libproc/common/Pzone.c

	Pzone.c revision 2a12f85ad140e332791b4bad1208a734c3f26bf3
/*
 * 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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright (c) 2013, Joyent, Inc. All rights reserved.
 * Copyright (c) 2013 by Delphix. All rights reserved.
 */

#include <assert.h>
#include <dlfcn.h>
#include <errno.h>
#include <libzonecfg.h>
#include <link.h>
#include <string.h>
#include <strings.h>
#include <sys/list.h>
#include <sys/types.h>
#include <sys/mkdev.h>
#include <sys/mman.h>
#include <sys/mnttab.h>

#include "Pcontrol.h"

struct path_node {
    struct path_node    *pn_next;
    char            *pn_path;
};
typedef struct path_node path_node_t;

/*
 * Parameters of the lofs lookup cache.
 */
static struct stat64 lofs_mstat; /* last stat() of MNTTAB */
static struct lofs_mnttab { /* linked list of all lofs mount points */
    struct lofs_mnttab *l_next;
    char    *l_special; /* extracted from MNTTAB */
    char    *l_mountp;  /* ditto */
} *lofs_mnttab = NULL;
static mutex_t lofs_lock = DEFAULTMUTEX;    /* protects the lofs cache */

static void
rebuild_lofs_cache(void)
{
    struct mnttab mt;
    struct mnttab mt_find;
    struct lofs_mnttab *lmt;
    struct lofs_mnttab *next;
    FILE *fp;

    assert(MUTEX_HELD(&lofs_lock));

    /* destroy the old cache */
    for (lmt = lofs_mnttab; lmt != NULL; lmt = next) {
        next = lmt->l_next;
        free(lmt->l_special);
        free(lmt->l_mountp);
        free(lmt);
    }
    lofs_mnttab = NULL;

    /* prepare to create the new cache */
    if ((fp = fopen(MNTTAB, "r")) == NULL)
        return;

    /*
     * We only care about lofs mount points.  But we need to
     * ignore lofs mounts where the source path is the same
     * as the target path.  (This can happen when a non-global
     * zone has a lofs mount of a global zone filesystem, since
     * the source path can't expose information about global
     * zone paths to the non-global zone.)
     */
    bzero(&mt_find, sizeof (mt_find));
    mt_find.mnt_fstype = "lofs";
    while (getmntany(fp, &mt, &mt_find) == 0 &&
        (strcmp(mt.mnt_fstype, "lofs") == 0) &&
        (strcmp(mt.mnt_special, mt.mnt_mountp) != 0)) {
        if ((lmt = malloc(sizeof (struct lofs_mnttab))) == NULL)
            break;
        lmt->l_special = strdup(mt.mnt_special);
        lmt->l_mountp = strdup(mt.mnt_mountp);
        lmt->l_next = lofs_mnttab;
        lofs_mnttab = lmt;
    }

    (void) fclose(fp);
}

static const char *
lookup_lofs_mount_point(const char *mountp)
{
    struct lofs_mnttab *lmt;

    assert(MUTEX_HELD(&lofs_lock));

    for (lmt = lofs_mnttab; lmt != NULL; lmt = lmt->l_next) {
        if (strcmp(lmt->l_mountp, mountp) == 0)
            return (lmt->l_special);
    }
    return (NULL);
}

static path_node_t *
pn_push(path_node_t **pnp, char *path)
{
    path_node_t *pn;

    if ((pn = calloc(sizeof (path_node_t), 1)) == NULL)
        return (NULL);

    if ((pn->pn_path = strdup(path)) == NULL) {
        free(pn);
        return (NULL);
    }
    pn->pn_next = *pnp;
    return (*pnp = pn);
}

static void
pn_free(path_node_t **pnp)
{
    path_node_t *pn;

    while (*pnp != NULL) {
        pn = *pnp;
        *pnp = pn->pn_next;
        free(pn->pn_path);
        free(pn);
    }
}

static void
pn_free2(path_node_t **pn1, path_node_t **pn2)
{
    pn_free(pn1);
    pn_free(pn2);
}

static char *
pn_pop(path_node_t **pnp, char *path)
{
    path_node_t *pn;

    if (*pnp == NULL)
        return (NULL);

    pn = *pnp;
    *pnp = pn->pn_next;
    pn->pn_next = NULL;

    if (path == NULL) {
        pn_free(&pn);
        return (NULL);
    }
    (void) strlcpy(path, pn->pn_path, PATH_MAX);
    pn_free(&pn);
    return (path);
}


/*
 * Libzonecfg.so links against libproc, so libproc can't link against
 * libzonecfg.so.  Also, libzonecfg.so is optional and might not be
 * installed.  Hence instead of relying on linking to access libzonecfg.so,
 * we'll try dlopening it here.  This trick is borrowed from
 * libc`zone_get_id(), see that function for more detailed comments.
 */
static int
i_zone_get_zonepath(char *zone_name, char *zonepath, size_t rp_sz)
{
    typedef int (*zone_get_zonepath_t)(char *, char *, size_t);
    static zone_get_zonepath_t zone_get_zonepath_fp = NULL;

    if (zone_get_zonepath_fp == NULL) {
        /* There's no harm in doing this multiple times. */
        void *dlhandle = dlopen("libzonecfg.so.1", RTLD_LAZY);
        void *sym = (void *)(-1);
        if (dlhandle != NULL &&
            (sym = dlsym(dlhandle, "zone_get_zonepath")) == NULL) {
            sym = (void *)(-1);
            (void) dlclose(dlhandle);
        }
        zone_get_zonepath_fp = (zone_get_zonepath_t)sym;
    }

    /* If we've successfully loaded it, call the real function */
    if (zone_get_zonepath_fp != (zone_get_zonepath_t)(-1))
        return (zone_get_zonepath_fp(zone_name, zonepath, rp_sz));
    return (Z_NO_ZONE);
}

char *
Pbrandname(struct ps_prochandle *P, char *buf, size_t buflen)
{
    long    addr;

    if ((addr = Pgetauxval(P, AT_SUN_BRANDNAME)) == -1)
        return (NULL);

    if (Pread_string(P, buf, buflen, addr) == -1)
        return (NULL);

    return (buf);
}

/*
 * Get the zone name from the core file if we have it; look up the
 * name based on the zone id if this is a live process.
 */
char *
Pzonename(struct ps_prochandle *P, char *s, size_t n)
{
    return (P->ops.pop_zonename(P, s, n, P->data));
}

char *
Pzoneroot(struct ps_prochandle *P, char *s, size_t n)
{
    char zname[ZONENAME_MAX], zpath[PATH_MAX], tmp[PATH_MAX];
    int rv;

    if (P->zoneroot != NULL) {
        (void) strlcpy(s, P->zoneroot, n);
        return (s);
    }

    if ((Pzonename(P, zname, sizeof (zname)) == NULL) ||
        (strcmp(zname, GLOBAL_ZONENAME) == 0)) {
        if ((P->zoneroot = strdup("")) == NULL) {
            errno = ENOMEM;
            return (NULL);
        }
        dprintf("Pzoneroot defaulting to '%s'\n", GLOBAL_ZONENAME);
        (void) strlcpy(s, P->zoneroot, n);
        return (s);
    }

    if (i_zone_get_zonepath(zname, zpath, sizeof (zpath)) != Z_OK) {
        if ((P->zoneroot = strdup("")) == NULL) {
            errno = ENOMEM;
            return (NULL);
        }
        dprintf(
            "Pzoneroot zone not found '%s', defaulting to '%s'\n",
            zname, GLOBAL_ZONENAME);
        (void) strlcpy(s, P->zoneroot, n);
        return (s);
    }
    (void) strlcat(zpath, "/root", sizeof (zpath));

    if ((rv = resolvepath(zpath, tmp, sizeof (tmp) - 1)) < 0) {
        if ((P->zoneroot = strdup("")) == NULL) {
            errno = ENOMEM;
            return (NULL);
        }
        dprintf(
            "Pzoneroot can't access '%s:%s', defaulting to '%s'\n",
            zname, zpath, GLOBAL_ZONENAME);
        (void) strlcpy(s, P->zoneroot, n);
        return (s);
    }
    tmp[rv] = '\0';
    (void) strlcpy(zpath, tmp, sizeof (zpath));

    if ((P->zoneroot = strdup(zpath)) == NULL) {
        errno = ENOMEM;
        return (NULL);
    }
    dprintf("Pzoneroot found zone root '%s:%s'\n", zname, zpath);
    (void) strlcpy(s, P->zoneroot, n);
    return (s);
}

/*
 * Plofspath() takes a path, "path",  and removes any lofs components from
 * that path.  The resultant path (if different from the starting path)
 * is placed in "s", which is limited to "n" characters, and the return
 * value is the pointer s.  If there are no lofs components in the path
 * the NULL is returned and s is not modified.  It's ok for "path" and
 * "s" to be the same pointer.  (ie, the results can be stored directly
 * in the input buffer.)  The path that is passed in must be an absolute
 * path.
 *
 * Example:
 *  if "path" == "/foo/bar", and "/candy/" is lofs mounted on "/foo/"
 *  then "/candy/bar/" will be written into "s" and "s" will be returned.
 */
char *
Plofspath(const char *path, char *s, size_t n)
{
    char tmp[PATH_MAX + 1];
    struct stat64 statb;
    const char *special;
    char *p, *p2;
    int rv;

    dprintf("Plofspath path '%s'\n", path);

    /* We only deal with absolute paths */
    if (path[0] != '/')
        return (NULL);

    /* Make a copy of the path so that we can muck with it */
    (void) strlcpy(tmp, path, sizeof (tmp) - 1);

    /*
     * Use resolvepath() to make sure there are no consecutive or
     * trailing '/'s in the path.
     */
    if ((rv = resolvepath(tmp, tmp, sizeof (tmp) - 1)) >= 0)
        tmp[rv] = '\0';

    (void) mutex_lock(&lofs_lock);

    /*
     * If /etc/mnttab has been modified since the last time
     * we looked, then rebuild the lofs lookup cache.
     */
    if (stat64(MNTTAB, &statb) == 0 &&
        (statb.st_mtim.tv_sec != lofs_mstat.st_mtim.tv_sec ||
        statb.st_mtim.tv_nsec != lofs_mstat.st_mtim.tv_nsec ||
        statb.st_ctim.tv_sec != lofs_mstat.st_ctim.tv_sec ||
        statb.st_ctim.tv_nsec != lofs_mstat.st_ctim.tv_nsec)) {
        lofs_mstat = statb;
        rebuild_lofs_cache();
    }

    /*
     * So now we're going to search the path for any components that
     * might be lofs mounts.  We'll start out search from the full
     * path and then step back through each parent directly till
     * we reach the root.  If we find a lofs mount point in the path
     * then we'll replace the initial portion of the path (up
     * to that mount point) with the source of that mount point
     * and then start our search over again.
     *
     * Here's some of the variables we're going to use:
     *
     *  tmp - A pointer to our working copy of the path.  Sometimes
     *      this path will be divided into two strings by a
     *      '\0' (NUL) character.  The first string is the
     *      component we're currently checking and the second
     *      string is the path components we've already checked.
     *
     *  p - A pointer to the last '/' seen in the string.
     *
     *  p[1] - A pointer to the component of the string we've already
     *      checked.
     *
     * Initially, p will point to the end of our path and p[1] will point
     * to an extra '\0' (NUL) that we'll append to the end of the string.
     * (This is why we declared tmp with a size of PATH_MAX + 1).
     */
    p = &tmp[strlen(tmp)];
    p[1] = '\0';
    for (;;) {
        if ((special = lookup_lofs_mount_point(tmp)) != NULL) {
            char tmp2[PATH_MAX + 1];

            /*
             * We found a lofs mount.  Update the path that we're
             * checking and start over.  This means append the
             * portion of the path we've already checked to the
             * source of the lofs mount and re-start this entire
             * lofs resolution loop.  Use resolvepath() to make
             * sure there are no consecutive or trailing '/'s
             * in the path.
             */
            (void) strlcpy(tmp2, special, sizeof (tmp2) - 1);
            (void) strlcat(tmp2, "/", sizeof (tmp2) - 1);
            (void) strlcat(tmp2, &p[1], sizeof (tmp2) - 1);
            (void) strlcpy(tmp, tmp2, sizeof (tmp) - 1);
            if ((rv = resolvepath(tmp, tmp, sizeof (tmp) - 1)) >= 0)
                tmp[rv] = '\0';
            p = &tmp[strlen(tmp)];
            p[1] = '\0';
            continue;
        }

        /* No lofs mount found */
        if ((p2 = strrchr(tmp, '/')) == NULL) {
            char tmp2[PATH_MAX];

            (void) mutex_unlock(&lofs_lock);

            /*
             * We know that tmp was an absolute path, so if we
             * made it here we know that (p == tmp) and that
             * (*p == '\0').  This means that we've managed
             * to check the whole path and so we're done.
             */
            assert(p == tmp);
            assert(p[0] == '\0');

            /* Restore the leading '/' in the path */
            p[0] = '/';

            if (strcmp(tmp, path) == 0) {
                /* The path didn't change */
                return (NULL);
            }

            /*
             * It's possible that lofs source path we just
             * obtained contains a symbolic link.  Use
             * resolvepath() to clean it up.
             */
            (void) strlcpy(tmp2, tmp, sizeof (tmp2));
            if ((rv = resolvepath(tmp, tmp, sizeof (tmp) - 1)) >= 0)
                tmp[rv] = '\0';

            /*
             * It's always possible that our lofs source path is
             * actually another lofs mount.  So call ourselves
             * recursively to resolve that path.
             */
            (void) Plofspath(tmp, tmp, PATH_MAX);

            /* Copy out our final resolved lofs source path */
            (void) strlcpy(s, tmp, n);
            dprintf("Plofspath path result '%s'\n", s);
            return (s);
        }

        /*
         * So the path we just checked is not a lofs mount.  Next we
         * want to check the parent path component for a lofs mount.
         *
         * First, restore any '/' that we replaced with a '\0' (NUL).
         * We can determine if we should do this by looking at p[1].
         * If p[1] points to a '\0' (NUL) then we know that p points
         * to the end of the string and there is no '/' to restore.
         * if p[1] doesn't point to a '\0' (NUL) then it points to
         * the part of the path that we've already verified so there
         * is a '/' to restore.
         */
        if (p[1] != '\0')
            p[0] = '/';

        /*
         * Second, replace the last '/' in the part of the path
         * that we've already checked with a '\0' (NUL) so that
         * when we loop around we check the parent component of the
         * path.
         */
        p2[0] = '\0';
        p = p2;
    }
    /*NOTREACHED*/
}

/*
 * Pzonepath() - Way too much code to attempt to derive the full path of
 * an object within a zone.
 *
 * Pzonepath() takes a path and attempts to resolve it relative to the
 * root associated with the current process handle.  If it fails it will
 * not update the results string.  It is safe to specify the same pointer
 * for the file string and the results string.
 *
 * Doing this resolution is more difficult than it initially sounds.
 * We can't simply append the file path to the zone root, because in
 * a root directory, '..' is treated the same as '.'.  Also, symbolic
 * links that specify an absolute path need to be interpreted relative
 * to the zone root.
 *
 * It seems like perhaps we could do a chroot(<zone root>) followed by a
 * resolvepath().  But we can't do this because chroot requires special
 * privileges and affects the entire process.  Perhaps if there was a
 * special version of resolvepath() which took an addition root path
 * we could use that, but this isn't ideal either.  The reason is
 * that we want to have special handling for native paths.  (A native path
 * is a path that begins with "/native/" or "/.SUNWnative/".)  Native
 * paths could be passed explicity to this function or could be embedded
 * in a symlink that is part of the path passed into this function.
 * These paths are always lofs mounts of global zone paths, but lofs
 * mounts only exist when a zone is booted.  So if we were to try to do
 * a resolvepath() on a native path when the zone wasn't booted the
 * resolvepath() would fail even though we know that the components
 * exists in the global zone.
 *
 * Given all these constraints, we just implement a path walking function
 * that resolves a file path relative to a zone root by manually inspecting
 * each of the path components and verifying its existence.  This means that
 * we must have access to the zone and that all the components of the
 * path must exist for this operation to succeed.
 */
char *
Pzonepath(struct ps_prochandle *P, const char *path, char *s, size_t n)
{
    char zroot[PATH_MAX], zpath[PATH_MAX], tmp[PATH_MAX], link[PATH_MAX];
    path_node_t *pn_stack = NULL, *pn_links = NULL, *pn;
    struct stat64 sb;
    char *p;
    int i, rv;

    dprintf("Pzonepath lookup '%s'\n", path);

    /* First lookup the zone root */
    if (Pzoneroot(P, zroot, sizeof (zroot)) == NULL)
        return (NULL);

    /*
     * Make a temporary copy of the path specified.
     * If it's a relative path then make it into an absolute path.
     */
    tmp[0] = '\0';
    if (path[0] != '/')
        (void) strlcat(tmp, "/", sizeof (tmp));
    (void) strlcat(tmp, path, sizeof (tmp));

    /*
     * If the path that was passed in is the zone root, we're done.
     * If the path that was passed in already contains the zone root
     * then strip the zone root out and verify the rest of the path.
     */
    if (strcmp(tmp, zroot) == 0) {
        (void) Plofspath(zroot, zroot, sizeof (zroot));
        dprintf("Pzonepath found zone path (1) '%s'\n", zroot);
        (void) strlcpy(s, zroot, n);
        return (s);
    }
    i = strlen(zroot);
    if ((strncmp(tmp, zroot, i) == 0) && (tmp[i] == '/'))
        (void) memmove(tmp, tmp + i, strlen(tmp + i) + 1);

    /* If no path is passed in, then it maps to the zone root */
    if (strlen(tmp) == 0) {
        (void) Plofspath(zroot, zroot, sizeof (zroot));
        dprintf("Pzonepath found zone path (2) '%s'\n", zroot);
        (void) strlcpy(s, zroot, n);
        return (s);
    }

    /*
     * Push each path component that we plan to verify onto a stack of
     * path components, with parent components at the top of the stack.
     * So for example, if we're going to verify the path /foo/bar/bang
     * then our stack will look like:
     *  foo (top)
     *  bar
     *  bang    (bottom)
     */
    while ((p = strrchr(tmp, '/')) != NULL) {
        *p = '\0';
        if (pn_push(&pn_stack, &p[1]) != NULL)
            continue;
        pn_free(&pn_stack);
        return (NULL);
    }

    /* We're going to store the final zone relative path in zpath */
    *zpath = '\0';

    while (pn_pop(&pn_stack, tmp) != NULL) {
        /*
         * Drop zero length path components (which come from
         * consecutive '/'s) and '.' path components.
         */
        if ((strlen(tmp) == 0) || (strcmp(tmp, ".") == 0))
            continue;

        /*
         * Check the current path component for '..', if found
         * drop any previous path component.
         */
        if (strcmp(tmp, "..") == 0) {
            if ((p = strrchr(zpath, '/')) != NULL)
                *p = '\0';
            continue;
        }

        /* The path we want to verify now is zpath + / + tmp. */
        (void) strlcat(zpath, "/", sizeof (zpath));
        (void) strlcat(zpath, tmp, sizeof (zpath));

        /*
         * Check if this is a native object.  A native object is an
         * object from the global zone that is running in a branded
         * zone.  These objects are lofs mounted into a zone.  So if a
         * branded zone is not booted then lofs mounts won't be setup
         * so we won't be able to find these objects.  Luckily, we know
         * that they exist in the global zone with the same path sans
         * the initial native component, so we'll just strip out the
         * native component here.
         */
        if ((strncmp(zpath, "/native", sizeof ("/native")) == 0) ||
            (strncmp(zpath, "/.SUNWnative",
            sizeof ("/.SUNWnative")) == 0)) {

            /* Free any cached symlink paths */
            pn_free(&pn_links);

            /* Reconstruct the path from our path component stack */
            *zpath = '\0';
            while (pn_pop(&pn_stack, tmp) != NULL) {
                (void) strlcat(zpath, "/", sizeof (zpath));
                (void) strlcat(zpath, tmp, sizeof (zpath));
            }

            /* Verify that the path actually exists */
            rv = resolvepath(zpath, tmp, sizeof (tmp) - 1);
            if (rv < 0) {
                dprintf("Pzonepath invalid native path '%s'\n",
                    zpath);
                return (NULL);
            }
            tmp[rv] = '\0';

            /* Return the path */
            dprintf("Pzonepath found native path '%s'\n", tmp);
            (void) Plofspath(tmp, tmp, sizeof (tmp));
            (void) strlcpy(s, tmp, n);
            return (s);
        }

        /*
         * Check if the path points to a symlink.  We do this
         * explicitly since any absolute symlink needs to be
         * interpreted relativly to the zone root and not "/".
         */
        (void) strlcpy(tmp, zroot, sizeof (tmp));
        (void) strlcat(tmp, zpath, sizeof (tmp));
        if (lstat64(tmp, &sb) != 0) {
            pn_free2(&pn_stack, &pn_links);
            return (NULL);
        }
        if (!S_ISLNK(sb.st_mode)) {
            /*
             * Since the lstat64() above succeeded we know that
             * zpath exists, since this is not a symlink loop
             * around and check the next path component.
             */
            continue;
        }

        /*
         * Symlink allow for paths with loops.  Make sure
         * we're not stuck in a loop.
         */
        for (pn = pn_links; pn != NULL; pn = pn->pn_next) {
            if (strcmp(zpath, pn->pn_path) != 0)
                continue;

            /* We have a loop.  Fail. */
            dprintf("Pzonepath symlink loop '%s'\n", zpath);
            pn_free2(&pn_stack, &pn_links);
            return (NULL);
        }

        /* Save this symlink path for future loop checks */
        if (pn_push(&pn_links, zpath) == NULL) {
            /* Out of memory */
            pn_free2(&pn_stack, &pn_links);
            return (NULL);
        }

        /* Now follow the contents of the symlink */
        bzero(link, sizeof (link));
        if (readlink(tmp, link, sizeof (link)) == -1) {
            pn_free2(&pn_stack, &pn_links);
            return (NULL);
        }

        dprintf("Pzonepath following symlink '%s' -> '%s'\n",
            zpath, link);

        /*
         * Push each path component of the symlink target onto our
         * path components stack since we need to verify each one.
         */
        while ((p = strrchr(link, '/')) != NULL) {
            *p = '\0';
            if (pn_push(&pn_stack, &p[1]) != NULL)
                continue;
            pn_free2(&pn_stack, &pn_links);
            return (NULL);
        }

        /* absolute or relative symlink? */
        if (*link == '\0') {
            /* Absolute symlink, nuke existing zpath. */
            *zpath = '\0';
            continue;
        }

        /*
         * Relative symlink.  Push the first path component of the
         * symlink target onto our stack for verification and then
         * remove the current path component from zpath.
         */
        if (pn_push(&pn_stack, link) == NULL) {
            pn_free2(&pn_stack, &pn_links);
            return (NULL);
        }
        p = strrchr(zpath, '/');
        assert(p != NULL);
        *p = '\0';
        continue;
    }
    pn_free(&pn_links);

    /* Place the final result in zpath */
    (void) strlcpy(tmp, zroot, sizeof (tmp));
    (void) strlcat(tmp, zpath, sizeof (tmp));
    (void) strlcpy(zpath, tmp, sizeof (zpath));

    (void) Plofspath(zpath, zpath, sizeof (zpath));
    dprintf("Pzonepath found zone path (3) '%s'\n", zpath);

    (void) strlcpy(s, zpath, n);
    return (s);
}

char *
Pfindobj(struct ps_prochandle *P, const char *path, char *s, size_t n)
{
    int len;

    dprintf("Pfindobj '%s'\n", path);

    /* We only deal with absolute paths */
    if (path[0] != '/')
        return (NULL);

    /* First try to resolve the path to some zone */
    if (Pzonepath(P, path, s, n) != NULL)
        return (s);

    /* If that fails resolve any lofs links in the path */
    if (Plofspath(path, s, n) != NULL)
        return (s);

    /* If that fails then just see if the path exists */
    if ((len = resolvepath(path, s, n)) > 0) {
        s[len] = '\0';
        return (s);
    }

    return (NULL);
}

char *
Pfindmap(struct ps_prochandle *P, map_info_t *mptr, char *s, size_t n)
{
    file_info_t *fptr = mptr->map_file;
    char buf[PATH_MAX];
    int len;

    /* If it's already been explicity set return that */
    if ((fptr != NULL) && (fptr->file_rname != NULL)) {
        (void) strlcpy(s, fptr->file_rname, n);
        return (s);
    }

    /* If it's the a.out segment, defer to the magical Pexecname() */
    if ((P->map_exec == mptr) ||
        (strcmp(mptr->map_pmap.pr_mapname, "a.out") == 0) ||
        ((fptr != NULL) && (fptr->file_lname != NULL) &&
        (strcmp(fptr->file_lname, "a.out") == 0))) {
        if (Pexecname(P, buf, sizeof (buf)) != NULL) {
            (void) strlcpy(s, buf, n);
            return (s);
        }
    }

    /* Try /proc first to get the real object name */
    if ((Pstate(P) != PS_DEAD) && (mptr->map_pmap.pr_mapname[0] != '\0')) {
        (void) snprintf(buf, sizeof (buf), "%s/%d/path/%s",
            procfs_path, (int)P->pid, mptr->map_pmap.pr_mapname);
        if ((len = readlink(buf, buf, sizeof (buf))) > 0) {
            buf[len] = '\0';
            (void) Plofspath(buf, buf, sizeof (buf));
            (void) strlcpy(s, buf, n);
            return (s);
        }
    }

    /*
     * If we couldn't get the name from /proc, take the lname and
     * try to expand it on the current system to a real object path.
     */
    fptr = mptr->map_file;
    if ((fptr != NULL) && (fptr->file_lname != NULL)) {
        (void) strlcpy(buf, fptr->file_lname, sizeof (buf));
        if (Pfindobj(P, buf, buf, sizeof (buf)) == NULL)
            return (NULL);
        (void) strlcpy(s, buf, n);
        return (s);
    }

    return (NULL);
}