * Process should now either be stopped via /proc or there
                 * should be an outstanding stop directive.
                 */
                if (!(P->status.pr_flags & (PR_ISTOP|PR_DSTOP))) {
                        dprintf("Pgrab: process is not stopped\n");
                        rc = G_STRANGE;
                        goto err;
                }
#ifndef _LP64
                /*
                 * Test this again now because the 32-bit victim process may
                 * have exec'd a 64-bit process in the meantime.
                 */
                if (P->status.pr_dmodel == PR_MODEL_LP64) {
                        rc = G_LP64;
                        goto err;
                }
#endif
        }

        /*
         * Cancel all tracing flags unless the PGRAB_RETAIN flag is set.
         */
        if (!(flags & PGRAB_RETAIN)) {
                (void) Psysentry(P, 0, FALSE);
                (void) Psysexit(P, 0, FALSE);
                (void) Psignal(P, 0, FALSE);
                (void) Pfault(P, 0, FALSE);
                Psync(P);
        }

        *perr = 0;
        return (P);

err:
        Pfree(P);
        *perr = rc;
        return (NULL);
}

/*
 * Return a printable string corresponding to a Pgrab() error return.
 */
const char *
Pgrab_error(int error)
{
        const char *str;

        switch (error) {
        case G_NOPROC:
                str = "no such process";
                break;
        case G_NOCORE:
                str = "no such core file";
                break;
        case G_NOPROCORCORE:
                str = "no such process or core file";
                break;
        case G_NOEXEC:
                str = "cannot find executable file";
                break;
        case G_ZOMB:
                str = "zombie process";
                break;
        case G_PERM:
                str = "permission denied";
                break;
        case G_BUSY:
                str = "process is traced";
                break;
        case G_SYS:
                str = "system process";
                break;
        case G_SELF:
                str = "attempt to grab self";
                break;
        case G_INTR:
                str = "operation interrupted";
                break;
        case G_LP64:
                str = "program is _LP64, self is not";
                break;
        case G_FORMAT:
                str = "file is not an ELF core file";
                break;
        case G_ELF:
                str = "libelf error";
                break;
        case G_NOTE:
                str = "core file is corrupt or missing required data";
                break;
        case G_STRANGE:
                str = "unanticipated system error";
                break;
        case G_ISAINVAL:
                str = "wrong ELF machine type";
                break;
        case G_BADLWPS:
                str = "bad lwp specification";
                break;
        case G_NOFD:
                str = "too many open files";
                break;
        default:
                str = "unknown error";
                break;
        }

        return (str);
}

/*
 * Free a process control structure.
 * Close the file descriptors but don't do the Prelease logic.
 */
void
Pfree(struct ps_prochandle *P)
{
        uint_t i;

        if (P->ucaddrs != NULL) {
                free(P->ucaddrs);
                P->ucaddrs = NULL;
                P->ucnelems = 0;
        }

        (void) mutex_lock(&P->proc_lock);
        if (P->hashtab != NULL) {
                struct ps_lwphandle *L;
                for (i = 0; i < HASHSIZE; i++) {
                        while ((L = P->hashtab[i]) != NULL)
                                Lfree_internal(P, L);
                }
                free(P->hashtab);
        }

        while (P->num_fd > 0) {
                fd_info_t *fip = list_next(&P->fd_head);
                list_unlink(fip);
                free(fip);
                P->num_fd--;
        }
        (void) mutex_unlock(&P->proc_lock);
        (void) mutex_destroy(&P->proc_lock);

        if (P->agentctlfd >= 0)
                (void) close(P->agentctlfd);
        if (P->agentstatfd >= 0)
                (void) close(P->agentstatfd);
        if (P->ctlfd >= 0)
                (void) close(P->ctlfd);
        if (P->asfd >= 0)
                (void) close(P->asfd);
        if (P->statfd >= 0)
                (void) close(P->statfd);
        Preset_maps(P);
        P->ops.pop_fini(P, P->data);

        /* clear out the structure as a precaution against reuse */
        (void) memset(P, 0, sizeof (*P));
        P->ctlfd = -1;
        P->asfd = -1;
        P->statfd = -1;
        P->agentctlfd = -1;
        P->agentstatfd = -1;

        free(P);
}

/*
 * Return the state of the process, one of the PS_* values.
 */
int
Pstate(struct ps_prochandle *P)
{
        return (P->state);
}

/*
 * Return the open address space file descriptor for the process.
 * Clients must not close this file descriptor, not use it
 * after the process is freed.
 */
int
Pasfd(struct ps_prochandle *P)
{
        return (P->asfd);
}

/*
 * Return the open control file descriptor for the process.
 * Clients must not close this file descriptor, not use it
 * after the process is freed.
 */
int
Pctlfd(struct ps_prochandle *P)
{
        return (P->ctlfd);
}

/*
 * Return a pointer to the process psinfo structure.
 * Clients should not hold on to this pointer indefinitely.
 * It will become invalid on Prelease().
 */
const psinfo_t *
Ppsinfo(struct ps_prochandle *P)
{
        return (P->ops.pop_psinfo(P, &P->psinfo, P->data));
}

/*
 * Return a pointer to the process status structure.
 * Clients should not hold on to this pointer indefinitely.
 * It will become invalid on Prelease().
 */
const pstatus_t *
Pstatus(struct ps_prochandle *P)
{
        return (&P->status);
}

static void
Pread_status(struct ps_prochandle *P)
{
        P->ops.pop_status(P, &P->status, P->data);
}

/*
 * Fill in a pointer to a process credentials structure.  The ngroups parameter
 * is the number of supplementary group entries allocated in the caller's cred
 * structure.  It should equal zero or one unless extra space has been
 * allocated for the group list by the caller.
 */
int
Pcred(struct ps_prochandle *P, prcred_t *pcrp, int ngroups)
{
        return (P->ops.pop_cred(P, pcrp, ngroups, P->data));
}

/* Return an allocated prsecflags_t */
int
Psecflags(struct ps_prochandle *P, prsecflags_t **psf)
{
        int ret;

        if ((ret = P->ops.pop_secflags(P, psf, P->data)) == 0) {
                if ((*psf)->pr_version != PRSECFLAGS_VERSION_1) {
                        errno = EINVAL;
                        return (-1);
                }
        }

        return (ret);
}

void
Psecflags_free(prsecflags_t *psf)
{
        free(psf);
}

static prheader_t *
Plstatus(struct ps_prochandle *P)
{
        return (P->ops.pop_lstatus(P, P->data));
}

static prheader_t *
Plpsinfo(struct ps_prochandle *P)
{
        return (P->ops.pop_lpsinfo(P, P->data));
}


#if defined(__i386) || defined(__amd64)
/*
 * Fill in a pointer to a process LDT structure.
 * The caller provides a buffer of size 'nldt * sizeof (struct ssd)';
 * If pldt == NULL or nldt == 0, we return the number of existing LDT entries.
 * Otherwise we return the actual number of LDT entries fetched (<= nldt).
 */
int
Pldt(struct ps_prochandle *P, struct ssd *pldt, int nldt)
{
        return (P->ops.pop_ldt(P, pldt, nldt, P->data));

}
#endif  /* __i386 */

/* ARGSUSED */
void
Ppriv_free(struct ps_prochandle *P, prpriv_t *prv)
{
        free(prv);
}

/*
 * Return a malloced process privilege structure in *pprv.
 */
int
Ppriv(struct ps_prochandle *P, prpriv_t **pprv)
{
        return (P->ops.pop_priv(P, pprv, P->data));
}

int
Psetpriv(struct ps_prochandle *P, prpriv_t *pprv)
{
        int rc;
        long *ctl;
        size_t sz;

        if (P->state == PS_DEAD) {
                errno = EBADF;
                return (-1);
        }

        sz = PRIV_PRPRIV_SIZE(pprv) + sizeof (long);

        sz = ((sz - 1) / sizeof (long) + 1) * sizeof (long);

        ctl = malloc(sz);
        if (ctl == NULL)
                return (-1);

        ctl[0] = PCSPRIV;

        (void) memcpy(&ctl[1], pprv, PRIV_PRPRIV_SIZE(pprv));

        if (write(P->ctlfd, ctl, sz) != sz)
                rc = -1;
        else
                rc = 0;

        free(ctl);

        return (rc);
}

void *
Pprivinfo(struct ps_prochandle *P)
{
        core_info_t *core = P->data;

        /* Use default from libc */
        if (P->state != PS_DEAD)
                return (NULL);

        return (core->core_privinfo);
}

/*
 * Ensure that all cached state is written to the process.
 * The cached state is the LWP's signal mask and registers
 * and the process's tracing flags.
 */
void
Psync(struct ps_prochandle *P)
{
        int ctlfd = (P->agentctlfd >= 0)? P->agentctlfd : P->ctlfd;
        long cmd[6];
        iovec_t iov[12];
        int n = 0;

        if (P->flags & SETHOLD) {
                cmd[0] = PCSHOLD;
                iov[n].iov_base = (caddr_t)&cmd[0];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&P->status.pr_lwp.pr_lwphold;
                iov[n++].iov_len = sizeof (P->status.pr_lwp.pr_lwphold);
        }
        if (P->flags & SETREGS) {
                cmd[1] = PCSREG;
#ifdef __i386
                /* XX64 we should probably restore REG_GS after this */
                if (ctlfd == P->agentctlfd)
                        P->status.pr_lwp.pr_reg[GS] = 0;
#elif defined(__amd64)
                /* XX64 */
#endif
                iov[n].iov_base = (caddr_t)&cmd[1];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&P->status.pr_lwp.pr_reg[0];
                iov[n++].iov_len = sizeof (P->status.pr_lwp.pr_reg);
        }
        if (P->flags & SETSIG) {
                cmd[2] = PCSTRACE;
                iov[n].iov_base = (caddr_t)&cmd[2];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&P->status.pr_sigtrace;
                iov[n++].iov_len = sizeof (P->status.pr_sigtrace);
        }
        if (P->flags & SETFAULT) {
                cmd[3] = PCSFAULT;
                iov[n].iov_base = (caddr_t)&cmd[3];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&P->status.pr_flttrace;
                iov[n++].iov_len = sizeof (P->status.pr_flttrace);
        }
        if (P->flags & SETENTRY) {
                cmd[4] = PCSENTRY;
                iov[n].iov_base = (caddr_t)&cmd[4];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&P->status.pr_sysentry;
                iov[n++].iov_len = sizeof (P->status.pr_sysentry);
        }
        if (P->flags & SETEXIT) {
                cmd[5] = PCSEXIT;
                iov[n].iov_base = (caddr_t)&cmd[5];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&P->status.pr_sysexit;
                iov[n++].iov_len = sizeof (P->status.pr_sysexit);
        }

        if (n == 0 || writev(ctlfd, iov, n) < 0)
                return;         /* nothing to do or write failed */

        P->flags &= ~(SETSIG|SETFAULT|SETENTRY|SETEXIT|SETHOLD|SETREGS);
}

/*
 * Reopen the /proc file (after PS_LOST).
 */
int
Preopen(struct ps_prochandle *P)
{
        int fd;
        char procname[PATH_MAX];
        char *fname;

        if (P->state == PS_DEAD || P->state == PS_IDLE)
                return (0);

        if (P->agentcnt > 0) {
                P->agentcnt = 1;
                Pdestroy_agent(P);
        }

        (void) snprintf(procname, sizeof (procname), "%s/%d/",
            procfs_path, (int)P->pid);
        fname = procname + strlen(procname);

        (void) strcpy(fname, "as");
        if ((fd = open(procname, O_RDWR)) < 0 ||
            close(P->asfd) < 0 ||
            (fd = dupfd(fd, P->asfd)) != P->asfd) {
                dprintf("Preopen: failed to open %s: %s\n",
                    procname, strerror(errno));
                if (fd >= 0)
                        (void) close(fd);
                return (-1);
        }
        P->asfd = fd;

        (void) strcpy(fname, "status");
        if ((fd = open(procname, O_RDONLY)) < 0 ||
            close(P->statfd) < 0 ||
            (fd = dupfd(fd, P->statfd)) != P->statfd) {
                dprintf("Preopen: failed to open %s: %s\n",
                    procname, strerror(errno));
                if (fd >= 0)
                        (void) close(fd);
                return (-1);
        }
        P->statfd = fd;

        (void) strcpy(fname, "ctl");
        if ((fd = open(procname, O_WRONLY)) < 0 ||
            close(P->ctlfd) < 0 ||
            (fd = dupfd(fd, P->ctlfd)) != P->ctlfd) {
                dprintf("Preopen: failed to open %s: %s\n",
                    procname, strerror(errno));
                if (fd >= 0)
                        (void) close(fd);
                return (-1);
        }
        P->ctlfd = fd;

        /*
         * Set the state to PS_RUN and wait for the process to stop so that
         * we re-read the status from the new P->statfd.  If this fails, Pwait
         * will reset the state to PS_LOST and we fail the reopen.  Before
         * returning, we also forge a bit of P->status to allow the debugger to
         * see that we are PS_LOST following a successful exec.
         */
        P->state = PS_RUN;
        if (Pwait(P, 0) == -1) {
#ifdef _ILP32
                if (errno == EOVERFLOW)
                        P->status.pr_dmodel = PR_MODEL_LP64;
#endif
                P->status.pr_lwp.pr_why = PR_SYSEXIT;
                P->status.pr_lwp.pr_what = SYS_execve;
                P->status.pr_lwp.pr_errno = 0;
                return (-1);
        }

        /*
         * The process should be stopped on exec (REQUESTED)
         * or else should be stopped on exit from exec() (SYSEXIT)
         */
        if (P->state == PS_STOP &&
            (P->status.pr_lwp.pr_why == PR_REQUESTED ||
            (P->status.pr_lwp.pr_why == PR_SYSEXIT &&
            P->status.pr_lwp.pr_what == SYS_execve))) {
                /* fake up stop-on-exit-from-execve */
                if (P->status.pr_lwp.pr_why == PR_REQUESTED) {
                        P->status.pr_lwp.pr_why = PR_SYSEXIT;
                        P->status.pr_lwp.pr_what = SYS_execve;
                        P->status.pr_lwp.pr_errno = 0;
                }
        } else {
                dprintf("Preopen: expected REQUESTED or "
                    "SYSEXIT(SYS_execve) stop\n");
        }

        return (0);
}

/*
 * Define all settable flags other than the microstate accounting flags.
 */
#define ALL_SETTABLE_FLAGS (PR_FORK|PR_RLC|PR_KLC|PR_ASYNC|PR_BPTADJ|PR_PTRACE)

/*
 * Restore /proc tracing flags to their original values
 * in preparation for releasing the process.
 * Also called by Pcreate() to clear all tracing flags.
 */
static void
restore_tracing_flags(struct ps_prochandle *P)
{
        long flags;
        long cmd[4];
        iovec_t iov[8];

        if (P->flags & CREATED) {
                /* we created this process; clear all tracing flags */
                premptyset(&P->status.pr_sigtrace);
                premptyset(&P->status.pr_flttrace);
                premptyset(&P->status.pr_sysentry);
                premptyset(&P->status.pr_sysexit);
                if ((P->status.pr_flags & ALL_SETTABLE_FLAGS) != 0)
                        (void) Punsetflags(P, ALL_SETTABLE_FLAGS);
        } else {
                /* we grabbed the process; restore its tracing flags */
                P->status.pr_sigtrace = P->orig_status.pr_sigtrace;
                P->status.pr_flttrace = P->orig_status.pr_flttrace;
                P->status.pr_sysentry = P->orig_status.pr_sysentry;
                P->status.pr_sysexit  = P->orig_status.pr_sysexit;
                if ((P->status.pr_flags & ALL_SETTABLE_FLAGS) !=
                    (flags = (P->orig_status.pr_flags & ALL_SETTABLE_FLAGS))) {
                        (void) Punsetflags(P, ALL_SETTABLE_FLAGS);
                        if (flags)
                                (void) Psetflags(P, flags);
                }
        }

        cmd[0] = PCSTRACE;
        iov[0].iov_base = (caddr_t)&cmd[0];
        iov[0].iov_len = sizeof (long);
        iov[1].iov_base = (caddr_t)&P->status.pr_sigtrace;
        iov[1].iov_len = sizeof (P->status.pr_sigtrace);

        cmd[1] = PCSFAULT;
        iov[2].iov_base = (caddr_t)&cmd[1];
        iov[2].iov_len = sizeof (long);
        iov[3].iov_base = (caddr_t)&P->status.pr_flttrace;
        iov[3].iov_len = sizeof (P->status.pr_flttrace);

        cmd[2] = PCSENTRY;
        iov[4].iov_base = (caddr_t)&cmd[2];
        iov[4].iov_len = sizeof (long);
        iov[5].iov_base = (caddr_t)&P->status.pr_sysentry;
        iov[5].iov_len = sizeof (P->status.pr_sysentry);

        cmd[3] = PCSEXIT;
        iov[6].iov_base = (caddr_t)&cmd[3];
        iov[6].iov_len = sizeof (long);
        iov[7].iov_base = (caddr_t)&P->status.pr_sysexit;
        iov[7].iov_len = sizeof (P->status.pr_sysexit);

        (void) writev(P->ctlfd, iov, 8);

        P->flags &= ~(SETSIG|SETFAULT|SETENTRY|SETEXIT);
}

/*
 * Release the process.  Frees the process control structure.
 * flags:
 *      PRELEASE_CLEAR  Clear all tracing flags.
 *      PRELEASE_RETAIN Retain current tracing flags.
 *      PRELEASE_HANG   Leave the process stopped and abandoned.
 *      PRELEASE_KILL   Terminate the process with SIGKILL.
 */
void
Prelease(struct ps_prochandle *P, int flags)
{
        if (P->state == PS_DEAD) {
                dprintf("Prelease: releasing handle %p PS_DEAD of pid %d\n",
                    (void *)P, (int)P->pid);
                Pfree(P);
                return;
        }

        if (P->state == PS_IDLE) {
                file_info_t *fptr = list_next(&P->file_head);
                dprintf("Prelease: releasing handle %p PS_IDLE of file %s\n",
                    (void *)P, fptr->file_pname);
                Pfree(P);
                return;
        }

        dprintf("Prelease: releasing handle %p pid %d\n",
            (void *)P, (int)P->pid);

        if (P->ctlfd == -1) {
                Pfree(P);
                return;
        }

        if (P->agentcnt > 0) {
                P->agentcnt = 1;
                Pdestroy_agent(P);
        }

        /*
         * Attempt to stop the process.
         */
        P->state = PS_RUN;
        (void) Pstop(P, 1000);

        if (flags & PRELEASE_KILL) {
                if (P->state == PS_STOP)
                        (void) Psetrun(P, SIGKILL, 0);
                (void) kill(P->pid, SIGKILL);
                Pfree(P);
                return;
        }

        /*
         * If we lost control, all we can do now is close the files.
         * In this case, the last close sets the process running.
         */
        if (P->state != PS_STOP &&
            (P->status.pr_lwp.pr_flags & (PR_ISTOP|PR_DSTOP)) == 0) {
                Pfree(P);
                return;
        }

        /*
         * We didn't lose control; we do more.
         */
        Psync(P);

        if (flags & PRELEASE_CLEAR)
                P->flags |= CREATED;

        if (!(flags & PRELEASE_RETAIN))
                restore_tracing_flags(P);

        if (flags & PRELEASE_HANG) {
                /* Leave the process stopped and abandoned */
                (void) Punsetflags(P, PR_RLC|PR_KLC);
                Pfree(P);
                return;
        }

        /*
         * Set the process running if we created it or if it was
         * not originally stopped or directed to stop via /proc
         * or if we were given the PRELEASE_CLEAR flag.
         */
        if ((P->flags & CREATED) ||
            (P->orig_status.pr_lwp.pr_flags & (PR_ISTOP|PR_DSTOP)) == 0) {
                (void) Psetflags(P, PR_RLC);
                /*
                 * We do this repeatedly because the process may have
                 * more than one LWP stopped on an event of interest.
                 * This makes sure all of them are set running.
                 */
                do {
                        if (Psetrun(P, 0, 0) == -1 && errno == EBUSY)
                                break; /* Agent LWP may be stuck */
                } while (Pstopstatus(P, PCNULL, 0) == 0 &&
                    P->status.pr_lwp.pr_flags & (PR_ISTOP|PR_DSTOP));

                if (P->status.pr_lwp.pr_flags & (PR_ISTOP|PR_DSTOP))
                        dprintf("Prelease: failed to set process running\n");
        }

        Pfree(P);
}

/* debugging */
void
prldump(const char *caller, lwpstatus_t *lsp)
{
        char name[32];
        uint32_t bits;

        switch (lsp->pr_why) {
        case PR_REQUESTED:
                dprintf("%s: REQUESTED\n", caller);
                break;
        case PR_SIGNALLED:
                dprintf("%s: SIGNALLED %s\n", caller,
                    proc_signame(lsp->pr_what, name, sizeof (name)));
                break;
        case PR_FAULTED:
                dprintf("%s: FAULTED %s\n", caller,
                    proc_fltname(lsp->pr_what, name, sizeof (name)));
                break;
        case PR_SYSENTRY:
                dprintf("%s: SYSENTRY %s\n", caller,
                    proc_sysname(lsp->pr_what, name, sizeof (name)));
                break;
        case PR_SYSEXIT:
                dprintf("%s: SYSEXIT %s\n", caller,
                    proc_sysname(lsp->pr_what, name, sizeof (name)));
                break;
        case PR_JOBCONTROL:
                dprintf("%s: JOBCONTROL %s\n", caller,
                    proc_signame(lsp->pr_what, name, sizeof (name)));
                break;
        case PR_SUSPENDED:
                dprintf("%s: SUSPENDED\n", caller);
                break;
        default:
                dprintf("%s: Unknown\n", caller);
                break;
        }

        if (lsp->pr_cursig)
                dprintf("%s: p_cursig  = %d\n", caller, lsp->pr_cursig);

        bits = *((uint32_t *)&lsp->pr_lwppend);
        if (bits)
                dprintf("%s: pr_lwppend = 0x%.8X\n", caller, bits);
}

/* debugging */
static void
prdump(struct ps_prochandle *P)
{
        uint32_t bits;

        prldump("Pstopstatus", &P->status.pr_lwp);

        bits = *((uint32_t *)&P->status.pr_sigpend);
        if (bits)
                dprintf("Pstopstatus: pr_sigpend = 0x%.8X\n", bits);
}

/*
 * Wait for the specified process to stop or terminate.
 * Or, just get the current status (PCNULL).
 * Or, direct it to stop and get the current status (PCDSTOP).
 * If the agent LWP exists, do these things to the agent,
 * else do these things to the process as a whole.
 */
int
Pstopstatus(struct ps_prochandle *P,
    long request,               /* PCNULL, PCDSTOP, PCSTOP, PCWSTOP */
    uint_t msec)                /* if non-zero, timeout in milliseconds */
{
        int ctlfd = (P->agentctlfd >= 0)? P->agentctlfd : P->ctlfd;
        long ctl[3];
        ssize_t rc;
        int err;
        int old_state = P->state;

        switch (P->state) {
        case PS_RUN:
                break;
        case PS_STOP:
                if (request != PCNULL && request != PCDSTOP)
                        return (0);
                break;
        case PS_LOST:
                if (request != PCNULL) {
                        errno = EAGAIN;
                        return (-1);
                }
                break;
        case PS_UNDEAD:
        case PS_DEAD:
        case PS_IDLE:
                if (request != PCNULL) {
                        errno = ENOENT;
                        return (-1);
                }
                break;
        default:        /* corrupted state */
                dprintf("Pstopstatus: corrupted state: %d\n", P->state);
                errno = EINVAL;
                return (-1);
        }

        ctl[0] = PCDSTOP;
        ctl[1] = PCTWSTOP;
        ctl[2] = (long)msec;
        rc = 0;
        switch (request) {
        case PCSTOP:
                rc = write(ctlfd, &ctl[0], 3*sizeof (long));
                break;
        case PCWSTOP:
                rc = write(ctlfd, &ctl[1], 2*sizeof (long));
                break;
        case PCDSTOP:
                rc = write(ctlfd, &ctl[0], 1*sizeof (long));
                break;
        case PCNULL:
                if (P->state == PS_DEAD || P->state == PS_IDLE)
                        return (0);
                break;
        default:        /* programming error */
                errno = EINVAL;
                return (-1);
        }
        err = (rc < 0)? errno : 0;
        Psync(P);

        if (P->agentstatfd < 0) {
                if (pread(P->statfd, &P->status,
                    sizeof (P->status), (off_t)0) < 0)
                        err = errno;
        } else {
                if (pread(P->agentstatfd, &P->status.pr_lwp,
                    sizeof (P->status.pr_lwp), (off_t)0) < 0)
                        err = errno;
                P->status.pr_flags = P->status.pr_lwp.pr_flags;
        }

        if (err) {
                switch (err) {
                case EINTR:             /* user typed ctl-C */
                case ERESTART:
                        dprintf("Pstopstatus: EINTR\n");
                        break;
                case EAGAIN:            /* we lost control of the the process */
                case EOVERFLOW:
                        dprintf("Pstopstatus: PS_LOST, errno=%d\n", err);
                        P->state = PS_LOST;
                        break;
                default:                /* check for dead process */
                        if (_libproc_debug) {
                                const char *errstr;

                                switch (request) {
                                case PCNULL:
                                        errstr = "Pstopstatus PCNULL"; break;
                                case PCSTOP:
                                        errstr = "Pstopstatus PCSTOP"; break;
                                case PCDSTOP:
                                        errstr = "Pstopstatus PCDSTOP"; break;
                                case PCWSTOP:
                                        errstr = "Pstopstatus PCWSTOP"; break;
                                default:
                                        errstr = "Pstopstatus PC???"; break;
                                }
                                dprintf("%s: %s\n", errstr, strerror(err));
                        }
                        deadcheck(P);
                        break;
                }
                if (err != EINTR && err != ERESTART) {
                        errno = err;
                        return (-1);
                }
        }

        if (!(P->status.pr_flags & PR_STOPPED)) {
                P->state = PS_RUN;
                if (request == PCNULL || request == PCDSTOP || msec != 0)
                        return (0);
                dprintf("Pstopstatus: process is not stopped\n");
                errno = EPROTO;
                return (-1);
        }

        P->state = PS_STOP;

        if (_libproc_debug)     /* debugging */
                prdump(P);

        /*
         * If the process was already stopped coming into Pstopstatus(),
         * then don't use its PC to set P->sysaddr since it may have been
         * changed since the time the process originally stopped.
         */
        if (old_state == PS_STOP)
                return (0);

        switch (P->status.pr_lwp.pr_why) {
        case PR_SYSENTRY:
        case PR_SYSEXIT:
                if (Pissyscall_prev(P, P->status.pr_lwp.pr_reg[R_PC],
                    &P->sysaddr) == 0)
                        P->sysaddr = P->status.pr_lwp.pr_reg[R_PC];
                break;
        case PR_REQUESTED:
        case PR_SIGNALLED:
        case PR_FAULTED:
        case PR_JOBCONTROL:
        case PR_SUSPENDED:
                break;
        default:
                errno = EPROTO;
                return (-1);
        }

        return (0);
}

/*
 * Wait for the process to stop for any reason.
 */
int
Pwait(struct ps_prochandle *P, uint_t msec)
{
        return (Pstopstatus(P, PCWSTOP, msec));
}

/*
 * Direct the process to stop; wait for it to stop.
 */
int
Pstop(struct ps_prochandle *P, uint_t msec)
{
        return (Pstopstatus(P, PCSTOP, msec));
}

/*
 * Direct the process to stop; don't wait.
 */
int
Pdstop(struct ps_prochandle *P)
{
        return (Pstopstatus(P, PCDSTOP, 0));
}

static void
deadcheck(struct ps_prochandle *P)
{
        int fd;
        void *buf;
        size_t size;

        if (P->statfd < 0)
                P->state = PS_UNDEAD;
        else {
                if (P->agentstatfd < 0) {
                        fd = P->statfd;
                        buf = &P->status;
                        size = sizeof (P->status);
                } else {
                        fd = P->agentstatfd;
                        buf = &P->status.pr_lwp;
                        size = sizeof (P->status.pr_lwp);
                }
                while (pread(fd, buf, size, (off_t)0) != size) {
                        switch (errno) {
                        default:
                                P->state = PS_UNDEAD;
                                break;
                        case EINTR:
                        case ERESTART:
                                continue;
                        case EAGAIN:
                                P->state = PS_LOST;
                                break;
                        }
                        break;
                }
                P->status.pr_flags = P->status.pr_lwp.pr_flags;
        }
}

/*
 * Get the value of one register from stopped process.
 */
int
Pgetareg(struct ps_prochandle *P, int regno, prgreg_t *preg)
{
        if (regno < 0 || regno >= NPRGREG) {
                errno = EINVAL;
                return (-1);
        }

        if (P->state == PS_IDLE) {
                errno = ENODATA;
                return (-1);
        }

        if (P->state != PS_STOP && P->state != PS_DEAD) {
                errno = EBUSY;
                return (-1);
        }

        *preg = P->status.pr_lwp.pr_reg[regno];
        return (0);
}

/*
 * Put value of one register into stopped process.
 */
int
Pputareg(struct ps_prochandle *P, int regno, prgreg_t reg)
{
        if (regno < 0 || regno >= NPRGREG) {
                errno = EINVAL;
                return (-1);
        }

        if (P->state != PS_STOP) {
                errno = EBUSY;
                return (-1);
        }

        P->status.pr_lwp.pr_reg[regno] = reg;
        P->flags |= SETREGS;    /* set registers before continuing */
        return (0);
}

int
Psetrun(struct ps_prochandle *P,
    int sig,    /* signal to pass to process */
    int flags)  /* PRSTEP|PRSABORT|PRSTOP|PRCSIG|PRCFAULT */
{
        int ctlfd = (P->agentctlfd >= 0) ? P->agentctlfd : P->ctlfd;
        int sbits = (PR_DSTOP | PR_ISTOP | PR_ASLEEP);

        long ctl[1 +                                    /* PCCFAULT     */
            1 + sizeof (siginfo_t)/sizeof (long) +      /* PCSSIG/PCCSIG */
            2 ];                                        /* PCRUN        */

        long *ctlp = ctl;
        size_t size;

        if (P->state != PS_STOP && (P->status.pr_lwp.pr_flags & sbits) == 0) {
                errno = EBUSY;
                return (-1);
        }

        Psync(P);       /* flush tracing flags and registers */

        if (flags & PRCFAULT) {         /* clear current fault */
                *ctlp++ = PCCFAULT;
                flags &= ~PRCFAULT;
        }

        if (flags & PRCSIG) {           /* clear current signal */
                *ctlp++ = PCCSIG;
                flags &= ~PRCSIG;
        } else if (sig && sig != P->status.pr_lwp.pr_cursig) {
                /* make current signal */
                siginfo_t *infop;

                *ctlp++ = PCSSIG;
                infop = (siginfo_t *)ctlp;
                (void) memset(infop, 0, sizeof (*infop));
                infop->si_signo = sig;
                ctlp += sizeof (siginfo_t) / sizeof (long);
        }

        *ctlp++ = PCRUN;
        *ctlp++ = flags;
        size = (char *)ctlp - (char *)ctl;

        P->info_valid = 0;      /* will need to update map and file info */

        /*
         * If we've cached ucontext-list information while we were stopped,
         * free it now.
         */
        if (P->ucaddrs != NULL) {
                free(P->ucaddrs);
                P->ucaddrs = NULL;
                P->ucnelems = 0;
        }

        if (write(ctlfd, ctl, size) != size) {
                /* If it is dead or lost, return the real status, not PS_RUN */
                if (errno == ENOENT || errno == EAGAIN) {
                        (void) Pstopstatus(P, PCNULL, 0);
                        return (0);
                }
                /* If it is not in a jobcontrol stop, issue an error message */
                if (errno != EBUSY ||
                    P->status.pr_lwp.pr_why != PR_JOBCONTROL) {
                        dprintf("Psetrun: %s\n", strerror(errno));
                        return (-1);
                }
                /* Otherwise pretend that the job-stopped process is running */
        }

        P->state = PS_RUN;
        return (0);
}

ssize_t
Pread(struct ps_prochandle *P,
    void *buf,          /* caller's buffer */
    size_t nbyte,       /* number of bytes to read */
    uintptr_t address)  /* address in process */
{
        return (P->ops.pop_pread(P, buf, nbyte, address, P->data));
}

ssize_t
Pread_string(struct ps_prochandle *P,
    char *buf,                  /* caller's buffer */
    size_t size,                /* upper limit on bytes to read */
    uintptr_t addr)             /* address in process */
{
        enum { STRSZ = 40 };
        char string[STRSZ + 1];
        ssize_t leng = 0;
        int nbyte;

        if (size < 2) {
                errno = EINVAL;
                return (-1);
        }

        size--;                 /* ensure trailing null fits in buffer */

        *buf = '\0';
        string[STRSZ] = '\0';

        for (nbyte = STRSZ; nbyte == STRSZ && leng < size; addr += STRSZ) {
                if ((nbyte = P->ops.pop_pread(P, string, STRSZ, addr,
                    P->data)) <= 0) {
                        buf[leng] = '\0';
                        return (leng ? leng : -1);
                }
                if ((nbyte = strlen(string)) > 0) {
                        if (leng + nbyte > size)
                                nbyte = size - leng;
                        (void) strncpy(buf + leng, string, nbyte);
                        leng += nbyte;
                }
        }
        buf[leng] = '\0';
        return (leng);
}

ssize_t
Pwrite(struct ps_prochandle *P,
    const void *buf,    /* caller's buffer */
    size_t nbyte,       /* number of bytes to write */
    uintptr_t address)  /* address in process */
{
        return (P->ops.pop_pwrite(P, buf, nbyte, address, P->data));
}

int
Pclearsig(struct ps_prochandle *P)
{
        int ctlfd = (P->agentctlfd >= 0)? P->agentctlfd : P->ctlfd;
        long ctl = PCCSIG;

        if (write(ctlfd, &ctl, sizeof (ctl)) != sizeof (ctl))
                return (-1);
        P->status.pr_lwp.pr_cursig = 0;
        return (0);
}

int
Pclearfault(struct ps_prochandle *P)
{
        int ctlfd = (P->agentctlfd >= 0)? P->agentctlfd : P->ctlfd;
        long ctl = PCCFAULT;

        if (write(ctlfd, &ctl, sizeof (ctl)) != sizeof (ctl))
                return (-1);
        return (0);
}

/*
 * Set a breakpoint trap, return original instruction.
 */
int
Psetbkpt(struct ps_prochandle *P, uintptr_t address, ulong_t *saved)
{
        long ctl[1 + sizeof (priovec_t) / sizeof (long) +       /* PCREAD */
            1 + sizeof (priovec_t) / sizeof (long)];    /* PCWRITE */
        long *ctlp = ctl;
        size_t size;
        priovec_t *iovp;
        instr_t bpt = BPT;
        instr_t old;

        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE) {
                errno = ENOENT;
                return (-1);
        }

        /* fetch the old instruction */
        *ctlp++ = PCREAD;
        iovp = (priovec_t *)ctlp;
        iovp->pio_base = &old;
        iovp->pio_len = sizeof (old);
        iovp->pio_offset = address;
        ctlp += sizeof (priovec_t) / sizeof (long);

        /* write the BPT instruction */
        *ctlp++ = PCWRITE;
        iovp = (priovec_t *)ctlp;
        iovp->pio_base = &bpt;
        iovp->pio_len = sizeof (bpt);
        iovp->pio_offset = address;
        ctlp += sizeof (priovec_t) / sizeof (long);

        size = (char *)ctlp - (char *)ctl;
        if (write(P->ctlfd, ctl, size) != size)
                return (-1);

        /*
         * Fail if there was already a breakpoint there from another debugger
         * or DTrace's user-level tracing on x86.
         */
        if (old == BPT) {
                errno = EBUSY;
                return (-1);
        }

        *saved = (ulong_t)old;
        return (0);
}

/*
 * Restore original instruction where a breakpoint was set.
 */
int
Pdelbkpt(struct ps_prochandle *P, uintptr_t address, ulong_t saved)
{
        instr_t old = (instr_t)saved;
        instr_t cur;

        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE) {
                errno = ENOENT;
                return (-1);
        }

        /*
         * If the breakpoint instruction we had placed has been overwritten
         * with a new instruction, then don't try to replace it with the
         * old instruction. Doing do can cause problems with self-modifying
         * code -- PLTs for example. If the Pread() fails, we assume that we
         * should proceed though most likely the Pwrite() will also fail.
         */
        if (Pread(P, &cur, sizeof (cur), address) == sizeof (cur) &&
            cur != BPT)
                return (0);

        if (Pwrite(P, &old, sizeof (old), address) != sizeof (old))
                return (-1);

        return (0);
}

/*
 * Common code for Pxecbkpt() and Lxecbkpt().
 * Develop the array of requests that will do the job, then
 * write them to the specified control file descriptor.
 * Return the non-zero errno if the write fails.
 */
static int
execute_bkpt(
        int ctlfd,              /* process or LWP control file descriptor */
        const fltset_t *faultset,       /* current set of traced faults */
        const sigset_t *sigmask,        /* current signal mask */
        uintptr_t address,              /* address of breakpint */
        ulong_t saved)                  /* the saved instruction */
{
        long ctl[
            1 + sizeof (sigset_t) / sizeof (long) +             /* PCSHOLD */
            1 + sizeof (fltset_t) / sizeof (long) +             /* PCSFAULT */
            1 + sizeof (priovec_t) / sizeof (long) +            /* PCWRITE */
            2 +                                                 /* PCRUN */
            1 +                                                 /* PCWSTOP */
            1 +                                                 /* PCCFAULT */
            1 + sizeof (priovec_t) / sizeof (long) +            /* PCWRITE */
            1 + sizeof (fltset_t) / sizeof (long) +             /* PCSFAULT */
            1 + sizeof (sigset_t) / sizeof (long)];             /* PCSHOLD */
        long *ctlp = ctl;
        sigset_t unblock;
        size_t size;
        ssize_t ssize;
        priovec_t *iovp;
        sigset_t *holdp;
        fltset_t *faultp;
        instr_t old = (instr_t)saved;
        instr_t bpt = BPT;
        int error = 0;

        /* block our signals for the duration */
        (void) sigprocmask(SIG_BLOCK, &blockable_sigs, &unblock);

        /* hold posted signals */
        *ctlp++ = PCSHOLD;
        holdp = (sigset_t *)ctlp;
        prfillset(holdp);
        prdelset(holdp, SIGKILL);
        prdelset(holdp, SIGSTOP);
        ctlp += sizeof (sigset_t) / sizeof (long);

        /* force tracing of FLTTRACE */
        if (!(prismember(faultset, FLTTRACE))) {
                *ctlp++ = PCSFAULT;
                faultp = (fltset_t *)ctlp;
                *faultp = *faultset;
                praddset(faultp, FLTTRACE);
                ctlp += sizeof (fltset_t) / sizeof (long);
        }

        /* restore the old instruction */
        *ctlp++ = PCWRITE;
        iovp = (priovec_t *)ctlp;
        iovp->pio_base = &old;
        iovp->pio_len = sizeof (old);
        iovp->pio_offset = address;
        ctlp += sizeof (priovec_t) / sizeof (long);

        /* clear current signal and fault; set running w/ single-step */
        *ctlp++ = PCRUN;
        *ctlp++ = PRCSIG | PRCFAULT | PRSTEP;

        /* wait for stop, cancel the fault */
        *ctlp++ = PCWSTOP;
        *ctlp++ = PCCFAULT;

        /* restore the breakpoint trap */
        *ctlp++ = PCWRITE;
        iovp = (priovec_t *)ctlp;
        iovp->pio_base = &bpt;
        iovp->pio_len = sizeof (bpt);
        iovp->pio_offset = address;
        ctlp += sizeof (priovec_t) / sizeof (long);

        /* restore fault tracing set */
        if (!(prismember(faultset, FLTTRACE))) {
                *ctlp++ = PCSFAULT;
                *(fltset_t *)ctlp = *faultset;
                ctlp += sizeof (fltset_t) / sizeof (long);
        }

        /* restore the hold mask */
        *ctlp++ = PCSHOLD;
        *(sigset_t *)ctlp = *sigmask;
        ctlp += sizeof (sigset_t) / sizeof (long);

        size = (char *)ctlp - (char *)ctl;
        if ((ssize = write(ctlfd, ctl, size)) != size)
                error = (ssize == -1)? errno : EINTR;
        (void) sigprocmask(SIG_SETMASK, &unblock, NULL);
        return (error);
}

/*
 * Step over a breakpoint, i.e., execute the instruction that
 * really belongs at the breakpoint location (the current %pc)
 * and leave the process stopped at the next instruction.
 */
int
Pxecbkpt(struct ps_prochandle *P, ulong_t saved)
{
        int ctlfd = (P->agentctlfd >= 0)? P->agentctlfd : P->ctlfd;
        int rv, error;

        if (P->state != PS_STOP) {
                errno = EBUSY;
                return (-1);
        }

        Psync(P);

        error = execute_bkpt(ctlfd,
            &P->status.pr_flttrace, &P->status.pr_lwp.pr_lwphold,
            P->status.pr_lwp.pr_reg[R_PC], saved);
        rv = Pstopstatus(P, PCNULL, 0);

        if (error != 0) {
                if (P->status.pr_lwp.pr_why == PR_JOBCONTROL &&
                    error == EBUSY) {   /* jobcontrol stop -- back off */
                        P->state = PS_RUN;
                        return (0);
                }
                if (error == ENOENT)
                        return (0);
                errno = error;
                return (-1);
        }

        return (rv);
}

/*
 * Install the watchpoint described by wp.
 */
int
Psetwapt(struct ps_prochandle *P, const prwatch_t *wp)
{
        long ctl[1 + sizeof (prwatch_t) / sizeof (long)];
        prwatch_t *cwp = (prwatch_t *)&ctl[1];

        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE) {
                errno = ENOENT;
                return (-1);
        }

        ctl[0] = PCWATCH;
        cwp->pr_vaddr = wp->pr_vaddr;
        cwp->pr_size = wp->pr_size;
        cwp->pr_wflags = wp->pr_wflags;

        if (write(P->ctlfd, ctl, sizeof (ctl)) != sizeof (ctl))
                return (-1);

        return (0);
}

/*
 * Remove the watchpoint described by wp.
 */
int
Pdelwapt(struct ps_prochandle *P, const prwatch_t *wp)
{
        long ctl[1 + sizeof (prwatch_t) / sizeof (long)];
        prwatch_t *cwp = (prwatch_t *)&ctl[1];

        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE) {
                errno = ENOENT;
                return (-1);
        }

        ctl[0] = PCWATCH;
        cwp->pr_vaddr = wp->pr_vaddr;
        cwp->pr_size = wp->pr_size;
        cwp->pr_wflags = 0;

        if (write(P->ctlfd, ctl, sizeof (ctl)) != sizeof (ctl))
                return (-1);

        return (0);
}

/*
 * Common code for Pxecwapt() and Lxecwapt().  Develop the array of requests
 * that will do the job, then write them to the specified control file
 * descriptor.  Return the non-zero errno if the write fails.
 */
static int
execute_wapt(
        int ctlfd,              /* process or LWP control file descriptor */
        const fltset_t *faultset,       /* current set of traced faults */
        const sigset_t *sigmask,        /* current signal mask */
        const prwatch_t *wp)            /* watchpoint descriptor */
{
        long ctl[
            1 + sizeof (sigset_t) / sizeof (long) +             /* PCSHOLD */
            1 + sizeof (fltset_t) / sizeof (long) +             /* PCSFAULT */
            1 + sizeof (prwatch_t) / sizeof (long) +            /* PCWATCH */
            2 +                                                 /* PCRUN */
            1 +                                                 /* PCWSTOP */
            1 +                                                 /* PCCFAULT */
            1 + sizeof (prwatch_t) / sizeof (long) +            /* PCWATCH */
            1 + sizeof (fltset_t) / sizeof (long) +             /* PCSFAULT */
            1 + sizeof (sigset_t) / sizeof (long)];             /* PCSHOLD */

        long *ctlp = ctl;
        int error = 0;

        sigset_t unblock;
        sigset_t *holdp;
        fltset_t *faultp;
        prwatch_t *prw;
        ssize_t ssize;
        size_t size;

        (void) sigprocmask(SIG_BLOCK, &blockable_sigs, &unblock);

        /*
         * Hold all posted signals in the victim process prior to stepping.
         */
        *ctlp++ = PCSHOLD;
        holdp = (sigset_t *)ctlp;
        prfillset(holdp);
        prdelset(holdp, SIGKILL);
        prdelset(holdp, SIGSTOP);
        ctlp += sizeof (sigset_t) / sizeof (long);

        /*
         * Force tracing of FLTTRACE since we need to single step.
         */
        if (!(prismember(faultset, FLTTRACE))) {
                *ctlp++ = PCSFAULT;
                faultp = (fltset_t *)ctlp;
                *faultp = *faultset;
                praddset(faultp, FLTTRACE);
                ctlp += sizeof (fltset_t) / sizeof (long);
        }

        /*
         * Clear only the current watchpoint by setting pr_wflags to zero.
         */
        *ctlp++ = PCWATCH;
        prw = (prwatch_t *)ctlp;
        prw->pr_vaddr = wp->pr_vaddr;
        prw->pr_size = wp->pr_size;
        prw->pr_wflags = 0;
        ctlp += sizeof (prwatch_t) / sizeof (long);

        /*
         * Clear the current signal and fault; set running with single-step.
         * Then wait for the victim to stop and cancel the FLTTRACE.
         */
        *ctlp++ = PCRUN;
        *ctlp++ = PRCSIG | PRCFAULT | PRSTEP;
        *ctlp++ = PCWSTOP;
        *ctlp++ = PCCFAULT;

        /*
         * Restore the current watchpoint.
         */
        *ctlp++ = PCWATCH;
        (void) memcpy(ctlp, wp, sizeof (prwatch_t));
        ctlp += sizeof (prwatch_t) / sizeof (long);

        /*
         * Restore fault tracing set if we modified it.
         */
        if (!(prismember(faultset, FLTTRACE))) {
                *ctlp++ = PCSFAULT;
                *(fltset_t *)ctlp = *faultset;
                ctlp += sizeof (fltset_t) / sizeof (long);
        }

        /*
         * Restore the hold mask to the current hold mask (i.e. the one
         * before we executed any of the previous operations).
         */
        *ctlp++ = PCSHOLD;
        *(sigset_t *)ctlp = *sigmask;
        ctlp += sizeof (sigset_t) / sizeof (long);

        size = (char *)ctlp - (char *)ctl;
        if ((ssize = write(ctlfd, ctl, size)) != size)
                error = (ssize == -1)? errno : EINTR;
        (void) sigprocmask(SIG_SETMASK, &unblock, NULL);
        return (error);
}

/*
 * Step over a watchpoint, i.e., execute the instruction that was stopped by
 * the watchpoint, and then leave the LWP stopped at the next instruction.
 */
int
Pxecwapt(struct ps_prochandle *P, const prwatch_t *wp)
{
        int ctlfd = (P->agentctlfd >= 0)? P->agentctlfd : P->ctlfd;
        int rv, error;

        if (P->state != PS_STOP) {
                errno = EBUSY;
                return (-1);
        }

        Psync(P);
        error = execute_wapt(ctlfd,
            &P->status.pr_flttrace, &P->status.pr_lwp.pr_lwphold, wp);
        rv = Pstopstatus(P, PCNULL, 0);

        if (error != 0) {
                if (P->status.pr_lwp.pr_why == PR_JOBCONTROL &&
                    error == EBUSY) {   /* jobcontrol stop -- back off */
                        P->state = PS_RUN;
                        return (0);
                }
                if (error == ENOENT)
                        return (0);
                errno = error;
                return (-1);
        }

        return (rv);
}

int
Psetflags(struct ps_prochandle *P, long flags)
{
        int rc;
        long ctl[2];

        ctl[0] = PCSET;
        ctl[1] = flags;

        if (write(P->ctlfd, ctl, 2*sizeof (long)) != 2*sizeof (long)) {
                rc = -1;
        } else {
                P->status.pr_flags |= flags;
                P->status.pr_lwp.pr_flags |= flags;
                rc = 0;
        }

        return (rc);
}

int
Punsetflags(struct ps_prochandle *P, long flags)
{
        int rc;
        long ctl[2];

        ctl[0] = PCUNSET;
        ctl[1] = flags;

        if (write(P->ctlfd, ctl, 2*sizeof (long)) != 2*sizeof (long)) {
                rc = -1;
        } else {
                P->status.pr_flags &= ~flags;
                P->status.pr_lwp.pr_flags &= ~flags;
                rc = 0;
        }

        return (rc);
}

/*
 * Common function to allow clients to manipulate the action to be taken
 * on receipt of a signal, receipt of machine fault, entry to a system call,
 * or exit from a system call.  We make use of our private prset_* functions
 * in order to make this code be common.  The 'which' parameter identifies
 * the code for the event of interest (0 means change the entire set), and
 * the 'stop' parameter is a boolean indicating whether the process should
 * stop when the event of interest occurs.  The previous value is returned
 * to the caller; -1 is returned if an error occurred.
 */
static int
Psetaction(struct ps_prochandle *P, void *sp, size_t size,
    uint_t flag, int max, int which, int stop)
{
        int oldval;

        if (which < 0 || which > max) {
                errno = EINVAL;
                return (-1);
        }

        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE) {
                errno = ENOENT;
                return (-1);
        }

        oldval = prset_ismember(sp, size, which) ? TRUE : FALSE;

        if (stop) {
                if (which == 0) {
                        prset_fill(sp, size);
                        P->flags |= flag;
                } else if (!oldval) {
                        prset_add(sp, size, which);
                        P->flags |= flag;
                }
        } else {
                if (which == 0) {
                        prset_empty(sp, size);
                        P->flags |= flag;
                } else if (oldval) {
                        prset_del(sp, size, which);
                        P->flags |= flag;
                }
        }

        if (P->state == PS_RUN)
                Psync(P);

        return (oldval);
}

/*
 * Set action on specified signal.
 */
int
Psignal(struct ps_prochandle *P, int which, int stop)
{
        int oldval;

        if (which == SIGKILL && stop != 0) {
                errno = EINVAL;
                return (-1);
        }

        oldval = Psetaction(P, &P->status.pr_sigtrace, sizeof (sigset_t),
            SETSIG, PRMAXSIG, which, stop);

        if (oldval != -1 && which == 0 && stop != 0)
                prdelset(&P->status.pr_sigtrace, SIGKILL);

        return (oldval);
}

/*
 * Set all signal tracing flags.
 */
void
Psetsignal(struct ps_prochandle *P, const sigset_t *set)
{
        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE)
                return;

        P->status.pr_sigtrace = *set;
        P->flags |= SETSIG;

        if (P->state == PS_RUN)
                Psync(P);
}

/*
 * Set action on specified fault.
 */
int
Pfault(struct ps_prochandle *P, int which, int stop)
{
        return (Psetaction(P, &P->status.pr_flttrace, sizeof (fltset_t),
            SETFAULT, PRMAXFAULT, which, stop));
}

/*
 * Set all machine fault tracing flags.
 */
void
Psetfault(struct ps_prochandle *P, const fltset_t *set)
{
        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE)
                return;

        P->status.pr_flttrace = *set;
        P->flags |= SETFAULT;

        if (P->state == PS_RUN)
                Psync(P);
}

/*
 * Set action on specified system call entry.
 */
int
Psysentry(struct ps_prochandle *P, int which, int stop)
{
        return (Psetaction(P, &P->status.pr_sysentry, sizeof (sysset_t),
            SETENTRY, PRMAXSYS, which, stop));
}

/*
 * Set all system call entry tracing flags.
 */
void
Psetsysentry(struct ps_prochandle *P, const sysset_t *set)
{
        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE)
                return;

        P->status.pr_sysentry = *set;
        P->flags |= SETENTRY;

        if (P->state == PS_RUN)
                Psync(P);
}

/*
 * Set action on specified system call exit.
 */
int
Psysexit(struct ps_prochandle *P, int which, int stop)
{
        return (Psetaction(P, &P->status.pr_sysexit, sizeof (sysset_t),
            SETEXIT, PRMAXSYS, which, stop));
}

/*
 * Set all system call exit tracing flags.
 */
void
Psetsysexit(struct ps_prochandle *P, const sysset_t *set)
{
        if (P->state == PS_DEAD || P->state == PS_UNDEAD ||
            P->state == PS_IDLE)
                return;

        P->status.pr_sysexit = *set;
        P->flags |= SETEXIT;

        if (P->state == PS_RUN)
                Psync(P);
}

/*
 * Utility function to read the contents of a file that contains a
 * prheader_t at the start (/proc/pid/lstatus or /proc/pid/lpsinfo).
 * Returns a malloc()d buffer or NULL on failure.
 */
static prheader_t *
read_lfile(struct ps_prochandle *P, const char *lname)
{
        prheader_t *Lhp;
        char lpath[PATH_MAX];
        struct stat64 statb;
        int fd;
        size_t size;
        ssize_t rval;

        (void) snprintf(lpath, sizeof (lpath), "%s/%d/%s", procfs_path,
            (int)P->status.pr_pid, lname);
        if ((fd = open(lpath, O_RDONLY)) < 0 || fstat64(fd, &statb) != 0) {
                if (fd >= 0)
                        (void) close(fd);
                return (NULL);
        }

        /*
         * 'size' is just the initial guess at the buffer size.
         * It will have to grow if the number of lwps increases
         * while we are looking at the process.
         * 'size' must be larger than the actual file size.
         */
        size = statb.st_size + 32;

        for (;;) {
                if ((Lhp = malloc(size)) == NULL)
                        break;
                if ((rval = pread(fd, Lhp, size, 0)) < 0 ||
                    rval <= sizeof (prheader_t)) {
                        free(Lhp);
                        Lhp = NULL;
                        break;
                }
                if (rval < size)
                        break;
                /* need a bigger buffer */
                free(Lhp);
                size *= 2;
        }

        (void) close(fd);
        return (Lhp);
}

/*
 * LWP iteration interface.
 */
int
Plwp_iter(struct ps_prochandle *P, proc_lwp_f *func, void *cd)
{
        prheader_t *Lhp;
        lwpstatus_t *Lsp;
        long nlwp;
        int rv;

        switch (P->state) {
        case PS_RUN:
                (void) Pstopstatus(P, PCNULL, 0);
                break;

        case PS_STOP:
                Psync(P);
                break;

        case PS_IDLE:
                errno = ENODATA;
                return (-1);
        }

        /*
         * For either live processes or cores, the single LWP case is easy:
         * the pstatus_t contains the lwpstatus_t for the only LWP.
         */
        if (P->status.pr_nlwp <= 1)
                return (func(cd, &P->status.pr_lwp));

        /*
         * For the core file multi-LWP case, we just iterate through the
         * list of LWP structs we read in from the core file.
         */
        if (P->state == PS_DEAD) {
                core_info_t *core = P->data;
                lwp_info_t *lwp = list_prev(&core->core_lwp_head);
                uint_t i;

                for (i = 0; i < core->core_nlwp; i++, lwp = list_prev(lwp)) {
                        if (lwp->lwp_psinfo.pr_sname != 'Z' &&
                            (rv = func(cd, &lwp->lwp_status)) != 0)
                                break;
                }

                return (rv);
        }

        /*
         * For the live process multi-LWP case, we have to work a little
         * harder: the /proc/pid/lstatus file has the array of LWP structs.
         */
        if ((Lhp = Plstatus(P)) == NULL)
                return (-1);

        for (nlwp = Lhp->pr_nent, Lsp = (lwpstatus_t *)(uintptr_t)(Lhp + 1);
            nlwp > 0;
            nlwp--, Lsp = (lwpstatus_t *)((uintptr_t)Lsp + Lhp->pr_entsize)) {
                if ((rv = func(cd, Lsp)) != 0)
                        break;
        }

        free(Lhp);
        return (rv);
}

/*
 * Extended LWP iteration interface.
 * Iterate over all LWPs, active and zombie.
 */
int
Plwp_iter_all(struct ps_prochandle *P, proc_lwp_all_f *func, void *cd)
{
        prheader_t *Lhp = NULL;
        lwpstatus_t *Lsp;
        lwpstatus_t *sp;
        prheader_t *Lphp = NULL;
        lwpsinfo_t *Lpsp;
        long nstat;
        long ninfo;
        int rv;

retry:
        free(Lhp);
        free(Lphp);
        if (P->state == PS_RUN)
                (void) Pstopstatus(P, PCNULL, 0);
        (void) Ppsinfo(P);

        if (P->state == PS_STOP)
                Psync(P);

        /*
         * For either live processes or cores, the single LWP case is easy:
         * the pstatus_t contains the lwpstatus_t for the only LWP and
         * the psinfo_t contains the lwpsinfo_t for the only LWP.
         */
        if (P->status.pr_nlwp + P->status.pr_nzomb <= 1)
                return (func(cd, &P->status.pr_lwp, &P->psinfo.pr_lwp));

        /*
         * For the core file multi-LWP case, we just iterate through the
         * list of LWP structs we read in from the core file.
         */
        if (P->state == PS_DEAD) {
                core_info_t *core = P->data;
                lwp_info_t *lwp = list_prev(&core->core_lwp_head);
                uint_t i;

                for (i = 0; i < core->core_nlwp; i++, lwp = list_prev(lwp)) {
                        sp = (lwp->lwp_psinfo.pr_sname == 'Z')? NULL :
                            &lwp->lwp_status;
                        if ((rv = func(cd, sp, &lwp->lwp_psinfo)) != 0)
                                break;
                }

                return (rv);
        }

        /*
         * For all other cases retrieve the array of lwpstatus_t's and
         * lwpsinfo_t's.
         */
        if ((Lhp = Plstatus(P)) == NULL)
                return (-1);
        if ((Lphp = Plpsinfo(P)) == NULL) {
                free(Lhp);
                return (-1);
        }

        /*
         * If we are looking at a running process, or one we do not control,
         * the active and zombie lwps in the process may have changed since
         * we read the process status structure.  If so, just start over.
         */
        if (Lhp->pr_nent != P->status.pr_nlwp ||
            Lphp->pr_nent != P->status.pr_nlwp + P->status.pr_nzomb)
                goto retry;

        /*
         * To be perfectly safe, prescan the two arrays, checking consistency.
         * We rely on /proc giving us lwpstatus_t's and lwpsinfo_t's in the
         * same order (the lwp directory order) in their respective files.
         * We also rely on there being (possibly) more lwpsinfo_t's than
         * lwpstatus_t's (the extra lwpsinfo_t's are for zombie lwps).
         */
        Lsp = (lwpstatus_t *)(uintptr_t)(Lhp + 1);
        Lpsp = (lwpsinfo_t *)(uintptr_t)(Lphp + 1);
        nstat = Lhp->pr_nent;
        for (ninfo = Lphp->pr_nent; ninfo != 0; ninfo--) {
                if (Lpsp->pr_sname != 'Z') {
                        /*
                         * Not a zombie lwp; check for matching lwpids.
                         */
                        if (nstat == 0 || Lsp->pr_lwpid != Lpsp->pr_lwpid)
                                goto retry;
                        Lsp = (lwpstatus_t *)((uintptr_t)Lsp + Lhp->pr_entsize);
                        nstat--;
                }
                Lpsp = (lwpsinfo_t *)((uintptr_t)Lpsp + Lphp->pr_entsize);
        }
        if (nstat != 0)
                goto retry;

        /*
         * Rescan, this time for real.
         */
        Lsp = (lwpstatus_t *)(uintptr_t)(Lhp + 1);
        Lpsp = (lwpsinfo_t *)(uintptr_t)(Lphp + 1);
        for (ninfo = Lphp->pr_nent; ninfo != 0; ninfo--) {
                if (Lpsp->pr_sname != 'Z') {
                        sp = Lsp;
                        Lsp = (lwpstatus_t *)((uintptr_t)Lsp + Lhp->pr_entsize);
                } else {
                        sp = NULL;
                }
                if ((rv = func(cd, sp, Lpsp)) != 0)
                        break;
                Lpsp = (lwpsinfo_t *)((uintptr_t)Lpsp + Lphp->pr_entsize);
        }

        free(Lhp);
        free(Lphp);
        return (rv);
}

core_content_t
Pcontent(struct ps_prochandle *P)
{
        core_info_t *core = P->data;

        if (P->state == PS_DEAD)
                return (core->core_content);
        if (P->state == PS_IDLE)
                return (CC_CONTENT_TEXT | CC_CONTENT_DATA | CC_CONTENT_CTF);

        return (CC_CONTENT_ALL);
}

/*
 * =================================================================
 * The remainder of the functions in this file are for the
 * control of individual LWPs in the controlled process.
 * =================================================================
 */

/*
 * Find an entry in the process hash table for the specified lwpid.
 * The entry will either point to an existing struct ps_lwphandle
 * or it will point to an empty slot for a new struct ps_lwphandle.
 */
static struct ps_lwphandle **
Lfind(struct ps_prochandle *P, lwpid_t lwpid)
{
        struct ps_lwphandle **Lp;
        struct ps_lwphandle *L;

        for (Lp = &P->hashtab[lwpid % (HASHSIZE - 1)];
            (L = *Lp) != NULL; Lp = &L->lwp_hash)
                if (L->lwp_id == lwpid)
                        break;
        return (Lp);
}

/*
 * Grab an LWP contained within the controlled process.
 * Return an opaque pointer to its LWP control structure.
 *      perr: pointer to error return code.
 */
struct ps_lwphandle *
Lgrab(struct ps_prochandle *P, lwpid_t lwpid, int *perr)
{
        struct ps_lwphandle **Lp;
        struct ps_lwphandle *L;
        int fd;
        char procname[PATH_MAX];
        char *fname;
        int rc = 0;

        (void) mutex_lock(&P->proc_lock);

        if (P->state == PS_UNDEAD || P->state == PS_IDLE)
                rc = G_NOPROC;
        else if (P->hashtab == NULL &&
            (P->hashtab = calloc(HASHSIZE, sizeof (struct ps_lwphandle *)))
            == NULL)
                rc = G_STRANGE;
        else if (*(Lp = Lfind(P, lwpid)) != NULL)
                rc = G_BUSY;
        else if ((L = malloc(sizeof (struct ps_lwphandle))) == NULL)
                rc = G_STRANGE;
        if (rc) {
                *perr = rc;
                (void) mutex_unlock(&P->proc_lock);
                return (NULL);
        }

        (void) memset(L, 0, sizeof (*L));
        L->lwp_ctlfd = -1;
        L->lwp_statfd = -1;
        L->lwp_proc = P;
        L->lwp_id = lwpid;
        *Lp = L;        /* insert into the hash table */

        if (P->state == PS_DEAD) {      /* core file */
                if (getlwpstatus(P, lwpid, &L->lwp_status) == -1) {
                        rc = G_NOPROC;
                        goto err;
                }
                L->lwp_state = PS_DEAD;
                *perr = 0;
                (void) mutex_unlock(&P->proc_lock);
                return (L);
        }

        /*
         * Open the /proc/<pid>/lwp/<lwpid> files
         */
        (void) snprintf(procname, sizeof (procname), "%s/%d/lwp/%d/",
            procfs_path, (int)P->pid, (int)lwpid);
        fname = procname + strlen(procname);
        (void) set_minfd();

        (void) strcpy(fname, "lwpstatus");
        if ((fd = open(procname, O_RDONLY)) < 0 ||
            (fd = dupfd(fd, 0)) < 0) {
                switch (errno) {
                case ENOENT:
                        rc = G_NOPROC;
                        break;
                default:
                        dprintf("Lgrab: failed to open %s: %s\n",
                            procname, strerror(errno));
                        rc = G_STRANGE;
                        break;
                }
                goto err;
        }
        L->lwp_statfd = fd;

        if (pread(fd, &L->lwp_status, sizeof (L->lwp_status), (off_t)0) < 0) {
                switch (errno) {
                case ENOENT:
                        rc = G_NOPROC;
                        break;
                default:
                        dprintf("Lgrab: failed to read %s: %s\n",
                            procname, strerror(errno));
                        rc = G_STRANGE;
                        break;
                }
                goto err;
        }

        (void) strcpy(fname, "lwpctl");
        if ((fd = open(procname, O_WRONLY)) < 0 ||
            (fd = dupfd(fd, 0)) < 0) {
                switch (errno) {
                case ENOENT:
                        rc = G_NOPROC;
                        break;
                default:
                        dprintf("Lgrab: failed to open %s: %s\n",
                            procname, strerror(errno));
                        rc = G_STRANGE;
                        break;
                }
                goto err;
        }
        L->lwp_ctlfd = fd;

        L->lwp_state =
            ((L->lwp_status.pr_flags & (PR_STOPPED|PR_ISTOP))
            == (PR_STOPPED|PR_ISTOP))?
            PS_STOP : PS_RUN;

        *perr = 0;
        (void) mutex_unlock(&P->proc_lock);
        return (L);

err:
        Lfree_internal(P, L);
        *perr = rc;
        (void) mutex_unlock(&P->proc_lock);
        return (NULL);
}

/*
 * Return a printable string corresponding to an Lgrab() error return.
 */
const char *
Lgrab_error(int error)
{
        const char *str;

        switch (error) {
        case G_NOPROC:
                str = "no such LWP";
                break;
        case G_BUSY:
                str = "LWP already grabbed";
                break;
        case G_STRANGE:
                str = "unanticipated system error";
                break;
        default:
                str = "unknown error";
                break;
        }

        return (str);
}

/*
 * Free an LWP control structure.
 */
void
Lfree(struct ps_lwphandle *L)
{
        struct ps_prochandle *P = L->lwp_proc;

        (void) mutex_lock(&P->proc_lock);
        Lfree_internal(P, L);
        (void) mutex_unlock(&P->proc_lock);
}

static void
Lfree_internal(struct ps_prochandle *P, struct ps_lwphandle *L)
{
        *Lfind(P, L->lwp_id) = L->lwp_hash;     /* delete from hash table */
        if (L->lwp_ctlfd >= 0)
                (void) close(L->lwp_ctlfd);
        if (L->lwp_statfd >= 0)
                (void) close(L->lwp_statfd);

        /* clear out the structure as a precaution against reuse */
        (void) memset(L, 0, sizeof (*L));
        L->lwp_ctlfd = -1;
        L->lwp_statfd = -1;

        free(L);
}

/*
 * Return the state of the process, one of the PS_* values.
 */
int
Lstate(struct ps_lwphandle *L)
{
        return (L->lwp_state);
}

/*
 * Return the open control file descriptor for the LWP.
 * Clients must not close this file descriptor, nor use it
 * after the LWP is freed.
 */
int
Lctlfd(struct ps_lwphandle *L)
{
        return (L->lwp_ctlfd);
}

/*
 * Return a pointer to the LWP lwpsinfo structure.
 * Clients should not hold on to this pointer indefinitely.
 * It will become invalid on Lfree().
 */
const lwpsinfo_t *
Lpsinfo(struct ps_lwphandle *L)
{
        if (Plwp_getpsinfo(L->lwp_proc, L->lwp_id, &L->lwp_psinfo) == -1)
                return (NULL);

        return (&L->lwp_psinfo);
}

/*
 * Return a pointer to the LWP status structure.
 * Clients should not hold on to this pointer indefinitely.
 * It will become invalid on Lfree().
 */
const lwpstatus_t *
Lstatus(struct ps_lwphandle *L)
{
        return (&L->lwp_status);
}

/*
 * Given an LWP handle, return the process handle.
 */
struct ps_prochandle *
Lprochandle(struct ps_lwphandle *L)
{
        return (L->lwp_proc);
}

/*
 * Ensure that all cached state is written to the LWP.
 * The cached state is the LWP's signal mask and registers.
 */
void
Lsync(struct ps_lwphandle *L)
{
        int ctlfd = L->lwp_ctlfd;
        long cmd[2];
        iovec_t iov[4];
        int n = 0;

        if (L->lwp_flags & SETHOLD) {
                cmd[0] = PCSHOLD;
                iov[n].iov_base = (caddr_t)&cmd[0];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&L->lwp_status.pr_lwphold;
                iov[n++].iov_len = sizeof (L->lwp_status.pr_lwphold);
        }
        if (L->lwp_flags & SETREGS) {
                cmd[1] = PCSREG;
                iov[n].iov_base = (caddr_t)&cmd[1];
                iov[n++].iov_len = sizeof (long);
                iov[n].iov_base = (caddr_t)&L->lwp_status.pr_reg[0];
                iov[n++].iov_len = sizeof (L->lwp_status.pr_reg);
        }

        if (n == 0 || writev(ctlfd, iov, n) < 0)
                return;         /* nothing to do or write failed */

        L->lwp_flags &= ~(SETHOLD|SETREGS);
}

/*
 * Wait for the specified LWP to stop or terminate.
 * Or, just get the current status (PCNULL).
 * Or, direct it to stop and get the current status (PCDSTOP).
 */
static int
Lstopstatus(struct ps_lwphandle *L,
    long request,               /* PCNULL, PCDSTOP, PCSTOP, PCWSTOP */
    uint_t msec)                /* if non-zero, timeout in milliseconds */
{
        int ctlfd = L->lwp_ctlfd;
        long ctl[3];
        ssize_t rc;
        int err;

        switch (L->lwp_state) {
        case PS_RUN:
                break;
        case PS_STOP:
                if (request != PCNULL && request != PCDSTOP)
                        return (0);
                break;
        case PS_LOST:
                if (request != PCNULL) {
                        errno = EAGAIN;
                        return (-1);
                }
                break;
        case PS_UNDEAD:
        case PS_DEAD:
                if (request != PCNULL) {
                        errno = ENOENT;
                        return (-1);
                }
                break;
        default:        /* corrupted state */
                dprintf("Lstopstatus: corrupted state: %d\n", L->lwp_state);
                errno = EINVAL;
                return (-1);
        }

        ctl[0] = PCDSTOP;
        ctl[1] = PCTWSTOP;
        ctl[2] = (long)msec;
        rc = 0;
        switch (request) {
        case PCSTOP:
                rc = write(ctlfd, &ctl[0], 3*sizeof (long));
                break;
        case PCWSTOP:
                rc = write(ctlfd, &ctl[1], 2*sizeof (long));
                break;
        case PCDSTOP:
                rc = write(ctlfd, &ctl[0], 1*sizeof (long));
                break;
        case PCNULL:
                if (L->lwp_state == PS_DEAD)
                        return (0); /* Nothing else to do for cores */
                break;
        default:        /* programming error */
                errno = EINVAL;
                return (-1);
        }
        err = (rc < 0)? errno : 0;
        Lsync(L);

        if (pread(L->lwp_statfd, &L->lwp_status,
            sizeof (L->lwp_status), (off_t)0) < 0)
                err = errno;

        if (err) {
                switch (err) {
                case EINTR:             /* user typed ctl-C */
                case ERESTART:
                        dprintf("Lstopstatus: EINTR\n");
                        break;
                case EAGAIN:            /* we lost control of the the process */
                        dprintf("Lstopstatus: EAGAIN\n");
                        L->lwp_state = PS_LOST;
                        errno = err;
                        return (-1);
                default:
                        if (_libproc_debug) {
                                const char *errstr;

                                switch (request) {
                                case PCNULL:
                                        errstr = "Lstopstatus PCNULL"; break;
                                case PCSTOP:
                                        errstr = "Lstopstatus PCSTOP"; break;
                                case PCDSTOP:
                                        errstr = "Lstopstatus PCDSTOP"; break;
                                case PCWSTOP:
                                        errstr = "Lstopstatus PCWSTOP"; break;
                                default:
                                        errstr = "Lstopstatus PC???"; break;
                                }
                                dprintf("%s: %s\n", errstr, strerror(err));
                        }
                        L->lwp_state = PS_UNDEAD;
                        errno = err;
                        return (-1);
                }
        }

        if ((L->lwp_status.pr_flags & (PR_STOPPED|PR_ISTOP))
            != (PR_STOPPED|PR_ISTOP)) {
                L->lwp_state = PS_RUN;
                if (request == PCNULL || request == PCDSTOP || msec != 0)
                        return (0);
                dprintf("Lstopstatus: LWP is not stopped\n");
                errno = EPROTO;
                return (-1);
        }

        L->lwp_state = PS_STOP;

        if (_libproc_debug)     /* debugging */
                prldump("Lstopstatus", &L->lwp_status);

        switch (L->lwp_status.pr_why) {
        case PR_SYSENTRY:
        case PR_SYSEXIT:
        case PR_REQUESTED:
        case PR_SIGNALLED:
        case PR_FAULTED:
        case PR_JOBCONTROL:
        case PR_SUSPENDED:
                break;
        default:
                errno = EPROTO;
                return (-1);
        }

        return (0);
}

/*
 * Wait for the LWP to stop for any reason.
 */
int
Lwait(struct ps_lwphandle *L, uint_t msec)
{
        return (Lstopstatus(L, PCWSTOP, msec));
}

/*
 * Direct the LWP to stop; wait for it to stop.
 */
int
Lstop(struct ps_lwphandle *L, uint_t msec)
{
        return (Lstopstatus(L, PCSTOP, msec));
}

/*
 * Direct the LWP to stop; don't wait.
 */
int
Ldstop(struct ps_lwphandle *L)
{
        return (Lstopstatus(L, PCDSTOP, 0));
}

/*
 * Get the value of one register from stopped LWP.
 */
int
Lgetareg(struct ps_lwphandle *L, int regno, prgreg_t *preg)
{
        if (regno < 0 || regno >= NPRGREG) {
                errno = EINVAL;
                return (-1);
        }

        if (L->lwp_state != PS_STOP) {
                errno = EBUSY;
                return (-1);
        }

        *preg = L->lwp_status.pr_reg[regno];
        return (0);
}

/*
 * Put value of one register into stopped LWP.
 */
int
Lputareg(struct ps_lwphandle *L, int regno, prgreg_t reg)
{
        if (regno < 0 || regno >= NPRGREG) {
                errno = EINVAL;
                return (-1);
        }

        if (L->lwp_state != PS_STOP) {
                errno = EBUSY;
                return (-1);
        }

        L->lwp_status.pr_reg[regno] = reg;
        L->lwp_flags |= SETREGS;        /* set registers before continuing */
        return (0);
}

int
Lsetrun(struct ps_lwphandle *L,
    int sig,    /* signal to pass to LWP */
    int flags)  /* PRSTEP|PRSABORT|PRSTOP|PRCSIG|PRCFAULT */
{
        int ctlfd = L->lwp_ctlfd;
        int sbits = (PR_DSTOP | PR_ISTOP | PR_ASLEEP);

        long ctl[1 +                                    /* PCCFAULT     */
            1 + sizeof (siginfo_t)/sizeof (long) +      /* PCSSIG/PCCSIG */
            2 ];                                        /* PCRUN        */

        long *ctlp = ctl;
        size_t size;

        if (L->lwp_state != PS_STOP &&
            (L->lwp_status.pr_flags & sbits) == 0) {
                errno = EBUSY;
                return (-1);
        }

        Lsync(L);       /* flush registers */

        if (flags & PRCFAULT) {         /* clear current fault */
                *ctlp++ = PCCFAULT;
                flags &= ~PRCFAULT;
        }

        if (flags & PRCSIG) {           /* clear current signal */
                *ctlp++ = PCCSIG;
                flags &= ~PRCSIG;
        } else if (sig && sig != L->lwp_status.pr_cursig) {
                /* make current signal */
                siginfo_t *infop;

                *ctlp++ = PCSSIG;
                infop = (siginfo_t *)ctlp;
                (void) memset(infop, 0, sizeof (*infop));
                infop->si_signo = sig;
                ctlp += sizeof (siginfo_t) / sizeof (long);
        }

        *ctlp++ = PCRUN;
        *ctlp++ = flags;
        size = (char *)ctlp - (char *)ctl;

        L->lwp_proc->info_valid = 0; /* will need to update map and file info */
        L->lwp_proc->state = PS_RUN;
        L->lwp_state = PS_RUN;

        if (write(ctlfd, ctl, size) != size) {
                /* Pretend that a job-stopped LWP is running */
                if (errno != EBUSY || L->lwp_status.pr_why != PR_JOBCONTROL)
                        return (Lstopstatus(L, PCNULL, 0));
        }

        return (0);
}

int
Lclearsig(struct ps_lwphandle *L)
{
        int ctlfd = L->lwp_ctlfd;
        long ctl = PCCSIG;

        if (write(ctlfd, &ctl, sizeof (ctl)) != sizeof (ctl))
                return (-1);
        L->lwp_status.pr_cursig = 0;
        return (0);
}

int
Lclearfault(struct ps_lwphandle *L)
{
        int ctlfd = L->lwp_ctlfd;
        long ctl = PCCFAULT;

        if (write(ctlfd, &ctl, sizeof (ctl)) != sizeof (ctl))
                return (-1);
        return (0);
}

/*
 * Step over a breakpoint, i.e., execute the instruction that
 * really belongs at the breakpoint location (the current %pc)
 * and leave the LWP stopped at the next instruction.
 */
int
Lxecbkpt(struct ps_lwphandle *L, ulong_t saved)
{
        struct ps_prochandle *P = L->lwp_proc;
        int rv, error;

        if (L->lwp_state != PS_STOP) {
                errno = EBUSY;
                return (-1);
        }

        Lsync(L);
        error = execute_bkpt(L->lwp_ctlfd,
            &P->status.pr_flttrace, &L->lwp_status.pr_lwphold,
            L->lwp_status.pr_reg[R_PC], saved);
        rv = Lstopstatus(L, PCNULL, 0);

        if (error != 0) {
                if (L->lwp_status.pr_why == PR_JOBCONTROL &&
                    error == EBUSY) {   /* jobcontrol stop -- back off */
                        L->lwp_state = PS_RUN;
                        return (0);
                }
                if (error == ENOENT)
                        return (0);
                errno = error;
                return (-1);
        }

        return (rv);
}

/*
 * Step over a watchpoint, i.e., execute the instruction that was stopped by
 * the watchpoint, and then leave the LWP stopped at the next instruction.
 */
int
Lxecwapt(struct ps_lwphandle *L, const prwatch_t *wp)
{
        struct ps_prochandle *P = L->lwp_proc;
        int rv, error;

        if (L->lwp_state != PS_STOP) {
                errno = EBUSY;
                return (-1);
        }

        Lsync(L);
        error = execute_wapt(L->lwp_ctlfd,
            &P->status.pr_flttrace, &L->lwp_status.pr_lwphold, wp);
        rv = Lstopstatus(L, PCNULL, 0);

        if (error != 0) {
                if (L->lwp_status.pr_why == PR_JOBCONTROL &&
                    error == EBUSY) {   /* jobcontrol stop -- back off */
                        L->lwp_state = PS_RUN;
                        return (0);
                }
                if (error == ENOENT)
                        return (0);
                errno = error;
                return (-1);
        }

        return (rv);
}

int
Lstack(struct ps_lwphandle *L, stack_t *stkp)
{
        struct ps_prochandle *P = L->lwp_proc;
        uintptr_t addr = L->lwp_status.pr_ustack;

        if (P->status.pr_dmodel == PR_MODEL_NATIVE) {
                if (Pread(P, stkp, sizeof (*stkp), addr) != sizeof (*stkp))
                        return (-1);
#ifdef _LP64
        } else {
                stack32_t stk32;

                if (Pread(P, &stk32, sizeof (stk32), addr) != sizeof (stk32))
                        return (-1);

                stack_32_to_n(&stk32, stkp);
#endif
        }

        return (0);
}

int
Lmain_stack(struct ps_lwphandle *L, stack_t *stkp)
{
        struct ps_prochandle *P = L->lwp_proc;

        if (Lstack(L, stkp) != 0)
                return (-1);

        /*
         * If the SS_ONSTACK flag is set then this LWP is operating on the
         * alternate signal stack. We can recover the original stack from
         * pr_oldcontext.
         */
        if (!(stkp->ss_flags & SS_ONSTACK))
                return (0);

        if (P->status.pr_dmodel == PR_MODEL_NATIVE) {
                ucontext_t *ctxp = (void *)L->lwp_status.pr_oldcontext;

                if (Pread(P, stkp, sizeof (*stkp),
                    (uintptr_t)&ctxp->uc_stack) != sizeof (*stkp))
                        return (-1);
#ifdef _LP64
        } else {
                ucontext32_t *ctxp = (void *)L->lwp_status.pr_oldcontext;
                stack32_t stk32;

                if (Pread(P, &stk32, sizeof (stk32),
                    (uintptr_t)&ctxp->uc_stack) != sizeof (stk32))
                        return (-1);

                stack_32_to_n(&stk32, stkp);
#endif
        }

        return (0);
}

int
Lalt_stack(struct ps_lwphandle *L, stack_t *stkp)
{
        if (L->lwp_status.pr_altstack.ss_flags & SS_DISABLE) {
                errno = ENODATA;
                return (-1);
        }

        *stkp = L->lwp_status.pr_altstack;

        return (0);
}

/*
 * Add a mapping to the given proc handle.  Resizes the array as appropriate and
 * manages reference counts on the given file_info_t.
 *
 * The 'map_relocate' member is used to tell Psort_mappings() that the
 * associated file_map pointer needs to be relocated after the mappings have
 * been sorted.  It is only set for the first mapping, and has no meaning
 * outside these two functions.
 */
int
Padd_mapping(struct ps_prochandle *P, off64_t off, file_info_t *fp,
    prmap_t *pmap)
{
        map_info_t *mp;

        if (P->map_count == P->map_alloc) {
                size_t next = P->map_alloc ? P->map_alloc * 2 : 16;

                if ((P->mappings = reallocarray(P->mappings, next,
                    sizeof (map_info_t))) == NULL)
                        return (-1);

                P->map_alloc = next;
        }

        mp = &P->mappings[P->map_count++];

        mp->map_offset = off;
        mp->map_pmap = *pmap;
        mp->map_relocate = 0;
        if ((mp->map_file = fp) != NULL) {
                if (fp->file_map == NULL) {
                        fp->file_map = mp;
                        mp->map_relocate = 1;
                }
                fp->file_ref++;
        }

        return (0);
}

static int
map_sort(const void *a, const void *b)
{
        const map_info_t *ap = a, *bp = b;

        if (ap->map_pmap.pr_vaddr < bp->map_pmap.pr_vaddr)
                return (-1);
        else if (ap->map_pmap.pr_vaddr > bp->map_pmap.pr_vaddr)
                return (1);
        else
                return (0);
}

/*
 * Sort the current set of mappings.  Should be called during target
 * initialization after all calls to Padd_mapping() have been made.
 */
void
Psort_mappings(struct ps_prochandle *P)
{
        int i;
        map_info_t *mp;

        qsort(P->mappings, P->map_count, sizeof (map_info_t), map_sort);

        /*
         * Update all the file_map pointers to refer to the new locations.
         */
        for (i = 0; i < P->map_count; i++) {
                mp = &P->mappings[i];
                if (mp->map_relocate)
                        mp->map_file->file_map = mp;
                mp->map_relocate = 0;
        }
}

struct ps_prochandle *
Pgrab_ops(pid_t pid, void *data, const ps_ops_t *ops, int flags)
{
        struct ps_prochandle *P;

        if ((P = calloc(1, sizeof (*P))) == NULL) {
                return (NULL);
        }

        Pinit_ops(&P->ops, ops);
        (void) mutex_init(&P->proc_lock, USYNC_THREAD, NULL);
        P->pid = pid;
        P->state = PS_STOP;
        P->asfd = -1;
        P->ctlfd = -1;
        P->statfd = -1;
        P->agentctlfd = -1;
        P->agentstatfd = -1;
        Pinitsym(P);
        P->data = data;
        Pread_status(P);

        if (flags & PGRAB_INCORE) {
                P->flags |= INCORE;
        }

        return (P);
}