(dl_main): First check existence of ld.so.preload with access.

diff --git a/elf/rtld.c b/elf/rtld.c
index a65e9c4..e015477 100644 (file)
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1138,103 +1138,114 @@ of this helper program; chances are you did not intend to run this program.\n\
       HP_TIMING_ACCUM_NT (load_time, diff);
     }
 
-  /* Read the contents of the file.  */
-  const char preload_file[] = "/etc/ld.so.preload";
-  file = _dl_sysdep_read_whole_file (preload_file, &file_size,
-                                    PROT_READ | PROT_WRITE);
-  if (__builtin_expect (file != MAP_FAILED, 0))
+  /* There usually is no ld.so.preload file, it should only be used
+     for emergencies and testing.  So the open call etc should usually
+     fail.  Using access() on a non-existing file is faster than using
+     open().  So we do this first.  If it succeeds we do almost twice
+     the work but this does not matter, since it is not for production
+     use.  */
+  static const char preload_file[] = "/etc/ld.so.preload";
+  if (__builtin_expect (__access (preload_file, R_OK) == 0, 0))
     {
-      /* Parse the file.  It contains names of libraries to be loaded,
-        separated by white spaces or `:'.  It may also contain
-        comments introduced by `#'.  */
-      char *problem;
-      char *runp;
-      size_t rest;
-
-      /* Eliminate comments.  */
-      runp = file;
-      rest = file_size;
-      while (rest > 0)
+      /* Read the contents of the file.  */
+      file = _dl_sysdep_read_whole_file (preload_file, &file_size,
+                                        PROT_READ | PROT_WRITE);
+      if (__builtin_expect (file != MAP_FAILED, 0))
        {
-         char *comment = memchr (runp, '#', rest);
-         if (comment == NULL)
-           break;
-
-         rest -= comment - runp;
-         do
-           *comment = ' ';
-         while (--rest > 0 && *++comment != '\n');
-       }
-
-      /* We have one problematic case: if we have a name at the end of
-        the file without a trailing terminating characters, we cannot
-        place the \0.  Handle the case separately.  */
-      if (file[file_size - 1] != ' ' && file[file_size - 1] != '\t'
-         && file[file_size - 1] != '\n' && file[file_size - 1] != ':')
-       {
-         problem = &file[file_size];
-         while (problem > file && problem[-1] != ' ' && problem[-1] != '\t'
-                && problem[-1] != '\n' && problem[-1] != ':')
-           --problem;
-
-         if (problem > file)
-           problem[-1] = '\0';
-       }
-      else
-       {
-         problem = NULL;
-         file[file_size - 1] = '\0';
-       }
+         /* Parse the file.  It contains names of libraries to be loaded,
+            separated by white spaces or `:'.  It may also contain
+            comments introduced by `#'.  */
+         char *problem;
+         char *runp;
+         size_t rest;
+
+         /* Eliminate comments.  */
+         runp = file;
+         rest = file_size;
+         while (rest > 0)
+           {
+             char *comment = memchr (runp, '#', rest);
+             if (comment == NULL)
+               break;
 
-      HP_TIMING_NOW (start);
+             rest -= comment - runp;
+             do
+               *comment = ' ';
+             while (--rest > 0 && *++comment != '\n');
+           }
 
-      if (file != problem)
-       {
-         char *p;
-         runp = file;
-         while ((p = strsep (&runp, ": \t\n")) != NULL)
-           if (p[0] != '\0')
-             {
-               const char *objname;
-               const char *err_str = NULL;
-               struct map_args args;
+         /* We have one problematic case: if we have a name at the end of
+            the file without a trailing terminating characters, we cannot
+            place the \0.  Handle the case separately.  */
+         if (file[file_size - 1] != ' ' && file[file_size - 1] != '\t'
+             && file[file_size - 1] != '\n' && file[file_size - 1] != ':')
+           {
+             problem = &file[file_size];
+             while (problem > file && problem[-1] != ' '
+                    && problem[-1] != '\t'
+                    && problem[-1] != '\n' && problem[-1] != ':')
+               --problem;
+
+             if (problem > file)
+               problem[-1] = '\0';
+           }
+         else
+           {
+             problem = NULL;
+             file[file_size - 1] = '\0';
+           }
 
-               args.str = p;
-               args.loader = GL(dl_loaded);
-               args.is_preloaded = 1;
-               args.mode = 0;
+         HP_TIMING_NOW (start);
 
-               (void) _dl_catch_error (&objname, &err_str, map_doit, &args);
-               if (__builtin_expect (err_str != NULL, 0))
+         if (file != problem)
+           {
+             char *p;
+             runp = file;
+             while ((p = strsep (&runp, ": \t\n")) != NULL)
+               if (p[0] != '\0')
                  {
-                   _dl_error_printf ("\
+                   const char *objname;
+                   const char *err_str = NULL;
+                   struct map_args args;
+
+                   args.str = p;
+                   args.loader = GL(dl_loaded);
+                   args.is_preloaded = 1;
+                   args.mode = 0;
+
+                   (void) _dl_catch_error (&objname, &err_str, map_doit,
+                                           &args);
+                   if (__builtin_expect (err_str != NULL, 0))
+                     {
+                       _dl_error_printf ("\
 ERROR: ld.so: object '%s' from %s cannot be preloaded: ignored.\n",
-                                     p, preload_file);
-                   /* No need to call free, this is still before the libc's
-                      malloc is used.  */
+                                         p, preload_file);
+                       /* No need to call free, this is still before
+                          the libc's malloc is used.  */
+                     }
+                   else if (++args.map->l_opencount == 1)
+                     /* It is no duplicate.  */
+                     ++npreloads;
                  }
-               else if (++args.map->l_opencount == 1)
-                 /* It is no duplicate.  */
-                 ++npreloads;
-             }
-       }
+           }
 
-      if (problem != NULL)
-       {
-         char *p = strndupa (problem, file_size - (problem - file));
-         struct link_map *new_map = _dl_map_object (GL(dl_loaded), p, 1,
-                                                    lt_library, 0, 0);
-         if (++new_map->l_opencount == 1)
-           /* It is no duplicate.  */
-           ++npreloads;
-       }
+         if (problem != NULL)
+           {
+             char *p = strndupa (problem, file_size - (problem - file));
+             struct link_map *new_map = _dl_map_object (GL(dl_loaded), p, 1,
+                                                        lt_library, 0, 0);
+             if (++new_map->l_opencount == 1)
+               /* It is no duplicate.  */
+               ++npreloads;
+           }
 
-      HP_TIMING_NOW (stop);
-      HP_TIMING_DIFF (diff, start, stop);
-      HP_TIMING_ACCUM_NT (load_time, diff);
+         HP_TIMING_NOW (stop);
+         HP_TIMING_DIFF (diff, start, stop);
+         HP_TIMING_ACCUM_NT (load_time, diff);
 
-      /* We don't need the file anymore.  */
-      __munmap (file, file_size);
+         /* We don't need the file anymore.  */
+         __munmap (file, file_size);
+       }
     }
 
   if (__builtin_expect (npreloads, 0) != 0)