[PATCH] PR ld/18720: Properly merge hidden versioned symbol

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Sun, Jul 26, 2015 at 03:15:50PM -0700, H.J. Lu wrote:
> The non-default versioned symbol can only be merged with the versioned
> symbol with the same symbol version.  _bfd_elf_merge_symbol should
> check the symbol version before merging the new non-default versioned
> symbol with the existing symbol.  _bfd_elf_link_hash_copy_indirect can't
> copy any references to the non-default versioned symbol.   We need to
> bind a symbol locally when linking executable if it is locally defined,
> non-default versioned, not referenced by shared library and not exported.
> 
> OK for master?
> 
> Thanks.
> 
> H.J.
> ---
> bfd/
> 
> 	PR ld/18720
> 	* elf-bfd.h (elf_link_hash_entry): Add nondeflt_version.
> 	* elflink.c (_bfd_elf_merge_symbol): Add a parameter to indicate
> 	if the new symbol matches the existing one.  The new non-default
> 	versioned symbol symbol matches the existing symbol if they have
> 	the same symbol version. Update the existing symbol only if they
> 	match.
> 	(_bfd_elf_add_default_symbol): Update call to
> 	_bfd_elf_merge_symbol.
> 	(elf_link_add_object_symbols): Override a definition only if the
> 	new symbol matches the existing one.
> 	(_bfd_elf_link_hash_copy_indirect): Don't copy any references to
> 	the non-default versioned symbol.
> 	(elf_link_output_extsym): Bind a symbol locally when linking
> 	executable if it is locally defined, non-default versioned, not
> 	referenced by shared library and not exported.
> 

Here is the upated patch which uses the existing "hidden" field in
elf_link_hash_entry.  Any objections, comments?

Thanks.

H.J.
--
bfd/

	PR ld/18720
	* elflink.c (_bfd_elf_merge_symbol): Add a parameter to indicate
	if the new symbol matches the existing one.  The new hidden
	versioned symbol matches the existing symbol if they have the
	same symbol version. Update the existing symbol only if they
	match.
	(_bfd_elf_add_default_symbol): Update call to
	_bfd_elf_merge_symbol.
	(_bfd_elf_link_assign_sym_version): Don't set the hidden field
	here.
	(elf_link_add_object_symbols): Override a definition only if the
	new symbol matches the existing one.
	(_bfd_elf_link_hash_copy_indirect): Don't copy any references to
	the hidden versioned symbol.
	(elf_link_output_extsym): Bind a symbol locally when linking
	executable if it is locally defined, hidden versioned, not
	referenced by shared library and not exported.  Turn on
	VERSYM_HIDDEN only if the hidden vesioned symbol is defined
	locally.

ld/testsuite/

	PR ld/18720
	* ld-elf/indirect.exp: Run tests for PR ld/18720.
	* ld-elf/pr18720.out: New file.
	* ld-elf/pr18720a.c: Likewise.
	* ld-elf/pr18720b.c: Likewise.
	* ld-elf/pr18720c.c: Likewise.
---
 bfd/elflink.c                    | 134 +++++++++++++++++++++++++++++----------
 ld/testsuite/ld-elf/indirect.exp |  25 +++++++-
 ld/testsuite/ld-elf/pr18720.out  |   2 +
 ld/testsuite/ld-elf/pr18720a.c   |  27 ++++++++
 ld/testsuite/ld-elf/pr18720b.c   |  11 ++++
 ld/testsuite/ld-elf/pr18720c.c   |  15 +++++
 6 files changed, 178 insertions(+), 36 deletions(-)
 create mode 100644 ld/testsuite/ld-elf/pr18720.out
 create mode 100644 ld/testsuite/ld-elf/pr18720a.c
 create mode 100644 ld/testsuite/ld-elf/pr18720b.c
 create mode 100644 ld/testsuite/ld-elf/pr18720c.c

diff --git a/bfd/elflink.c b/bfd/elflink.c
index 846f35e..832b374 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -939,7 +939,8 @@ _bfd_elf_merge_symbol (bfd *abfd,
 		       bfd_boolean *skip,
 		       bfd_boolean *override,
 		       bfd_boolean *type_change_ok,
-		       bfd_boolean *size_change_ok)
+		       bfd_boolean *size_change_ok,
+		       bfd_boolean *matched)
 {
   asection *sec, *oldsec;
   struct elf_link_hash_entry *h;
@@ -950,6 +951,7 @@ _bfd_elf_merge_symbol (bfd *abfd,
   bfd_boolean newdyn, olddyn, olddef, newdef, newdyncommon, olddyncommon;
   bfd_boolean newweak, oldweak, newfunc, oldfunc;
   const struct elf_backend_data *bed;
+  char *new_version;
 
   *skip = FALSE;
   *override = FALSE;
@@ -968,6 +970,17 @@ _bfd_elf_merge_symbol (bfd *abfd,
 
   bed = get_elf_backend_data (abfd);
 
+  /* NEW_VERSION is the symbol version of the new symbol.  */
+  new_version = strrchr (name, ELF_VER_CHR);
+  if (new_version)
+    {
+      if (new_version > name && new_version[-1] != ELF_VER_CHR)
+	h->hidden = 1;
+      new_version += 1;
+      if (new_version[0] == '\0')
+	new_version = NULL;
+    }
+
   /* For merging, we only care about real symbols.  But we need to make
      sure that indirect symbol dynamic flags are updated.  */
   hi = h;
@@ -975,6 +988,45 @@ _bfd_elf_merge_symbol (bfd *abfd,
 	 || h->root.type == bfd_link_hash_warning)
     h = (struct elf_link_hash_entry *) h->root.u.i.link;
 
+  if (!*matched)
+    {
+      if (hi == h || h->root.type == bfd_link_hash_new)
+	*matched = TRUE;
+      else
+	{
+	  /* OLD_HIDDEN is true if the existing symbol is only visibile
+	     to the symbol with the same symbol version.  NEW_HIDDEN is
+	     true if the new symbol is only visibile to the symbol with
+	     the same symbol version.  */
+	  bfd_boolean old_hidden = h->hidden;
+	  bfd_boolean new_hidden = hi->hidden;
+	  if (!old_hidden && !new_hidden)
+	    /* The new symbol matches the existing symbol if both
+	       aren't hidden.  */
+	    *matched = TRUE;
+	  else
+	    {
+	      /* OLD_VERSION is the symbol version of the existing
+		 symbol. */
+	      char *old_version = strrchr (h->root.root.string,
+					   ELF_VER_CHR);
+	      if (old_version)
+		{
+		  old_version += 1;
+		  if (old_version[0] == '\0')
+		    old_version = NULL;
+		}
+
+	      /* The new symbol matches the existing symbol if they
+		 have the same symbol version.  */
+	      *matched = (old_version == new_version
+			  || (old_version != NULL
+			      && new_version != NULL
+			      && strcmp (old_version, new_version) == 0));
+	    }
+	}
+    }
+
   /* OLDBFD and OLDSEC are a BFD and an ASECTION associated with the
      existing symbol.  */
 
@@ -1047,7 +1099,9 @@ _bfd_elf_merge_symbol (bfd *abfd,
 	}
       else
 	{
-	  h->dynamic_def = 1;
+	  /* Update the existing symbol only if they match. */
+	  if (*matched)
+	    h->dynamic_def = 1;
 	  hi->dynamic_def = 1;
 	}
     }
@@ -1618,6 +1672,7 @@ _bfd_elf_add_default_symbol (bfd *abfd,
   char *p;
   size_t len, shortlen;
   asection *tmp_sec;
+  bfd_boolean matched;
 
   /* If this symbol has a version, and it is the default version, we
      create an indirect symbol from the default name to the fully
@@ -1644,10 +1699,11 @@ _bfd_elf_add_default_symbol (bfd *abfd,
      actually going to define an indirect symbol.  */
   type_change_ok = FALSE;
   size_change_ok = FALSE;
+  matched = TRUE;
   tmp_sec = sec;
   if (!_bfd_elf_merge_symbol (abfd, info, shortname, sym, &tmp_sec, &value,
 			      &hi, poldbfd, NULL, NULL, &skip, &override,
-			      &type_change_ok, &size_change_ok))
+			      &type_change_ok, &size_change_ok, &matched))
     return FALSE;
 
   if (skip)
@@ -1767,7 +1823,7 @@ nondefault:
   tmp_sec = sec;
   if (!_bfd_elf_merge_symbol (abfd, info, shortname, sym, &tmp_sec, &value,
 			      &hi, poldbfd, NULL, NULL, &skip, &override,
-			      &type_change_ok, &size_change_ok))
+			      &type_change_ok, &size_change_ok, &matched))
     return FALSE;
 
   if (skip)
@@ -1977,26 +2033,14 @@ _bfd_elf_link_assign_sym_version (struct elf_link_hash_entry *h, void *data)
   if (p != NULL && h->verinfo.vertree == NULL)
     {
       struct bfd_elf_version_tree *t;
-      bfd_boolean hidden;
 
-      hidden = TRUE;
-
-      /* There are two consecutive ELF_VER_CHR characters if this is
-	 not a hidden symbol.  */
       ++p;
       if (*p == ELF_VER_CHR)
-	{
-	  hidden = FALSE;
-	  ++p;
-	}
+	++p;
 
       /* If there is no version string, we can just return out.  */
       if (*p == '\0')
-	{
-	  if (hidden)
-	    h->hidden = 1;
-	  return TRUE;
-	}
+	return TRUE;
 
       /* Look for the version.  If we find it, it is no longer weak.  */
       for (t = sinfo->info->version_info; t != NULL; t = t->next)
@@ -2092,9 +2136,6 @@ _bfd_elf_link_assign_sym_version (struct elf_link_hash_entry *h, void *data)
 	  sinfo->failed = TRUE;
 	  return FALSE;
 	}
-
-      if (hidden)
-	h->hidden = 1;
     }
 
   /* If we don't have a version for this symbol, see if we can find
@@ -3885,6 +3926,7 @@ error_free_dyn:
       bfd_boolean common;
       unsigned int old_alignment;
       bfd *old_bfd;
+      bfd_boolean matched;
 
       override = FALSE;
 
@@ -4019,6 +4061,7 @@ error_free_dyn:
       size_change_ok = FALSE;
       type_change_ok = bed->type_change_ok;
       old_weak = FALSE;
+      matched = FALSE;
       old_alignment = 0;
       old_bfd = NULL;
       new_sec = sec;
@@ -4148,13 +4191,16 @@ error_free_dyn:
 	  if (!_bfd_elf_merge_symbol (abfd, info, name, isym, &sec, &value,
 				      sym_hash, &old_bfd, &old_weak,
 				      &old_alignment, &skip, &override,
-				      &type_change_ok, &size_change_ok))
+				      &type_change_ok, &size_change_ok,
+				      &matched))
 	    goto error_free_vers;
 
 	  if (skip)
 	    continue;
 
-	  if (override)
+	  /* Override a definition only if the new symbol matches the
+	     existing one.  */
+	  if (override && matched)
 	    definition = FALSE;
 
 	  h = *sym_hash;
@@ -6810,14 +6856,18 @@ _bfd_elf_link_hash_copy_indirect (struct bfd_link_info *info,
   struct elf_link_hash_table *htab;
 
   /* Copy down any references that we may have already seen to the
-     symbol which just became indirect.  */
+     symbol which just became indirect if DIR isn't a hidden versioned
+     symbol.  */
 
-  dir->ref_dynamic |= ind->ref_dynamic;
-  dir->ref_regular |= ind->ref_regular;
-  dir->ref_regular_nonweak |= ind->ref_regular_nonweak;
-  dir->non_got_ref |= ind->non_got_ref;
-  dir->needs_plt |= ind->needs_plt;
-  dir->pointer_equality_needed |= ind->pointer_equality_needed;
+  if (!dir->hidden)
+    {
+      dir->ref_dynamic |= ind->ref_dynamic;
+      dir->ref_regular |= ind->ref_regular;
+      dir->ref_regular_nonweak |= ind->ref_regular_nonweak;
+      dir->non_got_ref |= ind->non_got_ref;
+      dir->needs_plt |= ind->needs_plt;
+      dir->pointer_equality_needed |= ind->pointer_equality_needed;
+    }
 
   if (ind->root.type != bfd_link_hash_indirect)
     return;
@@ -8904,6 +8954,16 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
   const struct elf_backend_data *bed;
   long indx;
   int ret;
+  /* A symbol is bound locally if it is forced local or it is locally
+     defined, hidden versioned, not referenced by shared library and
+     not exported when linking executable.  */
+  bfd_boolean local_bind = (h->forced_local
+			    || (flinfo->info->executable
+				&& !flinfo->info->export_dynamic
+				&& !h->dynamic
+				&& !h->ref_dynamic
+				&& h->def_regular
+				&& h->hidden));
 
   if (h->root.type == bfd_link_hash_warning)
     {
@@ -8915,12 +8975,12 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
   /* Decide whether to output this symbol in this pass.  */
   if (eoinfo->localsyms)
     {
-      if (!h->forced_local)
+      if (!local_bind)
 	return TRUE;
     }
   else
     {
-      if (h->forced_local)
+      if (local_bind)
 	return TRUE;
     }
 
@@ -9041,7 +9101,7 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
   sym.st_value = 0;
   sym.st_size = h->size;
   sym.st_other = h->other;
-  if (h->forced_local)
+  if (local_bind)
     {
       sym.st_info = ELF_ST_INFO (STB_LOCAL, h->type);
       /* Turn off visibility on local symbol.  */
@@ -9223,8 +9283,10 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
       /* Since there is no version information in the dynamic string,
 	 if there is no version info in symbol version section, we will
 	 have a run-time problem if not linking executable, referenced
-	 by shared library, or not locally defined.  */
+	 by shared library, not locally defined, or not bound locally.
+      */
       if (h->verinfo.verdef == NULL
+	  && !local_bind
 	  && (!flinfo->info->executable
 	      || h->ref_dynamic
 	      || !h->def_regular))
@@ -9297,7 +9359,9 @@ elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
 		iversym.vs_vers++;
 	    }
 
-	  if (h->hidden)
+	  /* Turn on VERSYM_HIDDEN only if the hidden vesioned symbol is
+	     defined locally.  */
+	  if (h->hidden && h->def_regular)
 	    iversym.vs_vers |= VERSYM_HIDDEN;
 
 	  eversym = (Elf_External_Versym *) flinfo->symver_sec->contents;
diff --git a/ld/testsuite/ld-elf/indirect.exp b/ld/testsuite/ld-elf/indirect.exp
index 468ef2b..e8ac1ae 100644
--- a/ld/testsuite/ld-elf/indirect.exp
+++ b/ld/testsuite/ld-elf/indirect.exp
@@ -64,7 +64,9 @@ if { ![ld_compile $CC $srcdir/$subdir/indirect1a.c tmpdir/indirect1a.o]
      || ![ld_compile $CC $srcdir/$subdir/indirect3a.c tmpdir/indirect3a.o]
      || ![ld_compile $CC $srcdir/$subdir/indirect3b.c tmpdir/indirect3b.o]
      || ![ld_compile $CC $srcdir/$subdir/indirect4a.c tmpdir/indirect4a.o]
-     || ![ld_compile $CC $srcdir/$subdir/indirect4b.c tmpdir/indirect4b.o] } {
+     || ![ld_compile $CC $srcdir/$subdir/indirect4b.c tmpdir/indirect4b.o]
+     || ![ld_compile "$CC -O2 -fPIC -I../bfd" $srcdir/$subdir/pr18720a.c tmpdir/pr18720a.o]
+     || ![ld_compile $CC $srcdir/$subdir/pr18720b.c tmpdir/pr18720b.o] } {
     unresolved "Indirect symbol tests"
     return
 }
@@ -79,6 +81,12 @@ set build_tests {
   {"Build libindirect4c.so"
    "-shared" "-fPIC"
    {indirect4c.c} {} "libindirect4c.so"}
+  {"Build libpr18720c.so"
+   "-shared" "-fPIC"
+   {pr18720c.c} {} "libpr18720c.so"}
+  {"Build pr18720b1.o"
+   "-r -nostdlib tmpdir/pr18720b.o" ""
+   {dummy.c} {} "pr18720b1.o"}
 }
 
 run_cc_link_tests $build_tests
@@ -132,6 +140,21 @@ set run_tests {
     {"Run with libindirect4c.so 4"
      "tmpdir/libindirect4c.so tmpdir/indirect4b.o tmpdir/indirect4a.o" ""
      {dummy.c} "indirect4d" "indirect4.out"}
+    {"Run with libpr18720c.so 1"
+     "tmpdir/pr18720a.o tmpdir/pr18720b.o tmpdir/libpr18720c.so" ""
+     {check-ptr-eq.c} "pr18720a" "pr18720.out"}
+    {"Run with libpr18720c.so 2"
+     "tmpdir/pr18720a.o tmpdir/libpr18720c.so tmpdir/pr18720b.o" ""
+     {check-ptr-eq.c} "pr18720b" "pr18720.out"}
+    {"Run with libpr18720c.so 3"
+     "tmpdir/pr18720b.o tmpdir/libpr18720c.so tmpdir/pr18720a.o" ""
+     {check-ptr-eq.c} "pr18720c" "pr18720.out"}
+    {"Run with libpr18720c.so 4"
+     "tmpdir/libpr18720c.so tmpdir/pr18720b.o tmpdir/pr18720a.o" ""
+     {check-ptr-eq.c} "pr18720d" "pr18720.out"}
+    {"Run with libpr18720c.so 5"
+     "tmpdir/libpr18720c.so tmpdir/pr18720b1.o tmpdir/pr18720a.o" ""
+     {check-ptr-eq.c} "pr18720d" "pr18720.out"}
 }
 
 run_ld_link_exec_tests [] $run_tests
diff --git a/ld/testsuite/ld-elf/pr18720.out b/ld/testsuite/ld-elf/pr18720.out
new file mode 100644
index 0000000..482e981
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr18720.out
@@ -0,0 +1,2 @@
+MAIN
+DSO
diff --git a/ld/testsuite/ld-elf/pr18720a.c b/ld/testsuite/ld-elf/pr18720a.c
new file mode 100644
index 0000000..752623b
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr18720a.c
@@ -0,0 +1,27 @@
+#include <bfd_stdint.h>
+
+extern void bar (void);
+extern void foo (void);
+extern void foo_alias (void);
+extern void check_ptr_eq (void *, void *);
+
+#if defined(__GNUC__) && (__GNUC__ * 1000 + __GNUC_MINOR__) >= 4005
+__attribute__ ((noinline, noclone))
+#else
+__attribute__ ((noinline))
+#endif
+int
+foo_p (void)
+{
+  return (intptr_t) &foo == 0x12345678 ? 1 : 0;
+}
+
+int
+main (void)
+{
+  foo ();
+  foo_p ();
+  bar ();
+  check_ptr_eq (&foo, &foo_alias);
+  return 0;
+}
diff --git a/ld/testsuite/ld-elf/pr18720b.c b/ld/testsuite/ld-elf/pr18720b.c
new file mode 100644
index 0000000..90d376b
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr18720b.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+void
+foo (void)
+{
+  printf ("MAIN\n");
+}
+
+asm (".symver foo,foo@FOO");
+asm (".set foo_alias,foo");
+asm (".global foo_alias");
diff --git a/ld/testsuite/ld-elf/pr18720c.c b/ld/testsuite/ld-elf/pr18720c.c
new file mode 100644
index 0000000..b52cb95
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr18720c.c
@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+extern void foo (void);
+
+void
+foo (void)
+{
+  printf ("DSO\n");
+}
+
+void
+bar (void)
+{
+  foo ();
+}
-- 
2.4.3