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.

29 files changed, 529 insertions, 239 deletions

diff --git a/ChangeLog b/ChangeLog
index 6648ce1676..dcf86261ca 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,65 @@
 2017-08-10  Florian Weimer  <fweimer@redhat.com>
 
+	Introduce ld.so exceptions.
+	* sysdeps/generic/ldsodefs.h (struct dl_exception): Define.
+	(_dl_exception_create, _dl_exception_create_format)
+	(_dl_exception_free, _dl_signal_exception, _dl_signal_cexception)
+	(_dl_catch_exception): Declare.
+	(_dl_catch_error): Update comment.
+	* elf/dl-error-skeleton.c (struct catch): Replace objname,
+	errstring, malloced members with exception member.
+	(_dl_out_of_memory): Remove.
+	(fatal_error): New function, extracted from _dl_signal_error.
+	(_dl_signal_exception, _dl_signal_cexception): New functions.
+	(_dl_signal_error): Call _dl_exception_create to allocate an
+	exception object.
+	(_dl_catch_exception): New function, based on _dl_catch_error.
+	(_dl_catch_error): Implement using _dl_catch_exception.
+	* elf/dl-exception.c: New file.
+	* elf/Makefile (dl-routines): Add dl-exception.
+	(elide-routines.os): Likewise.
+	* elf/Version (ld/GLIBC_PRIVATE): Add _dl_exception_create,
+	_dl_exception_create_format, _dl_exception_free.
+	* elf/dl-deps.c (_dl_map_object_deps): Use _dl_catch_exception and
+	_dl_signal_exception.
+	* elf/dl-lookup.c (make_string): Remove.
+	(_dl_lookup_symbol_x): Use _dl_exception_create_format,
+	_dl_signal_cexception, _dl_exception_free.
+	* elf/dl-open.c (_dl_open): Use _dl_catch_exception and
+	_dl_signal_exception.
+	* elf/dl-sym.c (do_sym): Likewise.
+	* elf/dl-version.c (make_string): Remove.
+	(match_symbol): Use _dl_exception_create_format,
+	_dl_signal_cexception, _dl_exception_free.
+	(_dl_check_map_versions): Likewise.
+	* sysdeps/generic/localplt.data (ld.so): Add _dl_signal_exception,
+	_dl_catch_exception.
+	* sysdeps/unix/sysv/linux/aarch64/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/alpha/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/arm/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/hppa/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/i386/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/ia64/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/m68k/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/microblaze/localplt.data (ld.so):
+	Likewise.
+	* sysdeps/unix/sysv/linux/nios2/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/localplt.data
+	(ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/localplt.data
+	(ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/powerpc/powerpc64/localplt.data (ld.so):
+	Likewise.
+	* sysdeps/unix/sysv/linux/s390/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/sh/localplt.data (ld.so): Likewise.
+	* sysdeps/unix/sysv/linux/sparc/sparc32/localplt.data (ld.so):
+	Likewise.
+	* sysdeps/unix/sysv/linux/sparc/sparc64/localplt.data (ld.so):
+	Likewise.
+	* sysdeps/x86_64/localplt.data (ld.so): Likewise.
+
+2017-08-10  Florian Weimer  <fweimer@redhat.com>
+
 	* inet/net-internal.h (__inet6_scopeid_pton): Remove
 	attribute_hidden, internal_function.
 	* inet/inet6_scopeid_pton.c (__inet6_scopeid_pton): Remove
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