Implement STB_GNU_UNIQUE handling.

Some symbols have to be identified process-wide by their name.  This is
particularly important for some C++ features (e.g., class local static data
and static variables in inline functions).  This cannot completely be
implemented with ELF functionality so far.  The STB_GNU_UNIQUE binding
helps by ensuring the dynamic linker will always use the same definition for
all symbols with the same name and this binding.

11 files changed, 291 insertions, 11 deletions

diff --git a/elf/Makefile b/elf/Makefile
index 57febea..cc5caeb 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -111,7 +111,9 @@ distribute	:= rtld-Rules \
 		   ifuncdep5.c ifuncdep5pic.c ifuncmod5.c \
 		   ifuncmain6pie.c ifuncmod6.c \
 		   ifuncmain7.c ifuncmain7pic.c ifuncmain7picstatic.c \
-		   ifuncmain7pie.c ifuncmain7static.c
+		   ifuncmain7pie.c ifuncmain7static.c \
+		   tst-unique1.c tst-unique1mod1.c tst-unique1mod2.c \
+		   tst-unique2.c tst-unique2mod1.c tst-unique2mod2.c
 
 CFLAGS-dl-runtime.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-dl-lookup.c = -fexceptions -fasynchronous-unwind-tables
@@ -190,7 +192,8 @@ tests += loadtest restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-dlmopen1 tst-dlmopen2 tst-dlmopen3 \
 	 unload3 unload4 unload5 unload6 unload7 tst-global1 order2 \
 	 tst-audit1 tst-audit2 \
-	 tst-stackguard1 tst-addr1 tst-thrlock
+	 tst-stackguard1 tst-addr1 tst-thrlock \
+	 tst-unique1 tst-unique2
 #	 reldep9
 test-srcs = tst-pathopt
 tests-execstack-yes = tst-execstack tst-execstack-needed tst-execstack-prog
@@ -239,7 +242,9 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		unload4mod1 unload4mod2 unload4mod3 unload4mod4 \
 		unload6mod1 unload6mod2 unload6mod3 \
 		unload7mod1 unload7mod2 \
-		order2mod1 order2mod2 order2mod3 order2mod4
+		order2mod1 order2mod2 order2mod3 order2mod4 \
+		tst-unique1mod1 tst-unique1mod2 \
+		tst-unique2mod1 tst-unique2mod2
 ifeq (yes,$(have-initfini-array))
 modules-names += tst-array2dep tst-array5dep
 endif
@@ -1103,3 +1108,10 @@ $(objpfx)ifuncmain5pic: $(addprefix $(objpfx),ifuncmod5.so)
 $(objpfx)ifuncmain5static: $(addprefix $(objpfx),ifuncdep5.o)
 $(objpfx)ifuncmain5staticpic: $(addprefix $(objpfx),ifuncdep5pic.o)
 $(objpfx)ifuncmain5picstatic: $(addprefix $(objpfx),ifuncdep5pic.o)
+
+$(objpfx)tst-unique1: $(libdl)
+$(objpfx)tst-unique1.out: $(objpfx)tst-unique1mod1.so \
+			  $(objpfx)tst-unique1mod2.so
+
+$(objpfx)tst-unique2: $(libdl) $(objpfx)tst-unique2mod1.so
+$(objpfx)tst-unique2.out: $(objpfx)tst-unique2mod2.so
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index 707d650..2ba885a 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -337,7 +337,7 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
     {
       int res = do_lookup_x (undef_name, new_hash, &old_hash, *ref,
 			     &current_value, *scope, start, version, flags,
-			     skip_map, type_class);
+			     skip_map, type_class, undef_map);
       if (res > 0)
 	break;
 
@@ -410,7 +410,7 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
 	  for (scope = symbol_scope; *scope != NULL; i = 0, ++scope)
 	    if (do_lookup_x (undef_name, new_hash, &old_hash, *ref,
 			     &protected_value, *scope, i, version, flags,
-			     skip_map, ELF_RTYPE_CLASS_PLT) != 0)
+			     skip_map, ELF_RTYPE_CLASS_PLT, NULL) != 0)
 	      break;
 
 	  if (protected_value.s != NULL && protected_value.m != undef_map)
@@ -536,7 +536,7 @@ _dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
 
 	  do_lookup_x (undef_name, new_hash, &old_hash, *ref, &val,
 		       undef_map->l_local_scope[0], 0, version, 0, NULL,
-		       type_class);
+		       type_class, undef_map);
 
 	  if (val.s != value->s || val.m != value->m)
 	    conflict = 1;
diff --git a/elf/dl-open.c b/elf/dl-open.c
index c3f0e42..b8ebfe0 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -569,7 +569,7 @@ _dl_open (const char *file, int mode, const void *caller_dlopen, Lmid_t nsid,
 	if (GL(dl_ns)[nsid]._ns_loaded == NULL)
 	  break;
 
-      if (nsid == DL_NNS)
+      if (__builtin_expect (nsid == DL_NNS, 0))
 	{
 	  /* No more namespace available.  */
 	  __rtld_lock_unlock_recursive (GL(dl_load_lock));
@@ -579,7 +579,10 @@ no more namespaces available for dlmopen()"));
 	}
 
       if (nsid == GL(dl_nns))
-	++GL(dl_nns);
+	{
+	  __rtld_lock_initialize (GL(dl_ns)[nsid]._ns_unique_sym_table.lock);
+	  ++GL(dl_nns);
+	}
 
       _dl_debug_initialize (0, nsid)->r_state = RT_CONSISTENT;
     }
diff --git a/elf/do-lookup.h b/elf/do-lookup.h
index acbc53d..782f490 100644
--- a/elf/do-lookup.h
+++ b/elf/do-lookup.h
@@ -27,7 +27,7 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
 	     unsigned long int *old_hash, const ElfW(Sym) *ref,
 	     struct sym_val *result, struct r_scope_elem *scope, size_t i,
 	     const struct r_found_version *const version, int flags,
-	     struct link_map *skip, int type_class)
+	     struct link_map *skip, int type_class, struct link_map *undef_map)
 {
   size_t n = scope->r_nlist;
   /* Make sure we read the value before proceeding.  Otherwise we
@@ -233,7 +233,7 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
       if (sym != NULL)
 	{
 	found_it:
-	  switch (ELFW(ST_BIND) (sym->st_info))
+	  switch (__builtin_expect (ELFW(ST_BIND) (sym->st_info), STB_GLOBAL))
 	    {
 	    case STB_WEAK:
 	      /* Weak definition.  Use this value if we don't find another.  */
@@ -248,10 +248,124 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
 		}
 	      /* FALLTHROUGH */
 	    case STB_GLOBAL:
+	    success:
 	      /* Global definition.  Just what we need.  */
 	      result->s = sym;
 	      result->m = (struct link_map *) map;
 	      return 1;
+
+	    case STB_GNU_UNIQUE:;
+	      /* We have to determine whether we already found a
+		 symbol with this name before.  If not then we have to
+		 add it to the search table.  If we already found a
+		 definition we have to use it.  */
+	      void enter (struct unique_sym *table, size_t size,
+			  unsigned int hash, const char *name,
+			  const ElfW(Sym) *sym, const struct link_map *map)
+	      {
+		size_t idx = hash % size;
+		size_t hash2 = 1 + hash % (size - 2);
+		while (1)
+		  {
+		    if (table[idx].hashval == 0)
+		      {
+			table[idx].hashval = hash;
+			table[idx].name = strtab + sym->st_name;
+			if ((type_class & ELF_RTYPE_CLASS_COPY) != 0)
+			  {
+			    table[idx].sym = ref;
+			    table[idx].map = undef_map;
+			  }
+			else
+			  {
+			    table[idx].sym = sym;
+			    table[idx].map = map;
+			  }
+			return;
+		      }
+
+		    idx += hash2;
+		    if (idx >= size)
+		      idx -= size;
+		  }
+	      }
+
+	      struct unique_sym_table *tab
+		= &GL(dl_ns)[map->l_ns]._ns_unique_sym_table;
+
+	      __rtld_lock_lock_recursive (tab->lock);
+
+	      struct unique_sym *entries = tab->entries;
+	      size_t size = tab->size;
+	      if (entries != NULL)
+		{
+		  size_t idx = new_hash % size;
+		  size_t hash2 = 1 + new_hash % (size - 2);
+		  while (1)
+		    {
+		      if (entries[idx].hashval == new_hash
+			  && strcmp (entries[idx].name, undef_name) == 0)
+			{
+			  result->s = entries[idx].sym;
+			  result->m = (struct link_map *) entries[idx].map;
+			  __rtld_lock_unlock_recursive (tab->lock);
+			  return 1;
+			}
+
+		      if (entries[idx].hashval == 0
+			  && entries[idx].name == NULL)
+			break;
+
+		      idx += hash2;
+		      if (idx >= size)
+			idx -= size;
+		    }
+
+		  if (size * 3 <= tab->n_elements)
+		    {
+		      /* Expand the table.  */
+		      size_t newsize = _dl_higher_prime_number (size);
+		      struct unique_sym *newentries
+			= calloc (sizeof (struct unique_sym), newsize);
+		      if (newentries == NULL)
+			{
+			nomem:
+			  __rtld_lock_unlock_recursive (tab->lock);
+			  _dl_fatal_printf ("out of memory\n");
+			}
+
+		      for (idx = 0; idx < size; ++idx)
+			if (entries[idx].hashval != 0)
+			  enter (newentries, newsize, entries[idx].hashval,
+				 entries[idx].name, entries[idx].sym,
+				 entries[idx].map);
+
+		      tab->free (entries);
+		      tab->size = newsize;
+		      entries = tab->entries = newentries;
+		      tab->free = free;
+		    }
+		}
+	      else
+		{
+#define INITIAL_NUNIQUE_SYM_TABLE 31
+		  size = INITIAL_NUNIQUE_SYM_TABLE;
+		  entries = calloc (sizeof (struct unique_sym), size);
+		  if (entries == NULL)
+		    goto nomem;
+
+		  tab->entries = entries;
+		  tab->size = size;
+		  tab->free = free;
+		}
+
+	      enter (entries, size, new_hash, strtab + sym->st_name, sym, map);
+	      ++tab->n_elements;
+
+	      __rtld_lock_unlock_recursive (tab->lock);
+
+	      goto success;
+
 	    default:
 	      /* Local symbols are ignored.  */
 	      break;
diff --git a/elf/rtld.c b/elf/rtld.c
index f97de9a..55b84c3 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -127,7 +127,12 @@ struct rtld_global _rtld_global =
 #ifdef _LIBC_REENTRANT
     ._dl_load_lock = _RTLD_LOCK_RECURSIVE_INITIALIZER,
 #endif
-    ._dl_nns = 1
+    ._dl_nns = 1,
+    ._dl_ns =
+    {
+      [LM_ID_BASE] = { ._ns_unique_sym_table
+		       = { .lock = _RTLD_LOCK_RECURSIVE_INITIALIZER } }
+    }
   };
 /* If we would use strong_alias here the compiler would see a
    non-hidden definition.  This would undo the effect of the previous
diff --git a/elf/tst-unique1.c b/elf/tst-unique1.c
new file mode 100644
index 0000000..9b7996c
--- /dev/null
+++ b/elf/tst-unique1.c
@@ -0,0 +1,40 @@
+#include <config.h>
+#include <dlfcn.h>
+#include <stdio.h>
+
+static int
+do_test (void)
+{
+#ifdef HAVE_ASM_UNIQUE_OBJECT
+  void *h1 = dlopen ("tst-unique1mod1.so", RTLD_LAZY);
+  if (h1 == NULL)
+    {
+      puts ("cannot load tst-unique1mod1");
+      return 1;
+    }
+  int *(*f1) (void) = dlsym (h1, "f");
+  if (f1 == NULL)
+    {
+      puts ("cannot locate f in tst-unique1mod1");
+      return 1;
+    }
+  void *h2 = dlopen ("tst-unique1mod2.so", RTLD_LAZY);
+  if (h2 == NULL)
+    {
+      puts ("cannot load tst-unique1mod2");
+      return 1;
+    }
+  int (*f2) (int *) = dlsym (h2, "f");
+  if (f2 == NULL)
+    {
+      puts ("cannot locate f in tst-unique1mod2");
+      return 1;
+    }
+  return f2 (f1 ());
+#else
+  return 0;
+#endif
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/elf/tst-unique1mod1.c b/elf/tst-unique1mod1.c
new file mode 100644
index 0000000..16de28d
--- /dev/null
+++ b/elf/tst-unique1mod1.c
@@ -0,0 +1,21 @@
+#include <config.h>
+
+#ifdef HAVE_ASM_UNIQUE_OBJECT
+# define S(s) _S (s)
+# define _S(s) #s
+
+asm (".data;"
+     S (ASM_GLOBAL_DIRECTIVE) " var\n"
+     ".type var, " S (ASM_TYPE_DIRECTIVE_PREFIX) "gnu_unique_object\n"
+     ".size var, 4\n"
+     "var:.zero 4\n"
+     ".previous");
+extern int var;
+
+int *
+f (void)
+{
+  var = 1;
+  return &var;
+}
+#endif
diff --git a/elf/tst-unique1mod2.c b/elf/tst-unique1mod2.c
new file mode 100644
index 0000000..c075515
--- /dev/null
+++ b/elf/tst-unique1mod2.c
@@ -0,0 +1,20 @@
+#include <config.h>
+
+#ifdef HAVE_ASM_UNIQUE_OBJECT
+# define S(s) _S (s)
+# define _S(s) #s
+
+asm (".data;"
+     S (ASM_GLOBAL_DIRECTIVE) " var\n"
+     ".type var, " S (ASM_TYPE_DIRECTIVE_PREFIX) "gnu_unique_object\n"
+     ".size var, 4\n"
+     "var:.zero 4\n"
+     ".previous");
+extern int var;
+
+int
+f (int *p)
+{
+  return &var != p || *p != 1;
+}
+#endif
diff --git a/elf/tst-unique2.c b/elf/tst-unique2.c
new file mode 100644
index 0000000..7bb0687
--- /dev/null
+++ b/elf/tst-unique2.c
@@ -0,0 +1,32 @@
+#include <config.h>
+#include <dlfcn.h>
+#include <stdio.h>
+
+extern int var;
+
+static int
+do_test (void)
+{
+#ifdef HAVE_ASM_UNIQUE_OBJECT
+  var = 1;
+
+  void *h = dlopen ("tst-unique2mod2.so", RTLD_LAZY);
+  if (h == NULL)
+    {
+      puts ("cannot load tst-unique2mod2");
+      return 1;
+    }
+  int (*f) (int *) = dlsym (h, "f");
+  if (f == NULL)
+    {
+      puts ("cannot locate f in tst-unique2mod2");
+      return 1;
+    }
+  return f (&var);
+#else
+  return 0;
+#endif
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/elf/tst-unique2mod1.c b/elf/tst-unique2mod1.c
new file mode 100644
index 0000000..5e4ac4d
--- /dev/null
+++ b/elf/tst-unique2mod1.c
@@ -0,0 +1,13 @@
+#include <config.h>
+
+#ifdef HAVE_ASM_UNIQUE_OBJECT
+# define S(s) _S (s)
+# define _S(s) #s
+
+asm (".data;"
+     S (ASM_GLOBAL_DIRECTIVE) " var\n"
+     ".type var, " S (ASM_TYPE_DIRECTIVE_PREFIX) "gnu_unique_object\n"
+     ".size var, 4\n"
+     "var:.zero 4\n"
+     ".previous");
+#endif
diff --git a/elf/tst-unique2mod2.c b/elf/tst-unique2mod2.c
new file mode 100644
index 0000000..c075515
--- /dev/null
+++ b/elf/tst-unique2mod2.c
@@ -0,0 +1,20 @@
+#include <config.h>
+
+#ifdef HAVE_ASM_UNIQUE_OBJECT
+# define S(s) _S (s)
+# define _S(s) #s
+
+asm (".data;"
+     S (ASM_GLOBAL_DIRECTIVE) " var\n"
+     ".type var, " S (ASM_TYPE_DIRECTIVE_PREFIX) "gnu_unique_object\n"
+     ".size var, 4\n"
+     "var:.zero 4\n"
+     ".previous");
+extern int var;
+
+int
+f (int *p)
+{
+  return &var != p || *p != 1;
+}
+#endif