Wed Jul 17 21:53:45 1996 Roland McGrath <roland@delasyd.gnu.ai.mit.edu>

	* elf/Makefile (dl-routines): Add dl-cache.
	* elf/dl-cache.c: New file.
	* elf/dl-load.c (_dl_map_object): Check cache before default path.

3 files changed, 109 insertions, 1 deletions

diff --git a/elf/Makefile b/elf/Makefile
index 13fced3b85..3b3bd1457b 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -25,7 +25,7 @@ routines	= $(dl-routines) dl-open dl-close dl-symbol dl-support
 
 # The core dynamic linking functions are in libc for the static and
 # profiled libraries.
-dl-routines	= $(addprefix dl-,load lookup object reloc deps \
+dl-routines	= $(addprefix dl-,load cache lookup object reloc deps \
 			          runtime error init fini debug)
 # But they are absent from the shared libc, because that code is in ld.so.
 elide-routines.so = $(dl-routines) dl-support
diff --git a/elf/dl-cache.c b/elf/dl-cache.c
new file mode 100644
index 0000000000..a282d313cf
--- /dev/null
+++ b/elf/dl-cache.c
@@ -0,0 +1,85 @@
+/* Support for reading /etc/ld.so.cache files written by Linux ldconfig.
+Copyright (C) 1996 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <link.h>
+#include <sys/mman.h>
+
+/* System-dependent function to read a file's whole contents
+   in the most convenient manner available.  */
+extern void *_dl_sysdep_read_whole_file (const char *filename,
+					 size_t *filesize_ptr,
+					 int mmap_prot);
+
+#define CACHEMAGIC "ld.so-1.7.0"
+
+struct cache_file
+  {
+    char magic[sizeof CACHEMAGIC - 1];
+    unsigned int nlibs;
+    struct
+      {
+	int flags;		/* This is 1 for an ELF library.  */
+	unsigned int key, value; /* String table indices.  */
+      } libs[0];
+  };
+
+/* Look up NAME in ld.so.cache and return the file name stored there,
+   or null if none is found.  */
+
+const char *
+_dl_load_cache_lookup (const char *name)
+{
+  static struct cache_file *cache;
+  static size_t cachesize;
+  unsigned int i;
+
+  if (cache == (void *) -1)
+    /* Previously looked for the cache file and didn't find it.  */
+    return NULL;
+
+  if (cache == NULL)
+    {
+      /* Read the contents of the file.  */
+      void *file = _dl_sysdep_read_whole_file ("/etc/ld.so.cache", &cachesize,
+					       PROT_READ);
+      if (file && cachesize > sizeof *cache &&
+	  !memcmp (file, CACHEMAGIC, sizeof CACHEMAGIC - 1))
+	/* Looks ok.  */
+	cache = file;
+      else
+	{
+	  if (file)
+	    __munmap (file, cachesize);
+	  cache = (void *) -1;
+	  return NULL;
+	}
+    }
+
+  for (i = 0; i < cache->nlibs; ++i)
+    if (cache->libs[i].flags == 1 && /* ELF library entry.  */
+	/* Make sure string table indices are not bogus before using them.  */
+	cache->libs[i].key < cachesize - sizeof *cache &&
+	cache->libs[i].value < cachesize - sizeof *cache &&
+	/* Does the name match?  */
+	! strcmp (name, ((const char *) &cache->libs[cache->nlibs] +
+			 cache->libs[i].key)))
+      return (const char *) &cache->libs[cache->nlibs] + cache->libs[i].value;
+
+  return NULL;
+}
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 29ac0bfd87..fc2733252a 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -513,6 +513,29 @@ _dl_map_object (struct link_map *loader, const char *name, int type)
       /* Try an environment variable (unless setuid).  */
       if (fd == -1 && ! _dl_secure)
 	trypath (getenv ("LD_LIBRARY_PATH"));
+      if (fd == -1)
+	{
+	  /* Check the list of libraries in the file /etc/ld.so.cache,
+	     for compatibility with Linux's ldconfig program.  */
+	  extern const char *_dl_load_cache_lookup (const char *name);
+	  const char *cached = _dl_load_cache_lookup (name);
+	  if (cached)
+	    {
+	      fd = __open (cached, O_RDONLY);
+	      if (fd != -1)
+		{
+		  size_t cl = strlen (cached) + 1;
+		  realname = malloc (cl);
+		  if (realname)
+		    memcpy (realname, cached, cl);
+		  else
+		    {
+		      __close (fd);
+		      fd = -1;
+		    }
+		}
+	    }
+	}
       /* Finally, try the default path.  */
       if (fd == -1)
 	{