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Sourcecode: postgresql-8.4 version File versions

miscinit.c

/*-------------------------------------------------------------------------
 *
 * miscinit.c
 *      miscellaneous initialization support stuff
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.175 2009/06/11 14:49:05 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <sys/param.h>
#include <signal.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <fcntl.h>
#include <unistd.h>
#include <grp.h>
#include <pwd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#ifdef HAVE_UTIME_H
#include <utime.h>
#endif

#include "catalog/pg_authid.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "postmaster/autovacuum.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/pg_shmem.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/syscache.h"


#define DIRECTORY_LOCK_FILE         "postmaster.pid"

ProcessingMode Mode = InitProcessing;

/* Note: we rely on this to initialize as zeroes */
static char socketLockFile[MAXPGPATH];


/* ----------------------------------------------------------------
 *          ignoring system indexes support stuff
 *
 * NOTE: "ignoring system indexes" means we do not use the system indexes
 * for lookups (either in hardwired catalog accesses or in planner-generated
 * plans).  We do, however, still update the indexes when a catalog
 * modification is made.
 * ----------------------------------------------------------------
 */

bool        IgnoreSystemIndexes = false;

/* ----------------------------------------------------------------
 *          system index reindexing support
 *
 * When we are busy reindexing a system index, this code provides support
 * for preventing catalog lookups from using that index.
 * ----------------------------------------------------------------
 */

static Oid  currentlyReindexedHeap = InvalidOid;
static Oid  currentlyReindexedIndex = InvalidOid;

/*
 * ReindexIsProcessingHeap
 *          True if heap specified by OID is currently being reindexed.
 */
bool
ReindexIsProcessingHeap(Oid heapOid)
{
      return heapOid == currentlyReindexedHeap;
}

/*
 * ReindexIsProcessingIndex
 *          True if index specified by OID is currently being reindexed.
 */
bool
ReindexIsProcessingIndex(Oid indexOid)
{
      return indexOid == currentlyReindexedIndex;
}

/*
 * SetReindexProcessing
 *          Set flag that specified heap/index are being reindexed.
 */
void
SetReindexProcessing(Oid heapOid, Oid indexOid)
{
      Assert(OidIsValid(heapOid) && OidIsValid(indexOid));
      /* Reindexing is not re-entrant. */
      if (OidIsValid(currentlyReindexedIndex))
            elog(ERROR, "cannot reindex while reindexing");
      currentlyReindexedHeap = heapOid;
      currentlyReindexedIndex = indexOid;
}

/*
 * ResetReindexProcessing
 *          Unset reindexing status.
 */
void
ResetReindexProcessing(void)
{
      currentlyReindexedHeap = InvalidOid;
      currentlyReindexedIndex = InvalidOid;
}

/* ----------------------------------------------------------------
 *                      database path / name support stuff
 * ----------------------------------------------------------------
 */

void
SetDatabasePath(const char *path)
{
      if (DatabasePath)
      {
            free(DatabasePath);
            DatabasePath = NULL;
      }
      /* use strdup since this is done before memory contexts are set up */
      if (path)
      {
            DatabasePath = strdup(path);
            AssertState(DatabasePath);
      }
}

/*
 * Set data directory, but make sure it's an absolute path.  Use this,
 * never set DataDir directly.
 */
void
SetDataDir(const char *dir)
{
      char     *new;

      AssertArg(dir);

      /* If presented path is relative, convert to absolute */
      new = make_absolute_path(dir);

      if (DataDir)
            free(DataDir);
      DataDir = new;
}

/*
 * Change working directory to DataDir.  Most of the postmaster and backend
 * code assumes that we are in DataDir so it can use relative paths to access
 * stuff in and under the data directory.  For convenience during path
 * setup, however, we don't force the chdir to occur during SetDataDir.
 */
void
ChangeToDataDir(void)
{
      AssertState(DataDir);

      if (chdir(DataDir) < 0)
            ereport(FATAL,
                        (errcode_for_file_access(),
                         errmsg("could not change directory to \"%s\": %m",
                                    DataDir)));
}

/*
 * If the given pathname isn't already absolute, make it so, interpreting
 * it relative to the current working directory.
 *
 * Also canonicalizes the path.  The result is always a malloc'd copy.
 *
 * Note: interpretation of relative-path arguments during postmaster startup
 * should happen before doing ChangeToDataDir(), else the user will probably
 * not like the results.
 */
char *
make_absolute_path(const char *path)
{
      char     *new;

      /* Returning null for null input is convenient for some callers */
      if (path == NULL)
            return NULL;

      if (!is_absolute_path(path))
      {
            char     *buf;
            size_t            buflen;

            buflen = MAXPGPATH;
            for (;;)
            {
                  buf = malloc(buflen);
                  if (!buf)
                        ereport(FATAL,
                                    (errcode(ERRCODE_OUT_OF_MEMORY),
                                     errmsg("out of memory")));

                  if (getcwd(buf, buflen))
                        break;
                  else if (errno == ERANGE)
                  {
                        free(buf);
                        buflen *= 2;
                        continue;
                  }
                  else
                  {
                        free(buf);
                        elog(FATAL, "could not get current working directory: %m");
                  }
            }

            new = malloc(strlen(buf) + strlen(path) + 2);
            if (!new)
                  ereport(FATAL,
                              (errcode(ERRCODE_OUT_OF_MEMORY),
                               errmsg("out of memory")));
            sprintf(new, "%s/%s", buf, path);
            free(buf);
      }
      else
      {
            new = strdup(path);
            if (!new)
                  ereport(FATAL,
                              (errcode(ERRCODE_OUT_OF_MEMORY),
                               errmsg("out of memory")));
      }

      /* Make sure punctuation is canonical, too */
      canonicalize_path(new);

      return new;
}


/* ----------------------------------------------------------------
 *    User ID state
 *
 * We have to track several different values associated with the concept
 * of "user ID".
 *
 * AuthenticatedUserId is determined at connection start and never changes.
 *
 * SessionUserId is initially the same as AuthenticatedUserId, but can be
 * changed by SET SESSION AUTHORIZATION (if AuthenticatedUserIsSuperuser).
 * This is the ID reported by the SESSION_USER SQL function.
 *
 * OuterUserId is the current user ID in effect at the "outer level" (outside
 * any transaction or function).  This is initially the same as SessionUserId,
 * but can be changed by SET ROLE to any role that SessionUserId is a
 * member of.  (XXX rename to something like CurrentRoleId?)
 *
 * CurrentUserId is the current effective user ID; this is the one to use
 * for all normal permissions-checking purposes.  At outer level this will
 * be the same as OuterUserId, but it changes during calls to SECURITY
 * DEFINER functions, as well as locally in some specialized commands.
 *
 * SecurityDefinerContext is TRUE if we are within a SECURITY DEFINER function
 * or another context that temporarily changes CurrentUserId.
 * ----------------------------------------------------------------
 */
static Oid  AuthenticatedUserId = InvalidOid;
static Oid  SessionUserId = InvalidOid;
static Oid  OuterUserId = InvalidOid;
static Oid  CurrentUserId = InvalidOid;

/* We also have to remember the superuser state of some of these levels */
static bool AuthenticatedUserIsSuperuser = false;
static bool SessionUserIsSuperuser = false;

static bool SecurityDefinerContext = false;

/* We also remember if a SET ROLE is currently active */
static bool SetRoleIsActive = false;


/*
 * GetUserId - get the current effective user ID.
 *
 * Note: there's no SetUserId() anymore; use SetUserIdAndContext().
 */
Oid
GetUserId(void)
{
      AssertState(OidIsValid(CurrentUserId));
      return CurrentUserId;
}


/*
 * GetOuterUserId/SetOuterUserId - get/set the outer-level user ID.
 */
Oid
GetOuterUserId(void)
{
      AssertState(OidIsValid(OuterUserId));
      return OuterUserId;
}


static void
SetOuterUserId(Oid userid)
{
      AssertState(!SecurityDefinerContext);
      AssertArg(OidIsValid(userid));
      OuterUserId = userid;

      /* We force the effective user ID to match, too */
      CurrentUserId = userid;
}


/*
 * GetSessionUserId/SetSessionUserId - get/set the session user ID.
 */
Oid
GetSessionUserId(void)
{
      AssertState(OidIsValid(SessionUserId));
      return SessionUserId;
}


static void
SetSessionUserId(Oid userid, bool is_superuser)
{
      AssertState(!SecurityDefinerContext);
      AssertArg(OidIsValid(userid));
      SessionUserId = userid;
      SessionUserIsSuperuser = is_superuser;
      SetRoleIsActive = false;

      /* We force the effective user IDs to match, too */
      OuterUserId = userid;
      CurrentUserId = userid;
}


/*
 * GetUserIdAndContext/SetUserIdAndContext - get/set the current user ID
 * and the SecurityDefinerContext flag.
 *
 * Unlike GetUserId, GetUserIdAndContext does *not* Assert that the current
 * value of CurrentUserId is valid; nor does SetUserIdAndContext require
 * the new value to be valid.  In fact, these routines had better not
 * ever throw any kind of error.  This is because they are used by
 * StartTransaction and AbortTransaction to save/restore the settings,
 * and during the first transaction within a backend, the value to be saved
 * and perhaps restored is indeed invalid.      We have to be able to get
 * through AbortTransaction without asserting in case InitPostgres fails.
 */
void
GetUserIdAndContext(Oid *userid, bool *sec_def_context)
{
      *userid = CurrentUserId;
      *sec_def_context = SecurityDefinerContext;
}

void
SetUserIdAndContext(Oid userid, bool sec_def_context)
{
      CurrentUserId = userid;
      SecurityDefinerContext = sec_def_context;
}


/*
 * InSecurityDefinerContext - are we inside a SECURITY DEFINER context?
 */
bool
InSecurityDefinerContext(void)
{
      return SecurityDefinerContext;
}


/*
 * Initialize user identity during normal backend startup
 */
void
InitializeSessionUserId(const char *rolename)
{
      HeapTuple   roleTup;
      Form_pg_authid rform;
      Datum       datum;
      bool        isnull;
      Oid               roleid;

      /*
       * Don't do scans if we're bootstrapping, none of the system catalogs
       * exist yet, and they should be owned by postgres anyway.
       */
      AssertState(!IsBootstrapProcessingMode());

      /* call only once */
      AssertState(!OidIsValid(AuthenticatedUserId));

      roleTup = SearchSysCache(AUTHNAME,
                                           PointerGetDatum(rolename),
                                           0, 0, 0);
      if (!HeapTupleIsValid(roleTup))
            ereport(FATAL,
                        (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
                         errmsg("role \"%s\" does not exist", rolename)));

      rform = (Form_pg_authid) GETSTRUCT(roleTup);
      roleid = HeapTupleGetOid(roleTup);

      AuthenticatedUserId = roleid;
      AuthenticatedUserIsSuperuser = rform->rolsuper;

      /* This sets OuterUserId/CurrentUserId too */
      SetSessionUserId(roleid, AuthenticatedUserIsSuperuser);

      /* Also mark our PGPROC entry with the authenticated user id */
      /* (We assume this is an atomic store so no lock is needed) */
      MyProc->roleId = roleid;

      /*
       * These next checks are not enforced when in standalone mode, so that
       * there is a way to recover from sillinesses like "UPDATE pg_authid SET
       * rolcanlogin = false;".
       *
       * We do not enforce them for the autovacuum process either.
       */
      if (IsUnderPostmaster && !IsAutoVacuumWorkerProcess())
      {
            /*
             * Is role allowed to login at all?
             */
            if (!rform->rolcanlogin)
                  ereport(FATAL,
                              (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
                               errmsg("role \"%s\" is not permitted to log in",
                                          rolename)));

            /*
             * Check connection limit for this role.
             *
             * There is a race condition here --- we create our PGPROC before
             * checking for other PGPROCs.      If two backends did this at about the
             * same time, they might both think they were over the limit, while
             * ideally one should succeed and one fail.  Getting that to work
             * exactly seems more trouble than it is worth, however; instead we
             * just document that the connection limit is approximate.
             */
            if (rform->rolconnlimit >= 0 &&
                  !AuthenticatedUserIsSuperuser &&
                  CountUserBackends(roleid) > rform->rolconnlimit)
                  ereport(FATAL,
                              (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
                               errmsg("too many connections for role \"%s\"",
                                          rolename)));
      }

      /* Record username and superuser status as GUC settings too */
      SetConfigOption("session_authorization", rolename,
                              PGC_BACKEND, PGC_S_OVERRIDE);
      SetConfigOption("is_superuser",
                              AuthenticatedUserIsSuperuser ? "on" : "off",
                              PGC_INTERNAL, PGC_S_OVERRIDE);

      /*
       * Set up user-specific configuration variables.  This is a good place to
       * do it so we don't have to read pg_authid twice during session startup.
       */
      datum = SysCacheGetAttr(AUTHNAME, roleTup,
                                          Anum_pg_authid_rolconfig, &isnull);
      if (!isnull)
      {
            ArrayType  *a = DatumGetArrayTypeP(datum);

            /*
             * We process all the options at SUSET level.  We assume that the
             * right to insert an option into pg_authid was checked when it was
             * inserted.
             */
            ProcessGUCArray(a, PGC_SUSET, PGC_S_USER, GUC_ACTION_SET);
      }

      ReleaseSysCache(roleTup);
}


/*
 * Initialize user identity during special backend startup
 */
void
InitializeSessionUserIdStandalone(void)
{
      /* This function should only be called in a single-user backend. */
      AssertState(!IsUnderPostmaster || IsAutoVacuumWorkerProcess());

      /* call only once */
      AssertState(!OidIsValid(AuthenticatedUserId));

      AuthenticatedUserId = BOOTSTRAP_SUPERUSERID;
      AuthenticatedUserIsSuperuser = true;

      SetSessionUserId(BOOTSTRAP_SUPERUSERID, true);
}


/*
 * Change session auth ID while running
 *
 * Only a superuser may set auth ID to something other than himself.  Note
 * that in case of multiple SETs in a single session, the original userid's
 * superuserness is what matters.  But we set the GUC variable is_superuser
 * to indicate whether the *current* session userid is a superuser.
 *
 * Note: this is not an especially clean place to do the permission check.
 * It's OK because the check does not require catalog access and can't
 * fail during an end-of-transaction GUC reversion, but we may someday
 * have to push it up into assign_session_authorization.
 */
void
SetSessionAuthorization(Oid userid, bool is_superuser)
{
      /* Must have authenticated already, else can't make permission check */
      AssertState(OidIsValid(AuthenticatedUserId));

      if (userid != AuthenticatedUserId &&
            !AuthenticatedUserIsSuperuser)
            ereport(ERROR,
                        (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                         errmsg("permission denied to set session authorization")));

      SetSessionUserId(userid, is_superuser);

      SetConfigOption("is_superuser",
                              is_superuser ? "on" : "off",
                              PGC_INTERNAL, PGC_S_OVERRIDE);
}

/*
 * Report current role id
 *          This follows the semantics of SET ROLE, ie return the outer-level ID
 *          not the current effective ID, and return InvalidOid when the setting
 *          is logically SET ROLE NONE.
 */
Oid
GetCurrentRoleId(void)
{
      if (SetRoleIsActive)
            return OuterUserId;
      else
            return InvalidOid;
}

/*
 * Change Role ID while running (SET ROLE)
 *
 * If roleid is InvalidOid, we are doing SET ROLE NONE: revert to the
 * session user authorization.      In this case the is_superuser argument
 * is ignored.
 *
 * When roleid is not InvalidOid, the caller must have checked whether
 * the session user has permission to become that role.  (We cannot check
 * here because this routine must be able to execute in a failed transaction
 * to restore a prior value of the ROLE GUC variable.)
 */
void
SetCurrentRoleId(Oid roleid, bool is_superuser)
{
      /*
       * Get correct info if it's SET ROLE NONE
       *
       * If SessionUserId hasn't been set yet, just do nothing --- the eventual
       * SetSessionUserId call will fix everything.  This is needed since we
       * will get called during GUC initialization.
       */
      if (!OidIsValid(roleid))
      {
            if (!OidIsValid(SessionUserId))
                  return;

            roleid = SessionUserId;
            is_superuser = SessionUserIsSuperuser;

            SetRoleIsActive = false;
      }
      else
            SetRoleIsActive = true;

      SetOuterUserId(roleid);

      SetConfigOption("is_superuser",
                              is_superuser ? "on" : "off",
                              PGC_INTERNAL, PGC_S_OVERRIDE);
}


/*
 * Get user name from user oid
 */
char *
GetUserNameFromId(Oid roleid)
{
      HeapTuple   tuple;
      char     *result;

      tuple = SearchSysCache(AUTHOID,
                                       ObjectIdGetDatum(roleid),
                                       0, 0, 0);
      if (!HeapTupleIsValid(tuple))
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                         errmsg("invalid role OID: %u", roleid)));

      result = pstrdup(NameStr(((Form_pg_authid) GETSTRUCT(tuple))->rolname));

      ReleaseSysCache(tuple);
      return result;
}


/*-------------------------------------------------------------------------
 *                      Interlock-file support
 *
 * These routines are used to create both a data-directory lockfile
 * ($DATADIR/postmaster.pid) and a Unix-socket-file lockfile ($SOCKFILE.lock).
 * Both kinds of files contain the same info:
 *
 *          Owning process' PID
 *          Data directory path
 *
 * By convention, the owning process' PID is negated if it is a standalone
 * backend rather than a postmaster.  This is just for informational purposes.
 * The path is also just for informational purposes (so that a socket lockfile
 * can be more easily traced to the associated postmaster).
 *
 * A data-directory lockfile can optionally contain a third line, containing
 * the key and ID for the shared memory block used by this postmaster.
 *
 * On successful lockfile creation, a proc_exit callback to remove the
 * lockfile is automatically created.
 *-------------------------------------------------------------------------
 */

/*
 * proc_exit callback to remove a lockfile.
 */
static void
UnlinkLockFile(int status, Datum filename)
{
      char     *fname = (char *) DatumGetPointer(filename);

      if (fname != NULL)
      {
            if (unlink(fname) != 0)
            {
                  /* Should we complain if the unlink fails? */
            }
            free(fname);
      }
}

/*
 * Create a lockfile.
 *
 * filename is the name of the lockfile to create.
 * amPostmaster is used to determine how to encode the output PID.
 * isDDLock and refName are used to determine what error message to produce.
 */
static void
CreateLockFile(const char *filename, bool amPostmaster,
                     bool isDDLock, const char *refName)
{
      int               fd;
      char        buffer[MAXPGPATH + 100];
      int               ntries;
      int               len;
      int               encoded_pid;
      pid_t       other_pid;
      pid_t       my_pid = getpid();

      /*
       * We need a loop here because of race conditions.    But don't loop forever
       * (for example, a non-writable $PGDATA directory might cause a failure
       * that won't go away).  100 tries seems like plenty.
       */
      for (ntries = 0;; ntries++)
      {
            /*
             * Try to create the lock file --- O_EXCL makes this atomic.
             *
             * Think not to make the file protection weaker than 0600.  See
             * comments below.
             */
            fd = open(filename, O_RDWR | O_CREAT | O_EXCL, 0600);
            if (fd >= 0)
                  break;                        /* Success; exit the retry loop */

            /*
             * Couldn't create the pid file. Probably it already exists.
             */
            if ((errno != EEXIST && errno != EACCES) || ntries > 100)
                  ereport(FATAL,
                              (errcode_for_file_access(),
                               errmsg("could not create lock file \"%s\": %m",
                                          filename)));

            /*
             * Read the file to get the old owner's PID.  Note race condition
             * here: file might have been deleted since we tried to create it.
             */
            fd = open(filename, O_RDONLY, 0600);
            if (fd < 0)
            {
                  if (errno == ENOENT)
                        continue;         /* race condition; try again */
                  ereport(FATAL,
                              (errcode_for_file_access(),
                               errmsg("could not open lock file \"%s\": %m",
                                          filename)));
            }
            if ((len = read(fd, buffer, sizeof(buffer) - 1)) < 0)
                  ereport(FATAL,
                              (errcode_for_file_access(),
                               errmsg("could not read lock file \"%s\": %m",
                                          filename)));
            close(fd);

            buffer[len] = '\0';
            encoded_pid = atoi(buffer);

            /* if pid < 0, the pid is for postgres, not postmaster */
            other_pid = (pid_t) (encoded_pid < 0 ? -encoded_pid : encoded_pid);

            if (other_pid <= 0)
                  elog(FATAL, "bogus data in lock file \"%s\": \"%s\"",
                         filename, buffer);

            /*
             * Check to see if the other process still exists
             *
             * If the PID in the lockfile is our own PID or our parent's PID, then
             * the file must be stale (probably left over from a previous system
             * boot cycle).  We need this test because of the likelihood that a
             * reboot will assign exactly the same PID as we had in the previous
             * reboot.  Also, if there is just one more process launch in this
             * reboot than in the previous one, the lockfile might mention our
             * parent's PID.  We can reject that since we'd never be launched
             * directly by a competing postmaster.    We can't detect grandparent
             * processes unfortunately, but if the init script is written
             * carefully then all but the immediate parent shell will be
             * root-owned processes and so the kill test will fail with EPERM.
             *
             * We can treat the EPERM-error case as okay because that error
             * implies that the existing process has a different userid than we
             * do, which means it cannot be a competing postmaster.  A postmaster
             * cannot successfully attach to a data directory owned by a userid
             * other than its own.  (This is now checked directly in
             * checkDataDir(), but has been true for a long time because of the
             * restriction that the data directory isn't group- or
             * world-accessible.)  Also, since we create the lockfiles mode 600,
             * we'd have failed above if the lockfile belonged to another userid
             * --- which means that whatever process kill() is reporting about
             * isn't the one that made the lockfile.  (NOTE: this last
             * consideration is the only one that keeps us from blowing away a
             * Unix socket file belonging to an instance of Postgres being run by
             * someone else, at least on machines where /tmp hasn't got a
             * stickybit.)
             *
             * Windows hasn't got getppid(), but doesn't need it since it's not
             * using real kill() either...
             *
             * Normally kill() will fail with ESRCH if the given PID doesn't
             * exist.
             */
            if (other_pid != my_pid
#ifndef WIN32
                  && other_pid != getppid()
#endif
                  )
            {
                  if (kill(other_pid, 0) == 0 ||
                        (errno != ESRCH && errno != EPERM))
                  {
                        /* lockfile belongs to a live process */
                        ereport(FATAL,
                                    (errcode(ERRCODE_LOCK_FILE_EXISTS),
                                     errmsg("lock file \"%s\" already exists",
                                                filename),
                                     isDDLock ?
                                     (encoded_pid < 0 ?
                                      errhint("Is another postgres (PID %d) running in data directory \"%s\"?",
                                                  (int) other_pid, refName) :
                                      errhint("Is another postmaster (PID %d) running in data directory \"%s\"?",
                                                  (int) other_pid, refName)) :
                                     (encoded_pid < 0 ?
                                      errhint("Is another postgres (PID %d) using socket file \"%s\"?",
                                                  (int) other_pid, refName) :
                                      errhint("Is another postmaster (PID %d) using socket file \"%s\"?",
                                                  (int) other_pid, refName))));
                  }
            }

            /*
             * No, the creating process did not exist.      However, it could be that
             * the postmaster crashed (or more likely was kill -9'd by a clueless
             * admin) but has left orphan backends behind.  Check for this by
             * looking to see if there is an associated shmem segment that is
             * still in use.
             */
            if (isDDLock)
            {
                  char     *ptr;
                  unsigned long id1,
                                    id2;

                  ptr = strchr(buffer, '\n');
                  if (ptr != NULL &&
                        (ptr = strchr(ptr + 1, '\n')) != NULL)
                  {
                        ptr++;
                        if (sscanf(ptr, "%lu %lu", &id1, &id2) == 2)
                        {
                              if (PGSharedMemoryIsInUse(id1, id2))
                                    ereport(FATAL,
                                                (errcode(ERRCODE_LOCK_FILE_EXISTS),
                                                 errmsg("pre-existing shared memory block "
                                                            "(key %lu, ID %lu) is still in use",
                                                            id1, id2),
                                                 errhint("If you're sure there are no old "
                                                      "server processes still running, remove "
                                                             "the shared memory block "
                                                             "or just delete the file \"%s\".",
                                                             filename)));
                        }
                  }
            }

            /*
             * Looks like nobody's home.  Unlink the file and try again to create
             * it.      Need a loop because of possible race condition against other
             * would-be creators.
             */
            if (unlink(filename) < 0)
                  ereport(FATAL,
                              (errcode_for_file_access(),
                               errmsg("could not remove old lock file \"%s\": %m",
                                          filename),
                               errhint("The file seems accidentally left over, but "
                                       "it could not be removed. Please remove the file "
                                           "by hand and try again.")));
      }

      /*
       * Successfully created the file, now fill it.
       */
      snprintf(buffer, sizeof(buffer), "%d\n%s\n",
                   amPostmaster ? (int) my_pid : -((int) my_pid),
                   DataDir);
      errno = 0;
      if (write(fd, buffer, strlen(buffer)) != strlen(buffer))
      {
            int               save_errno = errno;

            close(fd);
            unlink(filename);
            /* if write didn't set errno, assume problem is no disk space */
            errno = save_errno ? save_errno : ENOSPC;
            ereport(FATAL,
                        (errcode_for_file_access(),
                         errmsg("could not write lock file \"%s\": %m", filename)));
      }
      if (close(fd))
      {
            int               save_errno = errno;

            unlink(filename);
            errno = save_errno;
            ereport(FATAL,
                        (errcode_for_file_access(),
                         errmsg("could not write lock file \"%s\": %m", filename)));
      }

      /*
       * Arrange for automatic removal of lockfile at proc_exit.
       */
      on_proc_exit(UnlinkLockFile, PointerGetDatum(strdup(filename)));
}

/*
 * Create the data directory lockfile.
 *
 * When this is called, we must have already switched the working
 * directory to DataDir, so we can just use a relative path.  This
 * helps ensure that we are locking the directory we should be.
 */
void
CreateDataDirLockFile(bool amPostmaster)
{
      CreateLockFile(DIRECTORY_LOCK_FILE, amPostmaster, true, DataDir);
}

/*
 * Create a lockfile for the specified Unix socket file.
 */
void
CreateSocketLockFile(const char *socketfile, bool amPostmaster)
{
      char        lockfile[MAXPGPATH];

      snprintf(lockfile, sizeof(lockfile), "%s.lock", socketfile);
      CreateLockFile(lockfile, amPostmaster, false, socketfile);
      /* Save name of lockfile for TouchSocketLockFile */
      strcpy(socketLockFile, lockfile);
}

/*
 * TouchSocketLockFile -- mark socket lock file as recently accessed
 *
 * This routine should be called every so often to ensure that the lock file
 * has a recent mod or access date.  That saves it
 * from being removed by overenthusiastic /tmp-directory-cleaner daemons.
 * (Another reason we should never have put the socket file in /tmp...)
 */
void
TouchSocketLockFile(void)
{
      /* Do nothing if we did not create a socket... */
      if (socketLockFile[0] != '\0')
      {
            /*
             * utime() is POSIX standard, utimes() is a common alternative; if we
             * have neither, fall back to actually reading the file (which only
             * sets the access time not mod time, but that should be enough in
             * most cases).  In all paths, we ignore errors.
             */
#ifdef HAVE_UTIME
            utime(socketLockFile, NULL);
#else                                     /* !HAVE_UTIME */
#ifdef HAVE_UTIMES
            utimes(socketLockFile, NULL);
#else                                     /* !HAVE_UTIMES */
            int               fd;
            char        buffer[1];

            fd = open(socketLockFile, O_RDONLY | PG_BINARY, 0);
            if (fd >= 0)
            {
                  read(fd, buffer, sizeof(buffer));
                  close(fd);
            }
#endif   /* HAVE_UTIMES */
#endif   /* HAVE_UTIME */
      }
}

/*
 * Append information about a shared memory segment to the data directory
 * lock file.
 *
 * This may be called multiple times in the life of a postmaster, if we
 * delete and recreate shmem due to backend crash.    Therefore, be prepared
 * to overwrite existing information.  (As of 7.1, a postmaster only creates
 * one shm seg at a time; but for the purposes here, if we did have more than
 * one then any one of them would do anyway.)
 */
void
RecordSharedMemoryInLockFile(unsigned long id1, unsigned long id2)
{
      int               fd;
      int               len;
      char     *ptr;
      char        buffer[BLCKSZ];

      fd = open(DIRECTORY_LOCK_FILE, O_RDWR | PG_BINARY, 0);
      if (fd < 0)
      {
            ereport(LOG,
                        (errcode_for_file_access(),
                         errmsg("could not open file \"%s\": %m",
                                    DIRECTORY_LOCK_FILE)));
            return;
      }
      len = read(fd, buffer, sizeof(buffer) - 100);
      if (len < 0)
      {
            ereport(LOG,
                        (errcode_for_file_access(),
                         errmsg("could not read from file \"%s\": %m",
                                    DIRECTORY_LOCK_FILE)));
            close(fd);
            return;
      }
      buffer[len] = '\0';

      /*
       * Skip over first two lines (PID and path).
       */
      ptr = strchr(buffer, '\n');
      if (ptr == NULL ||
            (ptr = strchr(ptr + 1, '\n')) == NULL)
      {
            elog(LOG, "bogus data in \"%s\"", DIRECTORY_LOCK_FILE);
            close(fd);
            return;
      }
      ptr++;

      /*
       * Append key information.    Format to try to keep it the same length
       * always (trailing junk won't hurt, but might confuse humans).
       */
      sprintf(ptr, "%9lu %9lu\n", id1, id2);

      /*
       * And rewrite the data.  Since we write in a single kernel call, this
       * update should appear atomic to onlookers.
       */
      len = strlen(buffer);
      errno = 0;
      if (lseek(fd, (off_t) 0, SEEK_SET) != 0 ||
            (int) write(fd, buffer, len) != len)
      {
            /* if write didn't set errno, assume problem is no disk space */
            if (errno == 0)
                  errno = ENOSPC;
            ereport(LOG,
                        (errcode_for_file_access(),
                         errmsg("could not write to file \"%s\": %m",
                                    DIRECTORY_LOCK_FILE)));
            close(fd);
            return;
      }
      if (close(fd))
      {
            ereport(LOG,
                        (errcode_for_file_access(),
                         errmsg("could not write to file \"%s\": %m",
                                    DIRECTORY_LOCK_FILE)));
      }
}


/*-------------------------------------------------------------------------
 *                      Version checking support
 *-------------------------------------------------------------------------
 */

/*
 * Determine whether the PG_VERSION file in directory `path' indicates
 * a data version compatible with the version of this program.
 *
 * If compatible, return. Otherwise, ereport(FATAL).
 */
void
ValidatePgVersion(const char *path)
{
      char        full_path[MAXPGPATH];
      FILE     *file;
      int               ret;
      long        file_major,
                        file_minor;
      long        my_major = 0,
                        my_minor = 0;
      char     *endptr;
      const char *version_string = PG_VERSION;

      my_major = strtol(version_string, &endptr, 10);
      if (*endptr == '.')
            my_minor = strtol(endptr + 1, NULL, 10);

      snprintf(full_path, sizeof(full_path), "%s/PG_VERSION", path);

      file = AllocateFile(full_path, "r");
      if (!file)
      {
            if (errno == ENOENT)
                  ereport(FATAL,
                              (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                               errmsg("\"%s\" is not a valid data directory",
                                          path),
                               errdetail("File \"%s\" is missing.", full_path)));
            else
                  ereport(FATAL,
                              (errcode_for_file_access(),
                               errmsg("could not open file \"%s\": %m", full_path)));
      }

      ret = fscanf(file, "%ld.%ld", &file_major, &file_minor);
      if (ret != 2)
            ereport(FATAL,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("\"%s\" is not a valid data directory",
                                    path),
                         errdetail("File \"%s\" does not contain valid data.",
                                       full_path),
                         errhint("You might need to initdb.")));

      FreeFile(file);

      if (my_major != file_major || my_minor != file_minor)
            ereport(FATAL,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("database files are incompatible with server"),
                         errdetail("The data directory was initialized by PostgreSQL version %ld.%ld, "
                                       "which is not compatible with this version %s.",
                                       file_major, file_minor, version_string)));
}

/*-------------------------------------------------------------------------
 *                      Library preload support
 *-------------------------------------------------------------------------
 */

/*
 * GUC variables: lists of library names to be preloaded at postmaster
 * start and at backend start
 */
char     *shared_preload_libraries_string = NULL;
char     *local_preload_libraries_string = NULL;

/* Flag telling that we are loading shared_preload_libraries */
bool        process_shared_preload_libraries_in_progress = false;

/*
 * load the shared libraries listed in 'libraries'
 *
 * 'gucname': name of GUC variable, for error reports
 * 'restricted': if true, force libraries to be in $libdir/plugins/
 */
static void
load_libraries(const char *libraries, const char *gucname, bool restricted)
{
      char     *rawstring;
      List     *elemlist;
      int               elevel;
      ListCell   *l;

      if (libraries == NULL || libraries[0] == '\0')
            return;                             /* nothing to do */

      /* Need a modifiable copy of string */
      rawstring = pstrdup(libraries);

      /* Parse string into list of identifiers */
      if (!SplitIdentifierString(rawstring, ',', &elemlist))
      {
            /* syntax error in list */
            pfree(rawstring);
            list_free(elemlist);
            ereport(LOG,
                        (errcode(ERRCODE_SYNTAX_ERROR),
                         errmsg("invalid list syntax in parameter \"%s\"",
                                    gucname)));
            return;
      }

      /*
       * Choose notice level: avoid repeat messages when re-loading a library
       * that was preloaded into the postmaster.      (Only possible in EXEC_BACKEND
       * configurations)
       */
#ifdef EXEC_BACKEND
      if (IsUnderPostmaster && process_shared_preload_libraries_in_progress)
            elevel = DEBUG2;
      else
#endif
            elevel = LOG;

      foreach(l, elemlist)
      {
            char     *tok = (char *) lfirst(l);
            char     *filename;

            filename = pstrdup(tok);
            canonicalize_path(filename);
            /* If restricting, insert $libdir/plugins if not mentioned already */
            if (restricted && first_dir_separator(filename) == NULL)
            {
                  char     *expanded;

                  expanded = palloc(strlen("$libdir/plugins/") + strlen(filename) + 1);
                  strcpy(expanded, "$libdir/plugins/");
                  strcat(expanded, filename);
                  pfree(filename);
                  filename = expanded;
            }
            load_file(filename, restricted);
            ereport(elevel,
                        (errmsg("loaded library \"%s\"", filename)));
            pfree(filename);
      }

      pfree(rawstring);
      list_free(elemlist);
}

/*
 * process any libraries that should be preloaded at postmaster start
 */
void
process_shared_preload_libraries(void)
{
      process_shared_preload_libraries_in_progress = true;
      load_libraries(shared_preload_libraries_string,
                           "shared_preload_libraries",
                           false);
      process_shared_preload_libraries_in_progress = false;
}

/*
 * process any libraries that should be preloaded at backend start
 */
void
process_local_preload_libraries(void)
{
      load_libraries(local_preload_libraries_string,
                           "local_preload_libraries",
                           true);
}

void
pg_bindtextdomain(const char *domain)
{
#ifdef ENABLE_NLS
      if (my_exec_path[0] != '\0')
      {
            char        locale_path[MAXPGPATH];

            get_locale_path(my_exec_path, locale_path);
            bindtextdomain(domain, locale_path);
            pg_bind_textdomain_codeset(domain);
      }
#endif
}

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