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Sourcecode: postgresql-8.4 version File versions

dfmgr.c

/*-------------------------------------------------------------------------
 *
 * dfmgr.c
 *      Dynamic function manager code.
 *
 * 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/fmgr/dfmgr.c,v 1.98 2009/01/01 17:23:51 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <sys/stat.h>

#ifndef WIN32_ONLY_COMPILER
#include "dynloader.h"
#else
#include "port/dynloader/win32.h"
#endif
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "utils/dynamic_loader.h"
#include "utils/hsearch.h"


/* signatures for PostgreSQL-specific library init/fini functions */
typedef void (*PG_init_t) (void);
typedef void (*PG_fini_t) (void);

/* hashtable entry for rendezvous variables */
typedef struct
{
      char        varName[NAMEDATALEN];   /* hash key (must be first) */
      void     *varValue;
} rendezvousHashEntry;

/*
 * List of dynamically loaded files (kept in malloc'd memory).
 */

typedef struct df_files
{
      struct df_files *next;        /* List link */
      dev_t       device;                 /* Device file is on */
#ifndef WIN32                             /* ensures we never again depend on this under
                                                 * win32 */
      ino_t       inode;                  /* Inode number of file */
#endif
      void     *handle;             /* a handle for pg_dl* functions */
      char        filename[1];      /* Full pathname of file */

      /*
       * we allocate the block big enough for actual length of pathname.
       * filename[] must be last item in struct!
       */
} DynamicFileList;

static DynamicFileList *file_list = NULL;
static DynamicFileList *file_tail = NULL;

/* stat() call under Win32 returns an st_ino field, but it has no meaning */
#ifndef WIN32
#define SAME_INODE(A,B) ((A).st_ino == (B).inode && (A).st_dev == (B).device)
#else
#define SAME_INODE(A,B) false
#endif

char     *Dynamic_library_path;

static void *internal_load_library(const char *libname);
static void incompatible_module_error(const char *libname,
                                                      const Pg_magic_struct *module_magic_data);
static void internal_unload_library(const char *libname);
static bool file_exists(const char *name);
static char *expand_dynamic_library_name(const char *name);
static void check_restricted_library_name(const char *name);
static char *substitute_libpath_macro(const char *name);
static char *find_in_dynamic_libpath(const char *basename);

/* Magic structure that module needs to match to be accepted */
static const Pg_magic_struct magic_data = PG_MODULE_MAGIC_DATA;


/*
 * Load the specified dynamic-link library file, and look for a function
 * named funcname in it.
 *
 * If the function is not found, we raise an error if signalNotFound is true,
 * else return (PGFunction) NULL.  Note that errors in loading the library
 * will provoke ereport() regardless of signalNotFound.
 *
 * If filehandle is not NULL, then *filehandle will be set to a handle
 * identifying the library file.  The filehandle can be used with
 * lookup_external_function to lookup additional functions in the same file
 * at less cost than repeating load_external_function.
 */
PGFunction
load_external_function(char *filename, char *funcname,
                                 bool signalNotFound, void **filehandle)
{
      char     *fullname;
      void     *lib_handle;
      PGFunction  retval;

      /* Expand the possibly-abbreviated filename to an exact path name */
      fullname = expand_dynamic_library_name(filename);

      /* Load the shared library, unless we already did */
      lib_handle = internal_load_library(fullname);

      /* Return handle if caller wants it */
      if (filehandle)
            *filehandle = lib_handle;

      /* Look up the function within the library */
      retval = (PGFunction) pg_dlsym(lib_handle, funcname);

      if (retval == NULL && signalNotFound)
            ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_FUNCTION),
                         errmsg("could not find function \"%s\" in file \"%s\"",
                                    funcname, fullname)));

      pfree(fullname);
      return retval;
}

/*
 * This function loads a shlib file without looking up any particular
 * function in it.      If the same shlib has previously been loaded,
 * unload and reload it.
 *
 * When 'restricted' is true, only libraries in the presumed-secure
 * directory $libdir/plugins may be referenced.
 */
void
load_file(const char *filename, bool restricted)
{
      char     *fullname;

      /* Apply security restriction if requested */
      if (restricted)
            check_restricted_library_name(filename);

      /* Expand the possibly-abbreviated filename to an exact path name */
      fullname = expand_dynamic_library_name(filename);

      /* Unload the library if currently loaded */
      internal_unload_library(fullname);

      /* Load the shared library */
      (void) internal_load_library(fullname);

      pfree(fullname);
}

/*
 * Lookup a function whose library file is already loaded.
 * Return (PGFunction) NULL if not found.
 */
PGFunction
lookup_external_function(void *filehandle, char *funcname)
{
      return (PGFunction) pg_dlsym(filehandle, funcname);
}


/*
 * Load the specified dynamic-link library file, unless it already is
 * loaded.  Return the pg_dl* handle for the file.
 *
 * Note: libname is expected to be an exact name for the library file.
 */
static void *
internal_load_library(const char *libname)
{
      DynamicFileList *file_scanner;
      PGModuleMagicFunction magic_func;
      char     *load_error;
      struct stat stat_buf;
      PG_init_t   PG_init;

      /*
       * Scan the list of loaded FILES to see if the file has been loaded.
       */
      for (file_scanner = file_list;
             file_scanner != NULL &&
             strcmp(libname, file_scanner->filename) != 0;
             file_scanner = file_scanner->next)
            ;

      if (file_scanner == NULL)
      {
            /*
             * Check for same files - different paths (ie, symlink or link)
             */
            if (stat(libname, &stat_buf) == -1)
                  ereport(ERROR,
                              (errcode_for_file_access(),
                               errmsg("could not access file \"%s\": %m",
                                          libname)));

            for (file_scanner = file_list;
                   file_scanner != NULL &&
                   !SAME_INODE(stat_buf, *file_scanner);
                   file_scanner = file_scanner->next)
                  ;
      }

      if (file_scanner == NULL)
      {
            /*
             * File not loaded yet.
             */
            file_scanner = (DynamicFileList *)
                  malloc(sizeof(DynamicFileList) + strlen(libname));
            if (file_scanner == NULL)
                  ereport(ERROR,
                              (errcode(ERRCODE_OUT_OF_MEMORY),
                               errmsg("out of memory")));

            MemSet(file_scanner, 0, sizeof(DynamicFileList));
            strcpy(file_scanner->filename, libname);
            file_scanner->device = stat_buf.st_dev;
#ifndef WIN32
            file_scanner->inode = stat_buf.st_ino;
#endif
            file_scanner->next = NULL;

            file_scanner->handle = pg_dlopen(file_scanner->filename);
            if (file_scanner->handle == NULL)
            {
                  load_error = (char *) pg_dlerror();
                  free((char *) file_scanner);
                  /* errcode_for_file_access might not be appropriate here? */
                  ereport(ERROR,
                              (errcode_for_file_access(),
                               errmsg("could not load library \"%s\": %s",
                                          libname, load_error)));
            }

            /* Check the magic function to determine compatibility */
            magic_func = (PGModuleMagicFunction)
                  pg_dlsym(file_scanner->handle, PG_MAGIC_FUNCTION_NAME_STRING);
            if (magic_func)
            {
                  const Pg_magic_struct *magic_data_ptr = (*magic_func) ();

                  if (magic_data_ptr->len != magic_data.len ||
                        memcmp(magic_data_ptr, &magic_data, magic_data.len) != 0)
                  {
                        /* copy data block before unlinking library */
                        Pg_magic_struct module_magic_data = *magic_data_ptr;

                        /* try to unlink library */
                        pg_dlclose(file_scanner->handle);
                        free((char *) file_scanner);

                        /* issue suitable complaint */
                        incompatible_module_error(libname, &module_magic_data);
                  }
            }
            else
            {
                  /* try to unlink library */
                  pg_dlclose(file_scanner->handle);
                  free((char *) file_scanner);
                  /* complain */
                  ereport(ERROR,
                          (errmsg("incompatible library \"%s\": missing magic block",
                                      libname),
                           errhint("Extension libraries are required to use the PG_MODULE_MAGIC macro.")));
            }

            /*
             * If the library has a _PG_init() function, call it.
             */
            PG_init = (PG_init_t) pg_dlsym(file_scanner->handle, "_PG_init");
            if (PG_init)
                  (*PG_init) ();

            /* OK to link it into list */
            if (file_list == NULL)
                  file_list = file_scanner;
            else
                  file_tail->next = file_scanner;
            file_tail = file_scanner;
      }

      return file_scanner->handle;
}

/*
 * Report a suitable error for an incompatible magic block.
 */
static void
incompatible_module_error(const char *libname,
                                      const Pg_magic_struct *module_magic_data)
{
      StringInfoData    details;

      /*
       * If the version doesn't match, just report that, because the rest of the
       * block might not even have the fields we expect.
       */
      if (magic_data.version != module_magic_data->version)
            ereport(ERROR,
                        (errmsg("incompatible library \"%s\": version mismatch",
                                    libname),
                         errdetail("Server is version %d.%d, library is version %d.%d.",
                                       magic_data.version / 100,
                                       magic_data.version % 100,
                                       module_magic_data->version / 100,
                                       module_magic_data->version % 100)));

      /*
       * Otherwise, spell out which fields don't agree.
       *
       * XXX this code has to be adjusted any time the set of fields in a magic
       * block change!
       */
      initStringInfo(&details);

      if (module_magic_data->funcmaxargs != magic_data.funcmaxargs)
      {
            if (details.len)
                  appendStringInfoChar(&details, '\n');
            appendStringInfo(&details,
                                     _("Server has FUNC_MAX_ARGS = %d, library has %d."),
                                     magic_data.funcmaxargs,
                                     module_magic_data->funcmaxargs);
      }
      if (module_magic_data->indexmaxkeys != magic_data.indexmaxkeys)
      {
            if (details.len)
                  appendStringInfoChar(&details, '\n');
            appendStringInfo(&details,
                                     _("Server has INDEX_MAX_KEYS = %d, library has %d."),
                                     magic_data.indexmaxkeys,
                                     module_magic_data->indexmaxkeys);
      }
      if (module_magic_data->namedatalen != magic_data.namedatalen)
      {
            if (details.len)
                  appendStringInfoChar(&details, '\n');
            appendStringInfo(&details,
                                     _("Server has NAMEDATALEN = %d, library has %d."),
                                     magic_data.namedatalen,
                                     module_magic_data->namedatalen);
      }
      if (module_magic_data->float4byval != magic_data.float4byval)
      {
            if (details.len)
                  appendStringInfoChar(&details, '\n');
            appendStringInfo(&details,
                                     _("Server has FLOAT4PASSBYVAL = %s, library has %s."),
                                     magic_data.float4byval ? "true" : "false",
                                     module_magic_data->float4byval ? "true" : "false");
      }
      if (module_magic_data->float8byval != magic_data.float8byval)
      {
            if (details.len)
                  appendStringInfoChar(&details, '\n');
            appendStringInfo(&details,
                                     _("Server has FLOAT8PASSBYVAL = %s, library has %s."),
                                     magic_data.float8byval ? "true" : "false",
                                     module_magic_data->float8byval ? "true" : "false");
      }

      if (details.len == 0)
            appendStringInfo(&details,
                                     _("Magic block has unexpected length or padding difference."));

      ereport(ERROR,
                  (errmsg("incompatible library \"%s\": magic block mismatch",
                              libname),
                   errdetail("%s", details.data)));
}

/*
 * Unload the specified dynamic-link library file, if it is loaded.
 *
 * Note: libname is expected to be an exact name for the library file.
 */
static void
internal_unload_library(const char *libname)
{
      DynamicFileList *file_scanner,
                     *prv,
                     *nxt;
      struct stat stat_buf;
      PG_fini_t   PG_fini;

      /*
       * We need to do stat() in order to determine whether this is the same
       * file as a previously loaded file; it's also handy so as to give a good
       * error message if bogus file name given.
       */
      if (stat(libname, &stat_buf) == -1)
            ereport(ERROR,
                        (errcode_for_file_access(),
                         errmsg("could not access file \"%s\": %m", libname)));

      /*
       * We have to zap all entries in the list that match on either filename or
       * inode, else internal_load_library() will still think it's present.
       */
      prv = NULL;
      for (file_scanner = file_list; file_scanner != NULL; file_scanner = nxt)
      {
            nxt = file_scanner->next;
            if (strcmp(libname, file_scanner->filename) == 0 ||
                  SAME_INODE(stat_buf, *file_scanner))
            {
                  if (prv)
                        prv->next = nxt;
                  else
                        file_list = nxt;

                  /*
                   * If the library has a _PG_fini() function, call it.
                   */
                  PG_fini = (PG_fini_t) pg_dlsym(file_scanner->handle, "_PG_fini");
                  if (PG_fini)
                        (*PG_fini) ();

                  clear_external_function_hash(file_scanner->handle);
                  pg_dlclose(file_scanner->handle);
                  free((char *) file_scanner);
                  /* prv does not change */
            }
            else
                  prv = file_scanner;
      }
}

static bool
file_exists(const char *name)
{
      struct stat st;

      AssertArg(name != NULL);

      if (stat(name, &st) == 0)
            return S_ISDIR(st.st_mode) ? false : true;
      else if (!(errno == ENOENT || errno == ENOTDIR || errno == EACCES))
            ereport(ERROR,
                        (errcode_for_file_access(),
                         errmsg("could not access file \"%s\": %m", name)));

      return false;
}


/* Example format: ".so" */
#ifndef DLSUFFIX
#error "DLSUFFIX must be defined to compile this file."
#endif

/*
 * If name contains a slash, check if the file exists, if so return
 * the name.  Else (no slash) try to expand using search path (see
 * find_in_dynamic_libpath below); if that works, return the fully
 * expanded file name.  If the previous failed, append DLSUFFIX and
 * try again.  If all fails, just return the original name.
 *
 * The result will always be freshly palloc'd.
 */
static char *
expand_dynamic_library_name(const char *name)
{
      bool        have_slash;
      char     *new;
      char     *full;

      AssertArg(name);

      have_slash = (first_dir_separator(name) != NULL);

      if (!have_slash)
      {
            full = find_in_dynamic_libpath(name);
            if (full)
                  return full;
      }
      else
      {
            full = substitute_libpath_macro(name);
            if (file_exists(full))
                  return full;
            pfree(full);
      }

      new = palloc(strlen(name) + strlen(DLSUFFIX) + 1);
      strcpy(new, name);
      strcat(new, DLSUFFIX);

      if (!have_slash)
      {
            full = find_in_dynamic_libpath(new);
            pfree(new);
            if (full)
                  return full;
      }
      else
      {
            full = substitute_libpath_macro(new);
            pfree(new);
            if (file_exists(full))
                  return full;
            pfree(full);
      }

      /*
       * If we can't find the file, just return the string as-is. The ensuing
       * load attempt will fail and report a suitable message.
       */
      return pstrdup(name);
}

/*
 * Check a restricted library name.  It must begin with "$libdir/plugins/"
 * and there must not be any directory separators after that (this is
 * sufficient to prevent ".." style attacks).
 */
static void
check_restricted_library_name(const char *name)
{
      if (strncmp(name, "$libdir/plugins/", 16) != 0 ||
            first_dir_separator(name + 16) != NULL)
            ereport(ERROR,
                        (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                         errmsg("access to library \"%s\" is not allowed",
                                    name)));
}

/*
 * Substitute for any macros appearing in the given string.
 * Result is always freshly palloc'd.
 */
static char *
substitute_libpath_macro(const char *name)
{
      const char *sep_ptr;
      char     *ret;

      AssertArg(name != NULL);

      /* Currently, we only recognize $libdir at the start of the string */
      if (name[0] != '$')
            return pstrdup(name);

      if ((sep_ptr = first_dir_separator(name)) == NULL)
            sep_ptr = name + strlen(name);

      if (strlen("$libdir") != sep_ptr - name ||
            strncmp(name, "$libdir", strlen("$libdir")) != 0)
            ereport(ERROR,
                        (errcode(ERRCODE_INVALID_NAME),
                         errmsg("invalid macro name in dynamic library path: %s",
                                    name)));

      ret = palloc(strlen(pkglib_path) + strlen(sep_ptr) + 1);

      strcpy(ret, pkglib_path);
      strcat(ret, sep_ptr);

      return ret;
}


/*
 * Search for a file called 'basename' in the colon-separated search
 * path Dynamic_library_path.  If the file is found, the full file name
 * is returned in freshly palloc'd memory.  If the file is not found,
 * return NULL.
 */
static char *
find_in_dynamic_libpath(const char *basename)
{
      const char *p;
      size_t            baselen;

      AssertArg(basename != NULL);
      AssertArg(first_dir_separator(basename) == NULL);
      AssertState(Dynamic_library_path != NULL);

      p = Dynamic_library_path;
      if (strlen(p) == 0)
            return NULL;

      baselen = strlen(basename);

      for (;;)
      {
            size_t            len;
            char     *piece;
            char     *mangled;
            char     *full;

            piece = first_path_separator(p);
            if (piece == p)
                  ereport(ERROR,
                              (errcode(ERRCODE_INVALID_NAME),
                               errmsg("zero-length component in parameter \"dynamic_library_path\"")));

            if (piece == 0)
                  len = strlen(p);
            else
                  len = piece - p;

            piece = palloc(len + 1);
            strlcpy(piece, p, len + 1);

            mangled = substitute_libpath_macro(piece);
            pfree(piece);

            canonicalize_path(mangled);

            /* only absolute paths */
            if (!is_absolute_path(mangled))
                  ereport(ERROR,
                              (errcode(ERRCODE_INVALID_NAME),
                               errmsg("component in parameter \"dynamic_library_path\" is not an absolute path")));

            full = palloc(strlen(mangled) + 1 + baselen + 1);
            sprintf(full, "%s/%s", mangled, basename);
            pfree(mangled);

            elog(DEBUG3, "find_in_dynamic_libpath: trying \"%s\"", full);

            if (file_exists(full))
                  return full;

            pfree(full);

            if (p[len] == '\0')
                  break;
            else
                  p += len + 1;
      }

      return NULL;
}


/*
 * Find (or create) a rendezvous variable that one dynamically
 * loaded library can use to meet up with another.
 *
 * On the first call of this function for a particular varName,
 * a "rendezvous variable" is created with the given name.
 * The value of the variable is a void pointer (initially set to NULL).
 * Subsequent calls with the same varName just return the address of
 * the existing variable.  Once created, a rendezvous variable lasts
 * for the life of the process.
 *
 * Dynamically loaded libraries can use rendezvous variables
 * to find each other and share information: they just need to agree
 * on the variable name and the data it will point to.
 */
void    **
find_rendezvous_variable(const char *varName)
{
      static HTAB *rendezvousHash = NULL;

      rendezvousHashEntry *hentry;
      bool        found;

      /* Create a hashtable if we haven't already done so in this process */
      if (rendezvousHash == NULL)
      {
            HASHCTL           ctl;

            MemSet(&ctl, 0, sizeof(ctl));
            ctl.keysize = NAMEDATALEN;
            ctl.entrysize = sizeof(rendezvousHashEntry);
            rendezvousHash = hash_create("Rendezvous variable hash",
                                                       16,
                                                       &ctl,
                                                       HASH_ELEM);
      }

      /* Find or create the hashtable entry for this varName */
      hentry = (rendezvousHashEntry *) hash_search(rendezvousHash,
                                                                         varName,
                                                                         HASH_ENTER,
                                                                         &found);

      /* Initialize to NULL if first time */
      if (!found)
            hentry->varValue = NULL;

      return &hentry->varValue;
}

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