Implement support for LD_PRELOAD in the dynamic linker. Remove

descriptions of LD_NO_INTERN_SEARCH and LD_NOSTD_PATH from the manual
page, since they are not supported.

Submitted by:	Doug Ambrisko <ambrisko@ambrisko.roble.com>

4 files changed, 126 insertions, 34 deletions

diff --git a/libexec/rtld-aout/rtld.1 b/libexec/rtld-aout/rtld.1
index 2b3c75a..a66a861 100644
--- a/libexec/rtld-aout/rtld.1
+++ b/libexec/rtld-aout/rtld.1
@@ -1,4 +1,4 @@
-.\"	$Id$
+.\"	$Id: rtld.1,v 1.2 1995/10/05 05:16:52 nate Exp $
 .\"
 .\" Copyright (c) 1995 Paul Kranenburg
 .\" All rights reserved.
@@ -110,6 +110,13 @@ its behaviour as follows:
 .It Ev LD_LIBRARY_PATH
 A colon separated list of directories, overriding the default search path
 for shared libraries.
+This is ignored for set-user-ID and set-group-ID programs.
+.It Ev LD_PRELOAD
+A colon separated list of shared libraries, to be linked in before any
+other shared libraries.  If the directory is not specified then
+the directories specified by LD_LIBRARY_PATH will be searched first
+followed by the set of built-in standard directories.
+This is ignored for set-user-ID and set-group-ID programs.
 .It Ev LD_WARN_NON_PURE_CODE
 When set, issue a warning whenever a link-editing operation requires
 modification of the text segment of some loaded object. This is usually
@@ -122,15 +129,6 @@ When set, causes
 .Nm
 to exit after loading the shared objects and printing a summary which includes
 the absolute pathnames of all objects, to standard output.
-.It Ev LD_NO_INTERN_SEARCH
-When set,
-.Nm
-does not process any internal search paths that were recorded in the
-executable.
-.It Ev LD_NOSTD_PATH
-When set, do not include a set of built-in standard directory paths for
-searching. This might be useful when running on a system with a completely
-non-standard filesystem layout.
 .El
 .Pp
 .Sh FILES
diff --git a/libexec/rtld-aout/rtld.1aout b/libexec/rtld-aout/rtld.1aout
index 2b3c75a..a66a861 100644
--- a/libexec/rtld-aout/rtld.1aout
+++ b/libexec/rtld-aout/rtld.1aout
@@ -1,4 +1,4 @@
-.\"	$Id$
+.\"	$Id: rtld.1,v 1.2 1995/10/05 05:16:52 nate Exp $
 .\"
 .\" Copyright (c) 1995 Paul Kranenburg
 .\" All rights reserved.
@@ -110,6 +110,13 @@ its behaviour as follows:
 .It Ev LD_LIBRARY_PATH
 A colon separated list of directories, overriding the default search path
 for shared libraries.
+This is ignored for set-user-ID and set-group-ID programs.
+.It Ev LD_PRELOAD
+A colon separated list of shared libraries, to be linked in before any
+other shared libraries.  If the directory is not specified then
+the directories specified by LD_LIBRARY_PATH will be searched first
+followed by the set of built-in standard directories.
+This is ignored for set-user-ID and set-group-ID programs.
 .It Ev LD_WARN_NON_PURE_CODE
 When set, issue a warning whenever a link-editing operation requires
 modification of the text segment of some loaded object. This is usually
@@ -122,15 +129,6 @@ When set, causes
 .Nm
 to exit after loading the shared objects and printing a summary which includes
 the absolute pathnames of all objects, to standard output.
-.It Ev LD_NO_INTERN_SEARCH
-When set,
-.Nm
-does not process any internal search paths that were recorded in the
-executable.
-.It Ev LD_NOSTD_PATH
-When set, do not include a set of built-in standard directory paths for
-searching. This might be useful when running on a system with a completely
-non-standard filesystem layout.
 .El
 .Pp
 .Sh FILES
diff --git a/libexec/rtld-aout/rtld.c b/libexec/rtld-aout/rtld.c
index 3300538..bade56e 100644
--- a/libexec/rtld-aout/rtld.c
+++ b/libexec/rtld-aout/rtld.c
@@ -27,7 +27,7 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- *	$Id: rtld.c,v 1.31.1.5 1995/11/28 01:15:45 jdp Exp jdp $
+ *	$Id: rtld.c,v 1.32 1996/01/13 00:15:25 jdp Exp $
  */
 
 #include <sys/param.h>
@@ -163,6 +163,7 @@ static char		*main_progname = __main_progname;
 static char		us[] = "/usr/libexec/ld.so";
 static int		anon_fd = -1;
 static char		*ld_library_path;
+static char		*ld_preload;
 static int		tracing;
 
 struct so_map		*link_map_head;
@@ -183,6 +184,7 @@ static struct ld_entry	ld_entry = {
 static struct so_map	*map_object __P((	char *,
 						struct sod *,
 						struct so_map *));
+static int		map_preload __P((void));
 static int		map_sods __P((struct so_map *));
 static int		reloc_and_init __P((struct so_map *));
 static void		unmap_object __P((struct so_map	*, int));
@@ -200,6 +202,7 @@ static void		init_sods __P((struct so_list *));
 static int		call_map __P((struct so_map *, char *));
 static char		*findhint __P((char *, int, int *));
 static char		*rtfindlib __P((char *, int, int));
+static char		*rtfindfile __P((char *));
 void			binder_entry __P((void));
 long			binder __P((jmpslot_t *));
 static struct nzlist	*lookup __P((char *, struct so_map **, int));
@@ -280,8 +283,10 @@ struct _dynamic		*dp;
 	if (careful) {
 		unsetenv("LD_LIBRARY_PATH");
 		unsetenv("LD_PRELOAD");
-	} else
+	} else {
 		ld_library_path = getenv("LD_LIBRARY_PATH");
+	        ld_preload = getenv("LD_PRELOAD");
+	}
 
 	tracing = getenv("LD_TRACE_LOADED_OBJECTS") != NULL;
 
@@ -312,6 +317,13 @@ struct _dynamic		*dp;
 	crtp->crt_dp->d_entry = &ld_entry;
 	crtp->crt_dp->d_un.d_sdt->sdt_loaded = link_map_head->som_next;
 
+	/* Map in LD_PRELOADs before the main program's shared objects so we
+	   can intercept those calls */
+	if (ld_preload != NULL && *ld_preload != '\0') {
+	        if(map_preload() == -1)			/* Failed */
+			return -1;
+	}
+
 	/* Map all the shared objects that the main program depends upon */
 	if(map_sods(main_map) == -1)
 		return -1;
@@ -595,6 +607,48 @@ map_object(path, sodp, parent)
 }
 
 /*
+ * Map all the shared libraries named in the LD_PRELOAD environment
+ * variable.
+ *
+ * Returns 0 on success, -1 on failure.  On failure, an error message can
+ * be gotten via dlerror().
+ */
+        static int
+map_preload __P((void)) {
+	char    *ld_name = ld_preload;
+	char	*name;
+
+	while ((name = strsep(&ld_name, ":")) != NULL) {
+		char		*path = NULL;
+		struct so_map	*smp = NULL;
+
+		if (*name != '\0') {
+			path = (strchr(name, '/') != NULL) ?  strdup(name) :
+				rtfindfile(name);
+		}
+		if (path == NULL) {
+			generror("Can't find LD_PRELOAD shared"
+				" library \"%s\"", name);
+		} else {
+			smp = map_object(path, (struct sod *) NULL,
+				(struct so_map *) NULL);
+			free(path);
+		}
+		if (ld_name != NULL)
+			*(ld_name - 1) = ':';
+		if (smp == NULL) {
+			/*
+			 * We don't bother to unmap already-loaded libraries
+			 * on failure, because in that case the program is
+			 * about to die anyway.
+			 */
+			return -1;
+		}
+	}
+	return 0;
+}
+
+/*
  * Map all of the shared objects that a given object depends upon.  PARENT is
  * a pointer to the link map for the shared object whose dependencies are
  * to be mapped.
@@ -1531,8 +1585,8 @@ rtfindlib(name, major, minor)
 
 		while (path == NULL && (dir = strsep(&ld_path, ":")) != NULL) {
 			path = search_lib_dir(dir, name, &major, &realminor, 0);
-			if (ld_path)
-				*(ld_path-1) = ':';
+			if (ld_path != NULL)
+				*(ld_path - 1) = ':';
 		}
 	}
 
@@ -1554,6 +1608,50 @@ rtfindlib(name, major, minor)
 }
 
 /*
+ * Search for the given shared library file.  This is similar to rtfindlib,
+ * except that the argument is the actual name of the desired library file.
+ * Thus there is no need to worry about version numbers.  The return value
+ * is a string containing the full pathname for the library.  This string
+ * is always dynamically allocated on the heap.
+ *
+ * Returns NULL if the library cannot be found.
+ */
+	static char *
+rtfindfile(name)
+	char	*name;
+{
+	char	*ld_path = ld_library_path;
+	char	*path = NULL;
+
+	if (ld_path != NULL) {	/* First, search the directories in ld_path */
+		char	*dir;
+
+		while (path == NULL && (dir = strsep(&ld_path, ":")) != NULL) {
+			struct stat	sb;
+
+			path = concat(dir, "/", name);
+			if (lstat(path, &sb) == -1) {	/* Does not exist */
+				free(path);
+				path = NULL;
+			}
+			if (ld_path != NULL)
+				*(ld_path - 1) = ':';
+		}
+	}
+
+	/*
+	 * We don't search the hints file.  It is organized around major
+	 * and minor version numbers, so it is not suitable for finding
+	 * a specific file name.
+	 */
+
+	if (path == NULL)	/* Search the standard directories */
+		path = find_lib_file(name);
+
+	return path;
+}
+
+/*
  * Buffer for error messages and a pointer that is set to point to the buffer
  * when a error occurs.  It acts as a last error flag, being set to NULL
  * after an error is returned.
diff --git a/libexec/rtld-elf/rtld.1 b/libexec/rtld-elf/rtld.1
index 2b3c75a..a66a861 100644
--- a/libexec/rtld-elf/rtld.1
+++ b/libexec/rtld-elf/rtld.1
@@ -1,4 +1,4 @@
-.\"	$Id$
+.\"	$Id: rtld.1,v 1.2 1995/10/05 05:16:52 nate Exp $
 .\"
 .\" Copyright (c) 1995 Paul Kranenburg
 .\" All rights reserved.
@@ -110,6 +110,13 @@ its behaviour as follows:
 .It Ev LD_LIBRARY_PATH
 A colon separated list of directories, overriding the default search path
 for shared libraries.
+This is ignored for set-user-ID and set-group-ID programs.
+.It Ev LD_PRELOAD
+A colon separated list of shared libraries, to be linked in before any
+other shared libraries.  If the directory is not specified then
+the directories specified by LD_LIBRARY_PATH will be searched first
+followed by the set of built-in standard directories.
+This is ignored for set-user-ID and set-group-ID programs.
 .It Ev LD_WARN_NON_PURE_CODE
 When set, issue a warning whenever a link-editing operation requires
 modification of the text segment of some loaded object. This is usually
@@ -122,15 +129,6 @@ When set, causes
 .Nm
 to exit after loading the shared objects and printing a summary which includes
 the absolute pathnames of all objects, to standard output.
-.It Ev LD_NO_INTERN_SEARCH
-When set,
-.Nm
-does not process any internal search paths that were recorded in the
-executable.
-.It Ev LD_NOSTD_PATH
-When set, do not include a set of built-in standard directory paths for
-searching. This might be useful when running on a system with a completely
-non-standard filesystem layout.
 .El
 .Pp
 .Sh FILES