ld.so: Introduce struct dl_exception

This commit separates allocating and raising exceptions.  This
simplifies catching and re-raising them because it is no longer
necessary to make a temporary, on-stack copy of the exception message.

9 files changed, 347 insertions, 218 deletions

diff --git a/elf/Makefile b/elf/Makefile
index b54ebf8a98..d314a5fa7e 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -31,7 +31,8 @@ routines	= $(all-dl-routines) dl-support dl-iteratephdr \
 dl-routines	= $(addprefix dl-,load lookup object reloc deps hwcaps \
 				  runtime init fini debug misc \
 				  version profile tls origin scope \
-				  execstack caller open close trampoline)
+				  execstack caller open close trampoline \
+				  exception)
 ifeq (yes,$(use-ldconfig))
 dl-routines += dl-cache
 endif
@@ -51,7 +52,7 @@ endif
 all-dl-routines = $(dl-routines) $(sysdep-dl-routines)
 # But they are absent from the shared libc, because that code is in ld.so.
 elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \
-		    dl-sysdep
+		    dl-sysdep dl-exception
 shared-only-routines += dl-caller
 
 # ld.so uses those routines, plus some special stuff for being the program
diff --git a/elf/Versions b/elf/Versions
index e65f2fac20..79ffaf73d2 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -28,6 +28,7 @@ libc {
     __libc_dlclose; __libc_dlopen_mode; __libc_dlsym;
 
     # Internal error handling support.  Interposes the functions in ld.so.
+    _dl_signal_exception; _dl_catch_exception;
     _dl_signal_error; _dl_catch_error;
   }
 }
@@ -68,7 +69,11 @@ ld {
     # Pointer protection.
     __pointer_chk_guard;
 
+    # Internal error handling support.
+    _dl_exception_create; _dl_exception_create_format; _dl_exception_free;
+
     # Internal error handling support.  Interposed by libc.so.
+    _dl_signal_exception; _dl_catch_exception;
     _dl_signal_error; _dl_catch_error;
 
     # Set value of a tunable.
diff --git a/elf/dl-deps.c b/elf/dl-deps.c
index 1b8bac6593..7c82d42be9 100644
--- a/elf/dl-deps.c
+++ b/elf/dl-deps.c
@@ -165,8 +165,7 @@ _dl_map_object_deps (struct link_map *map,
   const char *name;
   int errno_saved;
   int errno_reason;
-  const char *errstring;
-  const char *objname;
+  struct dl_exception exception;
 
   /* No loaded object so far.  */
   nlist = 0;
@@ -200,7 +199,6 @@ _dl_map_object_deps (struct link_map *map,
      alloca means we cannot use recursive function calls.  */
   errno_saved = errno;
   errno_reason = 0;
-  errstring = NULL;
   errno = 0;
   name = NULL;
   for (runp = known; runp; )
@@ -250,17 +248,9 @@ _dl_map_object_deps (struct link_map *map,
 		/* Store the tag in the argument structure.  */
 		args.name = name;
 
-		bool malloced;
-		int err = _dl_catch_error (&objname, &errstring, &malloced,
-					   openaux, &args);
-		if (__glibc_unlikely (errstring != NULL))
+		int err = _dl_catch_exception (&exception, openaux, &args);
+		if (__glibc_unlikely (exception.errstring != NULL))
 		  {
-		    char *new_errstring = strdupa (errstring);
-		    objname = strdupa (objname);
-		    if (malloced)
-		      free ((char *) errstring);
-		    errstring = new_errstring;
-
 		    if (err)
 		      errno_reason = err;
 		    else
@@ -313,31 +303,18 @@ _dl_map_object_deps (struct link_map *map,
 		/* We must be prepared that the addressed shared
 		   object is not available.  For filter objects the dependency
 		   must be available.  */
-		bool malloced;
-		int err = _dl_catch_error (&objname, &errstring, &malloced,
-					openaux, &args);
-
-		if (__glibc_unlikely (errstring != NULL))
+		int err = _dl_catch_exception (&exception, openaux, &args);
+		if (__glibc_unlikely (exception.errstring != NULL))
 		  {
 		    if (d->d_tag == DT_AUXILIARY)
 		      {
 			/* We are not interested in the error message.  */
-			assert (errstring != NULL);
-			if (malloced)
-			  free ((char *) errstring);
-
+			_dl_exception_free (&exception);
 			/* Simply ignore this error and continue the work.  */
 			continue;
 		      }
 		    else
 		      {
-
-			char *new_errstring = strdupa (errstring);
-			objname = strdupa (objname);
-			if (malloced)
-			  free ((char *) errstring);
-			errstring = new_errstring;
-
 			if (err)
 			  errno_reason = err;
 			else
@@ -683,6 +660,6 @@ Filters not supported with LD_TRACE_PRELINKING"));
     _dl_scope_free (old_l_initfini);
 
   if (errno_reason)
-    _dl_signal_error (errno_reason == -1 ? 0 : errno_reason, objname,
-		      NULL, errstring);
+    _dl_signal_exception (errno_reason == -1 ? 0 : errno_reason,
+			  &exception, NULL);
 }
diff --git a/elf/dl-error-skeleton.c b/elf/dl-error-skeleton.c
index 8e5888d4bd..8de6c87abf 100644
--- a/elf/dl-error-skeleton.c
+++ b/elf/dl-error-skeleton.c
@@ -39,10 +39,7 @@
    _dl_signal_error.  */
 struct catch
   {
-    const char **objname;	/* Object/File name.  */
-    const char **errstring;	/* Error detail filled in here.  */
-    bool *malloced;		/* Nonzero if the string is malloced
-				   by the libc malloc.  */
+    struct dl_exception *exception; /* The exception data is stored there.  */
     volatile int *errcode;	/* Return value of _dl_signal_error.  */
     jmp_buf env;		/* longjmp here on error.  */
   };
@@ -60,11 +57,6 @@ static __thread struct catch *catch_hook attribute_tls_model_ie;
 static struct catch *catch_hook;
 #endif
 
-/* This message we return as a last resort.  We define the string in a
-   variable since we have to avoid freeing it and so have to enable
-   a pointer comparison.  See below and in dlfcn/dlerror.c.  */
-static const char _dl_out_of_memory[] = "out of memory";
-
 #if DL_ERROR_BOOTSTRAP
 /* This points to a function which is called when an continuable error is
    received.  Unlike the handling of `catch' this function may return.
@@ -76,6 +68,41 @@ static const char _dl_out_of_memory[] = "out of memory";
 static receiver_fct receiver;
 #endif /* DL_ERROR_BOOTSTRAP */
 
+/* Lossage while resolving the program's own symbols is always fatal.  */
+static void
+__attribute__ ((noreturn))
+fatal_error (int errcode, const char *objname, const char *occasion,
+	     const char *errstring)
+{
+  char buffer[1024];
+  _dl_fatal_printf ("%s: %s: %s%s%s%s%s\n",
+		    RTLD_PROGNAME,
+		    occasion ?: N_("error while loading shared libraries"),
+		    objname, *objname ? ": " : "",
+		    errstring, errcode ? ": " : "",
+		    (errcode
+		     ? __strerror_r (errcode, buffer, sizeof buffer)
+		     : ""));
+}
+
+void
+_dl_signal_exception (int errcode, struct dl_exception *exception,
+		      const char *occasion)
+{
+  struct catch *lcatch = catch_hook;
+  if (lcatch != NULL)
+    {
+      *lcatch->exception = *exception;
+      *lcatch->errcode = errcode;
+
+      /* We do not restore the signal mask because none was saved.  */
+      __longjmp (lcatch->env[0].__jmpbuf, 1);
+    }
+  else
+    fatal_error (errcode, exception->objname, occasion, exception->errstring);
+}
+libc_hidden_def (_dl_signal_exception)
+
 void
 internal_function
 _dl_signal_error (int errcode, const char *objname, const char *occation,
@@ -86,66 +113,43 @@ _dl_signal_error (int errcode, const char *objname, const char *occation,
   if (! errstring)
     errstring = N_("DYNAMIC LINKER BUG!!!");
 
-  if (objname == NULL)
-    objname = "";
   if (lcatch != NULL)
     {
-      /* We are inside _dl_catch_error.  Return to it.  We have to
-	 duplicate the error string since it might be allocated on the
-	 stack.  The object name is always a string constant.  */
-      size_t len_objname = strlen (objname) + 1;
-      size_t len_errstring = strlen (errstring) + 1;
-
-      char *errstring_copy = malloc (len_objname + len_errstring);
-      if (errstring_copy != NULL)
-	{
-	  /* Make a copy of the object file name and the error string.  */
-	  *lcatch->objname = memcpy (__mempcpy (errstring_copy,
-						errstring, len_errstring),
-				     objname, len_objname);
-	  *lcatch->errstring = errstring_copy;
-
-	  /* If the main executable is relocated it means the libc's malloc
-	     is used.  */
-          bool malloced = true;
-#ifdef SHARED
-	  malloced = (GL(dl_ns)[LM_ID_BASE]._ns_loaded != NULL
-                      && (GL(dl_ns)[LM_ID_BASE]._ns_loaded->l_relocated != 0));
-#endif
-	  *lcatch->malloced = malloced;
-	}
-      else
-	{
-	  /* This is better than nothing.  */
-	  *lcatch->objname = "";
-	  *lcatch->errstring = _dl_out_of_memory;
-	  *lcatch->malloced = false;
-	}
-
+      _dl_exception_create (lcatch->exception, objname, errstring);
       *lcatch->errcode = errcode;
 
       /* We do not restore the signal mask because none was saved.  */
       __longjmp (lcatch->env[0].__jmpbuf, 1);
     }
   else
-    {
-      /* Lossage while resolving the program's own symbols is always fatal.  */
-      char buffer[1024];
-      _dl_fatal_printf ("%s: %s: %s%s%s%s%s\n",
-			RTLD_PROGNAME,
-			occation ?: N_("error while loading shared libraries"),
-			objname, *objname ? ": " : "",
-			errstring, errcode ? ": " : "",
-			(errcode
-			 ? __strerror_r (errcode, buffer, sizeof buffer)
-			 : ""));
-    }
+    fatal_error (errcode, objname, occation, errstring);
 }
 libc_hidden_def (_dl_signal_error)
 
 
 #if DL_ERROR_BOOTSTRAP
 void
+_dl_signal_cexception (int errcode, struct dl_exception *exception,
+		       const char *occasion)
+{
+  if (__builtin_expect (GLRO(dl_debug_mask)
+			& ~(DL_DEBUG_STATISTICS|DL_DEBUG_PRELINK), 0))
+    _dl_debug_printf ("%s: error: %s: %s (%s)\n",
+		      exception->objname, occasion,
+		      exception->errstring, receiver ? "continued" : "fatal");
+
+  if (receiver)
+    {
+      /* We are inside _dl_receive_error.  Call the user supplied
+	 handler and resume the work.  The receiver will still be
+	 installed.  */
+      (*receiver) (errcode, exception->objname, exception->errstring);
+    }
+  else
+    _dl_signal_exception (errcode, exception, occasion);
+}
+
+void
 internal_function
 _dl_signal_cerror (int errcode, const char *objname, const char *occation,
 		   const char *errstring)
@@ -167,11 +171,9 @@ _dl_signal_cerror (int errcode, const char *objname, const char *occation,
 }
 #endif /* DL_ERROR_BOOTSTRAP */
 
-
 int
-internal_function
-_dl_catch_error (const char **objname, const char **errstring,
-		 bool *mallocedp, void (*operate) (void *), void *args)
+_dl_catch_exception (struct dl_exception *exception,
+		     void (*operate) (void *), void *args)
 {
   /* We need not handle `receiver' since setting a `catch' is handled
      before it.  */
@@ -184,9 +186,7 @@ _dl_catch_error (const char **objname, const char **errstring,
 
   struct catch c;
   /* Don't use an initializer since we don't need to clear C.env.  */
-  c.objname = objname;
-  c.errstring = errstring;
-  c.malloced = mallocedp;
+  c.exception = exception;
   c.errcode = &errcode;
 
   struct catch *const old = catch_hook;
@@ -197,17 +197,30 @@ _dl_catch_error (const char **objname, const char **errstring,
     {
       (*operate) (args);
       catch_hook = old;
-      *objname = NULL;
-      *errstring = NULL;
-      *mallocedp = false;
+      *exception = (struct dl_exception) { NULL };
       return 0;
     }
 
-  /* We get here only if we longjmp'd out of OPERATE.  _dl_signal_error has
-     already stored values into *OBJNAME, *ERRSTRING, and *MALLOCEDP.  */
+  /* We get here only if we longjmp'd out of OPERATE.
+     _dl_signal_exception has already stored values into
+     *EXCEPTION.  */
   catch_hook = old;
   return errcode;
 }
+libc_hidden_def (_dl_catch_exception)
+
+int
+internal_function
+_dl_catch_error (const char **objname, const char **errstring,
+		 bool *mallocedp, void (*operate) (void *), void *args)
+{
+  struct dl_exception exception;
+  int errorcode = _dl_catch_exception (&exception, operate, args);
+  *objname = exception.objname;
+  *errstring = exception.errstring;
+  *mallocedp = exception.message_buffer == exception.errstring;
+  return errorcode;
+}
 libc_hidden_def (_dl_catch_error)
 
 #if DL_ERROR_BOOTSTRAP
diff --git a/elf/dl-exception.c b/elf/dl-exception.c
new file mode 100644
index 0000000000..b4d0ca7578
--- /dev/null
+++ b/elf/dl-exception.c
@@ -0,0 +1,202 @@
+/* ld.so error exception allocation and deallocation.
+   Copyright (C) 1995-2017 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 Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <ldsodefs.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include <unistd.h>
+
+/* This message we return as a last resort.  We define the string in a
+   variable since we have to avoid freeing it and so have to enable
+   a pointer comparison.  See below and in dlfcn/dlerror.c.  */
+static const char _dl_out_of_memory[] = "out of memory";
+
+/* Dummy allocation object used if allocating the message buffer
+   fails.  */
+static void
+oom_exception (struct dl_exception *exception)
+{
+  exception->objname = "";
+  exception->errstring = _dl_out_of_memory;
+  exception->message_buffer = NULL;
+}
+
+static void
+__attribute__ ((noreturn))
+length_mismatch (void)
+{
+  _dl_fatal_printf ("Fatal error: "
+                    "length accounting in _dl_exception_create_format\n");
+}
+
+/* Adjust the message buffer to indicate whether it is possible to
+   free it.  EXCEPTION->errstring must be a potentially deallocatable
+   pointer.  */
+static void
+adjust_message_buffer (struct dl_exception *exception)
+{
+  /* If the main executable is relocated it means the libc's malloc
+     is used.  */
+  bool malloced = true;
+#ifdef SHARED
+  malloced = (GL(dl_ns)[LM_ID_BASE]._ns_loaded != NULL
+              && (GL(dl_ns)[LM_ID_BASE]._ns_loaded->l_relocated != 0));
+#endif
+  if (malloced)
+    exception->message_buffer = (char *) exception->errstring;
+  else
+    exception->message_buffer = NULL;
+}
+
+void
+_dl_exception_create (struct dl_exception *exception, const char *objname,
+                      const char *errstring)
+{
+  if (objname == NULL)
+    objname = "";
+  size_t len_objname = strlen (objname) + 1;
+  size_t len_errstring = strlen (errstring) + 1;
+  char *errstring_copy = malloc (len_objname + len_errstring);
+  if (errstring_copy != NULL)
+    {
+      /* Make a copy of the object file name and the error string.  */
+      exception->objname = memcpy (__mempcpy (errstring_copy,
+                                              errstring, len_errstring),
+                                   objname, len_objname);
+      exception->errstring = errstring_copy;
+      adjust_message_buffer (exception);
+    }
+  else
+    oom_exception (exception);
+}
+rtld_hidden_def (_dl_exception_create)
+
+void
+_dl_exception_create_format (struct dl_exception *exception, const char *objname,
+                             const char *fmt, ...)
+{
+  if (objname == NULL)
+    objname = "";
+  size_t len_objname = strlen (objname) + 1;
+  /* Compute the length of the result.  Include room for two NUL
+     bytes.  */
+  size_t length = len_objname + 1;
+  {
+    va_list ap;
+    va_start (ap, fmt);
+    for (const char *p = fmt; *p != '\0'; ++p)
+      if (*p == '%')
+        {
+          ++p;
+          switch (*p)
+            {
+            case 's':
+              length += strlen (va_arg (ap, const char *));
+              break;
+            default:
+              /* Assumed to be '%'.  */
+              ++length;
+              break;
+            }
+        }
+      else
+        ++length;
+    va_end (ap);
+  }
+
+  if (length > PTRDIFF_MAX)
+    {
+      oom_exception (exception);
+      return;
+    }
+  char *errstring = malloc (length);
+  if (errstring == NULL)
+    {
+      oom_exception (exception);
+      return;
+    }
+  exception->errstring = errstring;
+  adjust_message_buffer (exception);
+
+  /* Copy the error message to errstring.  */
+  {
+    /* Next byte to be written in errstring.  */
+    char *wptr = errstring;
+    /* End of the allocated string.  */
+    char *const end = errstring + length;
+
+    va_list ap;
+    va_start (ap, fmt);
+
+    for (const char *p = fmt; *p != '\0'; ++p)
+      if (*p == '%')
+        {
+          ++p;
+          switch (*p)
+            {
+            case 's':
+              {
+                const char *ptr = va_arg (ap, const char *);
+                size_t len_ptr = strlen (ptr);
+                if (len_ptr > end - wptr)
+                  length_mismatch ();
+                wptr = __mempcpy (wptr, ptr, len_ptr);
+              }
+              break;
+            case '%':
+              if (wptr == end)
+                length_mismatch ();
+              *wptr = '%';
+              ++wptr;
+              break;
+            default:
+              _dl_fatal_printf ("Fatal error:"
+                                " invalid format in exception string\n");
+            }
+        }
+      else
+        {
+          if (wptr == end)
+            length_mismatch ();
+          *wptr = *p;
+          ++wptr;
+        }
+
+    if (wptr == end)
+      length_mismatch ();
+    *wptr = '\0';
+    ++wptr;
+    if (len_objname != end - wptr)
+      length_mismatch ();
+    exception->objname = memcpy (wptr, objname, len_objname);
+  }
+}
+rtld_hidden_def (_dl_exception_create_format)
+
+void
+_dl_exception_free (struct dl_exception *exception)
+{
+  free (exception->message_buffer);
+  exception->objname = NULL;
+  exception->errstring = NULL;
+  exception->message_buffer = NULL;
+}
+rtld_hidden_def (_dl_exception_free)
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index 3d2369dbf2..645dc3ebb4 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -47,23 +47,6 @@ struct sym_val
   };
 
 
-#define make_string(string, rest...) \
-  ({									      \
-    const char *all[] = { string, ## rest };				      \
-    size_t len, cnt;							      \
-    char *result, *cp;							      \
-									      \
-    len = 1;								      \
-    for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)		      \
-      len += strlen (all[cnt]);						      \
-									      \
-    cp = result = alloca (len);						      \
-    for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)		      \
-      cp = __stpcpy (cp, all[cnt]);					      \
-									      \
-    result;								      \
-  })
-
 /* Statistics function.  */
 #ifdef SHARED
 # define bump_num_relocations() ++GL(dl_num_relocations)
@@ -843,17 +826,16 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
 	     for unversioned lookups.  */
 	  assert (version != NULL);
 	  const char *reference_name = undef_map ? undef_map->l_name : "";
-
+	  struct dl_exception exception;
 	  /* XXX We cannot translate the message.  */
-	  _dl_signal_cerror (0, DSO_FILENAME (reference_name),
-			     N_("relocation error"),
-			     make_string ("symbol ", undef_name, ", version ",
-					  version->name,
-					  " not defined in file ",
-					  version->filename,
-					  " with link time reference",
-					  res == -2
-					  ? " (no version symbols)" : ""));
+	  _dl_exception_create_format
+	    (&exception, DSO_FILENAME (reference_name),
+	     "symbol %s version %s not defined in file %s"
+	     " with link time reference%s",
+	     undef_name, version->name, version->filename,
+	     res == -2 ? " (no version symbols)" : "");
+	  _dl_signal_cexception (0, &exception, N_("relocation error"));
+	  _dl_exception_free (&exception);
 	  *ref = NULL;
 	  return 0;
 	}
@@ -869,12 +851,14 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
 	  const char *versionstr = version ? ", version " : "";
 	  const char *versionname = (version && version->name
 				     ? version->name : "");
-
+	  struct dl_exception exception;
 	  /* XXX We cannot translate the message.  */
-	  _dl_signal_cerror (0, DSO_FILENAME (reference_name),
-			     N_("symbol lookup error"),
-			     make_string ("undefined symbol: ", undef_name,
-					  versionstr, versionname));
+	  _dl_exception_create_format
+	    (&exception, DSO_FILENAME (reference_name),
+	     "undefined symbol: %s%s%s",
+	     undef_name, versionstr, versionname);
+	  _dl_signal_cexception (0, &exception, N_("symbol lookup error"));
+	  _dl_exception_free (&exception);
 	}
       *ref = NULL;
       return 0;
diff --git a/elf/dl-open.c b/elf/dl-open.c
index cec54db413..91a1d1a4f8 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -643,11 +643,8 @@ no more namespaces available for dlmopen()"));
   args.argv = argv;
   args.env = env;
 
-  const char *objname;
-  const char *errstring;
-  bool malloced;
-  int errcode = _dl_catch_error (&objname, &errstring, &malloced,
-				 dl_open_worker, &args);
+  struct dl_exception exception;
+  int errcode = _dl_catch_exception (&exception, dl_open_worker, &args);
 
 #if defined USE_LDCONFIG && !defined MAP_COPY
   /* We must unmap the cache file.  */
@@ -655,7 +652,7 @@ no more namespaces available for dlmopen()"));
 #endif
 
   /* See if an error occurred during loading.  */
-  if (__glibc_unlikely (errstring != NULL))
+  if (__glibc_unlikely (exception.errstring != NULL))
     {
       /* Remove the object from memory.  It may be in an inconsistent
 	 state if relocation failed, for example.  */
@@ -679,28 +676,8 @@ no more namespaces available for dlmopen()"));
       /* Release the lock.  */
       __rtld_lock_unlock_recursive (GL(dl_load_lock));
 
-      /* Make a local copy of the error string so that we can release the
-	 memory allocated for it.  */
-      size_t len_errstring = strlen (errstring) + 1;
-      char *local_errstring;
-      if (objname == errstring + len_errstring)
-	{
-	  size_t total_len = len_errstring + strlen (objname) + 1;
-	  local_errstring = alloca (total_len);
-	  memcpy (local_errstring, errstring, total_len);
-	  objname = local_errstring + len_errstring;
-	}
-      else
-	{
-	  local_errstring = alloca (len_errstring);
-	  memcpy (local_errstring, errstring, len_errstring);
-	}
-
-      if (malloced)
-	free ((char *) errstring);
-
       /* Reraise the error.  */
-      _dl_signal_error (errcode, objname, NULL, local_errstring);
+      _dl_signal_exception (errcode, &exception, NULL);
     }
 
   assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);
diff --git a/elf/dl-sym.c b/elf/dl-sym.c
index 7cd6e97643..fb54a91858 100644
--- a/elf/dl-sym.c
+++ b/elf/dl-sym.c
@@ -119,26 +119,11 @@ do_sym (void *handle, const char *name, void *who,
 	  args.refp = &ref;
 
 	  THREAD_GSCOPE_SET_FLAG ();
-
-	  const char *objname;
-	  const char *errstring = NULL;
-	  bool malloced;
-	  int err = _dl_catch_error (&objname, &errstring, &malloced,
-				     call_dl_lookup, &args);
-
+	  struct dl_exception exception;
+	  int err = _dl_catch_exception (&exception, call_dl_lookup, &args);
 	  THREAD_GSCOPE_RESET_FLAG ();
-
-	  if (__glibc_unlikely (errstring != NULL))
-	    {
-	      /* The lookup was unsuccessful.  Rethrow the error.  */
-	      char *errstring_dup = strdupa (errstring);
-	      char *objname_dup = strdupa (objname);
-	      if (malloced)
-		free ((char *) errstring);
-
-	      _dl_signal_error (err, objname_dup, NULL, errstring_dup);
-	      /* NOTREACHED */
-	    }
+	  if (__glibc_unlikely (exception.errstring != NULL))
+	    _dl_signal_exception (err, &exception, NULL);
 
 	  result = args.map;
 	}
diff --git a/elf/dl-version.c b/elf/dl-version.c
index c00078e5e4..c0d76ad42a 100644
--- a/elf/dl-version.c
+++ b/elf/dl-version.c
@@ -27,25 +27,6 @@
 
 #include <assert.h>
 
-
-#define make_string(string, rest...) \
-  ({									      \
-    const char *all[] = { string, ## rest };				      \
-    size_t len, cnt;							      \
-    char *result, *cp;							      \
-									      \
-    len = 1;								      \
-    for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)		      \
-      len += strlen (all[cnt]);						      \
-									      \
-    cp = result = alloca (len);						      \
-    for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)		      \
-      cp = __stpcpy (cp, all[cnt]);					      \
-									      \
-    result;								      \
-  })
-
-
 static inline struct link_map *
 __attribute ((always_inline))
 find_needed (const char *name, struct link_map *map)
@@ -78,8 +59,8 @@ match_symbol (const char *name, Lmid_t ns, ElfW(Word) hash, const char *string,
   ElfW(Addr) def_offset;
   ElfW(Verdef) *def;
   /* Initialize to make the compiler happy.  */
-  const char *errstring = NULL;
   int result = 0;
+  struct dl_exception exception;
 
   /* Display information about what we are doing while debugging.  */
   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_VERSIONS))
@@ -96,8 +77,9 @@ checking for version `%s' in file %s [%lu] required by file %s [%lu]\n",
       if (verbose)
 	{
 	  /* XXX We cannot translate the messages.  */
-	  errstring = make_string ("\
-no version information available (required by ", name, ")");
+	  _dl_exception_create_format
+	    (&exception, DSO_FILENAME (map->l_name),
+	     "no version information available (required by %s)", name);
 	  goto call_cerror;
 	}
       return 0;
@@ -116,10 +98,10 @@ no version information available (required by ", name, ")");
 	  char buf[20];
 	  buf[sizeof (buf) - 1] = '\0';
 	  /* XXX We cannot translate the message.  */
-	  errstring = make_string ("unsupported version ",
-				   _itoa (def->vd_version,
-					  &buf[sizeof (buf) - 1], 10, 0),
-				   " of Verdef record");
+	  _dl_exception_create_format
+	    (&exception, DSO_FILENAME (map->l_name),
+	     "unsupported version %s of Verdef record",
+	     _itoa (def->vd_version, &buf[sizeof (buf) - 1], 10, 0));
 	  result = 1;
 	  goto call_cerror;
 	}
@@ -150,20 +132,22 @@ no version information available (required by ", name, ")");
       if (verbose)
 	{
 	  /* XXX We cannot translate the message.  */
-	  errstring = make_string ("weak version `", string,
-				   "' not found (required by ", name, ")");
+	  _dl_exception_create_format
+	    (&exception, DSO_FILENAME (map->l_name),
+	     "weak version `%s' not found (required by %s)", string, name);
 	  goto call_cerror;
 	}
       return 0;
     }
 
   /* XXX We cannot translate the message.  */
-  errstring = make_string ("version `", string, "' not found (required by ",
-			   name, ")");
+  _dl_exception_create_format
+    (&exception, DSO_FILENAME (map->l_name),
+     "version `%s' not found (required by %s)", string, name);
   result = 1;
  call_cerror:
-  _dl_signal_cerror (0, DSO_FILENAME (map->l_name),
-		     N_("version lookup error"), errstring);
+  _dl_signal_cexception (0, &exception, N_("version lookup error"));
+  _dl_exception_free (&exception);
   return result;
 }
 
@@ -181,8 +165,8 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
   /* We need to find out which is the highest version index used
     in a dependecy.  */
   unsigned int ndx_high = 0;
+  struct dl_exception exception;
   /* Initialize to make the compiler happy.  */
-  const char *errstring = NULL;
   int errval = 0;
 
   /* If we don't have a string table, we must be ok.  */
@@ -205,13 +189,12 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
 	  char buf[20];
 	  buf[sizeof (buf) - 1] = '\0';
 	  /* XXX We cannot translate the message.  */
-	  errstring = make_string ("unsupported version ",
-				   _itoa (ent->vn_version,
-					  &buf[sizeof (buf) - 1], 10, 0),
-				   " of Verneed record\n");
+	  _dl_exception_create_format
+	    (&exception, DSO_FILENAME (map->l_name),
+	     "unsupported version %s of Verneed record",
+	     _itoa (ent->vn_version, &buf[sizeof (buf) - 1], 10, 0));
 	call_error:
-	  _dl_signal_error (errval, DSO_FILENAME (map->l_name),
-			    NULL, errstring);
+	  _dl_signal_exception (errval, &exception, NULL);
 	}
 
       while (1)
@@ -293,7 +276,9 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
 	calloc (ndx_high + 1, sizeof (*map->l_versions));
       if (__glibc_unlikely (map->l_versions == NULL))
 	{
-	  errstring = N_("cannot allocate version reference table");
+	  _dl_exception_create
+	    (&exception, DSO_FILENAME (map->l_name),
+	     N_("cannot allocate version reference table"));
 	  errval = ENOMEM;
 	  goto call_error;
 	}